InVivo Therapeutics (NVIVQ) S-1 29 Jan 18 IPO registration Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2017
Document and Entity Information
Entity Registrant Name	INVIVO THERAPEUTICS HOLDINGS CORP.
Entity Central Index Key	1,292,519
Document Type	S1
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 16,434	$ 21,464	$ 25,261	$ 14,920	$ 13,459	$ 13,980
Restricted cash	361	361		361
Marketable securities	734	11,577		5,274
Prepaid expenses and other current assets	475	451		184
Total current assets	18,004	33,853		20,739
Property, equipment and leasehold improvements, net	190	510		938
Other assets	402	421		115
Total assets	18,596	34,784		21,792
Current liabilities:
Accounts payable	1,270	1,011		521
Loan payable, current portion	444	423		395
Derivative warrant liability	41	1,314		1,907
Deferred rent, current portion	30	141		115
Accrued expenses	1,784	1,959		374
Total current liabilities	3,569	4,848		3,312
Loan payable, net of current portion	516	852		1,275
Deferred rent, net of current portion	208	135		276
Total liabilities	4,345	5,835		4,863
Commitments and contingencies
Stockholders' equity:
Common stock, $0.00001 par value, authorized 100,000,000 shares, issued and outstanding 32,044,087 shares at December 31, 2016; and authorized 50,000,000 shares, issued and outstanding 27,555,948 shares at December 31, 2015	1	1		1
Additional paid-in capital	193,493	185,955		150,497
Accumulated deficit	(179,243)	(157,007)		(133,569)
Total stockholders' equity	14,251	28,949		16,929	$ 5,918	$ 12,890
Total liabilities and stockholders' equity	$ 18,596	$ 34,784		$ 21,792

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001	$ 0.00001
Common stock, authorized	100,000,000	100,000,000	50,000,000
Common stock, issued	34,234,580	32,044,087	27,555,948
Common stock, outstanding	34,234,580	32,044,087	27,555,948

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses:
Research and development	$ 2,928	$ 3,294	$ 9,522	$ 8,659	$ 12,557	$ 10,058	$ 10,273
General and administrative	3,388	2,584	10,389	8,573	11,506	12,340	7,566
Total operating expenses	6,316	5,878	19,911	17,232	24,063	22,398	17,839
Operating loss	(6,316)	(5,878)	(19,911)	(17,232)	(24,063)	(22,398)	(17,839)
Other income (expense):
Interest income	43	50	152	133	187	60	5
Interest expense	(18)	(32)	(58)	(117)	(155)	(172)	(136)
Derivatives gain (loss)	(3,059)	(336)	(2,264)	(788)	593	(10,804)	(376)
Other income (expense), net	$ (3,034)	$ (318)	$ (2,170)	$ (772)	625	(10,916)	(507)
Net loss					$ (23,438)	$ (33,314)	$ (18,346)
Net loss per share, basic and diluted (in dollars per share)	$ (0.28)	$ (0.19)	$ (0.68)	$ (0.59)	$ (0.76)	$ (1.26)	$ (0.83)
Weighted average number of common shares outstanding, basic and diluted	33,445,002	31,968,357	32,516,190	30,687,263	31,025,585	26,461,374	22,080,761

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2013	$ 1,000	$ 94,798,000	$ (81,909,000)	$ 12,890,000
Beginning Balance, (in shares) at Dec. 31, 2013	19,693,434
Share-based compensation expense		2,730,000		2,730,000
Issuance of common stock in public offerings		7,770,000		7,770,000
Issuance of stock in public offering (in shares)	3,500,312
Issuance of common stock for services		477,000		477,000
Issuance of common stock for services (in shares)	74,626
Issuance of common stock upon cashless exercise of warrants (in shares)	6,903
Issuance of common stock upon exercise of warrants		12,000		12,000
Issuance of common stock upon exercise of warrants (in shares)	9,975
Issuance of common stock upon exercise of stock options		212,000		212,000
Issuance of common stock upon exercise of stock options (in shares)	132,900
Issuance of common stock to 401(k) plan	$ 173,000	173,000		173,000
Issuance of common stock to 401(k) plan (in shares)	41,753
Net loss			(18,346,000)	(18,346,000)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2014	$ 1,000	106,172,000	(100,255,000)	5,918,000
Ending Balance, (in shares) at Dec. 31, 2014	23,453,000
Share-based compensation expense		4,666,000		4,666,000
Issuance of common stock in public offerings		14,480,000		14,480,000
Issuance of stock in public offering (in shares)	2,388,245
Issuance of common stock upon cashless exercise of warrants (in shares)	25,052
Issuance of common stock upon exercise of warrants		7,789,000		7,789,000
Issuance of common stock upon exercise of warrants (in shares)	1,379,575
Issuance of common stock upon exercise of stock options		1,068,000		1,068,000
Issuance of common stock upon exercise of stock options (in shares)	316,177
Fair value of derivative warrant liability reclassified to additional paid-in capital		16,121,000		16,121,000
Fractional shares issued due to reverse stock split	1,514
Issuance of common stock to 401(k) plan	$ 201,000	201,000		201,000
Issuance of common stock to 401(k) plan (in shares)	17,437
Net loss			(33,314,000)	(33,314,000)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2015	$ 1,000	150,497,000	(133,569,000)	$ 16,929,000
Ending Balance, (in shares) at Dec. 31, 2015	27,555,948			27,555,948
Share-based compensation expense		5,063,000		$ 5,063,000
Issuance of common stock and warrants in public offerings, net of $2,040 issuance costs		29,905,000		29,905,000
Issuance of common stock and warrants in public offerings, net of $2,040 issuance costs (in shares)	4,293,333
Issuance of common stock for services (in shares)	365
Issuance of common stock upon cashless exercise of warrants (in shares)	4,979
Issuance of common stock upon exercise of stock options		191,000		191,000
Issuance of common stock upon exercise of stock options (in shares)	135,205
Issuance of common stock under ESPP		91,000		91,000
Issuance of common stock under ESPP (in shares)	16,729
Issuance of common stock to 401(k) plan	$ 208,000	208,000		208,000
Issuance of common stock to 401(k) plan (in shares)	37,528
Net loss			(23,438,000)	(23,438,000)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2016	$ 1,000	$ 185,955,000	$ (157,007,000)	$ 28,949,000
Ending Balance, (in shares) at Dec. 31, 2016	32,044,087			32,044,087
Issuance of common stock upon exercise of stock options (in shares)	89,387
Issuance of common stock under ESPP (in shares)	17,750
Issuance of common stock to 401(k) plan	$ 154,000
Issuance of common stock to 401(k) plan (in shares)	61,587
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2017				$ 14,251,000
Ending Balance, (in shares) at Sep. 30, 2017				34,234,580

Consolidated Statements of Cha6

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Consolidated Statements of Changes in Stockholders' Equity (Deficit)
Issuance of common stock & warrants in a public offering, stock issuance costs	$ 2,040

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (23,438)	$ (33,314)	$ (18,346)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	553	689	752
Derivatives (gain) loss	(593)	10,804	376
Common stock issued to 401(k) plan	208	201	173
Common stock issued for services			477
Share-based compensation expense	5,063	4,666	2,730
Other non-cash investment activities	98
Changes in operating assets and liabilities:
Restricted cash		61	180
Prepaid expenses	(267)	888	(363)
Insurance receivable			(689)
Other assets	(324)	3	4
Accounts payable	489	(48)	(330)
Accrued expenses	1,471	(279)	(248)
Net cash used in operating activities	(16,740)	(16,329)	(15,284)
Cash flows from investing activities:
Purchases of marketable securities	(18,916)	(5,274)
Sales of marketable securities	12,515
Non-cash disposals of property and equipment			45
Purchases of property and equipment	(107)	(5)	(47)
Net cash used in investing activities	(6,508)	(5,279)	(2)
Cash flows from financing activities:
Proceeds from exercise of stock options	191	1,068	212
Proceeds from issuance of stock under ESPP	91
Proceeds from exercise of warrants		7,789	12
Repayment of note payable		(18)	(56)
Principal payments on capital lease obligation			(21)
Repayment of loan payable	(395)	(250)
Proceeds from issuance of common stock and warrants	29,905	14,480	14,618
Net cash provided by financing activities	29,792	23,069	14,765
Increase (decrease) in cash and cash equivalents	6,544	1,461	(521)
Cash and cash equivalents at beginning of period	14,920	13,459	13,980
Cash and cash equivalents at end of period	21,464	14,920	13,459
Supplemental disclosure of cash flow information and non-cash investing and financing activities:
Cash paid for interest	103	121	132
Fair value of warrants issued in connection with underwriting agreement			$ 6,848
Cashless exercise of equity-classified warrants to common stock	$ 90	251
Reclassification of derivative warrant liability to additional paid-in capital		$ 16,121

NATURE OF OPERATIONS AND GOING

NATURE OF OPERATIONS AND GOING CONCERN	12 Months Ended
	Dec. 31, 2016
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS
NATURE OF OPERATIONS AND GOING CONCERN	1. NATURE OF OPERATIONS AND GOING CONCERN Business InVivo Therapeutics Holdings Corp. (the “Company”) is a pioneering biomaterials and biotechnology company with a focus on the treatment of spinal cord injuries (“SCIs”). The Company’s proprietary technologies incorporate intellectual property that is licensed under an exclusive, worldwide license from Boston Children’s Hospital and the Massachusetts Institute of Technology, as well as intellectual property that has been developed internally in collaboration with its advisors and partners. Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff, acquiring operating assets, and raising capital. The Company has historically financed its operations primarily through the sale of equity-related securities. At December 31, 2016, the Company has consolidated cash, cash equivalents, and marketable securities of $33,041. The Company has not achieved profitability and may not be able to realize sufficient revenue to achieve or sustain profitability in the future. The Company does not expect to be profitable in the next several years, but rather expects to incur additional operating losses. The Company has limited liquidity and capital resources and must obtain significant additional capital resources in order to sustain its product development efforts, for acquisition of technologies and intellectual property rights, for preclinical and clinical testing of its anticipated products, pursuit of regulatory approvals, acquisition of capital equipment, laboratory and office facilities, establishment of production capabilities, for selling, general and administrative expenses, and other working capital requirements. The Company expects that it will need additional capital to fund its operations, which it may raise through a combination of equity offerings, debt financings, other third party funding, marketing and distribution arrangements, and other collaborations, strategic alliances, and licensing arrangements. Going Concern The Company’s financial statements as of December 31, 2016 were prepared under the assumption that the Company will continue as a going concern. At December 31, 2016, the Company had cash, cash equivalents, and marketable securities of $33,041. Given the Company’s development plans, it estimates cash resources will be sufficient to fund its operations into the beginning of the second quarter of 2018. This estimate is based on assumptions that may prove to be wrong; expenses could prove to be significantly higher, leading to a more rapid consumption of the Company’s existing resources. The Company’s ability to continue as a going concern depends on its ability to obtain additional equity or debt financing, attain further operating efficiencies, reduce expenditures, and, ultimately, to generate revenue. If the Company is unable to continue as a going concern, it may have to liquidate its assets and may receive less than the value at which those assets are carried on its audited financial statements, and it is likely that investors will lose all or part of their investment. If the Company seeks additional financing to fund its business activities in the future and there remains substantial doubt about its ability to continue as a going concern, investors or other financing sources may be unwilling to provide additional funding to the Company on commercially reasonable terms or at all. Based on these factors, management determined that there is substantial doubt regarding the Company’s ability to continue as a going concern.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2016
SIGNIFICANT ACCOUNTING POLICIES
SIGNIFICANT ACCOUNTING POLICIES	2. SIGNIFICANT ACCOUNTING POLICIES A summary of the significant accounting policies followed by the Company in the preparation of the financial statements is as follows: Use of estimates The process of preparing financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of assets and liabilities at the date of the financial statements and the reported amounts expensed during the reporting period. Actual results could differ from those estimates and changes in estimates may occur. Basis of presentation and principles of consolidation The consolidated financial statements include the accounts of InVivo Therapeutics Holdings Corp. and its wholly‑owned subsidiary, InVivo Therapeutics Corporation. All significant intercompany balances and transactions have been eliminated in consolidation. The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP. Cash and cash equivalents The Company considers only those investments that are highly liquid, readily convertible to cash, and that mature within three months from date of purchase to be cash equivalents. At December 31, 2016 and 2015, cash equivalents were comprised of money market funds and other short-term investments. Cash and cash equivalents consist of the following: December 31, 2016 2015 Cash $ $ Money market funds Total cash and cash equivalents $ $ Marketable securities The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars, including obligations of the U.S. government and its agencies, money market instruments, money market funds, corporate obligations, asset-backed securities, and municipal obligations. As of December 31, 2016, the Company’s investment portfolio consists of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore, such investments are reported at fair value. For securities sold prior to maturity, the cost of securities sold is based on the specific identification method. Realized gains and losses on the sale of investments are recorded in interest income (expense), net. Interest is recorded when earned. Investments with original maturities greater than approximately three months and remaining maturities less than one year are classified as short-term investments. Investments with remaining maturities greater than one year are classified as long-term investments. The Company considers securities with maturities of three months or less from the purchase date to be cash equivalents. At December 31, 2016, the aggregate fair value of the Company’s marketable securities was $11,577. At December 31, 2015, the aggregate fair value of the Company’s marketable securities was $5,274. Gross unrealized gains and losses were insignificant for the years ended December 31, 2016 and 2015. We conduct periodic reviews to identify and evaluate each investment that is in an unrealized loss position in order to determine whether an other-than-temporary impairment exists. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale debt securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income (loss). Restricted cash Restricted cash as of December 31, 2016 and 2015 was $361 and included a $50 security deposit related to the Company’s credit card account and a $311 standby letter of credit in favor of a landlord (see Note 17). Financial instruments The carrying amounts reported in the Company’s consolidated balance sheets for cash, cash equivalents, marketable securities and accounts payable approximate fair value based on the short‑term nature of these instruments. The carrying value of the loan payable approximates fair value due to market terms. Property and equipment Property and equipment are carried at cost. Depreciation and amortization expense are recorded over the estimated useful lives of the assets using the straight‑line method. A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 5 years Software 3 years Office furniture and equipment 5 years Research and lab equipment 5 years Leasehold improvements Remaining life of lease Research and development expenses Costs incurred for research and development are expensed as incurred. Concentrations of credit risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents, and marketable securities. The Company maintains cash in commercial banks, which may at times exceed Federally Insured limits. The Company has not experienced any loss in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents. Segment information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision making group, in making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and manages its business as principally one operating segment, which is developing and commercializing biopolymer scaffolding devices for the treatment of spinal cord injuries. As of December 31, 2016 and 2015, all of the Company’s assets were located in one location in the United States. Income taxes For federal and state income taxes, deferred tax assets and liabilities are recognized based upon temporary differences between the financial statement and the tax basis of assets and liabilities. Deferred income taxes are based upon prescribed rates and enacted laws applicable to periods in which differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that some portion or all of the deferred tax assets will not be realized. Accordingly, the Company provides a valuation allowance, if necessary, to reduce deferred tax assets to amounts that are realizable. Tax positions taken or expected to be taken in the course of preparing the Company’s tax returns are required to be evaluated to determine whether the tax positions are “more‑likely‑than‑not” of being sustained by the applicable tax authority. Tax positions not deemed to meet a more‑likely‑than‑not threshold would be recorded as a tax expense in the current year. There were no material uncertain tax positions that required accrual or disclosure to the financial statements as of December 31, 2016 or 2015. Tax years subsequent to 2013 remain open to examination by U.S. federal and state tax authorities. Impairment of long‑lived assets The Company continually monitors events and changes in circumstances that could indicate that carrying amounts of long‑lived assets may not be recoverable. An impairment loss is recognized when expected cash flows are less than an asset’s carrying value. Accordingly, when indicators of impairment are present, the Company evaluates the carrying value of such assets in relation to the operating performance and future undiscounted cash flows of the underlying assets. The Company’s policy is to record an impairment loss when it is determined that the carrying value of the asset may not be recoverable. No impairment charges were recorded for the years ended December 31, 2016, 2015, and 2014. Share‑based payments The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The Company’s stock-based payments include stock options and grants of common stock, including common stock subject to vesting. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on a straight-line basis. The measurement date for nonemployee awards is the date the services are completed, resulting in periodic adjustments to stock-based compensation during the vesting period for changes in the fair value of the awards. Stock-based compensation costs for nonemployees are recognized as expense over the vesting period on a straight-line basis. Stock-based compensation is classified in the accompanying consolidated statements of operations and comprehensive loss based on the department to which the related services are provided. Derivative instruments The Company generally does not use derivative instruments to hedge exposures to cash‑flow or market risks; however, certain warrants to purchase common stock that do not meet the requirements for classification as equity are classified as liabilities. In such instances, net‑cash settlement is assumed for financial reporting purposes, even when the terms of the underlying contracts do not provide for a net‑cash settlement. Such financial instruments are initially recorded at fair value, with subsequent changes in fair value charged (credited) to operations in each reporting period. If these instruments subsequently meet the requirements for classification as equity, the Company reclassifies the fair value to equity. Net loss per common share Basic net loss per share of common stock has been computed by dividing net loss by the weighted average number of shares outstanding during the period. Diluted net income per share of common stock has been computed by dividing net income by the weighted average number of shares outstanding plus the dilutive effect, if any, of outstanding stock options, warrants and convertible securities. Diluted net loss per share of common stock has been computed by dividing the net loss for the period by the weighted average number of shares of common stock outstanding during such period. In a net loss period, options, warrants related to the Company’s May 2014 capital raise, which include an anti-dilution provisions, and convertible securities are anti‑dilutive and therefore excluded from diluted loss per share calculations. For the year ended December 31, 2016, 2015, and 2014, the following potentially dilutive securities were not included in the computation of net loss per share because the effect would be anti-dilutive: 2016 2015 2014 Stock options Warrants Reclassifications Certain amounts in prior period financial statements have been reclassified to conform to the current period presentation. Marketable securities were previously included in cash and cash equivalents on the balance sheet but are now reflected as a separate line item on the balance sheet. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for all periods presented. Recent accounting pronouncements In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements—Going Concern , on disclosure of uncertainties about an entity's ability to continue as a going concern. This guidance addresses management's responsibility in evaluating whether there is substantial doubt about a company's ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for fiscal years ending after December 15, 2016 including interim reporting periods within each annual reporting period, with early adoption permitted. The Company adopted this guidance as of December 31, 2016. The adoption of ASU 2014-15 impacted presentation and disclosure only and did not have any impact on the Company’s financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606) : Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date of December 15, 2017. Currently, this guidance is not applicable to the Company as the Company is still in the research and development stage. However, the Company will continue to evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company will adopt this standard on January 1, 2017, and the adoption is not expected to have a material impact on the Company’s financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements.

MARKETABLE SECURITIES

MARKETABLE SECURITIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
MARKETABLE SECURITIES
MARKETABLE SECURITIES	4. MARKETABLE SECURITIES The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars, including money market accounts, commercial paper, asset-backed securities, and corporate obligations, in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. As of September 30, 2017 and December 31, 2016, the Company’s investment portfolio consisted of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore such investments are reported at fair value. Unrealized gains or losses on marketable securities are recorded in accumulated other comprehensive loss, a component of stockholders’ equity, on the balance sheet. The following table summarizes the Company’s investments in marketable securities by category as of September 30, 2017 and December 31, 2016: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2017 Current (due within 1 year or less) Corporate obligations 734 — — 734 Total $ 734 $ — $ — $ 734 December 31, 2016 Current (due within 1 year or less) Commercial paper 4,240 — — 4,240 Corporate obligations 7,337 — — 7,337 Total $ 11,577 $ — $ — $ 11,577	3. MARKETABLE SECURITIES The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars including money market accounts, commercial paper, and corporate obligations in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. The following table summarizes the Company’s cash, cash equivalents, and marketable securities as of December 31, 2016 and 2015: December 31, 2016 2015 Cash $ $ Money market funds Marketable securities Total cash, cash equivalents and marketable securities $ $ As of December 31, 2016, the Company’s investment portfolio consists of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore, such investments are reported at fair value. As of December 31, 2016, the fair value of the Company’s marketable securities approximates amortized cost and therefore the insignificant gains/losses on these securities have been included within Other Income (Expense) on the Statement of Operations. The following table summarizes the Company’s short-term investments in marketable securities by category as of December 31, 2016 and 2015: Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Commercial paper Corporate obligations — — Total $ $ — $ — $ December 31, 2015 Commercial paper Corporate obligations — — Total $ $ — $ — $ As of December 31, 2016 and 2015, the Company’s investments in marketable securities are classified in current assets as they are due in one year or less.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	12 Months Ended
	Dec. 31, 2016
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	4. PROPERTY AND EQUIPMENT Property and equipment, net consisted of the following: 2016 2015 Computer software and hardware $ $ Research and lab equipment Leasehold improvements Office equipment Less accumulated depreciation and amortization Property and equipment, net $ $ Depreciation and amortization expense for the years ended December 31, 2016, 2015, and 2014 was $536, $672, and $735, respectively. Maintenance and repairs are charged to expense as incurred and any additions or improvements are capitalized. The Company had no disposals for the years ended December 31, 2016 and 2015.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2016
INTANGIBLE ASSETS
INTANGIBLE ASSETS	5. INTANGIBLE ASSETS Intangible assets, included in “other assets,” consisted of patent licensing fees paid to license intellectual property (see Note 16). The Company is amortizing the license fee as a research and development expense over the 15–year term of the license. 2016 2015 Patent licensing fee $ $ Accumulated amortization $ $ For each of the years ended December 31, 2016, 2015, and 2014, the amortization expense was $17. Amortization expense is expected to be $17 per year for 2017, 2018, 2019, and 2020, and $10 in 2021.

ACCRUED EXPENSES

ACCRUED EXPENSES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
ACCRUED EXPENSES
ACCRUED EXPENSES	7. ACCRUED EXPENSES Accrued expenses consisted of the following: September 30, December 31, (In thousands) 2017 2016 Bonus $ 595 $ 906 Payroll 158 126 Vacation 231 91 Severance 455 385 Other accrued expenses 345 451 Total accrued expenses $ 1,784 $ 1,959	6. ACCRUED EXPENSES Accrued expenses consisted of the following: December 31, 2016 2015 Accrued bonus $ $ — Accrued payroll Accrued vacation Accrued severance — Other accrued expenses Total accrued expenses $ $

FAIR VALUE OF ASSETS AND LIABIL

FAIR VALUE OF ASSETS AND LIABILITIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
FAIR VALUE OF ASSETS AND LIABILITIES
FAIR VALUE OF ASSETS AND LIABILITIES	5. FAIR VALUE OF ASSETS AND LIABILITIES The Company groups its assets and liabilities generally measured at fair value into three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1 — Valuation is based on quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities generally include debt and equity securities that are traded in an active exchange market. Valuations are obtained from readily available pricing sources for market transactions involving identical assets or liabilities. Level 2 — Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. The Company uses valuation methods and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments (see Notes 11 and 12). Assets and liabilities measured at fair value on a recurring basis are summarized below: At September 30, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 16,524 $ — $ — $ 16,524 Marketable securities — 734 — 734 Derivative warrant liability $ — $ (41) $ — $ (41) At December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 21,353 $ — $ — $ 21,353 Marketable securities — 11,577 — 11,577 Derivative warrant liability $ — $ (1,314) $ — $ (1,314)	7. FAIR VALUES OF ASSETS AND LIABILITIES The Company groups its assets and liabilities generally measured at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1—Valuation is based on quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities, generally include debt and equity securities that are traded in an active exchange market. Valuations are obtained from readily available pricing sources for market transactions involving identical assets or liabilities. Level 2—Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. The Company uses valuation methods and assumptions that consider, among other factors, the fair value of the underlying stock, risk‑free interest rate, volatility, expected life, and dividend rates in estimating the fair value for the warrants considered to be derivative instruments. Assets and liabilities measured at fair value on a recurring basis are summarized below: At December 31, 2016 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $ At December 31, 2015 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $

NOTE PAYABLE

NOTE PAYABLE	12 Months Ended
	Dec. 31, 2016
NOTE PAYABLE
NOTE PAYABLE	8. NOTE PAYABLE In May 2013, the Company entered into a contract for the purchase of an enterprise resource planning (“ERP”) system for $150. The total cost for the ERP system, including interest, is $159, with an implicit interest rate of approximately 6%. This non-cancelable purchase agreement was still in effect at December 31, 2016, but there are no future minimum principal payments to be made under the agreement due to the fact that any amounts due have been paid in full. In the third quarter of 2013, the Company decided to abandon the implementation of the ERP system. As such, the ERP system cost of $150 was fully expensed in 2013. The Company reserves the right to implement the ERP system at a future date.

