InVivo Therapeutics (NVIVQ) 10-K 12 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 09, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	INVIVO THERAPEUTICS HOLDINGS CORP.
Entity Central Index Key	1,292,519
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 86,007,844
Entity Common Stock, Shares Outstanding		38,054,036
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 12,910	$ 21,464
Restricted cash	361	361
Marketable securities		11,577
Prepaid expenses and other current assets	535	451
Total current assets	13,806	33,853
Property, equipment and leasehold improvements, net	157	510
Other assets	82	421
Total assets	14,045	34,784
Current liabilities:
Accounts payable	988	1,011
Loan payable, current portion	452	423
Derivative warrant liability	4	1,314
Deferred rent, current portion	30	141
Accrued expenses	1,638	1,959
Total current liabilities	3,112	4,848
Loan payable, net of current portion	400	852
Deferred rent, net of current portion	367	135
Other liabilities	56
Total liabilities	3,935	5,835
Commitments and contingencies (Note 16)
Stockholders' equity:
Common stock, $0.00001 par value, authorized 100,000,000 shares; 34,274,776 shares issued and outstanding at December 31, 2017; 32,044,087 shares issued and outstanding at December 31, 2016	1	1
Additional paid-in capital	194,016	185,955
Accumulated deficit	(183,907)	(157,007)
Total stockholders' equity	10,110	28,949
Total liabilities and stockholders' equity	$ 14,045	$ 34,784

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, authorized	100,000,000	100,000,000
Common stock, issued	34,274,776	32,044,087
Common stock, outstanding	34,274,776	32,044,087

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating expenses:
Research and development	$ 11,083	$ 12,557	$ 10,058
General and administrative	13,510	11,506	12,340
Total operating expenses	24,593	24,063	22,398
Operating loss	(24,593)	(24,063)	(22,398)
Other income (expense):
Interest income	189	187	60
Interest expense	(74)	(155)	(172)
Derivatives gain (loss)	(2,267)	593	(10,804)
Other income (expense), net	(2,152)	625	(10,916)
Net loss	$ (26,745)	$ (23,438)	$ (33,314)
Net loss per share, basic and diluted (in dollars per share)	$ (0.81)	$ (0.76)	$ (1.26)
Weighted average number of common shares outstanding, basic and diluted	32,950,068	31,025,585	26,461,374
Other comprehensive loss:
Net loss	$ (26,745)	$ (23,438)	$ (33,314)
Other comprehensive loss:
Comprehensive loss	$ (26,745)	$ (23,438)	$ (33,314)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Stockholders' Equity Attributable to Parent, Beginning Balance at Dec. 31, 2014	$ 1	$ 106,172	$ (100,255)	$ 5,918
Beginning Balance, (in shares) at Dec. 31, 2014	23,453,000
Share-based compensation expense		4,666		4,666
Issuance of common stock in public offerings		14,480		14,480
Issuance of stock in public offering (in shares)	2,388,245
Fair value of derivative warrant liability reclassified to additional paid-in capital		16,121		16,121
Issuance of common stock upon cashless exercise of warrants (in shares)	25,052
Issuance of common stock upon exercise of warrants		7,789		7,789
Issuance of common stock upon exercise of warrants (in shares)	1,379,575
Issuance of common stock upon exercise of stock options		1,068		1,068
Issuance of common stock upon exercise of stock options (in shares)	316,177
Fractional shares issued due to reverse stock split	1,514
Issuance of common stock to 401(k) plan	$ 201	201		201
Issuance of common stock to 401(k) plan (in shares)	17,437
Net loss			(33,314)	(33,314)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2015	$ 1	150,497	(133,569)	16,929
Ending Balance, (in shares) at Dec. 31, 2015	27,555,948
Share-based compensation expense		5,063		5,063
Issuance of common stock and warrants in public offerings, net of $2,040 issuance costs		29,905		29,905
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		191
Issuance of common stock upon exercise of stock options (in shares)	135,205
Issuance of common stock under ESPP		91		91
Issuance of common stock under ESPP (in shares)	16,729
Issuance of common stock to 401(k) plan	$ 208	208		208
Issuance of common stock to 401(k) plan (in shares)	37,528
Net loss			(23,438)	(23,438)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2016	$ 1	185,955	(157,007)	$ 28,949
Ending Balance, (in shares) at Dec. 31, 2016	32,044,087			32,044,087
Share-based compensation expense		4,106		$ 4,106
Issuance of common stock on warrant exchange		3,537		3,537
Issuance of common stock on warrant exchange (in shares)	2,021,419
Issuance of common stock for services (in shares)	350
Issuance of common stock upon exercise of warrants		3		3
Issuance of common stock upon exercise of warrants (in shares)	3,464
Issuance of common stock upon exercise of stock options		26		26
Issuance of common stock upon exercise of stock options (in shares)	89,387
Issuance of common stock under ESPP		51		51
Issuance of common stock under ESPP (in shares)	17,750
Issuance of common stock to 401(k) plan	$ 183	183		183
Issuance of common stock to 401(k) plan (in shares)	98,319
Net loss			(26,745)	(26,745)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2017	$ 1	194,016	(183,907)	$ 10,110
Ending Balance, (in shares) at Dec. 31, 2017	34,274,776			34,274,776
Cumulative Adjustment on adoption of ASU 2016-09. | ASU 2016-09		$ 155	$ (155)