LOAN PAYABLE

LOAN PAYABLE	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
LOAN PAYABLE
LOAN PAYABLE	8. LOAN PAYABLE In October 2012, the Company entered into a loan agreement with the Massachusetts Development Finance Agency (“MassDev”). The loan agreement provided the Company with a $2.0 million line of credit from the Commonwealth of Massachusetts’ Emerging Technology Fund, with $200,000 designated to be used for working capital purposes and the remainder to be used for the purchase of capital equipment. The annual interest rate on the loan is fixed at 6.5% with interest-only payments for the first thirty months, commencing on November 1, 2012, and then equal installments of interest and principal over the next fifty-four months, until the final maturity of the loan on October 5, 2019. Commencing on May 1, 2015, equal monthly payments of $41,000 are due until loan maturity. For the remainder of the year ending December 31, 2017, $108,000 will be due. For the years ending December 31, 2018 and 2019, $452,000 and $400,000, respectively, will be due. In October 2012, as part of the agreement, the Company issued MassDev a warrant for the purchase of 9,037 shares of the Company’s common stock. The warrant has a seven-year term and is exercisable at $6.64 per share. The fair value of the warrant was determined to be $32,000 and is being amortized through interest expense over the life of the note. Amortization expense was $1,000 in each of the three-month periods ended September 30, 2017 and 2016, and $3,000 in each of the nine-month periods ended September 30, 2017 and 2016. This amortization expense was included in interest expense in the Company’s consolidated statements of operations. The equipment line of credit is secured by substantially all the assets of the Company, excluding intellectual property. Interest expense related to this loan for the three-month periods ended September 30, 2017 and 2016 was $17,000 and $24,000, respectively. Interest expense related to this loan for the nine-month periods ended September 30, 2017 and 2016 was $56,000 and $76,000, respectively.	9. LOAN PAYABLE In October 2012, the Company entered into a loan agreement with the Massachusetts Development Finance Agency (“MassDev”). The loan agreement provided the Company with a $2,000 line of credit from the Commonwealth of Massachusetts’s Emerging Technology fund, with $200 designated to be used for working capital purposes and the remainder to be used for the purchase of capital equipment. The annual interest rate on the loan is fixed at 6.5% with interest-only payments for the first thirty months, commencing on November 1, 2012, and then equal interest and principal payments over the next fifty‑four months, until the final maturity of the loan on October 5, 2019. Commencing on May 1, 2015, equal monthly principal payments of $41 are due until loan maturity. Therefore, for the years ending December 31, 2017, 2018, and 2019, principal payments of $423, $452, and $400, respectively, will be due. In October 2012, as part of the agreement, the Company issued MassDev a warrant for the purchase of 9,037 shares of the Company’s common stock. The warrant has a seven-year term and is exercisable at $6.64 per share. The fair value of the warrant was determined to be $32 and is being amortized through interest expense over the life of the note. For each of the years ended December 31, 2016, 2015, and 2014, amortization expense was $5, and was included in interest expense in the Company’s consolidated statements of operations. The equipment line of credit is secured by substantially all the assets of the Company, excluding intellectual property. Interest expense related to this loan was $99, $126, and $127 for the years ended December 31, 2016, 2015, and 2014, respectively. At December 31, loans payable consisted of the following: December 31, 2016 2015 MassDev Loan $ $ Less: current portion $ $

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2016
INCOME TAXES
INCOME TAXES	10. INCOME TAXES No provision or benefit for federal or state income taxes has been recorded as the Company has incurred a net loss for all of the periods presented and the Company has provided a full valuation allowance against its deferred tax assets. At December 31, 2016, the Company had U.S. federal and Massachusetts net operating loss carryforwards of $95,872 and $88,041, respectively, of which federal carryforwards will expire in varying amounts beginning in 2026. Massachusetts net operating losses begin to expire in 2029. Utili zation of net operating losses may be subject to substantial annual limitations due to the “change in ownership” provisions of the Internal Revenue Code, and similar state provisions. The annual limitations may result in the expiration of net operating losses before utilization. The Company has completed several financings since its inception, which may have resulted in a change in ownership, or could result in a change in ownership in the future, but has not yet completed an analysis of whether an ownership change limitation exists. The Company will complete an appropriate analysis before its tax attributes are utilized. The Company also had federal and state research and development tax credits of $944 and $183, respectively, at December 31, 2016, which will begin to expire in 2025 unless previously utilized. Significant components of the Company’s net deferred tax assets are as follows: December 31, 2016 2015 Net operating loss carryforward $ $ Research and development credit carryforward Stock-based compensation Depreciation and amortization Accrued expenses Charitable contributions Subtotal Valuation allowance Net deferred taxes $ — $ — The Company has maintained a full valuation allowance against its deferred tax assets in all periods presented. A valuation allowance is required to be recorded when it is more likely than not that some portion or all of the net deferred tax assets will not be realized. Since the Company cannot be assured of generating taxable income and thereby realizing the net deferred tax assets, a full valuation allowance has been provided. In the years ended December 31, 2016 and 2015, the valuation allowance increased by $9,406 and $8,727, respectively. The Company has no uncertain tax positions at December 31, 2016 and 2015 that would affect its effective tax rate. The Company does not anticipate a significant change in the amount of uncertain tax positions over the next twelve months. Since the Company is in a loss carryforward position, the Company is generally subject to U.S. federal and state income tax examinations by tax authorities for all years for which a loss carryforward is available. Income tax benefits computed using the federal statutory income tax rate differ from the same benefits computed using the Company’s effective tax rate primarily due to the following: December 31, 2016 2015 2014 Statutory rate % % % State taxes, net of benefit % % % Permanent differences: Derivative losses % % % Other % % % R&D tax credit % % % Other % % % Increase in valuation reserve % % % Effective tax rate % % %

COMMON STOCK

COMMON STOCK	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMON STOCK.
COMMON STOCK	9. COMMON STOCK The Company has authorized 100,000,000 shares of common stock, $0.00001 par value per share, of which 34,234,580 shares were issued and outstanding as of September 30, 2017 and 32,044,087 shares were issued and outstanding as of December 31, 2016. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 89,387 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $26,000. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 61,587 shares of common stock with a fair value of $154,000 to the Company’s 401(k) plan as a matching contribution. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 17,750 shares of common stock under the Company’s Employee Stock Purchase Plan (the “ESPP”) and received cash proceeds of approximately $51,000. During the year ended December 31, 2016, the Company issued an aggregate of 135,205 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $191,000. During the year ended December 31, 2016, the Company issued an aggregate of 4,979 shares of common stock upon the cashless exercise of warrants. During the year ended December 31, 2016, the Company issued an aggregate of 37,528 shares of common stock with a fair value of $208,000 to the Company’s 401(k) plan as a matching contribution. During the year ended December 31, 2016, the Company issued an aggregate of 16,729 shares of common stock under the ESPP and received cash proceeds of $91,000. In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29.9 million. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants contain a cashless exercise feature whereby shares are withheld to cover the exercise cost and the warrant holder receives a net issuance of the remaining shares. The Company is utilizing the net proceeds from the offering to fund ongoing clinical trials and for general corporate purposes.	11. COMMON STOCK The Company has authorized 100,000,000 shares of common stock, $0.00001 par value per share, of which 32,044,087, shares were issued and outstanding as of December 31, 2016 and 27,555,948 shares were issued and outstanding as of December 31, 2015. During the year ended December 31, 2016, the Company issued an aggregate of 135,205 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $191. During the year ended December 31, 2016, the Company issued an aggregate of 4,979 shares of common stock upon the cashless exercise of warrants. During the year ended December 31, 2016, the Company issued an aggregate of 37,528 shares of common stock with a fair value of $208 to the Company’s 401(k) plan as a matching contribution. During the year ended December 31, 2016, the Company issued an aggregate of 16,729 shares of common stock under the Company’s Employee Stock Purchase Plan (the “ESPP”) and received cash proceeds of $91. In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29,905. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants contain a cashless exercise feature whereby shares are withheld to cover the exercise cost and the warrant holder receives a net issuance of the remaining shares. The Company intends to use the net proceeds from the offering to fund ongoing clinical trials and for general corporate purposes. During the year ended December 31, 2015, the Company issued an aggregate of 316,177 shares of common stock upon the exercise of stock options, including stock options to purchase 52,224 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 14,961 shares of common stock and stock options to purchase 301,216 shares of common stock exercised for cash, providing cash proceeds of $1,068. During the year ended December 31, 2015, the Company issued an aggregate of 1,379,575 shares of common stock upon the exercise of warrants, including warrants to purchase 40,955 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 25,052 shares of common stock and warrants to purchase 1,354,523 shares of common stock exercised for cash, providing net cash proceeds of $7,789. During the year ended December 31, 2015, the Company issued an aggregate of 17,437 shares of common stock with a fair value of $201 to the Company’s 401(k) plan as a matching contribution. In January 2015, the Company closed a registered direct offering of an aggregate of 2,000,000 shares of common stock, resulting in net proceeds of $11,038. As part of the adjustment to reflect the Company’s 1-for-4 reverse stock split on its common stock on April 8, 2015, the Company issued 1,514 shares of common stock to account for the fractional roundup of shareholders. In July 2015, the Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) pursuant to which the Company may issue and sell from time to time shares of common stock having aggregate sales proceeds of up to $50 million through an “at the market” equity offering program under which Cowen acts as the Company’s sales agent. The Company is required to pay Cowen a commission of 3% on the gross proceeds from the sale of shares of common stock under the Sales Agreement. The Company issued 388,245 shares of common stock under the Sales Agreement during the year ended December 31, 2015, providing cash proceeds of $3,442, net, through this facility. During the year ended December 31, 2014, the Company issued an aggregate of 132,900 shares of common stock upon the exercise of stock options and received cash proceeds of $212. During the year ended December 31, 2014, the Company issued an aggregate of 9,975 shares of common stock upon the exercise of warrants, including warrants to purchase 15,655 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 6,903 shares of common stock and warrants to purchase 3,072 shares of common stock exercised for cash, providing cash proceeds of $12. During the year ended December 31, 2014, the Company issued an aggregate of 41,753 shares of common stock with a fair value of $173 to the Company’s 401(k) plan as a matching contribution. In January 2014, the Company issued 27,212 and 5,594 shares of common stock to Michael J. Astrue, the Company’s then-Interim Chief Executive Officer, and Gregory D. Perry, the Company’s then-Interim Chief Financial Officer, respectively, in lieu of executive cash bonuses. Such shares had an aggregate fair value of approximately $282. In December 2014, the Company issued 41,821 shares of common stock to certain employees of the Company in lieu of cash bonuses. Such shares had an aggregate fair value of approximately $195. During the year ended December 31, 2014, the Company closed an underwritten public offering of an aggregate of 3,500,312 shares of common stock and warrants to purchase up to an aggregate of 1,750,156 shares of common stock, at a price to the public of $4.60 per share of common stock and $0.00001 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $14,600. The warrants have a per share price of $5.75, or 125% of the public offering of the common stock, and expire on May 9, 2019. Common Stock Reserves As of December 31, 2016, the Company had the following reserves established for the future issuance of common stock as follows: Reserves for the exercise of warrants Reserves for the exercise of stock options Total Reserves

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
DERIVATIVE INSTRUMENTS
DERIVATIVE INSTRUMENTS	12. DERIVATIVE INSTRUMENTS The Outstanding 2014 Warrants have anti-dilution protection provisions and, under certain conditions, require the Company to automatically reprice the warrants. Accordingly, these warrants are accounted for as derivative warrant liabilities. The Company used the Binomial Lattice option pricing model and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments. Changes in the fair value of the derivative warrant liabilities are recognized currently in the Company’s consolidated statement of operations as a non-cash derivative gain or loss. For the three-month periods ended September 30, 2017 and 2016, the Company recorded a loss of $3.1 million and $336,000, respectively, in other income (expense) in the statement of operations. For the nine-month periods ended September 30, 2017 and 2016, the Company recorded a loss of $2.3 million and $788,000, respectively, in other income (expense) in the statement of operations. The fair value of these derivative instruments, net of the impact of the August 2017 warrant exchange discussed above, at September 30, 2017 and December 31, 2016 was $41,000 and $1.3 million, respectively, and included as a derivative warrant liability in current liabilities on the balance sheet. The assumptions used principally in determining the fair value of the warrants were as follows: September 30, December 31, 2017 2016 Risk free interest rate 1.5 % % Expected dividend yield — % — % Contractual term (in years) 1.6 Expected volatility 86 % 89 % The primary underlying risk exposure pertaining to the warrants is the change in fair value of the underlying common stock for each reporting period. The table below presents the changes in the derivative warrant liability during the three-month and nine-month periods ended September 30, 2017 and 2016: Three Months Ended September 30, 2017 2016 Balance at June 30, $ 519 $ 2,359 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants 30 336 Balance at September 30, $ 41 $ 2,695 Nine Months Ended September 30, 2017 2016 Balance at December 31, $ 1,314 $ 1,907 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants (765) 788 Balance at September 30, $ 41 $ 2,695 The Company’s March 2016 public offering resulted in a repricing of the existing warrants. The warrants’ prices were decreased from $5.75 per share to $3.87 per share. In addition, the number of warrants increased from 395,716 to 587,950. The Company’s August 2017 warrant exchange resulted in a repricing of the Outstanding 2014 Warrants. The exercise price of the Outstanding 2014 Warrants was decreased from $3.87 per share to $0.83 per share. In addition, the number of Outstanding 2014 Warrants increased from 10,403 to 48,507. The decrease in the liability for the nine-month period ended September 30, 2017 was primarily driven by the impact of the warrant exchange and to a lesser degree due to the decrease in the fair value of the underlying stock price since December 31, 2016.	12. DERIVATIVE INSTRUMENTS The warrants issued in connection with the Company’s May 2014 public offering to purchase 1,750,156 shares of the common stock (see Note 11) have anti-dilution protection provisions and, under certain conditions, require the Company to automatically reprice the warrants. Accordingly, these warrants are accounted for as derivative warrant liabilities. The Company used the Binomial Lattice option pricing model and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments. Changes in the fair value of the derivative financial instruments are recognized currently in the Company’s consolidated statement of operations as a derivative gain or loss. The warrant derivative gains or losses are non-cash expenses and for the years ended December 31, 2016, 2015, and 2014, a (gain) loss of $(593), $10,804 and $376, respectively, were included in other income (expense) in the Company’s consolidated statement of operations. The fair value of these derivative instruments at December 31, 2016 and 2015 was $1,314 and $1,907, respectively, and was included as a derivative warrant liability in current liabilities. The assumptions used principally in determining the fair value of warrants were as follows: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.20 % 0.65 % 1.47 % Expected dividend yield % % % Contractual term years years years Expected volatility % % % The primary underlying risk exposure pertaining to the warrants is the change in fair value of the underlying common stock for each reporting period. The table below presents the changes in derivative warrant liability during the years ended December 31, 2016, 2015, and 2014: Year Ended December 31, 2016 2015 2014 Balance at beginning of year $ $ $ — Issuance of warrants — — (Decrease) increase in the fair value of the warrants Fair value of derivative warrant liability reclassified to additional paid in capital — — Balance at end of year $ $ $

STOCK OPTIONS

STOCK OPTIONS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
STOCK-BASED COMPENSATION.
STOCK OPTIONS	10. STOCK-BASED COMPENSATION In 2007, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2007 Employee, Director and Consultant Stock Plan (the “2007 Plan”). Pursuant to the 2007 Plan, the Company’s Board of Directors (or committees and/or executive officers delegated by the Board of Directors) may grant incentive and nonqualified stock options to the Company’s employees, officers, directors, consultants and advisors. On October 26, 2010, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2010 Equity Incentive Plan (as subsequently amended, the “2010 Plan”). The 2010 Plan provided for grants of incentive stock options to employees, and nonqualified stock options and restricted common stock to employees, consultants, and non-employee directors of the Company. In April 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2015 Equity Incentive Plan (the “2015 Plan”). The 2015 Plan provides for grants of incentive stock options to employees, and nonqualified stock options, restricted common stock, restricted stock units, and stock appreciation rights to employees, consultants, and non-employee directors of the Company. As of September 30, 2017, the total number of shares authorized for issuance under the 2015 Plan was 4,322,355 shares, consisting of 4,000,000 initially approved under the 2015 Plan shares plus the 322,355 shares that remained available for grant under the 2010 Plan at the time of its termination. Upon approval of the 2015 Plan by the Company’s shareholders on June 16, 2015, the 2010 Plan was terminated and no additional shares or share awards have been subsequently granted under the 2010 Plan. Options issued under the 2007 Plan, 2010 Plan, and 2015 Plan (collectively, the “Plans”) are exercisable for up to 10 years from the date of issuance. As of September 30, 2017, there were outstanding options to purchase an aggregate of 2,256,351, 1,670,171 and 46,476 shares under the 2015 Plan, 2010 Plan, and 2007 Plan, respectively. As of December 31, 2016, there were outstanding options to purchase an aggregate of 1,222,085, 1,821,487 and 150,207 shares under the 2015 Plan, 2010 Plan, and 2007 Plan, respectively. In March 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the ESPP. The ESPP allows employees to buy company stock twice per year through after-tax payroll deductions at a discount from market. The Company’s Board of Directors initially authorized 187,500 shares for issuance under the ESPP. Commencing on the first day of the year ended December 31, 2016 and on the first day of each year thereafter during the term of the ESPP, the number of shares of common stock reserved for issuance shall be increased by the lesser of (i) 1% of the Company’s outstanding shares of common stock on such date, (ii) 50,000 shares, or (iii) a lesser amount determined by the Board of Directors. Under the terms of the ESPP, in no event shall the aggregate number of shares reserved for issuance during the term of the ESPP exceed 1,250,000 shares. As of September 30, 2017 and December 31, 2016, there were 253,021 and 220,771 shares reserved for issuance under the ESPP, respectively. In January 2017, 7,986 shares that were purchased in the offering period commencing on July 1, 2016 and ending on Decemer 31, 2016 were issued under the ESPP. In July 2017, 9,764 shares that were purchased in the offering period commencing on January 1, 2017 and ending on June 30, 2017 were issued under the ESPP. The ESPP is considered a compensatory plan with the related compensation cost recognized over each six-month offering period. The compensation expense related to the ESPP for the three-month periods ended September 30, 2017 and 2016 was $3,000 and $12,000, respectively, and is included in share-based compensation expense. The share-based compensation expense related to the ESPP for the nine-month periods ended September 30, 2017 and 2016 was $16,000 and $39,000. Share-based compensation For the three-month periods ended September 30, 2017 and 2016, the Company recorded stock-based compensation expense of $1.0 million and $1.2 million, respectively, inclusive of the expense related to the ESPP. For the nine-month periods ended September 30, 2017 and 2016, the Company recorded stock-based compensation expense of $3.6 million and $3.6 million, respectively, inclusive of the expense related to the ESPP. Stock-based compensation expense for the three-month and nine-month periods ended September 30, 2017 includes $24,000 of expense related to a stock option modification. The Company granted 325,000 stock options to a non-employee consultant on July 5, 2017. The Company accounts for stock-based awards to non-employees in accordance with ASC Topic 505-50, Equity-Based Payments to Non-Employees (“ASC 505-50”). Stock-based awards to non-employees are remeasured at each reporting date until the options vest and expense is recognized on a straight-line basis as the services are being provided. The Company believes that the fair value of these awards is more reliably measurable than the fair value of the services rendered. The aggregate grant date fair value for the options granted on July 5, 2017 totaled approximately $764,000. The option award has a requisite service period of four years whereby the award vests 25% on the first anniversary of service, then ratably each month for the remaining 36 months, subject to continuous service by the individual. As of September 30, 2017, 325,000 options remained unvested. The fair value of the unvested options as of September 30, 2017 was estimated using a Black-Scholes model with the following assumptions: expected volatility of 108.5%, risk free interest rate of 2.3%, expected life of 9.8 years, and no dividends. Stock-based compensation expense for the three-month and nine-month periods ended September 30, 2017 includes $25,000 of expense related to the non-employee stock option grant, as a result of mark to market adjustments related to the non-employee. The stock options contain a termination clause whereby accelerated vesting occurs for 25% of the stock options if the Company does not hire the consultant as an employee on or before January 5, 2018. As discussed in Note 1, the Company adopted ASU 2016-09 on January 1, 2017. Prior to the adoption of this standard, the Company recognized share-based compensation, net of estimated forfeitures, over the vesting period of the grant. Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to recognize forfeitures as they occur. The Company continues to recognize share-based compensation expense over the vesting period of the grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $155,000 recorded to accumulated deficit on the balance sheet as of January 1, 2017. The Company estimates the fair value of each option award on the date of grant using the Black-Scholes option pricing model. The expected term of options granted under the Plans, all of which qualify as “plain vanilla,” is based on the average of the contractual term (10 years) and the vesting period (generally, 48 months). For non-employee options, the expected term is the contractual term. The risk-free rate is based on the yield of a U.S. Treasury security with a term consistent with the option. Stock options A summary of option activity as of September 30, 2017 and changes for the nine-month period then ended are presented below: Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2016 3,193,785 $ 7.52 Granted 1,439,463 $ 3.94 Forfeited (570,863) $ 6.54 Exercised (89,387) $ 0.29 Outstanding at September 30, 2017 3,972,998 $ 6.53 7.48 $ 53,894 Vested at September 30, 2017 2,146,415 $ 7.86 6.20 $ 53,894 The weighted average grant-date fair value of options granted during the nine months ended September 30, 2017 was $3.04 per share. The total fair value of options that vested in the three-month period ended September 30, 2017 was $1.1 million. The total fair value of options that vested in the nine months ended September 30, 2017 was $3.1 million. As of September 30, 2017, total unrecognized compensation expense related to non-vested share-based option compensation arrangements amounted to $6.5 million and is estimated to be recognized over a period of 2.53 years. Restricted Stock Units The following table summarizes the restricted stock unit (“RSU”) activity under the 2015 Equity Incentive Plan during the nine-month period ended September 30, 2017: Weighted-Average Number of Grants Grant Date Fair Value Unvested balance at December 31, 2016 — $ — Granted 295,000 1.25 Vested — — Forfeited — — Unvested balance at September 30, 2017 295,000 $ 1.25 On September 14, 2017, the Company issued 295,000 RSUs to employees. These RSUs are subject to time-based vesting. For the three-month period ended September 30, 2017, the Company recorded stock-based compensation expense of $9,000 related to the time-based RSUs, which the Company expects to recognize over a remaining weighted-average of 2.0 years. As of September 30, 2017, total unrecognized compensation expense related to non-vested RSUs amounted to $360,000. There are 295,000 RSUs subject to time-based vesting that remain unvested and outstanding at September 30, 2017.	13. STOCK OPTIONS In 2007, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2007 Employee, Director and Consultant Stock Plan (the “2007 Plan”). Pursuant to the 2007 Plan, the Company’s Board of Directors (or committees and/or executive officers delegated by the Board of Directors) may grant incentive and nonqualified stock options to the Company’s employees, officers, directors, consultants and advisors. As of December 31, 2016, there were options to purchase an aggregate of 150,207 shares of common stock outstanding under the 2007 Plan and no shares available for future grants under the 2007 Plan. On October 26, 2010, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2010 Equity Incentive Plan (as subsequently amended, the “2010 Plan”). The 2010 Plan provides for grants of incentive stock options to employees, and nonqualified stock options and restricted common stock to employees, consultants, and non‑employee directors of the Company. In April 2015, the Company’s Board of Directors adopted, and the Company’ shareholders subsequently approved, the 2015 Equity Incentive Plan (the “2015 Plan”). The 2015 Plan provides for grants of incentive stock options to employees, and nonqualified stock, restricted common stock, restricted stock units and stock appreciation rights to employees, consultants, and directors of the Company. As of December 31, 2016, the total number of shares authorized for issuance under the 2015 Plan was 4,322,355 shares, consisting of 4,000,000 shares initially approved under the 2015 Plan plus the 322,355 shares that remained available for grant under the 2010 Plan at the time of its termination. Upon approval of the 2015 Plan by the Company’s shareholders on June 16, 2016, the 2010 Plan was terminated and no additional shares or share awards have been subsequently granted under the 2010 Plan. As of December 31, 2016, there were outstanding options to purchase an aggregate of 1,222,085 and 1,821,487 shares of common stock under the 2015 Plan and 2010 Plan, respectively. Options issued under the Plans are exercisable for up to 10 years from the date of issuance. Options issued under the 2007 Plan, 2010 Plan, and 2015 Plan (collectively, the “Plans”) are exercisable for up to 10 years from the date of issuance. In March 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved the ESPP. The ESPP allows employees to buy company stock twice a year through after-tax payroll deductions at a discount from market. The Company’s Board of Directors initially authorized 187,500 shares for issuance under the ESPP. Commencing on the first day of the year ended December 31, 2016 and on the first day of each year thereafter during the term of the ESPP, the number of shares of common stock reserved for issuance shall be increased by the lesser of (i) 1% of the Company’s outstanding shares of common stock on such date, (ii) 50,000 shares or (iii) a lesser amount determined by the Board of Directors. Under the terms of the ESPP, in no event shall the aggregate number of shares reserved for issuance during the term of the ESPP exceed 1,250,000 shares. The 2015 ESPP is considered a compensatory plan with the related compensation cost recognized over each respective six month offering period. As of December 31, 2016, approximately $51 of employee payroll deductions had been withheld since July 1, 2016, the commencement of the offering period, and are included in accrued expenses in the accompanying balance sheet. The compensation expense related to the ESPP for the years ended December 31, 2016 and 2015 was $46 and $41, respectively, and is included in stock-based compensation expense. In January 2017, 7,986 shares that were purchased as of December 31, 2016 were issued under the ESPP. Share‑based compensation For the years ended December 31, 2016, 2015 and 2014, the Company recorded stock‑based compensation expense of $5,063, $4,666, and $2,730, respectively, net of forfeitures, inclusive of the expense related to the ESPP. The fair value of each option award is estimated on the date of grant using the Black‑Scholes option pricing model, which uses the assumptions noted in the following table. The Company uses historical data, as well as subsequent events occurring prior to the issuance of the financial statements, to estimate option exercises and employee terminations within the valuation model. The expected term of options granted under the Plans, all of which qualify as “plain vanilla,” is based on the average of the contractual term (10 years) and the vesting period (generally, 48 months). For non‑employee options, the expected term is the contractual term. The risk‑free rate is based on the yield of a U.S. Treasury security with a term consistent with the option. The assumptions used principally in determining the fair value of options granted were as follows: December 31, 2016 2015 2014 Risk-free interest rate 1.20 - 1.52% 1.53 - 1.89% 1.62 - 2.06% Expected dividend yield Expected term (employee grants) 5.99 years 6.00 years 6.03 years Expected volatility A summary of option activity as of December 31, 2016 and changes for the year then ended are presented below: Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2015 $ Granted $ Forfeited $ Exercised $ Outstanding at December 31, 2016 $ $ Vested at December 31, 2016 $ $ Vested and expected to vest at December 31, 2016 $ $ The weighted average grant‑date fair value of options granted during the years ended December 31, 2016, 2015, and 2014 was $5.23, $7.37, and $6.15 per share, respectively. The total fair value of options that vested in the years ended December 31, 2016, 2015, and 2014 was $5,179, $5,144, and $2,329, respectively. As of December 31, 2016, there was $5,630 of total unrecognized compensation expense related to non‑vested share‑based option compensation arrangements. The unrecognized compensation expense is estimated to be recognized over a period of 2.37 years at December 31, 2016.

WARRANTS

WARRANTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
WARRANTS.
WARRANTS	11. WARRANTS The following table presents information about warrants to purchase common stock issued and outstanding at September 30, 2017: Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity 343,931 $ 5.60 10/26/2017 - 12/03/2017 2010 Equity 253,088 $ 4.00 10/26/2017 - 12/03/2017 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 48,507 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,798,246 Weighted average exercise price $ 8.75 Weighted average life in years 2.71 In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29.9 million. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock issued in the March 2016 offering, and expire on March 18, 2021. The warrants are immediately exercisable at the option of each holder, in whole or in part, in cash (except in the case of a cashless exercise as discussed below). The exercise price and number of shares of common stock issuable upon exercise of the warrants will be subject to adjustment in the event of any stock split, reverse stock split, stock dividend, recapitalization, or similar transaction, among other events as described in the warrants. In the event that shares of common stock underlying the warrants are no longer registered under the Securities Exchange Act of 1934, as amended, the holder may, in its sole discretion, exercise the warrant in whole or in part and, in lieu of making cash payment, elect instead to receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the warrant. The fair value of the warrants was estimated at $11.7 million using a Black-Scholes model with the following assumptions: expected volatility of 112.8%, risk free interest rate of 1.3%, expected life of five years, and no dividends. The Company assessed whether the warrants required accounting as derivatives. With the exception of the warrants issued in 2014 (see Note 12), the Company determined that the warrants were (1) indexed to the Company’s own stock and (2) classified in stockholders’ equity in accordance with FASB Accounting Standards Codification Topic 815, Derivatives and Hedging . As such, the Company concluded that the warrants meet the scope exception for determining whether the instruments require accounting as derivatives and accordingly are classified in stockholders’ equity. Warrant Exchange On August 10, 2017, the Company entered into exchange agreements with certain holders of the warrants, dated May 9, 2014, to exchange such warrants for shares of common stock equivalent to 3.5 times the number of shares of common stock issuable to such holders at the $3.87 exercise price under the warrants as of the date of the exchanges. The Company issued an aggregate of 2,021,419 shares of common stock to the warrant holders in exchange for their warrants to purchase an aggregate of 577,548 shares of common stock. The warrants exchanged in this transaction were subsequently cancelled and terminated. The Company re-measured the fair value of the exchanged warrants immediately prior to the exchange and recorded a $3.0 million derivatives loss on the statement of operations and a corresponding increase to the warrant liability on the balance sheet. The fair value of the warrants immediately prior to the exchange was equivalent to 2,021,419 shares of common stock at the Company’s closing stock price of $1.75 on August 9, 2017, the day before execution of the exchange. As a result of the exchange, the Company recorded the settlement by removing the derivative liability related to the exchanged warrants and recorded the issuance of common stock for $3.5 million. Following the warrant exchange, there are additional warrants, dated May 9, 2014, to purchase shares of common stock that remain outstanding (“Outstanding 2014 Warrants”). As a result of the Company’s issuance of common stock in exchange for certain of the liability warrants, the exercise price of the Outstanding 2014 Warrants was adjusted downwards from $3.87 per share to $0.83 per share and additional warrants were issued such that the Outstanding 2014 Warrants are currently exercisable for an aggregate of 48,507 shares of common stock. The Outstanding 2014 Warrants are subject to further adjustment in the event of sales of the Company’s common stock at a price per share less than the exercise price of the Outstanding 2014 Warrants then in effect (or securities convertible or exercisable into common stock at a conversion or exercise price less than the exercise price then in effect).	14. WARRANTS The following table presents information about warrants to purchase common stock issued and outstanding at December 31, 2016: Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity $ 10/26/2017 - 12/3/2017 2010 Equity $ 8/30/2017 - 12/3/2017 2012 Equity $ 10/5/2019 2014 Liability $ 5/9/2019 2016 Equity $ 3/18/2021 Total Weighted average exercise price $ Weighted average life in years In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29,905. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants are immediately exercisable, at the option of each holder, in whole or in part, in cash (except in the case of a cashless exercise as discussed below). The exercise price and number of shares of common stock issuable upon exercise of the warrants will be subject to adjustment in the event of any stock split, reverse stock split, stock dividend, recapitalization, or similar transaction, among other events as described in the warrants. In the event that shares of common stock underlying the warrants are no longer registered under the Securities Exchange Act of 1934, as amended, the holder may, in its sole discretion, exercise the warrant in whole or in part and, in lieu of making cash payment, elect instead to receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the warrant. The fair value of the warrants was estimated at $11,726 using a Black-Scholes model with the following assumptions: expected volatility of 112.82%, risk free interest rate of 1.34%, expected life of five years and no dividends. The Company assessed whether the warrants require accounting as derivatives. The Company determined that the warrants were (1) indexed to the Company’s own stock and (2) classified in stockholders’ equity in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 815, Derivatives and Hedging. As such, the Company has concluded the warrants meet the scope exception for determining whether the instruments require accounting as derivatives and should be classified in stockholders’ equity.