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (26,745)	$ (23,438)	$ (33,314)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	395	548	684
Loss on impairment of fixed assets	41
Derivatives (gain) loss	2,267	(593)	10,804
Non-cash interest expense	5	5	5
Common stock issued to 401(k) plan	183	208	201
Share-based compensation expense	4,106	5,063	4,666
Non-cash investment (income) expense, net		98
Changes in operating assets and liabilities:
Restricted cash			61
Prepaid expenses	(89)	(267)	888
Other assets	321	(324)	3
Accounts payable	(23)	489	(48)
Accrued expenses and other liabilities	(144)	1,471	(279)
Net cash used in operating activities	(19,683)	(16,740)	(16,329)
Cash flows from investing activities:
Purchases of marketable securities	(8,256)	(18,916)	(5,274)
Sales of marketable securities	19,833	12,515
Purchases of property and equipment	(65)	(107)	(5)
Net cash (used in) provided by investing activities	11,512	(6,508)	(5,279)
Cash flows from financing activities:
Proceeds from exercise of stock options	26	191	1,068
Proceeds from issuance of stock under ESPP	51	91
Proceeds from exercise of warrants	3		7,789
Repayment of loan payable	(423)	(395)	(250)
Repayment of note payable			(18)
Repurchase of warrants	(40)
Proceeds from issuance of common stock and warrants		29,905	14,480
Net cash (used in) provided by financing activities	(383)	29,792	23,069
Increase (decrease) in cash and cash equivalents	(8,554)	6,544	1,461
Cash and cash equivalents at beginning of period	21,464	14,920	13,459
Cash and cash equivalents at end of period	12,910	21,464	14,920
Supplemental disclosure of cash flow information and non-cash transactions:
Cash paid for interest	71	103	121
Reclassification of derivative warrant liability to additional paid-in capital			16,121
Non-cash issuance of common stock for warrants	$ 3,537	$ 90	$ 251

NATURE OF OPERATIONS AND GOING

NATURE OF OPERATIONS AND GOING CONCERN	12 Months Ended
	Dec. 31, 2017
NATURE OF OPERATIONS AND GOING CONCERN
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, 2017, the Company has consolidated cash and cash equivalents of $12,910. 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, 2017 were prepared under the assumption that the Company will continue as a going concern. At December 31, 2017, the Company had cash and cash equivalents of $12,910. Given the Company’s development plans, we estimate cash resources will be sufficient to fund our operations into the fourth 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.

MARKETABLE SECURITIES

MARKETABLE SECURITIES	12 Months Ended
	Dec. 31, 2017
MARKETABLE SECURITIES.
MARKETABLE SECURITIES	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, 2017 and 2016: December 31, December 31, (In thousands) 2017 2016 Cash $ 23 $ 111 Money market funds 12,887 21,353 Marketable securities — 11,577 Total cash, cash equivalents and marketable securities $ 12,910 $ 33,041 As of December 31, 2017, the Company had no marketable securities. As of December 31, 2016, the Company’s investment portfolio consisted of cash, money market funds and 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. The following table summarizes the Company’s short-term investments in marketable securities by category as of December 31, 2016: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value 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 As of December 31, 2016, 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, 2017
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	4. PROPERTY AND EQUIPMENT Property and equipment, net consisted of the following: 2017 2016 Computer software and hardware $ 241 $ 606 Research and lab equipment 508 1,895 Leasehold improvements 431 431 Office equipment 796 796 Less accumulated depreciation and amortization (1,819) (3,218) Property and equipment, net $ 157 $ 510 Depreciation expense for the years ended December 31, 2017, 2016, and 2015 was $377, $536, and $672, respectively. Maintenance and repairs are charged to expense as incurred and any additions or improvements are capitalized. On August 28, 2017, the Company implemented a strategic restructuring and as a result wrote off $1,807 of fully depreciated assets and also recorded an impairment loss of $41 related to certain fixed assets in connection with the restructuring. The Company had no disposals for the years ended 2016.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2017
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 15). The Company is amortizing the license fee as a research and development expense over the 15–year term of the license. 2017 2016 Patent licensing fee $ 200 $ 200 Accumulated amortization (139) (122) $ 61 $ 78 For each of the years ended December 31, 2017, 2016, and 2015, the amortization expense was $17. Amortization expense is expected to be $17 per year for 2018, 2019, and 2020, and $10 in 2021.