EMPLOYEE BENEFIT PLAN

EMPLOYEE BENEFIT PLAN	12 Months Ended
	Dec. 31, 2016
EMPLOYEE BENEFIT PLAN
EMPLOYEE BENEFIT PLAN	15. EMPLOYEE BENEFIT PLAN In November 2006, the Company adopted a 401(k) plan (the “Plan”) covering all employees. Employees must be 21 years of age in order to participate in the Plan. Under the Plan, the Company has the option to make matching contributions. For the years ended December 31, 2016, 2015, and 2014, the Company made matching contributions in the form of shares of the Company’s common stock. For the years ended December 31, 2016, 2015, and 2014, the Company issued 37,528, 17,437, and 41,753 shares of its common stock, respectively, with related fair values of $208, $201, and $173, respectively, which were recorded as expense in the statement of operations.

INTELLECTUAL PROPERTY LICENSE

INTELLECTUAL PROPERTY LICENSE	12 Months Ended
	Dec. 31, 2016
INTELLECTUAL PROPERTY LICENSE
INTELLECTUAL PROPERTY LICENSE	16. INTELLECTUAL PROPERTY LICENSE In July 2007, the Company entered into a worldwide exclusive license (the “BCH License”) for patents co-owned by Boston Children’s Hospital (“BCH”) and the Massachusetts Institute of Technology initially covering the use of biopolymers to treat spinal cord injuries, and to promote the survival and proliferation of human stem cells in the spinal cord. During 2011, the BCH License was amended, and the Company obtained additional rights for use in the field of peripheral nerve injuries. The BCH License, as amended, has a 15‑year term, or as long as the life of the last expiring patent right thereunder, whichever is longer, unless terminated earlier by the licensor, under certain conditions as defined in the related license agreement. In connection with the BCH License, the Company paid an initial $75 licensing fee and is required to pay certain annual maintenance fees, milestone payments and royalties. License fees and milestone payments are capitalized and the gross total at December 31, 2016 and 2015 was $200 (see Note 5). Maintenance and royalty costs are expensed as incurred.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	6. COMMITMENTS AND CONTINGENCIES Leases On November 30, 2011, the Company entered into a commercial lease for 26,150 square feet of office, laboratory, and manufacturing space in Cambridge, Massachusetts (as amended on September 17, 2012, the “Cambridge Lease”). The term of the Cambridge Lease is six years and three months, with one five-year extension option. On August 21, 2017, the Company exercised its option for the five-year extension on the Cambridge Lease. The five-year renewal lease term commences on November 1, 2018 and ends on October 31, 2023. The terms of the Cambridge Lease require a standby letter of credit in the amount of $311,000 (see Note 3). The Cambridge Lease contains rent holidays and rent escalation clauses. The Company recognizes rent expense on a straight-line basis over the term of the Cambridge Lease and records the difference between the amount charged to expense and the rent paid as a deferred rent liability. As of September 30, 2017, the amount of deferred rent liability was $238,000. Pursuant to the terms of the non-cancelable lease agreements in effect at September 30, 2017, the future minimum rent commitments are as follows (in thousands): Year Ended December 31, 2017 314 2018 1,378 2019 1,945 2020 2,003 2021 2,063 Thereafter 3,941 Total $ 11,644 Total rent expense for the three-month periods ended September 30, 2017 and 2016 was $269,000 and $210,000, respectively. Total rent expense for the nine-month periods ended September 30, 2017 and 2016 was $828,000 and $707,000, respectively. On March 31, 2016, the Company entered into a short-term lease with CRISPR Therapeutics, as subtenant, to sub-lease 5,233 square feet of the Facility (the “CRISPR Sublease”). The lease term was from April 1, 2016 through January 31, 2017. On March 31, 2016, the Company received $51,000 covering the first month’s rent and a security deposit under the terms of the CRISPR Sublease. The funds received for the security deposit, $26,000, were classified as a component of accrued expenses on the balance sheet as of December 31, 2016. In connection with the CRISPR Sublease, the Company received sublease income for the nine-month periods ended September 30, 2017 and 2016 of $26,000 and $77,000, respectively, which was recorded as an offset to rent expense. The CRISPR Sublease terminated on January 31, 2017 and the security deposit was returned to the subtenant. On June 13, 2017, the Company entered into a short-term lease with Moderna Therapeutics, as subtenant, to sub-lease 5,233 square feet of the Facility (the “Moderna Sublease”). The lease term is from July 1, 2017 through October 26, 2018. On June 19, 2017, the Company received a $55,000 security deposit under the terms of the Moderna Sublease. This security deposit is classified as a component of accrued expenses on the balance sheet as of September 30, 2017. In connection with the Moderna Sublease, the Company received sublease income of $82,000 for the nine-month period ended September 30, 2017, which was recorded as an offset to rent expense. Litigation Lawsuits with Former Employee In November 2013, the Company filed a lawsuit against Francis Reynolds, its former Chairman, Chief Executive Officer and Chief Financial Officer, in Middlesex Superior Court, Middlesex County, Massachusetts ( InVivo Therapeutics Holdings Corp. v. Reynolds, Civil Action No. 13-5004 ). The complaint alleges breaches of fiduciary duties, breach of contract, conversion, misappropriation of corporate assets, unjust enrichment, and corporate waste, and seeks monetary damages and an accounting. The lawsuit involves approximately $500,000 worth of personal and/or exorbitant expenses that the Company alleges Mr. Reynolds inappropriately caused it to pay while he was serving as the Company’s Chief Executive Officer, Chief Financial Officer, President, and Chairman of the Company’s Board of Directors. On December 6, 2013, Mr. Reynolds answered the complaint, and filed counterclaims against the Company and the Company’s Board of Directors. The counterclaims allege two counts of breach of contract, two counts of breach of the covenant of good faith and fair-dealing, and tortious interference with a contract, and seek monetary damages and a declaratory judgment. The counterclaims relate to Mr. Reynolds’s allegations that the Company and the Company’s Board of Directors interfered with the performance of his duties under the terms of his employment agreement, and that Mr. Reynolds was entitled to additional shares upon the exercise of certain stock options that he did not receive. On January 9, 2014, the Company and the directors named in the counterclaim filed their answer denying that Mr. Reynolds is entitled to any relief. The parties have completed discovery. On March 3, 2017, the counterclaim defendants filed a motion for summary judgment on all counterclaims asserted by Mr. Reynolds. On October 18, 2017, the Court allowed the motion for summary judgment in substantial part, and denied it in part. The Court, citing disputed issues of fact, declined to dismiss the counterclaims for breach of contract, breach of implied covenant of good faith and fair dealing, and declaratory judgment concerning Mr. Reynolds' attempted exercise of certain stock options, which Mr. Reynolds claims is the equivalent of 47,864 shares of common stock, but dismissed all other claims asserted by Mr. Reynolds. The Company intends to continue to defend itself against the remaining counterclaims and, to date, the Company has not recorded any provision for losses that may arise.	17. COMMITMENTS AND CONTINGENCIES Leases On November 30, 2011, the Company entered into a commercial lease for 26,150 square feet of office, laboratory and manufacturing space in Cambridge, Massachusetts (as amended on September 17, 2012, the “Cambridge Lease”). The term of the Cambridge Lease is six years and three months, with one five‑year extension option. The terms of the Cambridge Lease require a standby letter of credit in the amount of $311 (see Note 2). The Cambridge Lease contains rent holidays and rent escalation clauses. The Company recognizes rent expense on a straight-line basis over the term of the Cambridge Lease and records the difference between the amount charged to expense and the rent paid as a deferred rent liability. As of December 31, 2016 and 2015, the amount of the deferred rent liability is $276 and $391, respectively, and is included in accrued expenses. It is the Company’s policy to assess whether improvements made to the space rented under operating leases should be accounted for as “lessor” or “lessee” assets. Such costs are recorded as leasehold improvements, which are amortized to rent expense over the term of the Cambridge Lease. As of December 31, 2016 and 2015, such leasehold improvements totaled $143 and $185, net of accumulated depreciation. Pursuant to the terms of the non‑cancelable lease agreements in effect at December 31, 2016, the future minimum rent commitments are as follows: Year Ended December 31, 2017 2018 Total $ Total rent expense for the years ended December 31, 2016, 2015, and 2014, including month‑to‑month leases, was $918, $1,123 and $1,148, respectively, net of sublease income of $230 for the year ended December 31, 2016. On September 4, 2013, the Company entered into a legal settlement agreement for $286 in connection with the Cambridge Lease. The settlement amount has been included in the deferred rent liability and the benefit is being amortized over the remainder of the term of the Cambridge Lease. On March 31, 2016, the Company entered into a short-term lease with CRISPR Therapeutics, as subtenant, to sub-lease 5,233 square feet of our Facility (the “Sublease”). The lease term was from April 1, 2016 through January 31, 2017. On March 31, 2016, the Company received $51 covering the first month’s rent and a security deposit under the terms of the Sublease. The funds received for the security deposit, $26, are classified as a component of accrued expenses in the financial statements. The Sublease was terminated on January 31, 2017. Compensation Commitment The Company entered into a compensation arrangement with an executive during September 2016 which provides for a future cash payment by the Company to the executive based on the February 13, 2017 stock price of the executive’s former employer. The award is earned over a period of one year. Accordingly, the expense related to the compensation arrangement was approximately $89 for the three months and $101 for the twelve months ended December 31, 2016. The liability is included within accrued expenses on the balance sheet and was recorded at fair value on a recurring basis until the final payment was determined on February 13, 2017. Lawsuits with Former Employee In November 2013, the Company filed a lawsuit against Francis Reynolds, its former Chairman, Chief Executive Officer and Chief Financial Officer, in Middlesex Superior Court, Middlesex County, Massachusetts ( InVivo Therapeutics Holdings Corp. v. Reynolds, Civil Action No. 13-5004 ). The complaint alleges breaches of fiduciary duties, breach of contract, conversion, misappropriation of corporate assets, unjust enrichment, and corporate waste, and seeks monetary damages and an accounting. The lawsuit involves approximately $500,000 worth of personal and/or exorbitant expenses that the Company alleges Mr. Reynolds inappropriately caused it to pay while he was serving as the Company’s Chief Executive Officer, Chief Financial Officer, President, and Chairman of the Company’s Board of Directors. On December 6, 2013, Mr. Reynolds answered the complaint, and filed counterclaims against the Company and the Company’s Board of Directors. The counterclaims allege two counts of breach of contract, two counts of breach of the covenant of good faith and fair-dealing, and tortious interference with a contract, and seek monetary damages and a declaratory judgment. The counterclaims related to Mr. Reynolds’s allegations that the Company and the Company’s Board of Directors interfered with the performance of his duties under the terms of his employment agreement, and that Mr. Reynolds was entitled to additional shares upon the exercise of certain stock options that he did not receive. On January 9, 2014, the Company, along with the directors named in the counterclaims, filed the Company’s answer. Discovery has now been completed and the Company’s motion for summary judgment on all counts of the complaint and Reynolds’ opposition to the motion for summary judgment was filed with the court on March 3, 2017. The Company intends to continue to defend itself against these claims and, to date, the Company has not recorded any provision for losses that may arise. On July 22, 2016, Mr. Reynolds filed a lawsuit against the Company, certain present and former members of the Company’s Board of Directors and an employee of the Company in Hillsborough County Superior Court, Southern District, Hillsborough County, New Hampshire ( Reynolds v. InVivo Therapeutics Holdings Corp, et al.) alleging defamation, conspiracy, and tortious interference, and seeking monetary damages. In August 2016, the lawsuit was removed to the United States District Court for the District of New Hampshire. The Company filed a motion to dismiss this action and after oral argument on November 28, 2016, the Court on November 30, 2016 issued an order dismissing the case for lack of personal jurisdiction. The judgment was entered on the docket on December 1, 2016, and the deadline for appealing that decision has passed. Shareholder Matters and Investigations On July 31, 2014, a putative securities class action lawsuit was filed in the United States District Court for the District of Massachusetts, naming the Company and Mr. Reynolds as defendants (the “Securities Class Action”). The lawsuit alleges violations of the Securities Exchange Act of 1934 in connection with allegedly false and misleading statements related to the timing and completion of the clinical study of the Company’s Neuro-Spinal Scaffold ™ implant. The plaintiff sought class certification for purchasers of the Company’s common stock during the period from April 5, 2013 through August 26, 2013 and unspecified damages. On April 3, 2015, the United States District Court for the District of Massachusetts dismissed the plaintiff’s claim with prejudice. On May 4, 2015, the plaintiff filed a notice of appeal of this decision. Following the submission of briefs by the parties, the Court of Appeals heard oral arguments on April 6, 2016. On January 9, 2017, the Court of Appeals for the First Circuit issued an order and opinion affirming the dismissal of the Securities Class Action with prejudice. Plaintiff has until April 10, 2017 to file a petition for certiorari to the United States Supreme Court. The Company intends to continue to defend itself against these claims and, to date, has not recorded any provision for losses that may arise. On January 23, 2015, Shawn Luger, a purported shareholder of the Company, sent the Company a letter (the “Shareholder Demand”) demanding that the Board of Directors take action to remedy purported breaches of fiduciary duties allegedly related to the claimed false and misleading statements that are the subject of the Securities Class Action. The Board of Directors completed its investigation of the matters raised in the Shareholder Demand and voted unanimously not to pursue any litigation against any current or former director, officer, or employee of the Company with respect to the matters set forth in the Shareholder Demand. On August 14, 2015, Mr. Luger filed a shareholder derivative lawsuit in the Superior Court of Suffolk County for the Commonwealth of Massachusetts on behalf of the Company against certain present and former board members and company executives alleging the same breaches of fiduciary duties purportedly set forth in the Shareholder Demand. On February 5, 2016, the Superior Court of Suffolk County dismissed the plaintiff’s claims with prejudice. On March 4, 2016, the plaintiff filed a notice of appeal of this decision. Following the submission of brief by the parties, the Appeals Court heard oral argument on December 13, 2016. On January 3, 2017, the Appeals Court issued an order and opinion affirming the dismissal of all claims with prejudice. The time period for Mr. Luger to appeal the Appeals Court’s judgment has expired. In addition, the Company received investigation subpoenas from the Boston Regional Office of the SEC and the Massachusetts Securities Division of the Secretary of the Commonwealth of Massachusetts (“MSD”) requesting corporate documents concerning, among other topics, the allegations raised by the Securities Class Action and the Shareholder Demand. On October 21, 2015, after responding to the SEC’s subpoena, the Company received a letter from the SEC notifying the Company that it had concluded its investigation of the Company and that it did not intend to recommend an enforcement action against the Company. The Company responded to the MSD’s subpoena on September 22, 2014 and October 8, 2014. On February 18, 2015, the Company received a second subpoena from the MSD requesting additional documents and information related to the same topics. The Company responded to this second subpoena on March 24, 2015. The Company has not further heard from the MSD since it responded to this last subpoena.

INSURANCE CLAIM

INSURANCE CLAIM	12 Months Ended
	Dec. 31, 2016
INSURANCE CLAIM
INSURANCE CLAIM	18. INSURANCE CLAIM During the year ended December 31, 2014, the Company settled an insurance claim of $621 for business interruption that covered the disruption of the Company’s operations at its facility in Cambridge, Massachusetts caused by water damage that occurred in September 2014. The insurance settlement reimburses the Company for costs incurred as a result of the disruption and is included as reduction of research and development expense in the consolidated statement of operations for the year ended December 31, 2014.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2016
RELATED PARTY TRANSACTIONS.
RELATED PARTY	19. RELATED PARTY TRANSACTIONS The Company has entered into a consulting agreement with Dr. Robert Langer, a member of the Company’s Scientific Advisory Board and a holder of over 5% of the Company’s common stock, for certain consulting services. Dr. Langer was one of the original co-founders of the Company. Pursuant to the terms of the agreement, the Company has agreed to pay Dr. Langer $250 per year in consulting fees.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	15. SUBSEQUENT EVENTS The Company has evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its financial statements or disclosures.	20. SUBSEQUENT EVENTS The Company has evaluated all events or transactions that occurred after December 31, 2016. In the judgment of management, there were no material events that impacted the consolidated financial statements or disclosures.

SIGNIFICANT ACCOUNTING POLICI28

SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
SIGNIFICANT ACCOUNTING POLICIES
Use of estimates		Use of estimates The process of preparing financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of assets and liabilities at the date of the financial statements and the reported amounts expensed during the reporting period. Actual results could differ from those estimates and changes in estimates may occur.
Basis of presentation and principles of consolidation		Basis of presentation and principles of consolidation The consolidated financial statements include the accounts of InVivo Therapeutics Holdings Corp. and its wholly‑owned subsidiary, InVivo Therapeutics Corporation. All significant intercompany balances and transactions have been eliminated in consolidation. The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP.
Cash and cash equivalents		Cash and cash equivalents The Company considers only those investments that are highly liquid, readily convertible to cash, and that mature within three months from date of purchase to be cash equivalents. At December 31, 2016 and 2015, cash equivalents were comprised of money market funds and other short-term investments. Cash and cash equivalents consist of the following: December 31, 2016 2015 Cash $ $ Money market funds Total cash and cash equivalents $ $
Marketable securities		Marketable securities The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars, including obligations of the U.S. government and its agencies, money market instruments, money market funds, corporate obligations, asset-backed securities, and municipal obligations. As of December 31, 2016, the Company’s investment portfolio consists of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore, such investments are reported at fair value. For securities sold prior to maturity, the cost of securities sold is based on the specific identification method. Realized gains and losses on the sale of investments are recorded in interest income (expense), net. Interest is recorded when earned. Investments with original maturities greater than approximately three months and remaining maturities less than one year are classified as short-term investments. Investments with remaining maturities greater than one year are classified as long-term investments. The Company considers securities with maturities of three months or less from the purchase date to be cash equivalents. At December 31, 2016, the aggregate fair value of the Company’s marketable securities was $11,577. At December 31, 2015, the aggregate fair value of the Company’s marketable securities was $5,274. Gross unrealized gains and losses were insignificant for the years ended December 31, 2016 and 2015. We conduct periodic reviews to identify and evaluate each investment that is in an unrealized loss position in order to determine whether an other-than-temporary impairment exists. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale debt securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income (loss).
Restricted cash		Restricted cash Restricted cash as of December 31, 2016 and 2015 was $361 and included a $50 security deposit related to the Company’s credit card account and a $311 standby letter of credit in favor of a landlord (see Note 17).
Financial instruments		Financial instruments The carrying amounts reported in the Company’s consolidated balance sheets for cash, cash equivalents, marketable securities and accounts payable approximate fair value based on the short‑term nature of these instruments. The carrying value of the loan payable approximates fair value due to market terms.
Property and equipment		Property and equipment Property and equipment are carried at cost. Depreciation and amortization expense are recorded over the estimated useful lives of the assets using the straight‑line method. A summary of the estimated useful lives is as follows: Classification Estimated Useful Life Computer hardware 5 years Software 3 years Office furniture and equipment 5 years Research and lab equipment 5 years Leasehold improvements Remaining life of lease
Research and development expenses		Research and development expenses Costs incurred for research and development are expensed as incurred.
Concentrations of credit risk		Concentrations of credit risk Financial instruments which potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents, and marketable securities. The Company maintains cash in commercial banks, which may at times exceed Federally Insured limits. The Company has not experienced any loss in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents.
Segment information		Segment information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision making group, in making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and manages its business as principally one operating segment, which is developing and commercializing biopolymer scaffolding devices for the treatment of spinal cord injuries. As of December 31, 2016 and 2015, all of the Company’s assets were located in one location in the United States.
Income taxes		Income taxes For federal and state income taxes, deferred tax assets and liabilities are recognized based upon temporary differences between the financial statement and the tax basis of assets and liabilities. Deferred income taxes are based upon prescribed rates and enacted laws applicable to periods in which differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that some portion or all of the deferred tax assets will not be realized. Accordingly, the Company provides a valuation allowance, if necessary, to reduce deferred tax assets to amounts that are realizable. Tax positions taken or expected to be taken in the course of preparing the Company’s tax returns are required to be evaluated to determine whether the tax positions are “more‑likely‑than‑not” of being sustained by the applicable tax authority. Tax positions not deemed to meet a more‑likely‑than‑not threshold would be recorded as a tax expense in the current year. There were no material uncertain tax positions that required accrual or disclosure to the financial statements as of December 31, 2016 or 2015. Tax years subsequent to 2013 remain open to examination by U.S. federal and state tax authorities.
Impairment of long-lived assets		Impairment of long‑lived assets The Company continually monitors events and changes in circumstances that could indicate that carrying amounts of long‑lived assets may not be recoverable. An impairment loss is recognized when expected cash flows are less than an asset’s carrying value. Accordingly, when indicators of impairment are present, the Company evaluates the carrying value of such assets in relation to the operating performance and future undiscounted cash flows of the underlying assets. The Company’s policy is to record an impairment loss when it is determined that the carrying value of the asset may not be recoverable. No impairment charges were recorded for the years ended December 31, 2016, 2015, and 2014.
Share-based payments		Share‑based payments The Company accounts for all stock-based payment awards granted to employees and nonemployees using a fair value method. The Company’s stock-based payments include stock options and grants of common stock, including common stock subject to vesting. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on a straight-line basis. The measurement date for nonemployee awards is the date the services are completed, resulting in periodic adjustments to stock-based compensation during the vesting period for changes in the fair value of the awards. Stock-based compensation costs for nonemployees are recognized as expense over the vesting period on a straight-line basis. Stock-based compensation is classified in the accompanying consolidated statements of operations and comprehensive loss based on the department to which the related services are provided.
Derivative instruments		Derivative instruments The Company generally does not use derivative instruments to hedge exposures to cash‑flow or market risks; however, certain warrants to purchase common stock that do not meet the requirements for classification as equity are classified as liabilities. In such instances, net‑cash settlement is assumed for financial reporting purposes, even when the terms of the underlying contracts do not provide for a net‑cash settlement. Such financial instruments are initially recorded at fair value, with subsequent changes in fair value charged (credited) to operations in each reporting period. If these instruments subsequently meet the requirements for classification as equity, the Company reclassifies the fair value to equity.
Net loss per common share		Net loss per common share Basic net loss per share of common stock has been computed by dividing net loss by the weighted average number of shares outstanding during the period. Diluted net income per share of common stock has been computed by dividing net income by the weighted average number of shares outstanding plus the dilutive effect, if any, of outstanding stock options, warrants and convertible securities. Diluted net loss per share of common stock has been computed by dividing the net loss for the period by the weighted average number of shares of common stock outstanding during such period. In a net loss period, options, warrants related to the Company’s May 2014 capital raise, which include an anti-dilution provisions, and convertible securities are anti‑dilutive and therefore excluded from diluted loss per share calculations. For the year ended December 31, 2016, 2015, and 2014, the following potentially dilutive securities were not included in the computation of net loss per share because the effect would be anti-dilutive: 2016 2015 2014 Stock options Warrants
Reclassifications	Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the current period presentation. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for the prior period presented.	Reclassifications Certain amounts in prior period financial statements have been reclassified to conform to the current period presentation. Marketable securities were previously included in cash and cash equivalents on the balance sheet but are now reflected as a separate line item on the balance sheet. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for all periods presented.
Recent accounting pronouncements	Recently Issued Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company adopted this standard on January 1, 2017. Prior to adoption, the Company recognized share-based compensation, net of estimated forfeitures, over the vesting period of the grant. Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to recognize forfeitures as they occur. The Company continues to recognize share-based compensation expense over the vesting period of the grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $155,000 recorded to accumulated deficit on the balance sheet as of January 1, 2017. Prior to January 1, 2017, the Company recognized the excess tax benefits of stock-based compensation expense as additional paid-in capital and tax deficiencies of stock-based compensation expense in the income tax provision or as additional paid-in capital to the extent that there were sufficient recognized excess tax benefits previously recognized. Previously, the excess tax benefits reduced taxes payable prior to being recognized as an increase in additional paid-in capital, and therefore the Company had not recognized certain deferred tax assets that could be attributed to tax deductions. As a result of the adoption, the deferred tax assets associated with certain net operating losses increased, which was offset by a corresponding increase in the valuation allowance and therefore the adoption of the tax-related guidance in this standard did not have an impact on our consolidated financial statements for the period ended September 30, 2017. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230) : Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”) to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In July 2017, the FASB issued ASU No. 2017-11, Part I. Accounting for Certain Financial Instruments with Down Round Features and Part II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I of this guidance applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down round features. Part II of this guidance replaces the indefinite deferrals for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities. ASU 2017-11 is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company has concluded that the adoption of this ASU will not have a material impact on the financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration, and the presentation of sales and other similar taxes collected from customers. These standards are effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. Currently, this guidance is not applicable to the Company as the Company does not generate revenue. However, the Company will evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue.	Recent accounting pronouncements In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements—Going Concern , on disclosure of uncertainties about an entity's ability to continue as a going concern. This guidance addresses management's responsibility in evaluating whether there is substantial doubt about a company's ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for fiscal years ending after December 15, 2016 including interim reporting periods within each annual reporting period, with early adoption permitted. The Company adopted this guidance as of December 31, 2016. The adoption of ASU 2014-15 impacted presentation and disclosure only and did not have any impact on the Company’s financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606) : Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date of December 15, 2017. Currently, this guidance is not applicable to the Company as the Company is still in the research and development stage. However, the Company will continue to evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company will adopt this standard on January 1, 2017, and the adoption is not expected to have a material impact on the Company’s financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements.