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2017
ACCRUED EXPENSES
ACCRUED EXPENSES	6. ACCRUED EXPENSES Accrued expenses consisted of the following: December 31, (In thousands) 2017 2016 Bonus $ 62 $ 906 Payroll 79 126 Vacation 55 91 Severance 1,160 385 Other accrued expenses 282 451 Total accrued expenses $ 1,638 $ 1,959

FAIR VALUE OF ASSETS AND LIABIL

FAIR VALUE OF ASSETS AND LIABILITIES	12 Months Ended
	Dec. 31, 2017
FAIR VALUE OF ASSETS AND LIABILITIES
FAIR VALUE OF ASSETS AND LIABILITIES	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, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 12,887 $ — $ — $ 12,887 Marketable securities $ — $ — $ — $ — Derivative warrant liability $ — $ 4 $ — $ 4 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

LOAN PAYABLE

LOAN PAYABLE	12 Months Ended
	Dec. 31, 2017
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 $2,000 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, 2018, and 2019, principal payments of $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, 2017, 2016, and 2015 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 $71, $99, and $126 for the years ended December 31, 2017, 2016, and 2015, respectively. At December 31, loans payable consisted of the following: December 31, 2017 2016 MassDev Loan $ 852 $ 1,275 Less: current portion (452) (423) $ 400 $ 852

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2017
INCOME TAXES
INCOME TAXES	9. 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, 2017, the Company had U.S. federal and Massachusetts net operating loss carryforwards of $117,298 and $109,183, 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 $991 and $230, respectively, at December 31, 2017, which will begin to expire in 2022 unless previously utilized. On December 22, 2017, the Tax Cuts and Jobs Act (“the Act”) was enacted in the United States. The Act reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign sourced earnings. At December 31, 2017, we have not completed our accounting for the tax effects of enactment of the Act, including the effects on our existing deferred tax balances. In addition to the reduction in the federal corporate tax rate, which we have accounted for with provision estimates at December 31, 2017, we continue to analyze the provisions of tax reform that become effective for the Company in 2018 including the provisions related to Global Intangible Low Taxed Income, Foreign Derived Intangible Income, Base Erosion Anti-Abuse Tax, as well as other provisions which would limit the deductibility of future expenses. As a result of the Act, we remeasured certain deferred tax assets and liabilities based on the rates at which they are anticipated to reverse in the future, which is generally 21%. This resulted in a decrease to our gross deferred tax assets and a corresponding decrease in our valuation allowance of $15,521. Any items reported are done so using provisional amounts until the initial accounting required by the Act is complete. Additional time and resources are needed to ensure the correct implementation of the Act. Significant components of the Company’s net deferred tax assets are as follows: December 31, 2017 2016 Net operating loss carryforward $ 31,533 $ 37,245 Research and development credit carryforward 1,173 1,065 Stock-based compensation 2,828 5,235 Depreciation and amortization 71 31 Accrued expenses 357 264 Charitable contributions 27 63 Subtotal 35,989 43,903 Valuation allowance (35,989) (43,903) 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. During the year ending December 31, 2017, the Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting. As part of the adoption, the Company recorded through retained earnings additional deferred tax assets of $642 related to previously unrecognized tax losses with an equal and offsetting adjustment to the Company's valuation allowance. The net impact of the adoption on the Company's deferred tax assets was $0. In the years ended December 31, 2017 and 2016, the valuation allowance decreased by $7,914 and increased $9,406, respectively. The Company has no uncertain tax positions at December 31, 2017 and 2016 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, 2017 2016 2015 Statutory rate (34.0) % (34.0) % (34.0) % State taxes, net of benefit (4.7) % (5.4) % (3.5) % Permanent differences: Derivative losses 2.9 % (0.9) % 11.0 % Other 1.1 % 0.2 % 0.3 % Research and development tax credit (0.2) % (0.5) % (0.4) % Other 1.4 % 0.5 % 0.4 % Adoption of ASU 2016-09 7.4 % — % — % Increase / (decrease) in valuation reserve (32.0) % 40.1 % 26.2 % Change in federal tax rate 58.1 % — % — % Effective tax rate % % %

COMMON STOCK

COMMON STOCK	12 Months Ended
	Dec. 31, 2017
COMMON STOCK.
COMMON STOCK	10. COMMON STOCK The Company has authorized 100,000,000 shares of common stock, $0.00001 par value per share, of which 34,274,776, shares were issued and outstanding as of December 31, 2017 and 32,044,087 shares were issued and outstanding as of December 31, 2016. During the year ended December 31, 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. During the year ended December 31, 2017, the Company issued an aggregate of 3,464 shares of common stock upon the exercise of warrants and received cash proceeds from such exercises of $3. During the year ended December 31, 2017, the Company issued an aggregate of 98,319 shares of common stock with a fair value of $183 to the Company’s 401(k) plan as a matching contribution. During the year ended December 31, 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 $51. During the year ended December 31, 2017, the Company issued an aggregate of 2,021,419 shares of common stock to certain holders of warrants, dated May 9, 2014, in exchange for their warrants to purchase an aggregate of 577,548 shares of common stock. The Company did not receive any cash proceeds from the warrant exchanges (see Note 13). On January 25, 2018, we entered into a purchase and a registration rights agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”), under which we have the right to sell up to $15,000 in shares of our common stock, $0.00001 par value per share, to Lincoln Park over a twenty-four-month period, subject to certain limitations and conditions set forth in the purchase agreement and registration rights agreement. In accordance with the terms of the purchase agreement, at the time we signed the purchase agreement and the registration rights agreement, we issued 429,800 shares to Lincoln Park as consideration for its commitment to purchase shares of our common stock under the purchase agreement (see Note 19). 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, 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 ESPP and received cash proceeds of $91. 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 $50,000 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. Common Stock Reserves As of December 31, 2017, the Company had the following reserves established for the future issuance of common stock as follows: Reserves for the exercise of warrants 2,166,149 Reserves for the exercise of stock options 3,369,245 Reserves for the vesting of restricted stock units 500,000 Total Reserves 6,035,394

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	12 Months Ended
	Dec. 31, 2017
DERIVATIVE INSTRUMENTS
DERIVATIVE INSTRUMENTS	11. 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 10) 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. Through the date of the warrant exchange (Note 13), 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. As of December 31, 2017 the derivative warrant liability was insignificant. 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, 2017, 2016, and 2015, a (gain) loss of $2,267, $(593) and $10,804, 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, 2017 and 2016 was $4 and $1,314, 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: December 31, 2017 2016 2015 Risk-free interest rate 1.91 % 1.20 % 0.65 % Expected dividend yield % % % Contractual term years years years Expected volatility 82 % 89 % 100 % 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, 2017, 2016, and 2015: Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 1,314 $ 1,907 $ 7,224 Increase in derivative liability prior to warrant exchange 3,029 — — Reduction in derivative liability due to warrant exchange (3,537) — — Repurchase of warrants (40) — — Fair value of derivative warrant liability reclassified to additional paid in capital — — (16,121) Increase (decrease) in the fair value of warrants (762) (593) 10,804 Balance at end of year $ 4 $ 1,314 $ 1,907