SIGNIFICANT ACCOUNTING POLICI29

SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
SIGNIFICANT ACCOUNTING POLICIES
Schedule of cash and cash equivalents	September 30, December 31, (In thousands) 2017 2016 Cash $ (90) $ 111 Money market funds 16,524 21,353 Total cash and cash equivalents $ 16,434 $ 21,464	December 31, 2016 2015 Cash $ $ Money market funds Total cash and cash equivalents $ $
Summary of estimated useful lives		Classification Estimated Useful Life Computer hardware 5 years Software 3 years Office furniture and equipment 5 years Research and lab equipment 5 years Leasehold improvements Remaining life of lease
Schedule of potentially dilutive securities were not included in the computation of net loss per share because effect would be anti-dilutive	September 30, 2017 2016 Stock options 3,972,998 3,152,775 Unvested restricted stock units 295,000 — Warrants 2,798,246 3,484,445 7,066,244 6,637,220	2016 2015 2014 Stock options Warrants

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
MARKETABLE SECURITIES
Schedule of cash, cash equivalents, and marketable securities		December 31, 2016 2015 Cash $ $ Money market funds Marketable securities Total cash, cash equivalents and marketable securities $ $
Schedule of short-term investments in marketable securities by category	(In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2017 Current (due within 1 year or less) Corporate obligations 734 — — 734 Total $ 734 $ — $ — $ 734 December 31, 2016 Current (due within 1 year or less) Commercial paper 4,240 — — 4,240 Corporate obligations 7,337 — — 7,337 Total $ 11,577 $ — $ — $ 11,577	Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Commercial paper Corporate obligations — — Total $ $ — $ — $ December 31, 2015 Commercial paper Corporate obligations — — Total $ $ — $ — $

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2016
PROPERTY AND EQUIPMENT
Schedule of property and equipment, net	2016 2015 Computer software and hardware $ $ Research and lab equipment Leasehold improvements Office equipment Less accumulated depreciation and amortization Property and equipment, net $ $

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2016
INTANGIBLE ASSETS
Summary of intangible assets	2016 2015 Patent licensing fee $ $ Accumulated amortization $ $

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
ACCRUED EXPENSES
Summary of accrued expenses	September 30, December 31, (In thousands) 2017 2016 Bonus $ 595 $ 906 Payroll 158 126 Vacation 231 91 Severance 455 385 Other accrued expenses 345 451 Total accrued expenses $ 1,784 $ 1,959	December 31, 2016 2015 Accrued bonus $ $ — Accrued payroll Accrued vacation Accrued severance — Other accrued expenses Total accrued expenses $ $

FAIR VALUE OF ASSETS AND LIAB34

FAIR VALUE OF ASSETS AND LIABILITIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
FAIR VALUE OF ASSETS AND LIABILITIES
Summary of assets and liabilities measured at fair value on a recurring basis	At September 30, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 16,524 $ — $ — $ 16,524 Marketable securities — 734 — 734 Derivative warrant liability $ — $ (41) $ — $ (41) At December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 21,353 $ — $ — $ 21,353 Marketable securities — 11,577 — 11,577 Derivative warrant liability $ — $ (1,314) $ — $ (1,314)	At December 31, 2016 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $ At December 31, 2015 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $

LOAN PAYABLE (Tables)

LOAN PAYABLE (Tables)	12 Months Ended
	Dec. 31, 2016
LOAN PAYABLE
Summary of loans payable	December 31, 2016 2015 MassDev Loan $ $ Less: current portion $ $

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2016
INCOME TAXES
Schedule of significant components of net deferred tax assets	December 31, 2016 2015 Net operating loss carryforward $ $ Research and development credit carryforward Stock-based compensation Depreciation and amortization Accrued expenses Charitable contributions Subtotal Valuation allowance Net deferred taxes $ — $ —
Schedule of income tax benefits computed using the federal statutory income tax rate	December 31, 2016 2015 2014 Statutory rate % % % State taxes, net of benefit % % % Permanent differences: Derivative losses % % % Other % % % R&D tax credit % % % Other % % % Increase in valuation reserve % % % Effective tax rate % % %

COMMON STOCK (Tables)

COMMON STOCK (Tables)	12 Months Ended
	Dec. 31, 2016
COMMON STOCK.
Schedule of reserves established for future issuance of Common Stock	Reserves for the exercise of warrants Reserves for the exercise of stock options Total Reserves

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
DERIVATIVE INSTRUMENTS
Assumptions used in determining fair value of warrants	September 30, December 31, 2017 2016 Risk free interest rate 1.5 % % Expected dividend yield — % — % Contractual term (in years) 1.6 Expected volatility 86 % 89 %	Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.20 % 0.65 % 1.47 % Expected dividend yield % % % Contractual term years years years Expected volatility % % %
Changes in derivative warrant liability	Three Months Ended September 30, 2017 2016 Balance at June 30, $ 519 $ 2,359 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants 30 336 Balance at September 30, $ 41 $ 2,695 Nine Months Ended September 30, 2017 2016 Balance at December 31, $ 1,314 $ 1,907 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants (765) 788 Balance at September 30, $ 41 $ 2,695	Year Ended December 31, 2016 2015 2014 Balance at beginning of year $ $ $ — Issuance of warrants — — (Decrease) increase in the fair value of the warrants Fair value of derivative warrant liability reclassified to additional paid in capital — — Balance at end of year $ $ $

STOCK OPTIONS (Tables)

STOCK OPTIONS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
STOCK-BASED COMPENSATION.
Summary of option activity	Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2016 3,193,785 $ 7.52 Granted 1,439,463 $ 3.94 Forfeited (570,863) $ 6.54 Exercised (89,387) $ 0.29 Outstanding at September 30, 2017 3,972,998 $ 6.53 7.48 $ 53,894 Vested at September 30, 2017 2,146,415 $ 7.86 6.20 $ 53,894	Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2015 $ Granted $ Forfeited $ Exercised $ Outstanding at December 31, 2016 $ $ Vested at December 31, 2016 $ $ Vested and expected to vest at December 31, 2016 $ $
Schedule of assumptions used principally in determining the fair value of options granted		December 31, 2016 2015 2014 Risk-free interest rate 1.20 - 1.52% 1.53 - 1.89% 1.62 - 2.06% Expected dividend yield Expected term (employee grants) 5.99 years 6.00 years 6.03 years Expected volatility

WARRANTS (Tables)

WARRANTS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
WARRANTS.
Schedule of information about warrants to purchase common stock issued and outstanding	Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity 343,931 $ 5.60 10/26/2017 - 12/03/2017 2010 Equity 253,088 $ 4.00 10/26/2017 - 12/03/2017 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 48,507 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,798,246 Weighted average exercise price $ 8.75 Weighted average life in years 2.71	Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity $ 10/26/2017 - 12/3/2017 2010 Equity $ 8/30/2017 - 12/3/2017 2012 Equity $ 10/5/2019 2014 Liability $ 5/9/2019 2016 Equity $ 3/18/2021 Total Weighted average exercise price $ Weighted average life in years

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
Future minimum rent commitments	Pursuant to the terms of the non-cancelable lease agreements in effect at September 30, 2017, the future minimum rent commitments are as follows (in thousands): Year Ended December 31, 2017 314 2018 1,378 2019 1,945 2020 2,003 2021 2,063 Thereafter 3,941 Total $ 11,644	Year Ended December 31, 2017 2018 Total $

NATURE OF OPERATIONS AND GOIN42

NATURE OF OPERATIONS AND GOING CONCERN (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS
Cash, cash equivalents and marketable securities	$ 17,200	$ 33,041	$ 20,194

SIGNIFICANT ACCOUNTING POLICI43

SIGNIFICANT ACCOUNTING POLICIES - CASH AND CASH EQUIVALENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and cash equivalents
Cash and cash equivalents	$ 16,434	$ 21,464	$ 25,261	$ 14,920	$ 13,459	$ 13,980
Marketable securities
Marketable securities	$ 734	11,577		5,274
Cash
Cash and cash equivalents
Cash and cash equivalents		111		116
Money market funds
Cash and cash equivalents
Cash and cash equivalents		$ 21,353		$ 14,804

SIGNIFICANT ACCOUNTING POLICI44

SIGNIFICANT ACCOUNTING POLICIES - RESTRICTED CASH (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted cash
Restricted cash	$ 361,000	$ 361,000	$ 361,000
Security deposit related to credit card account
Restricted cash
Restricted cash	50,000	50,000	50,000
Standby letter of credit in favor of a landlord
Restricted cash
Restricted cash	$ 311,000	$ 311,000	$ 311,000

SIGNIFICANT ACCOUNTING POLICI45

SIGNIFICANT ACCOUNTING POLICIES - PROPERTY AND EQUIPMENT (Details)	12 Months Ended
	Dec. 31, 2016
Computer hardware
Property and equipment
Estimated Useful Life	5 years
Software
Property and equipment
Estimated Useful Life	3 years
Office furniture and equipment
Property and equipment
Estimated Useful Life	5 years
Research and lab equipment
Property and equipment
Estimated Useful Life	5 years

SIGNIFICANT ACCOUNTING POLICI46

SIGNIFICANT ACCOUNTING POLICIES - SEGMENT, INCOME TAX AND IMPAIRMENT (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)
SIGNIFICANT ACCOUNTING POLICIES
Number of operating segments | segment	1
Impairment charges on long-lived assets | $	$ 0	$ 0

SIGNIFICANT ACCOUNTING POLICI47

SIGNIFICANT ACCOUNTING POLICIES - NET LOSS PER COMMON SHARE (Details) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would b anti-dilutive	7,066,244	6,637,220	6,585,224	4,410,089	12,815,586
Stock options
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would b anti-dilutive	3,972,998	3,152,775	3,193,785	3,253,310	2,606,737
Warrants
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would b anti-dilutive	2,798,246	3,484,445	3,391,439	1,156,779	10,208,849

MARKETABLE SECURITIES - CASH, C

MARKETABLE SECURITIES - CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
MARKETABLE SECURITIES
Cash.		$ 111	$ 116
Money market funds	$ 16,524	21,353	14,804
Marketable securities	734	11,577	5,274
Total cash, cash equivalents and marketable securities	$ 17,200	$ 33,041	$ 20,194

MARKETABLE SECURITIES - SHORT-T

MARKETABLE SECURITIES - SHORT-TERM INVESTMENT IN MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Marketable securities by category
Amortized Cost	$ 734	$ 11,577	$ 5,274
Fair value	734	11,577	5,274
Commercial paper
Marketable securities by category
Amortized Cost		4,240	349
Fair value		4,240	349
Corporate obligations
Marketable securities by category
Amortized Cost	$ 734	7,337	4,925
Fair value		$ 7,337	$ 4,925

PROPERTY AND EQUIPMENT - TABLE

PROPERTY AND EQUIPMENT - TABLE (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Less accumulated depreciation and amortization		$ (3,218)	$ (2,682)
Property and equipment, net	$ 190	510	938
Computer software and hardware
Property and equipment
Gross property and equipment		606	562
Research and lab equipment
Property and equipment
Gross property and equipment		1,895	1,874
Leasehold improvements
Property and equipment
Gross property and equipment		431	392
Office equipment
Property and equipment
Gross property and equipment		$ 796	$ 792

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Depreciation
Depreciation	$ 536	$ 672	$ 735
Disposals	$ 0	$ 0

INTANGIBLE ASSETS (Details)

INTANGIBLE ASSETS (Details) - Patent licensing fee - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Intangible assets
Useful life	15 years
Intangible assets - gross	$ 200	$ 200
Accumulated amortization	(122)	(104)
Total	$ 78	$ 96

INTANGIBLE ASSETS - AMORTIZATIO

INTANGIBLE ASSETS - AMORTIZATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization
Amortization expense	$ 17	$ 17	$ 17
Future amortization
2,017	17
2,018	17
2,019	17
2,020	17
2,021	$ 10

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
ACCRUED EXPENSES
Accrued bonus	$ 595	$ 906
Accrued payroll	158	126	$ 85
Accrued vacation	231	91	81
Accrued severance	455	385
Other accrued expenses	345	451	208
Total accrued expenses	$ 1,784	$ 1,959	$ 374

FAIR VALUES OF ASSETS AND LIABI

FAIR VALUES OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets and liabilities measured at fair value on a recurring basis
Marketable securities	$ 734	$ 11,577
Derivative warrant liability	41	1,314	$ 1,907
Recurring basis
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	16,524	21,353	14,804
Marketable securities	734	11,577	5,274
Derivative warrant liability	41	1,314	1,907
Recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	16,524	21,353	14,804
Recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Marketable securities	734	11,577	5,274
Derivative warrant liability	$ 41	$ 1,314	$ 1,907

NOTE PAYABLE (Details)

NOTE PAYABLE (Details) - USD ($) $ in Thousands	1 Months Ended	8 Months Ended	12 Months Ended
	May 31, 2013	Dec. 31, 2013	Dec. 31, 2016	Dec. 31, 2015
Note payable
ERP system fully expensed due to abandonment of implementation			$ 0	$ 0
Note Payable.
Note payable
Proceeds from issuance of note payable	$ 150
Total cost for ERP system including interest	$ 159
Implicit interest rate	6.00%
Future minimum principal payments			$ 0
ERP system fully expensed due to abandonment of implementation		$ 150

LOAN PAYABLE (Details)

LOAN PAYABLE (Details) - USD ($)	May 01, 2015	Oct. 31, 2012	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans Payable
Fair value of warrants							$ 90,000	$ 251,000
Interest expense			$ 18,000	$ 32,000	$ 58,000	$ 117,000	$ 155,000	172,000	$ 136,000
Equipment Line of Credit
Loans Payable
Interest expense			17,000	24,000	56,000	76,000
MassDev
Loans Payable
Line of credit, maximum		$ 2,000,000
Line of credit for working capital purpose		$ 200,000
Fixed interest rate (as a percent)		6.50%
Period for charging 6.5% interest rate		30 months
Period for charging equal interest and principal payments		54 months
Maturity date		Oct. 5, 2019
Commencement date of monthly installments	May 1, 2015						May 1, 2015
Amount of monthly principal payment	$ 41,000
Future Principal payment due: 2017							$ 423,000
Future Principal payment due : 2018			452,000		452,000		452,000
Future Principal payment due : 2019			400,000		400,000		400,000
MassDev | Common Stock
Loans Payable
Number of shares into which a warrant may be converted		9,037
MassDev | Warrants
Loans Payable
Warrant period		7 years
Exercise price of warrant (in dollars per share)		$ 6.64
Fair value of warrants		$ 32,000
MassDev | Warrants | Interest Expense
Loans Payable
Amortization of deferred financing costs			$ 1,000	$ 1,000	$ 3,000	$ 3,000	5,000	5,000	5,000
MassDev | Equipment Line of Credit
Loans Payable
Interest expense							$ 99,000	$ 126,000	$ 127,000

LOAN PAYABLE - EQUIPMENT LOAN (

LOAN PAYABLE - EQUIPMENT LOAN (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of loans payable
MassDev Loan		$ 1,275	$ 1,670
Less: current portion	$ (444)	(423)	(395)
Noncurrent portion of equipment loan	$ 516	$ 852	$ 1,275

INCOME TAXES (Details)

INCOME TAXES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
INCOME TAXES
Provision or benefit for federal or state income taxes	$ 0

INCOME TAXES - CARRYFORWARDS (D

INCOME TAXES - CARRYFORWARDS (Details) $ in Thousands	Dec. 31, 2016USD ($)
U.S. federal
Income Taxes
Net operating loss carryforwards	$ 95,872
U.S. federal | Research Tax Credit Carryforward
Income Taxes
Research and development tax credit carryforwards	944
Massachusetts
Income Taxes
Net operating loss carryforwards	88,041
Massachusetts | Research Tax Credit Carryforward
Income Taxes
Research and development tax credit carryforwards	$ 183

INCOME TAXES - NET DEFERRED TAX

INCOME TAXES - NET DEFERRED TAX ASSET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Significant components of net deferred tax asset
Net operating loss carryforward	$ 37,245	$ 30,014
Research and development credit carryforward	1,065	942
Stock-based compensation	5,235	3,307
Depreciation and amortization	31
Depreciation and amortization		(48)
Accrued expenses	264	186
Charitable contributions	63	96
Subtotal	43,903	34,497
Valuation allowance	(43,903)	(34,497)
Increase in valuation allowance	9,406	8,727
Uncertain tax positions that would affect its effective tax rate	$ 0	$ 0

INCOME TAXES - STATUTORY INCOME

INCOME TAXES - STATUTORY INCOME TAX RATES (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income tax benefits computed using the federal statutory income tax rate
Statutory rate	(34.00%)	(34.00%)	(34.00%)
State taxes, net of benefit	(5.40%)	(3.50%)	(4.80%)
Permanent differences:
Derivative losses	(0.90%)	11.00%	0.70%
Other	0.20%	0.30%	2.60%
R&D tax credit	(0.50%)	(0.40%)	(1.00%)
Other	0.50%	0.40%	2.20%
Increase in valuation reserve	40.10%	26.20%	34.30%
Effective tax rate	0.00%	0.00%	0.00%

COMMON STOCK - PAR VALUE (Detai

COMMON STOCK - PAR VALUE (Details) - $ / shares	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Common stock, number of shares, par value and other disclosures
Common stock, authorized	100,000,000	100,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001	$ 0.00001
Common stock, issued	34,234,580	32,044,087	27,555,948
Common stock, outstanding	34,234,580	32,044,087	27,555,948

COMMON STOCK - TRANSACTIONS (De

COMMON STOCK - TRANSACTIONS (Details)	Apr. 08, 2015shares	Jul. 31, 2017shares	Jan. 31, 2017shares	Mar. 31, 2016USD ($)$ / sharesshares	Jul. 31, 2015USD ($)	Jan. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)$ / sharesshares	Jan. 31, 2014USD ($)shares	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)$ / sharesshares
Common stock disclosures
Proceeds from exercise of stock options | $									$ 26,000	$ 191,000	$ 191,000	$ 1,068,000	$ 212,000
Issuance of common stock to 401(k) plan | $											208,000	201,000	173,000
Proceeds from issuance of stock under ESPP | $									$ 51,000	$ 91,000	$ 91,000
Proceeds from exercise of warrants | $												$ 7,789,000	12,000
Reverse stock split ratio	0.25
Stock issued during period, shares, reverse stock splits	1,514
Common stock issued for services | $													477,000
Fair value of stock issued for services | $													$ 477,000
Sales Agreement
Common stock disclosures
Issuance of stock in public offering (in shares)												388,245
Net proceeds from issuance of equity (in dollars) | $												$ 3,442,000
Aggregate proceeds from sale agreement of shares of common stock | $					$ 50,000,000
Percentage of Commission on the gross proceeds from sales agreement of shares of common stock					3.00%
Employee Stock Purchase Plan
Common stock disclosures
Stock issued under ESPP (in shares)		9,764	7,986
Common Stock
Common stock disclosures
Issuance of common stock upon exercise of stock options (in shares)									89,387		135,205	316,177	132,900
Proceeds from exercise of stock options | $									$ 26,000		$ 191,000	$ 1,068,000	$ 212,000
Issuance of common stock upon cashless exercise of warrants (in shares)											4,979	25,052	6,903
Issuance of common stock to 401(k) plan (in shares)									61,587		37,528	17,437	41,753
Issuance of common stock to 401(k) plan | $									$ 154,000		$ 208,000	$ 201,000	$ 173,000
Stock issued under ESPP (in shares)									17,750		16,729
Proceeds from issuance of stock under ESPP | $									$ 51,000		$ 91,000
Issuance of stock in public offering (in shares)												2,388,245	3,500,312
Number of shares for stock options in cashless exercise (in shares)												52,224
Issuance of stock for noncash exercise-stock options (in shares)												14,961
Issuance of stock for cash-stock options (in shares)												301,216
Issuance of common stock upon exercise of warrants (in shares)												1,379,575	9,975
Number of warrants to purchase common stock (in shares)												40,955	15,655
Shares issued through cashless exercise provision-warrants (in shares)											4,979	25,052	6,903
Issuance of stock for cash- warrants (in shares)												1,354,523	3,072
Proceeds from exercise of warrants | $												$ 7,789,000	$ 12,000
Issuance of common stock for services (in shares)											365		74,626
Common stock issued for services | $								$ 282,000
Common Stock | Michael J. Astrue, Interim Chief Executive Officer
Common stock disclosures
Issuance of common stock for services (in shares)								27,212
Common Stock | Gregory D. Perry, Interim Chief Financial Officer
Common stock disclosures
Issuance of common stock for services (in shares)								5,594
Common Stock | Certain Employees
Common stock disclosures
Issuance of common stock for services (in shares)							41,821
Fair value of stock issued for services | $							$ 195,000
Common Stock | Public offering
Common stock disclosures
Issuance of stock in public offering (in shares)						2,000,000
Net proceeds from issuance of equity (in dollars) | $						$ 11,038,000
Common Stock | Public Offering, March 2016
Common stock disclosures
Warrants for purchase of common stock (in shares)				2,146,666
Equity issuance (in price per unit) | $ / shares				$ 7.49
Common Stock | Public Offering - Underwritten
Common stock disclosures
Warrants for purchase of common stock (in shares)							1,750,156						1,750,156
Equity issuance (in price per unit) | $ / shares							$ 4.60						$ 4.60
Warrants | Public Offering, March 2016
Common stock disclosures
Equity issuance (in price per unit) | $ / shares				0.01
Exercise price (in dollars per unit) | $ / shares				$ 10
Percentage of warrant exercises price over public offering price				133.00%
Warrants | Public Offering - Underwritten
Common stock disclosures
Equity issuance (in price per unit) | $ / shares							0.00001						0.00001
Exercise price (in dollars per unit) | $ / shares							$ 5.75						$ 5.75
Percentage of warrant exercises price over public offering price													125.00%
Common Stock And Warrants | Public Offering, March 2016
Common stock disclosures
Issuance of stock in public offering (in shares)				4,293,333
Net proceeds from issuance of equity (in dollars) | $				$ 29,905,000
Common Stock And Warrants | Public Offering - Underwritten
Common stock disclosures
Issuance of stock in public offering (in shares)													3,500,312
Net proceeds from issuance of equity (in dollars) | $													$ 14,600,000

COMMON STOCK - RESERVES (Detail

COMMON STOCK - RESERVES (Details)	Dec. 31, 2016shares
Summary of common stock reserves
Total Reserves	6,585,224
Warrants
Summary of common stock reserves
Total Reserves	3,391,439
Stock options
Summary of common stock reserves
Total Reserves	3,193,785

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2017	Jun. 30, 2016
Class of Warrant or Right
Reclassification of derivative warrant liability to additional paid-in capital						$ 16,121,000
Derivatives (gain) loss	$ 3,059,000	$ 336,000	$ 2,264,000	$ 788,000	$ (593,000)	10,804,000	$ 376,000
Derivative instruments, fair value	41,000		41,000		$ 1,314,000	1,907,000
Common Stock | Public Offering, May 2014
Class of Warrant or Right
Number of shares into which a warrant may be converted					1,750,156
Warrants
Class of Warrant or Right
Reclassification of derivative warrant liability to additional paid-in capital						16,121,000
Non-cash loss from modification of warrants	(30,000)	(336,000)	765,000	(788,000)	$ 593,000	(10,804,000)	(376,000)
Derivative instruments, fair value	41,000	2,695,000	41,000	2,695,000	1,314,000	1,907,000	7,224,000	$ 519,000	$ 2,359,000
Warrants | Other Income (Expense)
Class of Warrant or Right
Derivatives (gain) loss	$ 3,100,000	$ 336,000	$ 2,300,000	$ 788,000	$ (593,000)	$ 10,804,000	$ 376,000

DERIVATIVE INSTRUMENTS - FAIR V

DERIVATIVE INSTRUMENTS - FAIR VALUE OF WARRANTS (Details) - Warrants	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair value of warrants
Risk-free interest rate (as a percent)	1.50%	1.20%	0.65%	1.47%
Expected dividend yield (as a percent)		0.00%	0.00%	0.00%
Expected term (in years)	1 year 7 months 6 days	2 years 4 months 24 days	3 years 4 months 24 days	4 years 4 months 24 days
Expected volatility (as a percent)	86.00%	89.00%	100.00%	119.00%

DERIVATIVE INSTRUMENTS - CHANGE

DERIVATIVE INSTRUMENTS - CHANGES IN DERIVATIVE WARRANT LIABILITY (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in Derivative Warrant Liability
Balance at beginning of year			$ 1,314	$ 1,907	$ 1,907
Issuance of warrants							$ 6,848
Fair value of derivative warrant liability reclassified to additional paid-in capital						$ (16,121)
Balance at end of period	$ 41		41		1,314	1,907
Warrants
Changes in Derivative Warrant Liability
Balance at beginning of year	519	$ 2,359	1,314	1,907	1,907	7,224
Issuance of warrants							6,848
(Decrease) increase in the fair value of the warrants	30	336	(765)	788	(593)	10,804	376
Fair value of derivative warrant liability reclassified to additional paid-in capital						(16,121)
Balance at end of period	$ 41	$ 2,695	$ 41	$ 2,695	$ 1,314	$ 1,907	$ 7,224

STOCK OPTIONS (Details)

STOCK OPTIONS (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended			28 Months Ended
	Jul. 31, 2017	Jan. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2017	Apr. 30, 2015	Mar. 31, 2015
Stock options
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan					6,585,224	6,585,224			6,585,224
Stock-based compensation			$ 1,000,000	$ 1,200,000			$ 3,600,000	$ 3,600,000	$ 5,063,000	$ 4,666,000	$ 2,730,000
Stock Options
Stock options
Options to purchase common stock outstanding			3,972,998		3,193,785	3,193,785	3,972,998		3,193,785	3,253,310		3,972,998
Granted (in shares)							1,439,463		333,250
Expected term							10 years		10 years
Vesting period							48 months		48 months
2007 Plan
Stock options
Options to purchase common stock outstanding			46,476		150,207	150,207	46,476		150,207			46,476
Shares available for future grants					0	0			0
Expected term									10 years
2007 Plan | Stock Options
Stock options
Expected term							10 years
2010 Plan
Stock options
Options to purchase common stock outstanding			1,670,171		1,821,487	1,821,487	1,670,171		1,821,487			1,670,171
Shares available for future grants			322,355		322,355	322,355	322,355		322,355			322,355
Granted (in shares)					0							0
Expected term									10 years
2015 Plan
Stock options
Options to purchase common stock outstanding			2,256,351		1,222,085	1,222,085	2,256,351		1,222,085			2,256,351
Shares authorized for issuance			4,322,355		4,322,355	4,322,355	4,322,355		4,322,355			4,322,355	4,000,000
Expected term									10 years
Employee Stock Purchase Plan
Stock options
Shares authorized for issuance														187,500
Percentage of outstanding shares reserved for future issuance							1.00%		1.00%
Increase in shares of common stock reserved for issuance							50,000		50,000
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan			253,021	220,771	1,250,000	1,250,000	253,021	220,771	1,250,000			253,021
Offering Period							6 months		6 months
Stock issued under ESPP (in shares)	9,764	7,986
Stock-based compensation			$ 3,000	$ 12,000			$ 16,000	$ 39,000	$ 46,000	$ 41,000
Common Stock
Stock options
Stock issued under ESPP (in shares)							17,750		16,729
Accrued expenses. | Employee Stock Purchase Plan
Stock options
Employee payroll deductions						$ 51,000