STOCK OPTIONS

STOCK OPTIONS	12 Months Ended
	Dec. 31, 2017
STOCK OPTIONS.
STOCK OPTIONS	12. 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, 2017, there were options to purchase an aggregate of 46,476 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, 2017, 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, 2017, there were outstanding options to purchase an aggregate of 1,878,125 and 1,444,644 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, 2017, approximately $3 of employee payroll deductions had been withheld since July 1, 2017, 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, 2017 and 2016 was $14 and $46, respectively, and is included in stock-based compensation expense. In January 2018, 4,691 shares that were purchased as of December 31, 2017 were issued under the ESPP. Share‑based compensation For the years ended December 31, 2017, 2016 and 2015, the Company recorded stock‑based compensation expense of $4,106, $5,063 and $4,666, 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 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, 2017 2016 2015 Risk-free interest rate 1.69 - 2.36% 1.20 - 1.52% 1.53 - 1.89% Expected dividend yield Expected term (employee grants) 6.22 Years 5.99 years 6.00 years Expected volatility A summary of option activity as of December 31, 2017 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, 2016 3,193,785 $ 7.52 Granted 1,439,463 $ 3.94 Forfeited (1,174,616) $ 6.40 Exercised (89,387) $ 0.29 Outstanding at December 31, 2017 3,369,245 $ 6.57 7.14 $ 22 Vested at December 31, 2017 2,224,246 $ 7.54 6.22 $ 22 Vested and expected to vest at December 31, 2017 3,369,245 $ 6.57 7.14 $ 22 The weighted average grant‑date fair value of options granted during the years ended December 31, 2017, 2016 and 2015 was $2.54, $5.23, and $7.37 per share, respectively. The total fair value of options that vested in the years ended December 31, 2017, 2016, and 2015 was $3,837, $5,179, and $5,144, respectively. As of December 31, 2017, there was $3,516 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 2.38 years at December 31, 2017. Restricted Stock Unit The following table summarizes the restricted stock unit (“RSU”) activity under the 2015 Equity Incentive Plan during the year ended December 31, 2017: Weighted-Average Number of Grants Grant Date Fair Value Unvested balance at December 31, 2016 — $ — Granted 595,000 1.06 Vested — — Forfeited (95,000) 1.25 Unvested balance at December 31, 2017 500,000 $ 1.03 For the year Ended December 31, 2017, the Company issued 595,000 RSUs to employees. These RSUs are subject to time-based vesting. For the year ended December 31, 2017, the Company recorded stock-based compensation expense of $40 related to the time-based RSUs. As of December 31, 2017, total unrecognized compensation expense related to non-vested RSUs amounted to $474, which the Company expects to recognize over a remaining weighted-average of 2.95 years. There are 500,000 RSUs subject to time-based vesting that remain unvested and outstanding at December 31, 2017.

WARRANTS

WARRANTS	12 Months Ended
	Dec. 31, 2017
WARRANTS.
WARRANTS	13. WARRANTS The following table presents information about warrants to purchase common stock issued and outstanding at December 31, 2017: Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 13,429 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,166,149 Weighted average exercise price $ 9.93 Weighted average life in years 3.20 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. At inception, 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. Warrant Exchange On August 10, 2017, the Company entered into exchange agreements with certain holders of the liability classified 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 $3,029 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 $3,537. As a result of the Company’s issuance of common stock in exchange for certain of the warrants, the per share exercise price of the remaining warrants, dated May 9, 2014, was adjusted downwards from $3.87 per share to $0.83 per share and additional warrants were issued such that the remaining warrants were exercisable at the time for an aggregate of 48,507 shares of common stock. The remaining 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 remaining 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). Warrant Cancellation In the fourth quarter of 2017, we entered into warrant cancellation agreements with certain remaining holders of our warrants, dated May 9, 2014, to cancel and terminate such warrants for total cash consideration of $40. As of December 31, 2017, the remaining warrants were exercisable for an aggregate of 13,429 shares of common stock.

EMPLOYEE BENEFIT PLAN

EMPLOYEE BENEFIT PLAN	12 Months Ended
	Dec. 31, 2017
EMPLOYEE BENEFIT PLAN
EMPLOYEE BENEFIT PLAN	14. 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, 2017, 2016 and 2015, the Company made matching contributions in the form of shares of the Company’s common stock. For the years ended December 31, 2017, 2016, and 2015, the Company issued 98,319, 37,528, and 17,437 shares of its common stock, respectively, with related fair values of $183, $208, and $201, respectively, which were recorded as expense in the statement of operations.