STOCK OPTIONS - ASSUMPTIONS USE

STOCK OPTIONS - ASSUMPTIONS USED IN DETERMINING THE FAIR VALUE (Details) - Stock Options	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assumptions used principally in determining the fair value of options granted
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected term (employee grants)	5 years 11 months 27 days	6 years	6 years 11 days
Expected volatility (as a percent)	111.00%	116.00%	124.00%
Minimum
Assumptions used principally in determining the fair value of options granted
Risk-free interest rate (as a percent)	1.20%	1.53%	1.62%
Maximum
Assumptions used principally in determining the fair value of options granted
Risk-free interest rate (as a percent)	1.52%	1.89%	2.06%

STOCK OPTIONS - SUMMARY OF OPTI

STOCK OPTIONS - SUMMARY OF OPTION ACTIVITY - (Details) - Stock Options $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / shares
Summary of option activity - Shares
Outstanding at the beginning of year (in shares) | shares		3,193,785	3,253,310
Granted (in shares) | shares		1,439,463	333,250
Forfeited (in shares) | shares		(570,863)	(257,570)
Exercised (in shares) | shares		(89,387)	(135,205)
Outstanding at the end of period (in shares) | shares	3,972,998	3,972,998	3,193,785	3,253,310
Vested at the end of period (in shares) | shares		2,146,415	1,811,996
Vested and expected to vest at the end of period (in shares) | shares			2,741,045
Summary of option activity - Weighted Average Exercise Price
Outstanding at the beginning of year (in dollars per shares)		$ 7.52	$ 7.47
Granted (in dollars per shares)		3.94	6.27
Forfeited (in dollars per shares)			8.47
Exercised (in dollars per shares)		0.29	1.41
Outstanding at the end of period (in dollars per shares)	$ 6.53	6.53	7.52	$ 7.47
Vested at the end of period (in dollars per share)	$ 7.86	$ 7.86	7.54
Vested and expected to vest at the end of period (in dollars per share)			$ 7.52
Option activity disclosures
Weighted Average Remaining Contractual Term - Outstanding		7 years 5 months 23 days	6 years 11 months 5 days
Weighted Average Remaining Contractual Term - Vested		6 years 2 months 12 days	6 years 3 months 26 days
Weighted Average Remaining Contractual Term - Vested and expected to vest			6 years 9 months 22 days
Aggregate Intrinsic Value - Outstanding (in dollars) | $	$ 53,894	$ 53,894	$ 571
Aggregate Intrinsic Value - Vested (in dollars) | $	53,894	$ 53,894	563
Aggregate Intrinsic Value - Vested and expected to vest (in dollars) | $			$ 568
Stock Option
Weighted average grant-date fair value of options granted		$ 3.04	$ 5.23	$ 7.37	$ 6.15
Total fair value of options vested | $	1,100	$ 3,100	$ 5,179	$ 5,144	$ 2,329
Total unrecognized compensation expense, related to non-vested share-based compensation arrangements | $	$ 6,500	$ 6,500	$ 5,630
Period for unrecognized compensation expense is estimated to be recognized		2 years 6 months 11 days	2 years 4 months 13 days

WARRANTS (Details)

WARRANTS (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2016	Jan. 31, 2015	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 11, 2017	Aug. 10, 2017	Aug. 09, 2017	Feb. 29, 2016
Warrants to purchase common stock issued and outstanding
Number of Warrants				3,391,439
Weighted average exercise price				$ 7.94
Weighted average life in years				3 years 2 months 27 days
Common stock, par value (in dollars per share)			$ 0.00001	$ 0.00001	$ 0.00001
Fair value of warrants
Fair value of warrants				$ 90	$ 251
Warrants | Public Offering, March 2016
Fair value of warrants
Fair value of warrants	$ 11,726
Expected volatility (as a percent)	112.82%
Risk-free interest rate (as a percent)	1.34%
Expected term (in years)	5 years
Expected dividend yield (as a percent)	0.00%
Common Stock
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)					2,388,245	3,500,312
Common Stock | Public Offering, March 2016
Warrants to purchase common stock issued and outstanding
Warrants for purchase of common stock (in shares)	2,146,666
Equity issuance (in price per unit)	$ 7.49
Common Stock | Public offering
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)		2,000,000
Net proceeds from issuance of equity (in dollars)		$ 11,038
Common Stock | Public Offering - Underwritten
Warrants to purchase common stock issued and outstanding
Warrants for purchase of common stock (in shares)						1,750,156
Equity issuance (in price per unit)						$ 4.60
Warrants
Warrants to purchase common stock issued and outstanding
Number of Warrants			2,798,246
Weighted average exercise price			$ 8.75
Weighted average life in years			2 years 8 months 16 days
Fair value of warrants
Expected volatility (as a percent)			86.00%	89.00%	100.00%	119.00%
Risk-free interest rate (as a percent)			1.50%	1.20%	0.65%	1.47%
Expected term (in years)			1 year 7 months 6 days	2 years 4 months 24 days	3 years 4 months 24 days	4 years 4 months 24 days
Expected dividend yield (as a percent)				0.00%	0.00%	0.00%
Warrants | Public Offering, March 2016
Warrants to purchase common stock issued and outstanding
Warrant Exercise Price	10
Equity issuance (in price per unit)	$ 0.01
Percentage of warrant exercises price over public offering price	133.00%
Fair value of warrants
Fair value of warrants			$ 11,700
Expected volatility (as a percent)			112.80%
Risk-free interest rate (as a percent)			1.30%
Expected term (in years)			5 years
Expected dividend yield (as a percent)			0.00%
Warrants | Public Offering - Underwritten
Warrants to purchase common stock issued and outstanding
Warrant Exercise Price						$ 5.75
Equity issuance (in price per unit)						$ 0.00001
Percentage of warrant exercises price over public offering price						125.00%
Warrants | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Number of Warrants								48,507	10,403
Warrant Exercise Price							$ 0.83	$ 3.87
Warrants for purchase of common stock (in shares)			48,507
Warrants | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Number of Warrants	587,950									395,716
Warrant Exercise Price	$ 3.87									$ 5.75
Common Stock And Warrants | Public Offering, March 2016
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)	4,293,333
Net proceeds from issuance of equity (in dollars)	$ 29,905
Common Stock And Warrants | Public Offering - Underwritten
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)						3,500,312
Net proceeds from issuance of equity (in dollars)						$ 14,600
Equity | Derivative with Exercise Price One
Warrants to purchase common stock issued and outstanding
Warrants Issued Year				2,010
Number of Warrants				343,931
Warrant Exercise Price				$ 5.60
Equity | Derivative with Exercise Price One | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date				Oct. 26, 2017
Equity | Derivative with Exercise Price One | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date				Dec. 3, 2017
Equity | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrants Issued Year				2,010
Number of Warrants				306,838
Warrant Exercise Price				$ 4
Equity | Derivative with Exercise Price Two | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date				Aug. 30, 2017
Equity | Derivative with Exercise Price Two | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date				Dec. 3, 2017
Equity | Derivative with Exercise Price Three
Warrants to purchase common stock issued and outstanding
Warrants Issued Year				2,012
Number of Warrants				6,054
Warrant Exercise Price				$ 6.64
Expiration date				Oct. 5, 2019
Equity | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Warrants Issued Year				2,016
Number of Warrants				2,146,666
Warrant Exercise Price				$ 10
Expiration date				Mar. 18, 2021
Equity | Warrants | Derivative with Exercise Price One
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,010
Number of Warrants			343,931
Warrant Exercise Price			$ 5.60
Equity | Warrants | Derivative with Exercise Price One | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date			Oct. 26, 2017
Equity | Warrants | Derivative with Exercise Price One | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date			Dec. 3, 2017
Equity | Warrants | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,010
Number of Warrants			253,088
Warrant Exercise Price			$ 4
Equity | Warrants | Derivative with Exercise Price Two | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date			Oct. 26, 2017
Equity | Warrants | Derivative with Exercise Price Two | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date			Dec. 3, 2017
Equity | Warrants | Derivative with Exercise Price Three
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,012
Number of Warrants			6,054
Warrant Exercise Price			$ 6.64
Expiration date			Oct. 5, 2019
Equity | Warrants | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,016
Number of Warrants			2,146,666
Warrant Exercise Price			$ 10
Expiration date			Mar. 18, 2021
Liability | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Warrants Issued Year				2,014
Number of Warrants				587,950
Warrant Exercise Price				$ 3.87
Expiration date				May 9, 2019
Liability | Warrants | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,014
Number of Warrants			48,507
Warrant Exercise Price			$ 0.83
Expiration date			May 9, 2019

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee benefit plan disclosures
Eligibility criteria for participation in the Plan		21 years
Expense portion of fair value of stock		$ 208	$ 201	$ 173
Common Stock
Employee benefit plan disclosures
Issuance of common stock to 401(k) plan (in shares)	61,587	37,528	17,437	41,753
Expense portion of fair value of stock		$ 208	$ 201	$ 173

INTELLECTUAL PROPERTY LICENSE (

INTELLECTUAL PROPERTY LICENSE (Details) - Boston Childrens Hospital Bch License - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2016	Dec. 31, 2015
Intellectual Property License
Useful life	15 years
Initial license fee paid	$ 75
Capitalized license fees and milestone payments, gross		$ 200	$ 200

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - LEASES (Details) - Cambridge Lease	Nov. 01, 2018	Sep. 17, 2012USD ($)ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017USD ($)
Commitments
Lease space (in square feet) | ft²		26,150
Term of commercial lease		6 years 3 months
Term of lease extension option	5 years	5 years
Standby letter of credit		$ 311,000
Deferred rent liability			$ 276,000	$ 391,000	$ 238,000
Leasehold improvements, net			$ 143,000	$ 185,000

COMMITMENTS AND CONTINGENCIES76

COMMITMENTS AND CONTINGENCIES - FUTURE MINIMUM RENT COMMITMENTS (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Mar. 31, 2016USD ($)ft²	Sep. 04, 2013USD ($)	Sep. 17, 2012ft²
Future minimum rent commitments
2,017	$ 314,000		$ 314,000
2,018	1,378,000		1,378,000
Total	11,644,000		11,644,000
Cambridge Lease
Future minimum rent commitments
2,017					$ 1,289,000
2,018					1,088,000
Total					2,377,000
Commitments
Total rent expense	$ 269,000	$ 210,000	828,000	$ 707,000	918,000	$ 1,123,000	$ 1,148,000
Sublease income recorded as offset to rent expense					$ 230,000
Legal settlement agreement accrual									$ 286,000
Lease space (in square feet) | ft²										26,150
CRISPR Therapeutics lease
Commitments
Sublease income recorded as offset to rent expense			$ 26,000	$ 77,000
Lease space (in square feet) | ft²								5,233
Tenant security deposit and first month's rent								$ 51,000
Tenant security deposit								$ 26,000

COMMITMENTS AND CONTINGENCIES77

COMMITMENTS AND CONTINGENCIES - COMPENSATION (Details) - Executive - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2016
Compensation Commitment
Term of award	1 year
Compensation expense		$ 89	$ 101

COMMITMENTS AND CONTINGENCIES78

COMMITMENTS AND CONTINGENCIES - LITIGATION (Details)	Dec. 06, 2013claim	Dec. 06, 2013item	Nov. 30, 2013USD ($)
InVivo Therapeutics Holdings Corp. v. Reynolds
Litigation
Value of damages sought worth of personal and/or exorbitant expenses			$ 500,000
Reynolds counterclaim against InVivo Therapeutics Holdings Corp.
Litigation
Number of breach of contract claims	2	2
Number of breach of covenant of good faith and fair-dealing claims	2	2

INSURANCE CLAIM (Details)

INSURANCE CLAIM (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2014USD ($)
September 2014 Water Damage Business Interruption | Research and development expenses
Insurance claim disclosures
Settlement amount	$ 621

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - Dr. Robert Langer - Consulting agreement $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Related Party Transactions
Holding percentage of common stock	5.00%
Consulting fees	$ 250

Consolidated Balance Sheets81

Consolidated Balance Sheets $ in Thousands	Sep. 30, 2017USD ($)
Current assets:
Cash and cash equivalents	$ 16,434
Restricted cash	361
Marketable securities	734
Prepaid expenses and other current assets	475
Total current assets	18,004
Property, equipment and leasehold improvements, net	190
Other assets	402
Total assets	18,596
Current liabilities:
Accounts payable	1,270
Loan payable, current portion	444
Derivative warrant liability	41
Deferred rent, current portion	30
Accrued expenses	1,784
Total current liabilities	3,569
Loan payable, net of current portion	516
Deferred rent, net of current portion	208
Other liabilities	52
Total liabilities	4,345
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock, $0.00001 par value, authorized 100,000,000 shares; 34,234,580 shares issued and outstanding at September 30, 2017; 32,044,087 shares issued and outstanding at December 31, 2016	1
Additional paid-in capital	193,493
Accumulated deficit	(179,243)
Total stockholders' equity	14,251
Total liabilities and stockholders' equity	$ 18,596

Consolidated Balance Sheets (82

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001	$ 0.00001
Common stock, authorized	100,000,000	100,000,000	50,000,000
Common stock, issued	34,234,580	32,044,087	27,555,948
Common stock, outstanding	34,234,580	32,044,087	27,555,948

Consolidated Statements of Op83

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating expenses:
Research and development	$ 2,928	$ 3,294	$ 9,522	$ 8,659
General and administrative	3,388	2,584	10,389	8,573
Total operating expenses	6,316	5,878	19,911	17,232
Operating loss	(6,316)	(5,878)	(19,911)	(17,232)
Other income (expense):
Interest income	43	50	152	133
Interest expense	(18)	(32)	(58)	(117)
Derivatives gain (loss)	(3,059)	(336)	(2,264)	(788)
Other income (expense), net	(3,034)	(318)	(2,170)	(772)
Net loss	$ (9,350)	$ (6,196)	$ (22,081)	$ (18,004)
Net loss per share, basic and diluted (in dollars per share)	$ (0.28)	$ (0.19)	$ (0.68)	$ (0.59)
Weighted average number of common shares outstanding, basic and diluted	33,445,002	31,968,357	32,516,190	30,687,263
Other comprehensive loss:
Net loss	$ (9,350)	$ (6,196)	$ (22,081)	$ (18,004)
Other comprehensive loss:
Comprehensive loss	$ (9,350)	$ (6,196)	$ (22,081)	$ (18,004)

Consolidated Statements of Ca84

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (22,081)	$ (18,004)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	387	417
Derivatives (gain) loss	2,264	788
Common stock issued to 401(k) plan	154	156
Share-based compensation expense	3,614	3,571
Non-cash investment (income) expense, net		(193)
Changes in operating assets and liabilities:
Prepaid expenses	(24)	(229)
Other assets	6	(308)
Accounts payable	259	35
Accrued expenses and other liabilities	(161)	1,248
Net cash used in operating activities	(15,582)	(12,519)
Cash flows from investing activities:
Purchases of marketable securities	(8,256)	(7,987)
Sales of marketable securities	19,100	1,050
Purchases of property and equipment	(54)	(96)
Net cash (used in) provided by investing activities	10,790	(7,033)
Cash flows from financing activities:
Proceeds from exercise of stock options	26	191
Proceeds from issuance of stock under ESPP	51	91
Repayment of loan payable	(315)	(294)
Proceeds from issuance of common stock and warrants		29,905
Net cash (used in) provided by financing activities	(238)	29,893
Increase (decrease) in cash and cash equivalents	(5,030)	10,341
Cash and cash equivalents at beginning of period	21,464	14,920
Cash and cash equivalents at end of period	16,434	25,261
Supplemental disclosure of cash flow information and non-cash transactions:
Cash paid for interest	56	54
Non-cash issuance of common stock for warrants	$ 3,537	$ 62

NATURE OF OPERATIONS, BASIS OF

NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS	9 Months Ended
	Sep. 30, 2017
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS	1. NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS Business InVivo Therapeutics Holdings Corp. was incorporated on April 2, 2003 under the name of Design Source, Inc., and on October 26, 2010 acquired the business of InVivo Therapeutics Corporation, which was incorporated on November 28, 2005, and continued the existing business operations of InVivo Therapeutics Corporation as a wholly-owned subsidiary of InVivo Therapeutics Holdings Corp. Unless otherwise noted herein, the “Company” refers to InVivo Therapeutics Holdings Corp. and its wholly-owned subsidiary on a consolidated basis. The Company is a research and clinical-stage biomaterials and biotechnology company with a focus on the treatment of spinal cord injuries. Its proprietary technologies incorporate intellectual property licensed under the Company’s exclusive, worldwide license from Boston Children’s Hospital and the Massachusetts Institute of Technology, as well as intellectual property that has been developed internally in collaboration with its advisors and partners. Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff, acquiring operating assets, and raising capital. The Company has historically financed its operations primarily through the sale of equity-related securities. At September 30, 2017, the Company had cash, cash equivalents, and marketable securities of $17.2 million. The Company has not achieved profitability and may not be able to realize sufficient revenue to achieve or sustain profitability in the future. The Company does not expect to be profitable in the next several years, but rather expects to incur additional operating losses. The Company has limited liquidity and capital resources and must obtain significant additional capital resources in order to sustain its product development efforts, for acquisition of technologies and intellectual property rights, for preclinical and clinical testing of its anticipated products, for pursuit of regulatory approvals, for acquisition of capital equipment, laboratory and office facilities, for establishment of production capabilities, for selling, general, and administrative expenses, and for other working capital requirements. The Company expects that it will need additional capital to fund its operations, which it may raise through a combination of equity offerings, debt financings, other third party funding, marketing and distribution arrangements, and other collaborations, strategic alliances, and licensing arrangements. The Company’s financial statements as of September 30, 2017 were prepared under the assumption that the Company will continue as a going concern. Given the Company’s development plans, it estimates cash resources will be sufficient to fund its operations into the third quarter of 2018. This estimate is based on assumptions that may prove to be wrong; expenses could prove to be significantly higher, leading to a more rapid consumption of the Company’s existing resources. Based on the forecast, management determined that there is substantial doubt regarding the Company’s ability to continue as a going concern. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“GAAP”) consistent with those applied in, and should be read in conjunction with, the Company’s audited financial statements and related footnotes for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K as filed with the United States Securities and Exchange Commission (“SEC”) on March 10, 2017. The unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the Company’s financial position as of September 30, 2017 and its results of operations and cash flows for the interim period presented, and are not necessarily indicative of results for subsequent interim periods or for the full year. The interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements, as allowed by the relevant SEC rules and regulations; however, the Company believes that its disclosures are adequate to ensure that the information presented is not misleading. Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the current period presentation. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for the prior period presented. Recently Issued Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company adopted this standard on January 1, 2017. Prior to adoption, the Company recognized share-based compensation, net of estimated forfeitures, over the vesting period of the grant. Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to recognize forfeitures as they occur. The Company continues to recognize share-based compensation expense over the vesting period of the grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $155,000 recorded to accumulated deficit on the balance sheet as of January 1, 2017. Prior to January 1, 2017, the Company recognized the excess tax benefits of stock-based compensation expense as additional paid-in capital and tax deficiencies of stock-based compensation expense in the income tax provision or as additional paid-in capital to the extent that there were sufficient recognized excess tax benefits previously recognized. Previously, the excess tax benefits reduced taxes payable prior to being recognized as an increase in additional paid-in capital, and therefore the Company had not recognized certain deferred tax assets that could be attributed to tax deductions. As a result of the adoption, the deferred tax assets associated with certain net operating losses increased, which was offset by a corresponding increase in the valuation allowance and therefore the adoption of the tax-related guidance in this standard did not have an impact on our consolidated financial statements for the period ended September 30, 2017. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230) : Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”) to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In July 2017, the FASB issued ASU No. 2017-11, Part I. Accounting for Certain Financial Instruments with Down Round Features and Part II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I of this guidance applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down round features. Part II of this guidance replaces the indefinite deferrals for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities. ASU 2017-11 is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company has concluded that the adoption of this ASU will not have a material impact on the financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration, and the presentation of sales and other similar taxes collected from customers. These standards are effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. Currently, this guidance is not applicable to the Company as the Company does not generate revenue. However, the Company will evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue.

CASH AND CASH EQUIVALENTS

CASH AND CASH EQUIVALENTS	9 Months Ended
	Sep. 30, 2017
CASH AND CASH EQUIVALENTS.
CASH AND CASH EQUIVALENTS	2. CASH AND CASH EQUIVALENTS As of September 30, 2017, the Company held $16.4 million in cash and cash equivalents. From time to time, the Company may have cash balances in financial institutions in excess of insurance limits. The Company has never experienced any losses related to these balances. The Company considers only those investments that are highly liquid, readily convertible to cash, and that mature within three months from date of purchase to be cash equivalents. At September 30, 2017 and December 31, 2016, cash equivalents were comprised of money market funds and other short-term investments. Cash and cash equivalents consisted of the following: September 30, December 31, (In thousands) 2017 2016 Cash $ (90) $ 111 Money market funds 16,524 21,353 Total cash and cash equivalents $ 16,434 $ 21,464

RESTRICTED CASH

RESTRICTED CASH	9 Months Ended
	Sep. 30, 2017
RESTRICTED CASH
RESTRICTED CASH	3. RESTRICTED CASH Restricted cash as of September 30, 2017 and December 31, 2016 was $361,000 and included a $50,000 security deposit related to the Company’s credit card account and a $311,000 standby letter of credit in favor of a landlord (see Note 6).

MARKETABLE SECURITIES88

MARKETABLE SECURITIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
MARKETABLE SECURITIES
MARKETABLE SECURITIES	4. MARKETABLE SECURITIES The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars, including money market accounts, commercial paper, asset-backed securities, and corporate obligations, in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. As of September 30, 2017 and December 31, 2016, the Company’s investment portfolio consisted of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore such investments are reported at fair value. Unrealized gains or losses on marketable securities are recorded in accumulated other comprehensive loss, a component of stockholders’ equity, on the balance sheet. The following table summarizes the Company’s investments in marketable securities by category as of September 30, 2017 and December 31, 2016: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2017 Current (due within 1 year or less) Corporate obligations 734 — — 734 Total $ 734 $ — $ — $ 734 December 31, 2016 Current (due within 1 year or less) Commercial paper 4,240 — — 4,240 Corporate obligations 7,337 — — 7,337 Total $ 11,577 $ — $ — $ 11,577	3. MARKETABLE SECURITIES The Company invests its excess cash in fixed income instruments denominated and payable in U.S. dollars including money market accounts, commercial paper, and corporate obligations in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital. The following table summarizes the Company’s cash, cash equivalents, and marketable securities as of December 31, 2016 and 2015: December 31, 2016 2015 Cash $ $ Money market funds Marketable securities Total cash, cash equivalents and marketable securities $ $ As of December 31, 2016, the Company’s investment portfolio consists of marketable securities with an original maturity of greater than 90 days. The Company has designated all investments as available-for-sale and therefore, such investments are reported at fair value. As of December 31, 2016, the fair value of the Company’s marketable securities approximates amortized cost and therefore the insignificant gains/losses on these securities have been included within Other Income (Expense) on the Statement of Operations. The following table summarizes the Company’s short-term investments in marketable securities by category as of December 31, 2016 and 2015: Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Commercial paper Corporate obligations — — Total $ $ — $ — $ December 31, 2015 Commercial paper Corporate obligations — — Total $ $ — $ — $ As of December 31, 2016 and 2015, the Company’s investments in marketable securities are classified in current assets as they are due in one year or less.

FAIR VALUE OF ASSETS AND LIAB89

FAIR VALUE OF ASSETS AND LIABILITIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
FAIR VALUE OF ASSETS AND LIABILITIES
FAIR VALUE OF ASSETS AND LIABILITIES	5. FAIR VALUE OF ASSETS AND LIABILITIES The Company groups its assets and liabilities generally measured at fair value into three levels based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1 — Valuation is based on quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities generally include debt and equity securities that are traded in an active exchange market. Valuations are obtained from readily available pricing sources for market transactions involving identical assets or liabilities. Level 2 — Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. The Company uses valuation methods and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments (see Notes 11 and 12). Assets and liabilities measured at fair value on a recurring basis are summarized below: At September 30, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 16,524 $ — $ — $ 16,524 Marketable securities — 734 — 734 Derivative warrant liability $ — $ (41) $ — $ (41) At December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 21,353 $ — $ — $ 21,353 Marketable securities — 11,577 — 11,577 Derivative warrant liability $ — $ (1,314) $ — $ (1,314)	7. FAIR VALUES OF ASSETS AND LIABILITIES The Company groups its assets and liabilities generally measured at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. Level 1—Valuation is based on quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities, generally include debt and equity securities that are traded in an active exchange market. Valuations are obtained from readily available pricing sources for market transactions involving identical assets or liabilities. Level 2—Valuation is based on observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Valuation is based on unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. The Company uses valuation methods and assumptions that consider, among other factors, the fair value of the underlying stock, risk‑free interest rate, volatility, expected life, and dividend rates in estimating the fair value for the warrants considered to be derivative instruments. Assets and liabilities measured at fair value on a recurring basis are summarized below: At December 31, 2016 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $ At December 31, 2015 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $

COMMITMENTS AND CONTINGENCIES90

COMMITMENTS AND CONTINGENCIES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	6. COMMITMENTS AND CONTINGENCIES Leases On November 30, 2011, the Company entered into a commercial lease for 26,150 square feet of office, laboratory, and manufacturing space in Cambridge, Massachusetts (as amended on September 17, 2012, the “Cambridge Lease”). The term of the Cambridge Lease is six years and three months, with one five-year extension option. On August 21, 2017, the Company exercised its option for the five-year extension on the Cambridge Lease. The five-year renewal lease term commences on November 1, 2018 and ends on October 31, 2023. The terms of the Cambridge Lease require a standby letter of credit in the amount of $311,000 (see Note 3). The Cambridge Lease contains rent holidays and rent escalation clauses. The Company recognizes rent expense on a straight-line basis over the term of the Cambridge Lease and records the difference between the amount charged to expense and the rent paid as a deferred rent liability. As of September 30, 2017, the amount of deferred rent liability was $238,000. Pursuant to the terms of the non-cancelable lease agreements in effect at September 30, 2017, the future minimum rent commitments are as follows (in thousands): Year Ended December 31, 2017 314 2018 1,378 2019 1,945 2020 2,003 2021 2,063 Thereafter 3,941 Total $ 11,644 Total rent expense for the three-month periods ended September 30, 2017 and 2016 was $269,000 and $210,000, respectively. Total rent expense for the nine-month periods ended September 30, 2017 and 2016 was $828,000 and $707,000, respectively. On March 31, 2016, the Company entered into a short-term lease with CRISPR Therapeutics, as subtenant, to sub-lease 5,233 square feet of the Facility (the “CRISPR Sublease”). The lease term was from April 1, 2016 through January 31, 2017. On March 31, 2016, the Company received $51,000 covering the first month’s rent and a security deposit under the terms of the CRISPR Sublease. The funds received for the security deposit, $26,000, were classified as a component of accrued expenses on the balance sheet as of December 31, 2016. In connection with the CRISPR Sublease, the Company received sublease income for the nine-month periods ended September 30, 2017 and 2016 of $26,000 and $77,000, respectively, which was recorded as an offset to rent expense. The CRISPR Sublease terminated on January 31, 2017 and the security deposit was returned to the subtenant. On June 13, 2017, the Company entered into a short-term lease with Moderna Therapeutics, as subtenant, to sub-lease 5,233 square feet of the Facility (the “Moderna Sublease”). The lease term is from July 1, 2017 through October 26, 2018. On June 19, 2017, the Company received a $55,000 security deposit under the terms of the Moderna Sublease. This security deposit is classified as a component of accrued expenses on the balance sheet as of September 30, 2017. In connection with the Moderna Sublease, the Company received sublease income of $82,000 for the nine-month period ended September 30, 2017, which was recorded as an offset to rent expense. Litigation Lawsuits with Former Employee In November 2013, the Company filed a lawsuit against Francis Reynolds, its former Chairman, Chief Executive Officer and Chief Financial Officer, in Middlesex Superior Court, Middlesex County, Massachusetts ( InVivo Therapeutics Holdings Corp. v. Reynolds, Civil Action No. 13-5004 ). The complaint alleges breaches of fiduciary duties, breach of contract, conversion, misappropriation of corporate assets, unjust enrichment, and corporate waste, and seeks monetary damages and an accounting. The lawsuit involves approximately $500,000 worth of personal and/or exorbitant expenses that the Company alleges Mr. Reynolds inappropriately caused it to pay while he was serving as the Company’s Chief Executive Officer, Chief Financial Officer, President, and Chairman of the Company’s Board of Directors. On December 6, 2013, Mr. Reynolds answered the complaint, and filed counterclaims against the Company and the Company’s Board of Directors. The counterclaims allege two counts of breach of contract, two counts of breach of the covenant of good faith and fair-dealing, and tortious interference with a contract, and seek monetary damages and a declaratory judgment. The counterclaims relate to Mr. Reynolds’s allegations that the Company and the Company’s Board of Directors interfered with the performance of his duties under the terms of his employment agreement, and that Mr. Reynolds was entitled to additional shares upon the exercise of certain stock options that he did not receive. On January 9, 2014, the Company and the directors named in the counterclaim filed their answer denying that Mr. Reynolds is entitled to any relief. The parties have completed discovery. On March 3, 2017, the counterclaim defendants filed a motion for summary judgment on all counterclaims asserted by Mr. Reynolds. On October 18, 2017, the Court allowed the motion for summary judgment in substantial part, and denied it in part. The Court, citing disputed issues of fact, declined to dismiss the counterclaims for breach of contract, breach of implied covenant of good faith and fair dealing, and declaratory judgment concerning Mr. Reynolds' attempted exercise of certain stock options, which Mr. Reynolds claims is the equivalent of 47,864 shares of common stock, but dismissed all other claims asserted by Mr. Reynolds. The Company intends to continue to defend itself against the remaining counterclaims and, to date, the Company has not recorded any provision for losses that may arise.	17. COMMITMENTS AND CONTINGENCIES Leases On November 30, 2011, the Company entered into a commercial lease for 26,150 square feet of office, laboratory and manufacturing space in Cambridge, Massachusetts (as amended on September 17, 2012, the “Cambridge Lease”). The term of the Cambridge Lease is six years and three months, with one five‑year extension option. The terms of the Cambridge Lease require a standby letter of credit in the amount of $311 (see Note 2). The Cambridge Lease contains rent holidays and rent escalation clauses. The Company recognizes rent expense on a straight-line basis over the term of the Cambridge Lease and records the difference between the amount charged to expense and the rent paid as a deferred rent liability. As of December 31, 2016 and 2015, the amount of the deferred rent liability is $276 and $391, respectively, and is included in accrued expenses. It is the Company’s policy to assess whether improvements made to the space rented under operating leases should be accounted for as “lessor” or “lessee” assets. Such costs are recorded as leasehold improvements, which are amortized to rent expense over the term of the Cambridge Lease. As of December 31, 2016 and 2015, such leasehold improvements totaled $143 and $185, net of accumulated depreciation. Pursuant to the terms of the non‑cancelable lease agreements in effect at December 31, 2016, the future minimum rent commitments are as follows: Year Ended December 31, 2017 2018 Total $ Total rent expense for the years ended December 31, 2016, 2015, and 2014, including month‑to‑month leases, was $918, $1,123 and $1,148, respectively, net of sublease income of $230 for the year ended December 31, 2016. On September 4, 2013, the Company entered into a legal settlement agreement for $286 in connection with the Cambridge Lease. The settlement amount has been included in the deferred rent liability and the benefit is being amortized over the remainder of the term of the Cambridge Lease. On March 31, 2016, the Company entered into a short-term lease with CRISPR Therapeutics, as subtenant, to sub-lease 5,233 square feet of our Facility (the “Sublease”). The lease term was from April 1, 2016 through January 31, 2017. On March 31, 2016, the Company received $51 covering the first month’s rent and a security deposit under the terms of the Sublease. The funds received for the security deposit, $26, are classified as a component of accrued expenses in the financial statements. The Sublease was terminated on January 31, 2017. Compensation Commitment The Company entered into a compensation arrangement with an executive during September 2016 which provides for a future cash payment by the Company to the executive based on the February 13, 2017 stock price of the executive’s former employer. The award is earned over a period of one year. Accordingly, the expense related to the compensation arrangement was approximately $89 for the three months and $101 for the twelve months ended December 31, 2016. The liability is included within accrued expenses on the balance sheet and was recorded at fair value on a recurring basis until the final payment was determined on February 13, 2017. Lawsuits with Former Employee In November 2013, the Company filed a lawsuit against Francis Reynolds, its former Chairman, Chief Executive Officer and Chief Financial Officer, in Middlesex Superior Court, Middlesex County, Massachusetts ( InVivo Therapeutics Holdings Corp. v. Reynolds, Civil Action No. 13-5004 ). The complaint alleges breaches of fiduciary duties, breach of contract, conversion, misappropriation of corporate assets, unjust enrichment, and corporate waste, and seeks monetary damages and an accounting. The lawsuit involves approximately $500,000 worth of personal and/or exorbitant expenses that the Company alleges Mr. Reynolds inappropriately caused it to pay while he was serving as the Company’s Chief Executive Officer, Chief Financial Officer, President, and Chairman of the Company’s Board of Directors. On December 6, 2013, Mr. Reynolds answered the complaint, and filed counterclaims against the Company and the Company’s Board of Directors. The counterclaims allege two counts of breach of contract, two counts of breach of the covenant of good faith and fair-dealing, and tortious interference with a contract, and seek monetary damages and a declaratory judgment. The counterclaims related to Mr. Reynolds’s allegations that the Company and the Company’s Board of Directors interfered with the performance of his duties under the terms of his employment agreement, and that Mr. Reynolds was entitled to additional shares upon the exercise of certain stock options that he did not receive. On January 9, 2014, the Company, along with the directors named in the counterclaims, filed the Company’s answer. Discovery has now been completed and the Company’s motion for summary judgment on all counts of the complaint and Reynolds’ opposition to the motion for summary judgment was filed with the court on March 3, 2017. The Company intends to continue to defend itself against these claims and, to date, the Company has not recorded any provision for losses that may arise. On July 22, 2016, Mr. Reynolds filed a lawsuit against the Company, certain present and former members of the Company’s Board of Directors and an employee of the Company in Hillsborough County Superior Court, Southern District, Hillsborough County, New Hampshire ( Reynolds v. InVivo Therapeutics Holdings Corp, et al.) alleging defamation, conspiracy, and tortious interference, and seeking monetary damages. In August 2016, the lawsuit was removed to the United States District Court for the District of New Hampshire. The Company filed a motion to dismiss this action and after oral argument on November 28, 2016, the Court on November 30, 2016 issued an order dismissing the case for lack of personal jurisdiction. The judgment was entered on the docket on December 1, 2016, and the deadline for appealing that decision has passed. Shareholder Matters and Investigations On July 31, 2014, a putative securities class action lawsuit was filed in the United States District Court for the District of Massachusetts, naming the Company and Mr. Reynolds as defendants (the “Securities Class Action”). The lawsuit alleges violations of the Securities Exchange Act of 1934 in connection with allegedly false and misleading statements related to the timing and completion of the clinical study of the Company’s Neuro-Spinal Scaffold ™ implant. The plaintiff sought class certification for purchasers of the Company’s common stock during the period from April 5, 2013 through August 26, 2013 and unspecified damages. On April 3, 2015, the United States District Court for the District of Massachusetts dismissed the plaintiff’s claim with prejudice. On May 4, 2015, the plaintiff filed a notice of appeal of this decision. Following the submission of briefs by the parties, the Court of Appeals heard oral arguments on April 6, 2016. On January 9, 2017, the Court of Appeals for the First Circuit issued an order and opinion affirming the dismissal of the Securities Class Action with prejudice. Plaintiff has until April 10, 2017 to file a petition for certiorari to the United States Supreme Court. The Company intends to continue to defend itself against these claims and, to date, has not recorded any provision for losses that may arise. On January 23, 2015, Shawn Luger, a purported shareholder of the Company, sent the Company a letter (the “Shareholder Demand”) demanding that the Board of Directors take action to remedy purported breaches of fiduciary duties allegedly related to the claimed false and misleading statements that are the subject of the Securities Class Action. The Board of Directors completed its investigation of the matters raised in the Shareholder Demand and voted unanimously not to pursue any litigation against any current or former director, officer, or employee of the Company with respect to the matters set forth in the Shareholder Demand. On August 14, 2015, Mr. Luger filed a shareholder derivative lawsuit in the Superior Court of Suffolk County for the Commonwealth of Massachusetts on behalf of the Company against certain present and former board members and company executives alleging the same breaches of fiduciary duties purportedly set forth in the Shareholder Demand. On February 5, 2016, the Superior Court of Suffolk County dismissed the plaintiff’s claims with prejudice. On March 4, 2016, the plaintiff filed a notice of appeal of this decision. Following the submission of brief by the parties, the Appeals Court heard oral argument on December 13, 2016. On January 3, 2017, the Appeals Court issued an order and opinion affirming the dismissal of all claims with prejudice. The time period for Mr. Luger to appeal the Appeals Court’s judgment has expired. In addition, the Company received investigation subpoenas from the Boston Regional Office of the SEC and the Massachusetts Securities Division of the Secretary of the Commonwealth of Massachusetts (“MSD”) requesting corporate documents concerning, among other topics, the allegations raised by the Securities Class Action and the Shareholder Demand. On October 21, 2015, after responding to the SEC’s subpoena, the Company received a letter from the SEC notifying the Company that it had concluded its investigation of the Company and that it did not intend to recommend an enforcement action against the Company. The Company responded to the MSD’s subpoena on September 22, 2014 and October 8, 2014. On February 18, 2015, the Company received a second subpoena from the MSD requesting additional documents and information related to the same topics. The Company responded to this second subpoena on March 24, 2015. The Company has not further heard from the MSD since it responded to this last subpoena.

ACCRUED EXPENSES91

ACCRUED EXPENSES	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
ACCRUED EXPENSES
ACCRUED EXPENSES	7. ACCRUED EXPENSES Accrued expenses consisted of the following: September 30, December 31, (In thousands) 2017 2016 Bonus $ 595 $ 906 Payroll 158 126 Vacation 231 91 Severance 455 385 Other accrued expenses 345 451 Total accrued expenses $ 1,784 $ 1,959	6. ACCRUED EXPENSES Accrued expenses consisted of the following: December 31, 2016 2015 Accrued bonus $ $ — Accrued payroll Accrued vacation Accrued severance — Other accrued expenses Total accrued expenses $ $

LOAN PAYABLE92

LOAN PAYABLE	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
LOAN PAYABLE
LOAN PAYABLE	8. LOAN PAYABLE In October 2012, the Company entered into a loan agreement with the Massachusetts Development Finance Agency (“MassDev”). The loan agreement provided the Company with a $2.0 million line of credit from the Commonwealth of Massachusetts’ Emerging Technology Fund, with $200,000 designated to be used for working capital purposes and the remainder to be used for the purchase of capital equipment. The annual interest rate on the loan is fixed at 6.5% with interest-only payments for the first thirty months, commencing on November 1, 2012, and then equal installments of interest and principal over the next fifty-four months, until the final maturity of the loan on October 5, 2019. Commencing on May 1, 2015, equal monthly payments of $41,000 are due until loan maturity. For the remainder of the year ending December 31, 2017, $108,000 will be due. For the years ending December 31, 2018 and 2019, $452,000 and $400,000, respectively, will be due. In October 2012, as part of the agreement, the Company issued MassDev a warrant for the purchase of 9,037 shares of the Company’s common stock. The warrant has a seven-year term and is exercisable at $6.64 per share. The fair value of the warrant was determined to be $32,000 and is being amortized through interest expense over the life of the note. Amortization expense was $1,000 in each of the three-month periods ended September 30, 2017 and 2016, and $3,000 in each of the nine-month periods ended September 30, 2017 and 2016. This amortization expense was included in interest expense in the Company’s consolidated statements of operations. The equipment line of credit is secured by substantially all the assets of the Company, excluding intellectual property. Interest expense related to this loan for the three-month periods ended September 30, 2017 and 2016 was $17,000 and $24,000, respectively. Interest expense related to this loan for the nine-month periods ended September 30, 2017 and 2016 was $56,000 and $76,000, respectively.	9. LOAN PAYABLE In October 2012, the Company entered into a loan agreement with the Massachusetts Development Finance Agency (“MassDev”). The loan agreement provided the Company with a $2,000 line of credit from the Commonwealth of Massachusetts’s Emerging Technology fund, with $200 designated to be used for working capital purposes and the remainder to be used for the purchase of capital equipment. The annual interest rate on the loan is fixed at 6.5% with interest-only payments for the first thirty months, commencing on November 1, 2012, and then equal interest and principal payments over the next fifty‑four months, until the final maturity of the loan on October 5, 2019. Commencing on May 1, 2015, equal monthly principal payments of $41 are due until loan maturity. Therefore, for the years ending December 31, 2017, 2018, and 2019, principal payments of $423, $452, and $400, respectively, will be due. In October 2012, as part of the agreement, the Company issued MassDev a warrant for the purchase of 9,037 shares of the Company’s common stock. The warrant has a seven-year term and is exercisable at $6.64 per share. The fair value of the warrant was determined to be $32 and is being amortized through interest expense over the life of the note. For each of the years ended December 31, 2016, 2015, and 2014, amortization expense was $5, and was included in interest expense in the Company’s consolidated statements of operations. The equipment line of credit is secured by substantially all the assets of the Company, excluding intellectual property. Interest expense related to this loan was $99, $126, and $127 for the years ended December 31, 2016, 2015, and 2014, respectively. At December 31, loans payable consisted of the following: December 31, 2016 2015 MassDev Loan $ $ Less: current portion $ $

COMMON STOCK93

COMMON STOCK	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMON STOCK.
COMMON STOCK	9. COMMON STOCK The Company has authorized 100,000,000 shares of common stock, $0.00001 par value per share, of which 34,234,580 shares were issued and outstanding as of September 30, 2017 and 32,044,087 shares were issued and outstanding as of December 31, 2016. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 89,387 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $26,000. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 61,587 shares of common stock with a fair value of $154,000 to the Company’s 401(k) plan as a matching contribution. During the nine-month period ended September 30, 2017, the Company issued an aggregate of 17,750 shares of common stock under the Company’s Employee Stock Purchase Plan (the “ESPP”) and received cash proceeds of approximately $51,000. During the year ended December 31, 2016, the Company issued an aggregate of 135,205 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $191,000. During the year ended December 31, 2016, the Company issued an aggregate of 4,979 shares of common stock upon the cashless exercise of warrants. During the year ended December 31, 2016, the Company issued an aggregate of 37,528 shares of common stock with a fair value of $208,000 to the Company’s 401(k) plan as a matching contribution. During the year ended December 31, 2016, the Company issued an aggregate of 16,729 shares of common stock under the ESPP and received cash proceeds of $91,000. In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29.9 million. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants contain a cashless exercise feature whereby shares are withheld to cover the exercise cost and the warrant holder receives a net issuance of the remaining shares. The Company is utilizing the net proceeds from the offering to fund ongoing clinical trials and for general corporate purposes.	11. COMMON STOCK The Company has authorized 100,000,000 shares of common stock, $0.00001 par value per share, of which 32,044,087, shares were issued and outstanding as of December 31, 2016 and 27,555,948 shares were issued and outstanding as of December 31, 2015. During the year ended December 31, 2016, the Company issued an aggregate of 135,205 shares of common stock upon the exercise of stock options and received cash proceeds from such exercises of $191. During the year ended December 31, 2016, the Company issued an aggregate of 4,979 shares of common stock upon the cashless exercise of warrants. During the year ended December 31, 2016, the Company issued an aggregate of 37,528 shares of common stock with a fair value of $208 to the Company’s 401(k) plan as a matching contribution. During the year ended December 31, 2016, the Company issued an aggregate of 16,729 shares of common stock under the Company’s Employee Stock Purchase Plan (the “ESPP”) and received cash proceeds of $91. In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29,905. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants contain a cashless exercise feature whereby shares are withheld to cover the exercise cost and the warrant holder receives a net issuance of the remaining shares. The Company intends to use the net proceeds from the offering to fund ongoing clinical trials and for general corporate purposes. During the year ended December 31, 2015, the Company issued an aggregate of 316,177 shares of common stock upon the exercise of stock options, including stock options to purchase 52,224 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 14,961 shares of common stock and stock options to purchase 301,216 shares of common stock exercised for cash, providing cash proceeds of $1,068. During the year ended December 31, 2015, the Company issued an aggregate of 1,379,575 shares of common stock upon the exercise of warrants, including warrants to purchase 40,955 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 25,052 shares of common stock and warrants to purchase 1,354,523 shares of common stock exercised for cash, providing net cash proceeds of $7,789. During the year ended December 31, 2015, the Company issued an aggregate of 17,437 shares of common stock with a fair value of $201 to the Company’s 401(k) plan as a matching contribution. In January 2015, the Company closed a registered direct offering of an aggregate of 2,000,000 shares of common stock, resulting in net proceeds of $11,038. As part of the adjustment to reflect the Company’s 1-for-4 reverse stock split on its common stock on April 8, 2015, the Company issued 1,514 shares of common stock to account for the fractional roundup of shareholders. In July 2015, the Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) pursuant to which the Company may issue and sell from time to time shares of common stock having aggregate sales proceeds of up to $50 million through an “at the market” equity offering program under which Cowen acts as the Company’s sales agent. The Company is required to pay Cowen a commission of 3% on the gross proceeds from the sale of shares of common stock under the Sales Agreement. The Company issued 388,245 shares of common stock under the Sales Agreement during the year ended December 31, 2015, providing cash proceeds of $3,442, net, through this facility. During the year ended December 31, 2014, the Company issued an aggregate of 132,900 shares of common stock upon the exercise of stock options and received cash proceeds of $212. During the year ended December 31, 2014, the Company issued an aggregate of 9,975 shares of common stock upon the exercise of warrants, including warrants to purchase 15,655 shares of common stock exercised through cashless exercise provisions resulting in the issuance of 6,903 shares of common stock and warrants to purchase 3,072 shares of common stock exercised for cash, providing cash proceeds of $12. During the year ended December 31, 2014, the Company issued an aggregate of 41,753 shares of common stock with a fair value of $173 to the Company’s 401(k) plan as a matching contribution. In January 2014, the Company issued 27,212 and 5,594 shares of common stock to Michael J. Astrue, the Company’s then-Interim Chief Executive Officer, and Gregory D. Perry, the Company’s then-Interim Chief Financial Officer, respectively, in lieu of executive cash bonuses. Such shares had an aggregate fair value of approximately $282. In December 2014, the Company issued 41,821 shares of common stock to certain employees of the Company in lieu of cash bonuses. Such shares had an aggregate fair value of approximately $195. During the year ended December 31, 2014, the Company closed an underwritten public offering of an aggregate of 3,500,312 shares of common stock and warrants to purchase up to an aggregate of 1,750,156 shares of common stock, at a price to the public of $4.60 per share of common stock and $0.00001 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $14,600. The warrants have a per share price of $5.75, or 125% of the public offering of the common stock, and expire on May 9, 2019. Common Stock Reserves As of December 31, 2016, the Company had the following reserves established for the future issuance of common stock as follows: Reserves for the exercise of warrants Reserves for the exercise of stock options Total Reserves

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
STOCK-BASED COMPENSATION.
STOCK-BASED COMPENSATION	10. STOCK-BASED COMPENSATION In 2007, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2007 Employee, Director and Consultant Stock Plan (the “2007 Plan”). Pursuant to the 2007 Plan, the Company’s Board of Directors (or committees and/or executive officers delegated by the Board of Directors) may grant incentive and nonqualified stock options to the Company’s employees, officers, directors, consultants and advisors. On October 26, 2010, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2010 Equity Incentive Plan (as subsequently amended, the “2010 Plan”). The 2010 Plan provided for grants of incentive stock options to employees, and nonqualified stock options and restricted common stock to employees, consultants, and non-employee directors of the Company. In April 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2015 Equity Incentive Plan (the “2015 Plan”). The 2015 Plan provides for grants of incentive stock options to employees, and nonqualified stock options, restricted common stock, restricted stock units, and stock appreciation rights to employees, consultants, and non-employee directors of the Company. As of September 30, 2017, the total number of shares authorized for issuance under the 2015 Plan was 4,322,355 shares, consisting of 4,000,000 initially approved under the 2015 Plan shares plus the 322,355 shares that remained available for grant under the 2010 Plan at the time of its termination. Upon approval of the 2015 Plan by the Company’s shareholders on June 16, 2015, the 2010 Plan was terminated and no additional shares or share awards have been subsequently granted under the 2010 Plan. Options issued under the 2007 Plan, 2010 Plan, and 2015 Plan (collectively, the “Plans”) are exercisable for up to 10 years from the date of issuance. As of September 30, 2017, there were outstanding options to purchase an aggregate of 2,256,351, 1,670,171 and 46,476 shares under the 2015 Plan, 2010 Plan, and 2007 Plan, respectively. As of December 31, 2016, there were outstanding options to purchase an aggregate of 1,222,085, 1,821,487 and 150,207 shares under the 2015 Plan, 2010 Plan, and 2007 Plan, respectively. In March 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the ESPP. The ESPP allows employees to buy company stock twice per year through after-tax payroll deductions at a discount from market. The Company’s Board of Directors initially authorized 187,500 shares for issuance under the ESPP. Commencing on the first day of the year ended December 31, 2016 and on the first day of each year thereafter during the term of the ESPP, the number of shares of common stock reserved for issuance shall be increased by the lesser of (i) 1% of the Company’s outstanding shares of common stock on such date, (ii) 50,000 shares, or (iii) a lesser amount determined by the Board of Directors. Under the terms of the ESPP, in no event shall the aggregate number of shares reserved for issuance during the term of the ESPP exceed 1,250,000 shares. As of September 30, 2017 and December 31, 2016, there were 253,021 and 220,771 shares reserved for issuance under the ESPP, respectively. In January 2017, 7,986 shares that were purchased in the offering period commencing on July 1, 2016 and ending on Decemer 31, 2016 were issued under the ESPP. In July 2017, 9,764 shares that were purchased in the offering period commencing on January 1, 2017 and ending on June 30, 2017 were issued under the ESPP. The ESPP is considered a compensatory plan with the related compensation cost recognized over each six-month offering period. The compensation expense related to the ESPP for the three-month periods ended September 30, 2017 and 2016 was $3,000 and $12,000, respectively, and is included in share-based compensation expense. The share-based compensation expense related to the ESPP for the nine-month periods ended September 30, 2017 and 2016 was $16,000 and $39,000. Share-based compensation For the three-month periods ended September 30, 2017 and 2016, the Company recorded stock-based compensation expense of $1.0 million and $1.2 million, respectively, inclusive of the expense related to the ESPP. For the nine-month periods ended September 30, 2017 and 2016, the Company recorded stock-based compensation expense of $3.6 million and $3.6 million, respectively, inclusive of the expense related to the ESPP. Stock-based compensation expense for the three-month and nine-month periods ended September 30, 2017 includes $24,000 of expense related to a stock option modification. The Company granted 325,000 stock options to a non-employee consultant on July 5, 2017. The Company accounts for stock-based awards to non-employees in accordance with ASC Topic 505-50, Equity-Based Payments to Non-Employees (“ASC 505-50”). Stock-based awards to non-employees are remeasured at each reporting date until the options vest and expense is recognized on a straight-line basis as the services are being provided. The Company believes that the fair value of these awards is more reliably measurable than the fair value of the services rendered. The aggregate grant date fair value for the options granted on July 5, 2017 totaled approximately $764,000. The option award has a requisite service period of four years whereby the award vests 25% on the first anniversary of service, then ratably each month for the remaining 36 months, subject to continuous service by the individual. As of September 30, 2017, 325,000 options remained unvested. The fair value of the unvested options as of September 30, 2017 was estimated using a Black-Scholes model with the following assumptions: expected volatility of 108.5%, risk free interest rate of 2.3%, expected life of 9.8 years, and no dividends. Stock-based compensation expense for the three-month and nine-month periods ended September 30, 2017 includes $25,000 of expense related to the non-employee stock option grant, as a result of mark to market adjustments related to the non-employee. The stock options contain a termination clause whereby accelerated vesting occurs for 25% of the stock options if the Company does not hire the consultant as an employee on or before January 5, 2018. As discussed in Note 1, the Company adopted ASU 2016-09 on January 1, 2017. Prior to the adoption of this standard, the Company recognized share-based compensation, net of estimated forfeitures, over the vesting period of the grant. Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to recognize forfeitures as they occur. The Company continues to recognize share-based compensation expense over the vesting period of the grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $155,000 recorded to accumulated deficit on the balance sheet as of January 1, 2017. The Company estimates the fair value of each option award on the date of grant using the Black-Scholes option pricing model. The expected term of options granted under the Plans, all of which qualify as “plain vanilla,” is based on the average of the contractual term (10 years) and the vesting period (generally, 48 months). For non-employee options, the expected term is the contractual term. The risk-free rate is based on the yield of a U.S. Treasury security with a term consistent with the option. Stock options A summary of option activity as of September 30, 2017 and changes for the nine-month period then ended are presented below: Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2016 3,193,785 $ 7.52 Granted 1,439,463 $ 3.94 Forfeited (570,863) $ 6.54 Exercised (89,387) $ 0.29 Outstanding at September 30, 2017 3,972,998 $ 6.53 7.48 $ 53,894 Vested at September 30, 2017 2,146,415 $ 7.86 6.20 $ 53,894 The weighted average grant-date fair value of options granted during the nine months ended September 30, 2017 was $3.04 per share. The total fair value of options that vested in the three-month period ended September 30, 2017 was $1.1 million. The total fair value of options that vested in the nine months ended September 30, 2017 was $3.1 million. As of September 30, 2017, total unrecognized compensation expense related to non-vested share-based option compensation arrangements amounted to $6.5 million and is estimated to be recognized over a period of 2.53 years. Restricted Stock Units The following table summarizes the restricted stock unit (“RSU”) activity under the 2015 Equity Incentive Plan during the nine-month period ended September 30, 2017: Weighted-Average Number of Grants Grant Date Fair Value Unvested balance at December 31, 2016 — $ — Granted 295,000 1.25 Vested — — Forfeited — — Unvested balance at September 30, 2017 295,000 $ 1.25 On September 14, 2017, the Company issued 295,000 RSUs to employees. These RSUs are subject to time-based vesting. For the three-month period ended September 30, 2017, the Company recorded stock-based compensation expense of $9,000 related to the time-based RSUs, which the Company expects to recognize over a remaining weighted-average of 2.0 years. As of September 30, 2017, total unrecognized compensation expense related to non-vested RSUs amounted to $360,000. There are 295,000 RSUs subject to time-based vesting that remain unvested and outstanding at September 30, 2017.	13. STOCK OPTIONS In 2007, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2007 Employee, Director and Consultant Stock Plan (the “2007 Plan”). Pursuant to the 2007 Plan, the Company’s Board of Directors (or committees and/or executive officers delegated by the Board of Directors) may grant incentive and nonqualified stock options to the Company’s employees, officers, directors, consultants and advisors. As of December 31, 2016, there were options to purchase an aggregate of 150,207 shares of common stock outstanding under the 2007 Plan and no shares available for future grants under the 2007 Plan. On October 26, 2010, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved, the 2010 Equity Incentive Plan (as subsequently amended, the “2010 Plan”). The 2010 Plan provides for grants of incentive stock options to employees, and nonqualified stock options and restricted common stock to employees, consultants, and non‑employee directors of the Company. In April 2015, the Company’s Board of Directors adopted, and the Company’ shareholders subsequently approved, the 2015 Equity Incentive Plan (the “2015 Plan”). The 2015 Plan provides for grants of incentive stock options to employees, and nonqualified stock, restricted common stock, restricted stock units and stock appreciation rights to employees, consultants, and directors of the Company. As of December 31, 2016, the total number of shares authorized for issuance under the 2015 Plan was 4,322,355 shares, consisting of 4,000,000 shares initially approved under the 2015 Plan plus the 322,355 shares that remained available for grant under the 2010 Plan at the time of its termination. Upon approval of the 2015 Plan by the Company’s shareholders on June 16, 2016, the 2010 Plan was terminated and no additional shares or share awards have been subsequently granted under the 2010 Plan. As of December 31, 2016, there were outstanding options to purchase an aggregate of 1,222,085 and 1,821,487 shares of common stock under the 2015 Plan and 2010 Plan, respectively. Options issued under the Plans are exercisable for up to 10 years from the date of issuance. Options issued under the 2007 Plan, 2010 Plan, and 2015 Plan (collectively, the “Plans”) are exercisable for up to 10 years from the date of issuance. In March 2015, the Company’s Board of Directors adopted, and the Company’s shareholders subsequently approved the ESPP. The ESPP allows employees to buy company stock twice a year through after-tax payroll deductions at a discount from market. The Company’s Board of Directors initially authorized 187,500 shares for issuance under the ESPP. Commencing on the first day of the year ended December 31, 2016 and on the first day of each year thereafter during the term of the ESPP, the number of shares of common stock reserved for issuance shall be increased by the lesser of (i) 1% of the Company’s outstanding shares of common stock on such date, (ii) 50,000 shares or (iii) a lesser amount determined by the Board of Directors. Under the terms of the ESPP, in no event shall the aggregate number of shares reserved for issuance during the term of the ESPP exceed 1,250,000 shares. The 2015 ESPP is considered a compensatory plan with the related compensation cost recognized over each respective six month offering period. As of December 31, 2016, approximately $51 of employee payroll deductions had been withheld since July 1, 2016, the commencement of the offering period, and are included in accrued expenses in the accompanying balance sheet. The compensation expense related to the ESPP for the years ended December 31, 2016 and 2015 was $46 and $41, respectively, and is included in stock-based compensation expense. In January 2017, 7,986 shares that were purchased as of December 31, 2016 were issued under the ESPP. Share‑based compensation For the years ended December 31, 2016, 2015 and 2014, the Company recorded stock‑based compensation expense of $5,063, $4,666, and $2,730, respectively, net of forfeitures, inclusive of the expense related to the ESPP. The fair value of each option award is estimated on the date of grant using the Black‑Scholes option pricing model, which uses the assumptions noted in the following table. The Company uses historical data, as well as subsequent events occurring prior to the issuance of the financial statements, to estimate option exercises and employee terminations within the valuation model. The expected term of options granted under the Plans, all of which qualify as “plain vanilla,” is based on the average of the contractual term (10 years) and the vesting period (generally, 48 months). For non‑employee options, the expected term is the contractual term. The risk‑free rate is based on the yield of a U.S. Treasury security with a term consistent with the option. The assumptions used principally in determining the fair value of options granted were as follows: December 31, 2016 2015 2014 Risk-free interest rate 1.20 - 1.52% 1.53 - 1.89% 1.62 - 2.06% Expected dividend yield Expected term (employee grants) 5.99 years 6.00 years 6.03 years Expected volatility A summary of option activity as of December 31, 2016 and changes for the year then ended are presented below: Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2015 $ Granted $ Forfeited $ Exercised $ Outstanding at December 31, 2016 $ $ Vested at December 31, 2016 $ $ Vested and expected to vest at December 31, 2016 $ $ The weighted average grant‑date fair value of options granted during the years ended December 31, 2016, 2015, and 2014 was $5.23, $7.37, and $6.15 per share, respectively. The total fair value of options that vested in the years ended December 31, 2016, 2015, and 2014 was $5,179, $5,144, and $2,329, respectively. As of December 31, 2016, there was $5,630 of total unrecognized compensation expense related to non‑vested share‑based option compensation arrangements. The unrecognized compensation expense is estimated to be recognized over a period of 2.37 years at December 31, 2016.