INTELLECTUAL PROPERTY LICENSE

INTELLECTUAL PROPERTY LICENSE	12 Months Ended
	Dec. 31, 2017
INTELLECTUAL PROPERTY LICENSE
INTELLECTUAL PROPERTY LICENSE	15. 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 are capitalized and the gross total at December 31, 2017 and 2016 was $200 (see Note 5). The Company accounts for milestone payments, maintenance fees and royalties when they become due and payable. For the year ended December 31, 2017, the Company expensed milestone payments of $175.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2017
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	16. COMMITMENTS AND CONTINGENCIES Leases On November 30, 2011, the Company entered into a commercial lease for 26,342 square feet of office, laboratory and manufacturing space in Cambridge, Massachusetts (as amended on September 17, 2012 and October 31, 2017, 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 (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, 2017 and 2016, the amount of the deferred rent liability is $397 and $276, respectively. 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, 2017 and 2016, such leasehold improvements totaled $ 61 and $143, net of accumulated depreciation. Pursuant to the terms of the non‑cancelable lease agreements in effect at December 31, 2017, the future minimum rent commitments are as follows: Year Ended December 31, 2018 1,380 2019 1,959 2020 2,018 2021 2,078 2022 2,141 Thereafter 1,828 Total $ 11,404 Total rent expense for the years ended December 31, 2017, 2016, and 2015, including month‑to‑month leases, was $1,231 , $918 and $1,123, respectively. On March 31, 2016, the Company entered into a short-term lease, 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, were classified as a component of accrued expenses on balance sheet as of December 31, 2016. In connection with the CRISPR Sublease, the Company received sublease income of $26 and $230 for the year ended December 31, 2017 and 2016, respectively , which was recorded as an offset to rent expense. The Sublease was terminated on January 31, 2017. On June 13, 2017, the Company entered into a short-term lease, as subtenant, to sublease 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 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 December 31, 2017. In connection with the Moderna Sublease, the Company received sublease income of $164 for the year ended December 31, 2017, which was recorded as an offset to rent expense. Compensation Commitment The Company entered into a compensation arrangement with an executive during September 2016 which provided 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 was earned over a period of one year. The expense related to the compensation arrangement was $174 and $101 for the years ended December 31, 2017 and 2016 respectively. As of December 31, 2017 we had made all payments to the executive. 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 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 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 judgement 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 trial is scheduled to begin on June 16, 2018. 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.

RESTRUCTURING

RESTRUCTURING	12 Months Ended
	Dec. 31, 2017
RESTRUCTURING
RESTRUCTURING	17. RESTRUCTURING On August 28, 2017, the Company implemented a strategic restructuring. In conjunction with the strategic restructuring, the Company completed a reduction in force eliminating approximately 39% of its workforce. For the year ended December 31, 2017, the Company recorded $898 in restructuring expenses, including employee severance benefits and related costs, as well as a write-off of certain fixed assets. The following table summarizes the restructuring costs by category for the periods indicated: Year Ended December 31, 2017 Cash Non Cash (1) Total Research and development $ 669 $ 41 $ 710 General and administrative 188 — 188 $ 857 $ 41 $ 898 (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: Year Ended December 31, 2017 Restructuring reserve beginning balance $ — Cash restructuring expenses incurred during the period 857 Amounts paid during the period (509) Restructuring reserve ending balance $ 348