WARRANTS95

WARRANTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
WARRANTS.
WARRANTS	11. WARRANTS The following table presents information about warrants to purchase common stock issued and outstanding at September 30, 2017: Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity 343,931 $ 5.60 10/26/2017 - 12/03/2017 2010 Equity 253,088 $ 4.00 10/26/2017 - 12/03/2017 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 48,507 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,798,246 Weighted average exercise price $ 8.75 Weighted average life in years 2.71 In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29.9 million. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock issued in the March 2016 offering, and expire on March 18, 2021. The warrants are immediately exercisable at the option of each holder, in whole or in part, in cash (except in the case of a cashless exercise as discussed below). The exercise price and number of shares of common stock issuable upon exercise of the warrants will be subject to adjustment in the event of any stock split, reverse stock split, stock dividend, recapitalization, or similar transaction, among other events as described in the warrants. In the event that shares of common stock underlying the warrants are no longer registered under the Securities Exchange Act of 1934, as amended, the holder may, in its sole discretion, exercise the warrant in whole or in part and, in lieu of making cash payment, elect instead to receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the warrant. The fair value of the warrants was estimated at $11.7 million using a Black-Scholes model with the following assumptions: expected volatility of 112.8%, risk free interest rate of 1.3%, expected life of five years, and no dividends. The Company assessed whether the warrants required accounting as derivatives. With the exception of the warrants issued in 2014 (see Note 12), the Company determined that the warrants were (1) indexed to the Company’s own stock and (2) classified in stockholders’ equity in accordance with FASB Accounting Standards Codification Topic 815, Derivatives and Hedging . As such, the Company concluded that the warrants meet the scope exception for determining whether the instruments require accounting as derivatives and accordingly are classified in stockholders’ equity. Warrant Exchange On August 10, 2017, the Company entered into exchange agreements with certain holders of the warrants, dated May 9, 2014, to exchange such warrants for shares of common stock equivalent to 3.5 times the number of shares of common stock issuable to such holders at the $3.87 exercise price under the warrants as of the date of the exchanges. The Company issued an aggregate of 2,021,419 shares of common stock to the warrant holders in exchange for their warrants to purchase an aggregate of 577,548 shares of common stock. The warrants exchanged in this transaction were subsequently cancelled and terminated. The Company re-measured the fair value of the exchanged warrants immediately prior to the exchange and recorded a $3.0 million derivatives loss on the statement of operations and a corresponding increase to the warrant liability on the balance sheet. The fair value of the warrants immediately prior to the exchange was equivalent to 2,021,419 shares of common stock at the Company’s closing stock price of $1.75 on August 9, 2017, the day before execution of the exchange. As a result of the exchange, the Company recorded the settlement by removing the derivative liability related to the exchanged warrants and recorded the issuance of common stock for $3.5 million. Following the warrant exchange, there are additional warrants, dated May 9, 2014, to purchase shares of common stock that remain outstanding (“Outstanding 2014 Warrants”). As a result of the Company’s issuance of common stock in exchange for certain of the liability warrants, the exercise price of the Outstanding 2014 Warrants was adjusted downwards from $3.87 per share to $0.83 per share and additional warrants were issued such that the Outstanding 2014 Warrants are currently exercisable for an aggregate of 48,507 shares of common stock. The Outstanding 2014 Warrants are subject to further adjustment in the event of sales of the Company’s common stock at a price per share less than the exercise price of the Outstanding 2014 Warrants then in effect (or securities convertible or exercisable into common stock at a conversion or exercise price less than the exercise price then in effect).	14. WARRANTS The following table presents information about warrants to purchase common stock issued and outstanding at December 31, 2016: Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity $ 10/26/2017 - 12/3/2017 2010 Equity $ 8/30/2017 - 12/3/2017 2012 Equity $ 10/5/2019 2014 Liability $ 5/9/2019 2016 Equity $ 3/18/2021 Total Weighted average exercise price $ Weighted average life in years In March 2016, the Company closed an underwritten public offering of an aggregate of 4,293,333 shares of common stock and warrants to purchase an aggregate of 2,146,666 shares of common stock, at a price to the public of $7.49 per share of common stock and $0.01 per warrant. The net proceeds to the Company, after deducting underwriting discounts and offering expenses, were approximately $29,905. The warrants have a per share exercise price of $10.00, or approximately 133% of the public offering price of the common stock, are exercisable immediately, and expire on March 18, 2021. The warrants are immediately exercisable, at the option of each holder, in whole or in part, in cash (except in the case of a cashless exercise as discussed below). The exercise price and number of shares of common stock issuable upon exercise of the warrants will be subject to adjustment in the event of any stock split, reverse stock split, stock dividend, recapitalization, or similar transaction, among other events as described in the warrants. In the event that shares of common stock underlying the warrants are no longer registered under the Securities Exchange Act of 1934, as amended, the holder may, in its sole discretion, exercise the warrant in whole or in part and, in lieu of making cash payment, elect instead to receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the warrant. The fair value of the warrants was estimated at $11,726 using a Black-Scholes model with the following assumptions: expected volatility of 112.82%, risk free interest rate of 1.34%, expected life of five years and no dividends. The Company assessed whether the warrants require accounting as derivatives. The Company determined that the warrants were (1) indexed to the Company’s own stock and (2) classified in stockholders’ equity in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 815, Derivatives and Hedging. As such, the Company has concluded the warrants meet the scope exception for determining whether the instruments require accounting as derivatives and should be classified in stockholders’ equity.

DERIVATIVE INSTRUMENTS96

DERIVATIVE INSTRUMENTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
DERIVATIVE INSTRUMENTS
DERIVATIVE INSTRUMENTS	12. DERIVATIVE INSTRUMENTS The Outstanding 2014 Warrants have anti-dilution protection provisions and, under certain conditions, require the Company to automatically reprice the warrants. Accordingly, these warrants are accounted for as derivative warrant liabilities. The Company used the Binomial Lattice option pricing model and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments. Changes in the fair value of the derivative warrant liabilities are recognized currently in the Company’s consolidated statement of operations as a non-cash derivative gain or loss. For the three-month periods ended September 30, 2017 and 2016, the Company recorded a loss of $3.1 million and $336,000, respectively, in other income (expense) in the statement of operations. For the nine-month periods ended September 30, 2017 and 2016, the Company recorded a loss of $2.3 million and $788,000, respectively, in other income (expense) in the statement of operations. The fair value of these derivative instruments, net of the impact of the August 2017 warrant exchange discussed above, at September 30, 2017 and December 31, 2016 was $41,000 and $1.3 million, respectively, and included as a derivative warrant liability in current liabilities on the balance sheet. The assumptions used principally in determining the fair value of the warrants were as follows: September 30, December 31, 2017 2016 Risk free interest rate 1.5 % % Expected dividend yield — % — % Contractual term (in years) 1.6 Expected volatility 86 % 89 % The primary underlying risk exposure pertaining to the warrants is the change in fair value of the underlying common stock for each reporting period. The table below presents the changes in the derivative warrant liability during the three-month and nine-month periods ended September 30, 2017 and 2016: Three Months Ended September 30, 2017 2016 Balance at June 30, $ 519 $ 2,359 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants 30 336 Balance at September 30, $ 41 $ 2,695 Nine Months Ended September 30, 2017 2016 Balance at December 31, $ 1,314 $ 1,907 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants (765) 788 Balance at September 30, $ 41 $ 2,695 The Company’s March 2016 public offering resulted in a repricing of the existing warrants. The warrants’ prices were decreased from $5.75 per share to $3.87 per share. In addition, the number of warrants increased from 395,716 to 587,950. The Company’s August 2017 warrant exchange resulted in a repricing of the Outstanding 2014 Warrants. The exercise price of the Outstanding 2014 Warrants was decreased from $3.87 per share to $0.83 per share. In addition, the number of Outstanding 2014 Warrants increased from 10,403 to 48,507. The decrease in the liability for the nine-month period ended September 30, 2017 was primarily driven by the impact of the warrant exchange and to a lesser degree due to the decrease in the fair value of the underlying stock price since December 31, 2016.	12. DERIVATIVE INSTRUMENTS The warrants issued in connection with the Company’s May 2014 public offering to purchase 1,750,156 shares of the common stock (see Note 11) have anti-dilution protection provisions and, under certain conditions, require the Company to automatically reprice the warrants. Accordingly, these warrants are accounted for as derivative warrant liabilities. The Company used the Binomial Lattice option pricing model and assumptions that consider, among other factors, the fair value of the underlying stock, risk-free interest rate, volatility, expected life, and dividend rates in estimating fair value for the warrants considered to be derivative instruments. Changes in the fair value of the derivative financial instruments are recognized currently in the Company’s consolidated statement of operations as a derivative gain or loss. The warrant derivative gains or losses are non-cash expenses and for the years ended December 31, 2016, 2015, and 2014, a (gain) loss of $(593), $10,804 and $376, respectively, were included in other income (expense) in the Company’s consolidated statement of operations. The fair value of these derivative instruments at December 31, 2016 and 2015 was $1,314 and $1,907, respectively, and was included as a derivative warrant liability in current liabilities. The assumptions used principally in determining the fair value of warrants were as follows: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.20 % 0.65 % 1.47 % Expected dividend yield % % % Contractual term years years years Expected volatility % % % The primary underlying risk exposure pertaining to the warrants is the change in fair value of the underlying common stock for each reporting period. The table below presents the changes in derivative warrant liability during the years ended December 31, 2016, 2015, and 2014: Year Ended December 31, 2016 2015 2014 Balance at beginning of year $ $ $ — Issuance of warrants — — (Decrease) increase in the fair value of the warrants Fair value of derivative warrant liability reclassified to additional paid in capital — — Balance at end of year $ $ $

RESTRUCTURING

RESTRUCTURING	9 Months Ended
	Sep. 30, 2017
RESTRUCTURING
RESTRUCTURING	13. RESTRUCTURING On August 28, 2017, the Company implemented a strategic restructuring to refocus the Company’s efforts on re-opening enrollment for and completing the INSPIRE clinical trial. During the three months ended September 30, 2017, the Company recorded $738,000 in restructuring expenses, including employee severance benefits and related costs, as well as a write-off of certain fixed assets. The Company expects to incur an additional $94,000 in general and administrative expenses and $67,000 in research and development expenses associated with this restructuring. The following table summarizes the restructuring costs by category for the periods indicated: Three and Nine Months Ended September 30, 2017 Cash Non Cash (1) Total Research and development $ 602,000 $ 41,000 $ 643,000 General and administrative 95,000 — 95,000 $ 697,000 $ 41,000 $ 738,000 (1) The non-cash restructuring expenses represent write-offs of certain fixed assets in connection with the restructuring. The write-offs were recorded as a charge to research and development expense on the statement of operations. The following table summarizes the restructuring reserve for the periods indicated: Three and Nine Months Ended September 30, 2017 Restructuring reserve beginning balance $ — Cash restructuring expenses incurred during the period 697,000 Amounts paid during the period (348,000) Restructuring reserve ending balance $ 349,000

NET LOSS PER COMMON SHARE

NET LOSS PER COMMON SHARE	9 Months Ended
	Sep. 30, 2017
NET LOSS PER COMMON SHARE
NET LOSS PER COMMON SHARE	14. NET LOSS PER COMMON SHARE Basic and diluted net loss per share of common stock has been computed by dividing net loss by the weighted average number of shares outstanding during the period. Diluted net income per share of common stock is computed by dividing net income by the weighted average number of shares outstanding plus the dilutive effect, if any, of outstanding stock options, warrants and convertible securities. In a net loss period, options, warrants related to the Company’s May 2014 capital raise, which include an antidilution provisions, and convertible securities are anti-dilutive and therefore excluded from diluted loss per share calculations. For the three-month and nine-month periods ended September 30, 2017 and 2016, the following potentially dilutive securities were not included in the computation of net loss per share because the effect would be anti-dilutive: September 30, 2017 2016 Stock options 3,972,998 3,152,775 Unvested restricted stock units 295,000 — Warrants 2,798,246 3,484,445 7,066,244 6,637,220

SUBSEQUENT EVENTS99

SUBSEQUENT EVENTS	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	15. SUBSEQUENT EVENTS The Company has evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its financial statements or disclosures.	20. SUBSEQUENT EVENTS The Company has evaluated all events or transactions that occurred after December 31, 2016. In the judgment of management, there were no material events that impacted the consolidated financial statements or disclosures.

NATURE OF OPERATIONS, BASIS 100

NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“GAAP”) consistent with those applied in, and should be read in conjunction with, the Company’s audited financial statements and related footnotes for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K as filed with the United States Securities and Exchange Commission (“SEC”) on March 10, 2017. The unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the Company’s financial position as of September 30, 2017 and its results of operations and cash flows for the interim period presented, and are not necessarily indicative of results for subsequent interim periods or for the full year. The interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements, as allowed by the relevant SEC rules and regulations; however, the Company believes that its disclosures are adequate to ensure that the information presented is not misleading.
Reclassifications	Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the current period presentation. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for the prior period presented.	Reclassifications Certain amounts in prior period financial statements have been reclassified to conform to the current period presentation. Marketable securities were previously included in cash and cash equivalents on the balance sheet but are now reflected as a separate line item on the balance sheet. Cash activities related to the purchase and sale of marketable securities have been reflected within investing activities in the statement of cash flows. The unrealized gains or losses related to these marketable securities are immaterial for all periods presented.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company adopted this standard on January 1, 2017. Prior to adoption, the Company recognized share-based compensation, net of estimated forfeitures, over the vesting period of the grant. Upon adoption of ASU 2016-09, the Company elected to change its accounting policy to recognize forfeitures as they occur. The Company continues to recognize share-based compensation expense over the vesting period of the grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $155,000 recorded to accumulated deficit on the balance sheet as of January 1, 2017. Prior to January 1, 2017, the Company recognized the excess tax benefits of stock-based compensation expense as additional paid-in capital and tax deficiencies of stock-based compensation expense in the income tax provision or as additional paid-in capital to the extent that there were sufficient recognized excess tax benefits previously recognized. Previously, the excess tax benefits reduced taxes payable prior to being recognized as an increase in additional paid-in capital, and therefore the Company had not recognized certain deferred tax assets that could be attributed to tax deductions. As a result of the adoption, the deferred tax assets associated with certain net operating losses increased, which was offset by a corresponding increase in the valuation allowance and therefore the adoption of the tax-related guidance in this standard did not have an impact on our consolidated financial statements for the period ended September 30, 2017. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230) : Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”) to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this new guidance, modification accounting is required if the fair value, vesting conditions, or classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In July 2017, the FASB issued ASU No. 2017-11, Part I. Accounting for Certain Financial Instruments with Down Round Features and Part II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I of this guidance applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down round features. Part II of this guidance replaces the indefinite deferrals for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities. ASU 2017-11 is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company has concluded that the adoption of this ASU will not have a material impact on the financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients , which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration, and the presentation of sales and other similar taxes collected from customers. These standards are effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. Currently, this guidance is not applicable to the Company as the Company does not generate revenue. However, the Company will evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue.	Recent accounting pronouncements In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements—Going Concern , on disclosure of uncertainties about an entity's ability to continue as a going concern. This guidance addresses management's responsibility in evaluating whether there is substantial doubt about a company's ability to continue as a going concern and to provide related footnote disclosures. The guidance is effective for fiscal years ending after December 15, 2016 including interim reporting periods within each annual reporting period, with early adoption permitted. The Company adopted this guidance as of December 31, 2016. The adoption of ASU 2014-15 impacted presentation and disclosure only and did not have any impact on the Company’s financial position or results of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) to provide updated guidance on revenue recognition. ASU 2014-09 requires a company to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies may need to use more judgment and make more estimates than under today’s guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price, and allocating the transaction price to each separate performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date , which deferred the effective date of ASU 2014-09 by one year. Accordingly, ASU 2014-09 is effective for public business entities for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606) : Principal versus Agent Considerations (Reporting Revenue Gross Versus Net) , which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing , which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date of December 15, 2017. Currently, this guidance is not applicable to the Company as the Company is still in the research and development stage. However, the Company will continue to evaluate the impact of adopting ASU 2014-09 on its consolidated financial statements when the Company begins to generate revenue. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) . The guidance in this ASU supersedes the leasing guidance in Topic 840, Leases . Under the new guidance, lessees are required to recognize lease assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance leases or operating leases, with classification affecting the pattern of expense recognition in the statement of operations. The new standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Accounting (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes, forfeitures, and intrinsic value accounting for private entities. ASU 2016-09 is effective for annual reporting periods beginning after December 15, 2016, including interim reporting periods within each annual reporting period. The Company will adopt this standard on January 1, 2017, and the adoption is not expected to have a material impact on the Company’s financial statements. In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”) to address how certain cash receipts and cash payments are presented and classified in the statement of cash flows in an effort to reduce existing diversity in practice. The update includes eight specific cash flow issues and provides guidance on the appropriate cash flow presentation for each. ASU 2016-15 is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company does not expect the adoption of this guidance to have a material impact on the financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash to clarify how entities should present restricted cash and restricted cash equivalents in the statement of cash flows. Under this new update, entities are required to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows. This guidance will be applied retrospectively and is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within each annual reporting period. The Company is currently evaluating the impact of the adoption of this ASU on the financial statements.

CASH AND CASH EQUIVALENTS (Tabl

CASH AND CASH EQUIVALENTS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
CASH AND CASH EQUIVALENTS.
Schedule of cash and cash equivalents	September 30, December 31, (In thousands) 2017 2016 Cash $ (90) $ 111 Money market funds 16,524 21,353 Total cash and cash equivalents $ 16,434 $ 21,464	December 31, 2016 2015 Cash $ $ Money market funds Total cash and cash equivalents $ $

MARKETABLE SECURITIES (Table102

MARKETABLE SECURITIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
MARKETABLE SECURITIES
Schedule of short-term investments in marketable securities by category	(In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2017 Current (due within 1 year or less) Corporate obligations 734 — — 734 Total $ 734 $ — $ — $ 734 December 31, 2016 Current (due within 1 year or less) Commercial paper 4,240 — — 4,240 Corporate obligations 7,337 — — 7,337 Total $ 11,577 $ — $ — $ 11,577	Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2016 Commercial paper Corporate obligations — — Total $ $ — $ — $ December 31, 2015 Commercial paper Corporate obligations — — Total $ $ — $ — $

FAIR VALUE OF ASSETS AND LIA103

FAIR VALUE OF ASSETS AND LIABILITIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
FAIR VALUE OF ASSETS AND LIABILITIES
Summary of assets and liabilities measured at fair value on a recurring basis	At September 30, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 16,524 $ — $ — $ 16,524 Marketable securities — 734 — 734 Derivative warrant liability $ — $ (41) $ — $ (41) At December 31, 2016 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 21,353 $ — $ — $ 21,353 Marketable securities — 11,577 — 11,577 Derivative warrant liability $ — $ (1,314) $ — $ (1,314)	At December 31, 2016 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $ At December 31, 2015 Level 1 Level 2 Level 3 Fair Value Cash equivalents $ $ — $ — $ Marketable securities — — Derivative warrant liability $ — $ $ — $

COMMITMENTS AND CONTINGENCIE104

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
COMMITMENTS AND CONTINGENCIES
Future minimum rent commitments	Pursuant to the terms of the non-cancelable lease agreements in effect at September 30, 2017, the future minimum rent commitments are as follows (in thousands): Year Ended December 31, 2017 314 2018 1,378 2019 1,945 2020 2,003 2021 2,063 Thereafter 3,941 Total $ 11,644	Year Ended December 31, 2017 2018 Total $

ACCRUED EXPENSES (Tables)105

ACCRUED EXPENSES (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
ACCRUED EXPENSES
Summary of accrued expenses	September 30, December 31, (In thousands) 2017 2016 Bonus $ 595 $ 906 Payroll 158 126 Vacation 231 91 Severance 455 385 Other accrued expenses 345 451 Total accrued expenses $ 1,784 $ 1,959	December 31, 2016 2015 Accrued bonus $ $ — Accrued payroll Accrued vacation Accrued severance — Other accrued expenses Total accrued expenses $ $

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
STOCK-BASED COMPENSATION.
Summary of option activity	Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2016 3,193,785 $ 7.52 Granted 1,439,463 $ 3.94 Forfeited (570,863) $ 6.54 Exercised (89,387) $ 0.29 Outstanding at September 30, 2017 3,972,998 $ 6.53 7.48 $ 53,894 Vested at September 30, 2017 2,146,415 $ 7.86 6.20 $ 53,894	Weighted Weighted Average Average Remaining Aggregate Exercise Contractual Intrinsic Options Shares Price Term in Years Value Outstanding at December 31, 2015 $ Granted $ Forfeited $ Exercised $ Outstanding at December 31, 2016 $ $ Vested at December 31, 2016 $ $ Vested and expected to vest at December 31, 2016 $ $
Summary of restricted stock unit activity	Weighted-Average Number of Grants Grant Date Fair Value Unvested balance at December 31, 2016 — $ — Granted 295,000 1.25 Vested — — Forfeited — — Unvested balance at September 30, 2017 295,000 $ 1.25

WARRANTS (Tables)107

WARRANTS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
WARRANTS.
Schedule of information about warrants to purchase common stock issued and outstanding	Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity 343,931 $ 5.60 10/26/2017 - 12/03/2017 2010 Equity 253,088 $ 4.00 10/26/2017 - 12/03/2017 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 48,507 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,798,246 Weighted average exercise price $ 8.75 Weighted average life in years 2.71	Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2010 Equity $ 10/26/2017 - 12/3/2017 2010 Equity $ 8/30/2017 - 12/3/2017 2012 Equity $ 10/5/2019 2014 Liability $ 5/9/2019 2016 Equity $ 3/18/2021 Total Weighted average exercise price $ Weighted average life in years

DERIVATIVE INSTRUMENTS (Tabl108

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
DERIVATIVE INSTRUMENTS
Assumptions used in determining fair value of warrants	September 30, December 31, 2017 2016 Risk free interest rate 1.5 % % Expected dividend yield — % — % Contractual term (in years) 1.6 Expected volatility 86 % 89 %	Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.20 % 0.65 % 1.47 % Expected dividend yield % % % Contractual term years years years Expected volatility % % %
Changes in derivative warrant liability	Three Months Ended September 30, 2017 2016 Balance at June 30, $ 519 $ 2,359 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants 30 336 Balance at September 30, $ 41 $ 2,695 Nine Months Ended September 30, 2017 2016 Balance at December 31, $ 1,314 $ 1,907 Increase in derivative liability prior to warrant exchange 3,029 — Reduction in derivative liability due to warrant exchange (3,537) — Increase (decrease) in the fair value of warrants (765) 788 Balance at September 30, $ 41 $ 2,695	Year Ended December 31, 2016 2015 2014 Balance at beginning of year $ $ $ — Issuance of warrants — — (Decrease) increase in the fair value of the warrants Fair value of derivative warrant liability reclassified to additional paid in capital — — Balance at end of year $ $ $