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2017
RELATED PARTY TRANSACTIONS.
RELATED PARTY TRANSACTIONS	18. RELATED PARTY TRANSACTIONS In January 2017, the Company entered into a consulting agreement with Dr. Robert Langer, a member of our Scientific Advisory Board, who at the time of entering into the consulting agreement was 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 initially agreed to pay Dr. Langer $250 per year in consulting fees, but that amount was reduced effective October 2017 to $100 per year in consulting fees. For the year ended December 31, 2017 the Company paid Dr. Langer $204 in consulting fees.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2017
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	19. SUBSEQUENT EVENTS On January 25, 2018, the Company entered into a purchase and a registration rights agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”), under which the Company has the right to sell up to $15,000 in shares of common stock, $0.00001 par value per share, to Lincoln Park over a twenty-four-month period, subject to certain limitations and conditions set forth in the purchase agreement and registration rights agreement. In accordance with the terms of the purchase agreement, at the time the Company signed the purchase agreement and the registration rights agreement, the Company issued 429,800 shares to Lincoln Park as consideration for its commitment to purchase shares of its common stock under the purchase agreement. In addition, as of March 12, 2018 the Company had drawn $2,252 against the purchase agreement and issued an aggregate of 3,344,769 shares.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016, cash equivalents were comprised of money market funds and other short-term investments. Cash and cash equivalents consist of the following: December 31, (In thousands) 2017 2016 Cash $ 23 $ 111 Money market funds 12,887 21,353 Total cash and cash equivalents $ 12,910 $ 21,464
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, 2017, the Company had no marketable securities. As of 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. 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, 2017, the Company had no marketable securities. At December 31, 2016, the aggregate fair value of the Company’s marketable securities was $11,577. Gross unrealized gains and losses were insignificant for the years ended December 31, 2017 and 2016. 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, 2017 and 2016 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 16).
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 3 - 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, 2017 and 2016, 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, 2017 or 2016. Tax years subsequent to 2013 remain open to examination by U.S. federal and state tax authorities. The Tax Cuts and Jobs Act (“the Act”) was enacted on December 22, 2017. The Act reduces the US federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign sourced earnings. On December 22, 2017, the Securities and Exchange Commission issued guidance under Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”) directing taxpayers to consider the impact of the U.S. legislation as “provisional” when it does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete its accounting for the change in tax law. At December 31, 2017, we have not completed our accounting for the tax effects of enactment of the Act; however, as described below, we have made a reasonable estimate of the effects on our existing deferred tax balances. In all cases, we will continue to make and refine our calculations as additional analysis is completed. In addition, our estimates may also be affected as we gain a more thorough understanding of the tax law.
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. On August 28, 2017, the Company implemented a strategic restructuring and as a result recorded an impairment loss of $41 related to certain fixed assets (Note 4). No impairment charge was recorded for the year ended 2016.
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, unvested restricted stock units and convertible securities are anti‑dilutive and therefore excluded from diluted loss per share calculations. For the year ended December 31, 2017, 2016, and 2015, the following potentially dilutive securities were not included in the computation of net loss per share because the effect would be anti-dilutive: 2017 2016 2015 Stock options 3,369,245 3,193,785 3,253,310 Warrants 2,166,149 3,391,439 1,156,779 Unvested restricted stock units 500,000 — — 6,035,394 6,585,224 4,410,089
Recent accounting pronouncements	Recent 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 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 December 31, 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 adopt the guidance and evaluate the impact of adopting ASU 2014-09 on the consolidated financial statements when the Company begins to generate revenue.

SIGNIFICANT ACCOUNTING POLICI27

SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2017
SIGNIFICANT ACCOUNTING POLICIES
Schedule of cash and cash equivalents	December 31, (In thousands) 2017 2016 Cash $ 23 $ 111 Money market funds 12,887 21,353 Total cash and cash equivalents $ 12,910 $ 21,464
Summary of estimated useful lives	Classification Estimated Useful Life Computer hardware 3 - 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 not included in the computation of net loss per share because effect would be anti-dilutive	2017 2016 2015 Stock options 3,369,245 3,193,785 3,253,310 Warrants 2,166,149 3,391,439 1,156,779 Unvested restricted stock units 500,000 — — 6,035,394 6,585,224 4,410,089

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2017
MARKETABLE SECURITIES.
Schedule of cash, cash equivalents, and marketable securities	December 31, December 31, (In thousands) 2017 2016 Cash $ 23 $ 111 Money market funds 12,887 21,353 Marketable securities — 11,577 Total cash, cash equivalents and marketable securities $ 12,910 $ 33,041
Schedule of short-term investments in marketable securities by category	(In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value 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

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2017
PROPERTY AND EQUIPMENT
Schedule of property and equipment, net	2017 2016 Computer software and hardware $ 241 $ 606 Research and lab equipment 508 1,895 Leasehold improvements 431 431 Office equipment 796 796 Less accumulated depreciation and amortization (1,819) (3,218) Property and equipment, net $ 157 $ 510

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2017
INTANGIBLE ASSETS
Summary of intangible assets	2017 2016 Patent licensing fee $ 200 $ 200 Accumulated amortization (139) (122) $ 61 $ 78

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2017
ACCRUED EXPENSES
Summary of accrued expenses	December 31, (In thousands) 2017 2016 Bonus $ 62 $ 906 Payroll 79 126 Vacation 55 91 Severance 1,160 385 Other accrued expenses 282 451 Total accrued expenses $ 1,638 $ 1,959

FAIR VALUE OF ASSETS AND LIAB32

FAIR VALUE OF ASSETS AND LIABILITIES (Tables)	12 Months Ended
	Dec. 31, 2017
FAIR VALUE OF ASSETS AND LIABILITIES
Summary of assets and liabilities measured at fair value on a recurring basis	At December 31, 2017 (In thousands) Level 1 Level 2 Level 3 Fair Value Cash equivalents $ 12,887 $ — $ — $ 12,887 Marketable securities $ — $ — $ — $ — Derivative warrant liability $ — $ 4 $ — $ 4 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