RESTRUCTURING (Tables)

RESTRUCTURING (Tables)	9 Months Ended
	Sep. 30, 2017
RESTRUCTURING
Schedule of restructuring costs by category	Three and Nine Months Ended September 30, 2017 Cash Non Cash (1) Total Research and development $ 602,000 $ 41,000 $ 643,000 General and administrative 95,000 — 95,000 $ 697,000 $ 41,000 $ 738,000 (1) The non-cash restructuring expenses represent write-offs of certain fixed assets in connection with the restructuring. The write-offs were recorded as a charge to research and development expense on the statement of operations.
Schedule of restructuring reserve	Three and Nine Months Ended September 30, 2017 Restructuring reserve beginning balance $ — Cash restructuring expenses incurred during the period 697,000 Amounts paid during the period (348,000) Restructuring reserve ending balance $ 349,000

NET LOSS PER COMMON SHARE (Tabl

NET LOSS PER COMMON SHARE (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
NET LOSS PER COMMON SHARE
Schedule of potentially dilutive securities were not included in the computation of net loss per share because effect would be anti-dilutive	September 30, 2017 2016 Stock options 3,972,998 3,152,775 Unvested restricted stock units 295,000 — Warrants 2,798,246 3,484,445 7,066,244 6,637,220	2016 2015 2014 Stock options Warrants

NATURE OF OPERATIONS, BASIS 111

NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS
Cash, cash equivalents and marketable securities	$ 17,200	$ 33,041	$ 20,194

NATURE OF OPERATIONS, BASIS 112

NATURE OF OPERATIONS, BASIS OF PRESENTATION AND RECENT ACCOUNTING PRONOUNCEMENTS, ASU 2016-09 (Details)	Jan. 01, 2017USD ($)
ASU 2016-09
New accounting pronouncements
Cumulative effect adjustment	$ 155,000

CASH AND CASH EQUIVALENTS (Deta

CASH AND CASH EQUIVALENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH AND CASH EQUIVALENTS.
Cash.		$ 111		$ 116
Cash	$ (90)
Money market funds	16,524	21,353		14,804
Total cash and cash equivalents	$ 16,434	$ 21,464	$ 25,261	$ 14,920	$ 13,459	$ 13,980

RESTRICTED CASH (Details)

RESTRICTED CASH (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted cash
Restricted cash	$ 361,000	$ 361,000	$ 361,000
Security deposit related to credit card account
Restricted cash
Restricted cash	50,000	50,000	50,000
Standby letter of credit in favor of a landlord
Restricted cash
Restricted cash	$ 311,000	$ 311,000	$ 311,000

MARKETABLE SECURITIES, SHORT-TE

MARKETABLE SECURITIES, SHORT-TERM INVESTMENT IN MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Marketable securities by category
Amortized Cost	$ 734	$ 11,577	$ 5,274
Fair Value	$ 734	$ 11,577
Maximum
Marketable securities by category
Maturity period	1 year	1 year
Commercial paper
Marketable securities by category
Amortized Cost		$ 4,240	349
Fair Value		4,240
Corporate obligations
Marketable securities by category
Amortized Cost	$ 734	7,337	$ 4,925
Fair Value	$ 734	$ 7,337

FAIR VALUES OF ASSETS AND LI116

FAIR VALUES OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets and liabilities measured at fair value on a recurring basis
Marketable securities	$ 734	$ 11,577
Derivative warrant liability	(41)	(1,314)	$ (1,907)
Recurring basis
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	16,524	21,353	14,804
Marketable securities	734	11,577	5,274
Derivative warrant liability	(41)	(1,314)	(1,907)
Recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	16,524	21,353	14,804
Recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Marketable securities	734	11,577	5,274
Derivative warrant liability	$ (41)	$ (1,314)	$ (1,907)

COMMITMENTS AND CONTINGENCIES,

COMMITMENTS AND CONTINGENCIES, LEASES (Details) - Cambridge Lease	Nov. 01, 2018	Sep. 17, 2012USD ($)ft²item	Sep. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Commitments
Lease space (in square feet) | ft²		26,150
Term of commercial lease		6 years 3 months
Number of options to extend lease | item		1
Term of lease extension option	5 years	5 years
Standby letter of credit		$ 311,000
Deferred rent liability			$ 238,000	$ 276,000	$ 391,000

COMMITMENTS AND CONTINGENCIE118

COMMITMENTS AND CONTINGENCIES, FUTURE MINIMUM RENT COMMITMENTS (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 19, 2017USD ($)	Jun. 13, 2017ft²	Mar. 31, 2016USD ($)ft²	Sep. 17, 2012ft²
Future minimum rent commitments
2,017	$ 314,000		$ 314,000
2,018	1,378,000		1,378,000
2,019	1,945,000		1,945,000
2,020	2,003,000		2,003,000
2,021	2,063,000		2,063,000
Thereafter	3,941,000		3,941,000
Total	11,644,000		11,644,000
Cambridge Lease
Future minimum rent commitments
2,017					$ 1,289,000
2,018					1,088,000
Total					2,377,000
Commitments
Total rent expense	$ 269,000	$ 210,000	828,000	$ 707,000	918,000	$ 1,123,000	$ 1,148,000
Lease space (in square feet) | ft²											26,150
Sublease income recorded as offset to rent expense					$ 230,000
CRISPR Therapeutics lease
Commitments
Lease space (in square feet) | ft²										5,233
Tenant security deposit and first month's rent										$ 51,000
Tenant security deposit										$ 26,000
Sublease income recorded as offset to rent expense			26,000	$ 77,000
Moderna Therapeutics Lease
Commitments
Lease space (in square feet) | ft²									5,233
Tenant security deposit								$ 55,000
Sublease income recorded as offset to rent expense			$ 82,000

COMMITMENTS AND CONTINGENCIE119

COMMITMENTS AND CONTINGENCIES, LITIGATION (Details)	Mar. 03, 2017shares	Dec. 06, 2013claim	Dec. 06, 2013item	Nov. 30, 2013USD ($)
InVivo Therapeutics Holdings Corp. v. Reynolds
Litigation
Value of damages sought worth of personal and/or exorbitant expenses | $				$ 500,000
Reynolds counterclaim against InVivo Therapeutics Holdings Corp.
Litigation
Number of breach of contract claims		2	2
Number of breach of covenant of good faith and fair-dealing claims		2	2
Equivalent number of common shares related to attempted exercise of certain stock options | shares	47,864

ACCRUED EXPENSES (Details)120

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
ACCRUED EXPENSES
Bonus	$ 595	$ 906
Payroll	158	126	$ 85
Vacation	231	91	81
Severance	455	385
Other accrued expenses	345	451	208
Total accrued expenses	$ 1,784	$ 1,959	$ 374

LOAN PAYABLE (Details)121

LOAN PAYABLE (Details) - USD ($)	May 01, 2015	Oct. 31, 2012	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans Payable
Fair value of warrants							$ 90,000	$ 251,000
Interest expense			$ 18,000	$ 32,000	$ 58,000	$ 117,000	$ 155,000	172,000	$ 136,000
Equipment Line of Credit
Loans Payable
Interest expense			17,000	24,000	56,000	76,000
MassDev
Loans Payable
Line of credit, maximum		$ 2,000,000
Line of credit for working capital purpose		$ 200,000
Fixed interest rate (as a percent)		6.50%
Period for interest-only payments		30 months
Period for charging equal installments of interest and principal		54 months
Maturity date		Oct. 5, 2019
Commencement date of monthly installments	May 1, 2015						May 1, 2015
Amount of monthly payment	$ 41,000
Future Principal payment due remainder of year : 2017			108,000		108,000
Future Principal payment due : 2018			452,000		452,000		$ 452,000
Future Principal payment due : 2019			400,000		400,000		400,000
MassDev | Common Stock
Loans Payable
Number of shares into which a warrant may be converted		9,037
MassDev | Warrants
Loans Payable
Warrant period		7 years
Exercise price of warrant (in dollars per share)		$ 6.64
Fair value of warrants		$ 32,000
MassDev | Warrants | Interest Expense
Loans Payable
Amortization of deferred financing costs			$ 1,000	$ 1,000	$ 3,000	$ 3,000	5,000	5,000	5,000
MassDev | Equipment Line of Credit
Loans Payable
Interest expense							$ 99,000	$ 126,000	$ 127,000

COMMON STOCK, PAR VALUE (Detail

COMMON STOCK, PAR VALUE (Details) - $ / shares	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Common stock, number of shares, par value and other disclosures
Common stock, authorized	100,000,000	100,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001	$ 0.00001
Common stock, issued	34,234,580	32,044,087	27,555,948
Common stock, outstanding	34,234,580	32,044,087	27,555,948

COMMON STOCK, TRANSACTIONS (Det

COMMON STOCK, TRANSACTIONS (Details) - USD ($)	1 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common stock disclosures
Proceeds from exercise of stock options		$ 26,000	$ 191,000	$ 191,000	$ 1,068,000	$ 212,000
Issuance of common stock to 401(k) plan				208,000	201,000	173,000
Proceeds from issuance of stock under ESPP		$ 51,000	91,000	91,000
Proceeds from issuance of common stock and warrants			$ 29,905,000	$ 29,905,000	$ 14,480,000	$ 14,618,000
Common Stock
Common stock disclosures
Issuance of common stock upon exercise of stock options (in shares)		89,387		135,205	316,177	132,900
Proceeds from exercise of stock options		$ 26,000		$ 191,000	$ 1,068,000	$ 212,000
Issuance of common stock upon cashless exercise of warrants (in shares)				4,979	25,052	6,903
Issuance of common stock to 401(k) plan (in shares)		61,587		37,528	17,437	41,753
Issuance of common stock to 401(k) plan		$ 154,000		$ 208,000	$ 201,000	$ 173,000
Stock issued under ESPP (in shares)		17,750		16,729
Proceeds from issuance of stock under ESPP		$ 51,000		$ 91,000
Issuance of stock in public offering (in shares)					2,388,245	3,500,312
Common Stock | Public Offering, March 2016
Common stock disclosures
Warrants for purchase of common stock (in shares)	2,146,666
Equity issuance (in price per unit)	$ 7.49
Warrants | Public Offering, March 2016
Common stock disclosures
Equity issuance (in price per unit)	0.01
Exercise price (in dollars per unit)	$ 10
Percentage of warrant exercises price over public offering price	133.00%
Common Stock And Warrants | Public Offering, March 2016
Common stock disclosures
Issuance of stock in public offering (in shares)	4,293,333
Proceeds from issuance of common stock and warrants	$ 29,900,000

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($)	Jul. 05, 2017	Jan. 01, 2017	Jul. 31, 2017	Jan. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2017	Apr. 30, 2015	Mar. 31, 2015
Stock options
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan								6,585,224			6,585,224
Stock-based compensation (in dollars)					$ 1,000,000		$ 1,200,000		$ 3,600,000	$ 3,600,000	$ 5,063,000	$ 4,666,000	$ 2,730,000
Stock Options
Stock options
Granted (in shares)									1,439,463		333,250
Expected term									10 years		10 years
Options to purchase common stock outstanding (in shares)					3,972,998	3,972,998		3,193,785	3,972,998		3,193,785	3,253,310		3,972,998
Vesting period									48 months		48 months
Expected volatility (as a percent)											111.00%	116.00%	124.00%
Expected life											5 years 11 months 27 days	6 years	6 years 11 days
Expected dividend yield (as a percent)											0.00%	0.00%	0.00%
Stock option modification (in dollars)					$ 24,000				$ 24,000
Maximum | Stock Options
Stock options
Risk-free interest rate (as a percent)											1.52%	1.89%	2.06%
2007 Plan
Stock options
Shares available for future grants								0			0
Expected term											10 years
Options to purchase common stock outstanding (in shares)					46,476	46,476		150,207	46,476		150,207			46,476
2007 Plan | Stock Options
Stock options
Expected term									10 years
2010 Plan
Stock options
Shares available for future grants					322,355	322,355		322,355	322,355		322,355			322,355
Granted (in shares)								0						0
Expected term											10 years
Options to purchase common stock outstanding (in shares)					1,670,171	1,670,171		1,821,487	1,670,171		1,821,487			1,670,171
2010 Plan | Stock options
Stock options
Expected term									10 years
2015 Plan
Stock options
Shares authorized for issuance					4,322,355	4,322,355		4,322,355	4,322,355		4,322,355			4,322,355	4,000,000
Expected term											10 years
Options to purchase common stock outstanding (in shares)					2,256,351	2,256,351		1,222,085	2,256,351		1,222,085			2,256,351
2015 Plan | Stock options
Stock options
Expected term									10 years
Employee Stock Purchase Plan
Stock options
Shares authorized for issuance																187,500
Percentage of outstanding shares reserved for future issuance									1.00%		1.00%
Increase in shares of common stock reserved for issuance (in shares)									50,000		50,000
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan					253,021	253,021	220,771	1,250,000	253,021	220,771	1,250,000			253,021
Offering Period									6 months		6 months
Stock issued under ESPP (in shares)			9,764	7,986
Stock-based compensation (in dollars)					$ 3,000		$ 12,000		$ 16,000	$ 39,000	$ 46,000	$ 41,000
Employee Stock Purchase Plan | Maximum
Stock options
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan					1,250,000	1,250,000			1,250,000					1,250,000
Plan Non-Employee Consultant | Stock Options
Stock options
Granted (in shares)	325,000
Stock-based compensation (in dollars)					$ 25,000				$ 25,000
Fair value of options granted (in dollars)	$ 764,000
Requisite service period	4 years
Non-vested options outstanding (in shares)					325,000	325,000			325,000					325,000
Expected volatility (as a percent)						108.50%
Risk-free interest rate (as a percent)						2.30%
Expected life						9 years 9 months 18 days
Expected dividend yield (as a percent)						0.00%
Stock options accelerated vesting (as a percent)						25.00%
Plan Non-Employee Consultant | Vesting period one | First anniversary of service | Stock Options
Stock options
Vesting (as a percent)	25.00%
Plan Non-Employee Consultant | Vesting period two | Ratably each month of remaining 36 months | Stock Options
Stock options
Requisite service period	36 months
Common Stock
Stock options
Stock issued under ESPP (in shares)									17,750		16,729
ASU 2016-09
Stock options
Cumulative effect adjustment (in dollars)		$ 155,000

STOCK-BASED COMPENSATION, SUMMA

STOCK-BASED COMPENSATION, SUMMARY OF OPTION ACTIVITY - (Details) - Stock Options $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / shares
Summary of option activity - Shares
Outstanding at the beginning of year (in shares) | shares		3,193,785	3,253,310
Granted (in shares) | shares		1,439,463	333,250
Forfeited (in shares) | shares		(570,863)	(257,570)
Exercised (in shares) | shares		(89,387)	(135,205)
Outstanding at the end of period (in shares) | shares	3,972,998	3,972,998	3,193,785	3,253,310
Vested at the end of period (in shares) | shares		2,146,415	1,811,996
Summary of option activity - Weighted Average Exercise Price
Outstanding at the beginning of year (in dollars per shares)		$ 7.52	$ 7.47
Granted (in dollars per shares)		3.94	6.27
Forfeited (in dollars per shares)		6.54
Exercised (in dollars per shares)		0.29	1.41
Outstanding at the end of period (in dollars per shares)	$ 6.53	6.53	7.52	$ 7.47
Vested at the end of period (in dollars per share)	$ 7.86	$ 7.86	$ 7.54
Option activity disclosures
Weighted Average Remaining Contractual Term - Outstanding		7 years 5 months 23 days	6 years 11 months 5 days
Weighted Average Remaining Contractual Term - Vested		6 years 2 months 12 days	6 years 3 months 26 days
Aggregate Intrinsic Value - Outstanding (in dollars) | $	$ 53,894	$ 53,894	$ 571
Aggregate Intrinsic Value - Vested (in dollars) | $	53,894	$ 53,894	$ 563
Stock Option
Weighted average grant-date fair value of options granted		$ 3.04	$ 5.23	$ 7.37	$ 6.15
Total fair value of options vested | $	1,100	$ 3,100	$ 5,179	$ 5,144	$ 2,329
Total unrecognized compensation expense | $	$ 6,500	$ 6,500	$ 5,630
Period for unrecognized compensation expense is estimated to be recognized		2 years 6 months 11 days	2 years 4 months 13 days

STOCK-BASED COMPENSATION, RESTR

STOCK-BASED COMPENSATION, RESTRICTED STOCK (Details) - USD ($)	Sep. 14, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based compensation
Stock-based compensation (in dollars)			$ 1,000,000	$ 1,200,000	$ 3,600,000	$ 3,600,000	$ 5,063,000	$ 4,666,000	$ 2,730,000
Restricted Stock Units (RSUs)
Number of Grants
Granted (in shares)					295,000
Unvested balance at		295,000	295,000		295,000
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)					$ 1.25
Unvested balance at (in dollars per share)		$ 1.25	$ 1.25		$ 1.25
Restricted stock units issued
Number of shares issued to employees (in shares)	295,000
Share-based compensation
Stock-based compensation (in dollars)			$ 9,000
Unrecognized compensation
Total unrecognized compensation expense		$ 360,000	$ 360,000		$ 360,000
Period for unrecognized compensation expense is estimated to be recognized		2 years

WARRANTS (Details)127

WARRANTS (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 11, 2017	Aug. 10, 2017	Aug. 09, 2017	Mar. 31, 2016	Feb. 29, 2016
Warrants to purchase common stock issued and outstanding
Number of Warrants			3,391,439
Weighted average exercise price			$ 7.94
Weighted average life in years			3 years 2 months 27 days
Proceeds from issuance of common stock and warrants		$ 29,905	$ 29,905	$ 14,480	$ 14,618
Fair value of warrants
Fair value of warrants			$ 90	$ 251
Common Stock
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)				2,388,245	3,500,312
Warrants
Warrants to purchase common stock issued and outstanding
Number of Warrants	2,798,246
Weighted average exercise price	$ 8.75
Weighted average life in years	2 years 8 months 16 days
Fair value of warrants
Expected volatility (as a percent)	86.00%		89.00%	100.00%	119.00%
Risk-free interest rate (as a percent)	1.50%		1.20%	0.65%	1.47%
Expected term (in years)	1 year 7 months 6 days		2 years 4 months 24 days	3 years 4 months 24 days	4 years 4 months 24 days
Expected dividend yield (as a percent)			0.00%	0.00%	0.00%
Warrants | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Number of Warrants							48,507	10,403
Warrant Exercise Price						$ 0.83	$ 3.87
Warrants for purchase of common stock (in shares)	48,507
Warrants | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Number of Warrants									587,950	395,716
Warrant Exercise Price									$ 3.87	$ 5.75
Equity | Derivative with Exercise Price One
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,010
Number of Warrants			343,931
Warrant Exercise Price			$ 5.60
Equity | Derivative with Exercise Price One | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date			Oct. 26, 2017
Equity | Derivative with Exercise Price One | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date			Dec. 3, 2017
Equity | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,010
Number of Warrants			306,838
Warrant Exercise Price			$ 4
Equity | Derivative with Exercise Price Two | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date			Aug. 30, 2017
Equity | Derivative with Exercise Price Two | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date			Dec. 3, 2017
Equity | Derivative with Exercise Price Three
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,012
Number of Warrants			6,054
Warrant Exercise Price			$ 6.64
Expiration date			Oct. 5, 2019
Equity | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,016
Number of Warrants			2,146,666
Warrant Exercise Price			$ 10
Expiration date			Mar. 18, 2021
Equity | Warrants | Derivative with Exercise Price One
Warrants to purchase common stock issued and outstanding
Warrants Issued Year	2,010
Number of Warrants	343,931
Warrant Exercise Price	$ 5.60
Equity | Warrants | Derivative with Exercise Price One | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date	Oct. 26, 2017
Equity | Warrants | Derivative with Exercise Price One | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date	Dec. 3, 2017
Equity | Warrants | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrants Issued Year	2,010
Number of Warrants	253,088
Warrant Exercise Price	$ 4
Equity | Warrants | Derivative with Exercise Price Two | Minimum
Warrants to purchase common stock issued and outstanding
Expiration date	Oct. 26, 2017
Equity | Warrants | Derivative with Exercise Price Two | Maximum
Warrants to purchase common stock issued and outstanding
Expiration date	Dec. 3, 2017
Equity | Warrants | Derivative with Exercise Price Three
Warrants to purchase common stock issued and outstanding
Warrants Issued Year	2,012
Number of Warrants	6,054
Warrant Exercise Price	$ 6.64
Expiration date	Oct. 5, 2019
Equity | Warrants | Derivative with Exercise Price Five
Warrants to purchase common stock issued and outstanding
Warrants Issued Year	2,016
Number of Warrants	2,146,666
Warrant Exercise Price	$ 10
Expiration date	Mar. 18, 2021
Liability | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,014
Number of Warrants			587,950
Warrant Exercise Price			$ 3.87
Expiration date			May 9, 2019
Liability | Warrants | Derivative with Exercise Price Four
Warrants to purchase common stock issued and outstanding
Warrants Issued Year	2,014
Number of Warrants	48,507
Warrant Exercise Price	$ 0.83
Expiration date	May 9, 2019

WARRANTS, EXCHANGE (Details)

WARRANTS, EXCHANGE (Details) $ / shares in Units, $ in Thousands	Aug. 10, 2017USD ($)item$ / sharesshares	Aug. 09, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Aug. 11, 2017$ / shares
Warrants
Derivatives gain (loss) | $			$ (3,059)	$ (336)	$ (2,264)	$ (788)	$ 593	$ (10,804)	$ (376)
Value of stock issued | $								$ 14,480	$ 7,770
Number of warrants outstanding							3,391,439
Warrants
Warrants
Number of warrants outstanding			2,798,246		2,798,246
Warrants | Derivative with Exercise Price Four
Warrants
Exercise price (in dollars per unit) | $ / shares	$ 3.87									$ 0.83
Number of shares into which a warrant may be converted			48,507		48,507
Number of warrants outstanding	48,507	10,403
Warrant Exchange Agreement
Warrants
Number of times for exchange of warrants | item	3.5
Exercise price (in dollars per unit) | $ / shares	$ 3.87
Number of shares into which a warrant may be converted	577,548
Derivatives gain (loss) | $		$ (3,000)
Value of stock issued | $	$ 3,500
Warrant Exchange Agreement | Common Stock
Warrants
Number of shares issued (in shares)	2,021,419
Stock price (in dollars per share) | $ / shares		$ 1.75
Warrant Exchange Agreement | Fair Value | Common Stock
Warrants
Number of shares issued (in shares)		2,021,419

DERIVATIVE INSTRUMENTS (Deta129

DERIVATIVE INSTRUMENTS (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2017	Jun. 30, 2016
Derivative instruments
Derivatives gain (loss)	$ (3,059,000)	$ (336,000)	$ (2,264,000)	$ (788,000)	$ 593,000	$ (10,804,000)	$ (376,000)
Derivative instruments, fair value	41,000		41,000		1,314,000	1,907,000
Warrants
Derivative instruments
Derivative instruments, fair value	41,000	2,695,000	41,000	2,695,000	1,314,000	1,907,000	7,224,000	$ 519,000	$ 2,359,000
Warrants | Other Income (Expense)
Derivative instruments
Derivatives gain (loss)	$ (3,100,000)	$ (336,000)	$ (2,300,000)	$ (788,000)	$ 593,000	$ (10,804,000)	$ (376,000)

DERIVATIVE INSTRUMENTS, FAIR VA

DERIVATIVE INSTRUMENTS, FAIR VALUE OF WARRANTS (Details) - Warrants	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair value of warrants
Risk-free interest rate (as a percent)	1.50%	1.20%	0.65%	1.47%
Expected dividend yield (as a percent)		0.00%	0.00%	0.00%
Expected term (in years)	1 year 7 months 6 days	2 years 4 months 24 days	3 years 4 months 24 days	4 years 4 months 24 days
Expected volatility (as a percent)	86.00%	89.00%	100.00%	119.00%

DERIVATIVE INSTRUMENTS, CHANGES

DERIVATIVE INSTRUMENTS, CHANGES IN DERIVATIVE WARRANT LIABILITY (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in Derivative Warrant Liability
Balance at beginning of year			$ 1,314	$ 1,907	$ 1,907
Balance at end of period	$ 41		41		1,314	$ 1,907
Warrants
Changes in Derivative Warrant Liability
Balance at beginning of year	519	$ 2,359	1,314	1,907	1,907	7,224
Increase in derivative liability prior to warrant exchange	3,029		3,029
Reduction in derivative liability due to warrant exchange	(3,537)		(3,537)
Increase (decrease) in the fair value of warrants	30	336	(765)	788	(593)	10,804	$ 376
Balance at end of period	$ 41	$ 2,695	$ 41	$ 2,695	$ 1,314	$ 1,907	$ 7,224

DERIVATIVE INSTRUMENTS, WARRANT

DERIVATIVE INSTRUMENTS, WARRANT PRICES (Details) - $ / shares	Sep. 30, 2017	Aug. 11, 2017	Aug. 10, 2017	Aug. 09, 2017	Dec. 31, 2016	Mar. 31, 2016	Feb. 29, 2016
Class of Warrant or Right
Number of warrants outstanding					3,391,439
Warrants
Class of Warrant or Right
Number of warrants outstanding	2,798,246
Derivative with Exercise Price Five | Warrants
Class of Warrant or Right
Exercise price (in dollars per unit)						$ 3.87	$ 5.75
Number of warrants outstanding						587,950	395,716
Derivative with Exercise Price Four | Warrants
Class of Warrant or Right
Exercise price (in dollars per unit)		$ 0.83	$ 3.87
Warrants issued (in shares)	48,507
Number of warrants outstanding			48,507	10,403

RESTRUCTURING (Details)

RESTRUCTURING (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)
Restructuring and related costs
Cash restructuring expenses incurred during the period	$ 738,000	$ 697,000
General and administrative
Restructuring and related costs
Cash restructuring expenses incurred during the period		95,000
Expected restructuring costs	94,000	94,000
Research and development
Restructuring and related costs
Cash restructuring expenses incurred during the period		602,000
Expected restructuring costs	$ 67,000	$ 67,000

RESTRUCTURING, COSTS BY CATEGOR

RESTRUCTURING, COSTS BY CATEGORY (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Restructuring costs by category
Restructuring costs, cash	$ 738,000	$ 697,000
Restructuring costs, non cash		41,000
Restructuring costs		738,000
Research and development
Restructuring costs by category
Restructuring costs, cash		602,000
Restructuring costs, non cash		41,000
Restructuring costs		643,000
General and administrative
Restructuring costs by category
Restructuring costs, cash		95,000
Restructuring costs		$ 95,000

RESTRUCTURING, RESERVE (Details

RESTRUCTURING, RESERVE (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Restructuring reserve
Cash restructuring expenses incurred during the period	$ 738,000	$ 697,000
Amounts paid during the period		(348,000)
Restructuring reserve, ending balance	$ 349,000	$ 349,000

NET LOSS PER COMMON SHARE (Deta

NET LOSS PER COMMON SHARE (Details) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	7,066,244	6,637,220	6,585,224	4,410,089	12,815,586
Stock options
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	3,972,998	3,152,775	3,193,785	3,253,310	2,606,737
Restricted Stock Units (RSUs)
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	295,000
Warrants
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	2,798,246	3,484,445	3,391,439	1,156,779	10,208,849