LOAN PAYABLE (Tables)

LOAN PAYABLE (Tables)	12 Months Ended
	Dec. 31, 2017
LOAN PAYABLE
Summary of loans payable	December 31, 2017 2016 MassDev Loan $ 852 $ 1,275 Less: current portion (452) (423) $ 400 $ 852

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2017
INCOME TAXES
Schedule of significant components of net deferred tax assets	December 31, 2017 2016 Net operating loss carryforward $ 31,533 $ 37,245 Research and development credit carryforward 1,173 1,065 Stock-based compensation 2,828 5,235 Depreciation and amortization 71 31 Accrued expenses 357 264 Charitable contributions 27 63 Subtotal 35,989 43,903 Valuation allowance (35,989) (43,903) Net deferred taxes $ — $ —
Schedule of income tax benefits computed using the federal statutory income tax rate	December 31, 2017 2016 2015 Statutory rate (34.0) % (34.0) % (34.0) % State taxes, net of benefit (4.7) % (5.4) % (3.5) % Permanent differences: Derivative losses 2.9 % (0.9) % 11.0 % Other 1.1 % 0.2 % 0.3 % Research and development tax credit (0.2) % (0.5) % (0.4) % Other 1.4 % 0.5 % 0.4 % Adoption of ASU 2016-09 7.4 % — % — % Increase / (decrease) in valuation reserve (32.0) % 40.1 % 26.2 % Change in federal tax rate 58.1 % — % — % Effective tax rate % % %

COMMON STOCK (Tables)

COMMON STOCK (Tables)	12 Months Ended
	Dec. 31, 2017
COMMON STOCK.
Schedule of reserves established for future issuance of common stock	Reserves for the exercise of warrants 2,166,149 Reserves for the exercise of stock options 3,369,245 Reserves for the vesting of restricted stock units 500,000 Total Reserves 6,035,394

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2017
DERIVATIVE INSTRUMENTS
Assumptions used in determining fair value of warrants	December 31, 2017 2016 2015 Risk-free interest rate 1.91 % 1.20 % 0.65 % Expected dividend yield % % % Contractual term years years years Expected volatility 82 % 89 % 100 %
Changes in derivative warrant liability	Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 1,314 $ 1,907 $ 7,224 Increase in derivative liability prior to warrant exchange 3,029 — — Reduction in derivative liability due to warrant exchange (3,537) — — Repurchase of warrants (40) — — Fair value of derivative warrant liability reclassified to additional paid in capital — — (16,121) Increase (decrease) in the fair value of warrants (762) (593) 10,804 Balance at end of year $ 4 $ 1,314 $ 1,907

STOCK OPTIONS (Tables)

STOCK OPTIONS (Tables)	12 Months Ended
	Dec. 31, 2017
STOCK OPTIONS.
Schedule of assumptions used principally in determining the fair value of options granted	December 31, 2017 2016 2015 Risk-free interest rate 1.69 - 2.36% 1.20 - 1.52% 1.53 - 1.89% Expected dividend yield Expected term (employee grants) 6.22 Years 5.99 years 6.00 years Expected volatility
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 (1,174,616) $ 6.40 Exercised (89,387) $ 0.29 Outstanding at December 31, 2017 3,369,245 $ 6.57 7.14 $ 22 Vested at December 31, 2017 2,224,246 $ 7.54 6.22 $ 22 Vested and expected to vest at December 31, 2017 3,369,245 $ 6.57 7.14 $ 22
Summary of restricted stock unit activity	Weighted-Average Number of Grants Grant Date Fair Value Unvested balance at December 31, 2016 — $ — Granted 595,000 1.06 Vested — — Forfeited (95,000) 1.25 Unvested balance at December 31, 2017 500,000 $ 1.03

WARRANTS (Tables)

WARRANTS (Tables)	12 Months Ended
	Dec. 31, 2017
WARRANTS.
Schedule of information about warrants to purchase common stock issued and outstanding	Number of Exercise Year Issued Classification Warrants Price Date of Expiration 2012 Equity 6,054 $ 6.64 10/5/2019 2014 Liability 13,429 $ 0.83 5/9/2019 2016 Equity 2,146,666 $ 10.00 3/18/2021 Total 2,166,149 Weighted average exercise price $ 9.93 Weighted average life in years 3.20

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2017
COMMITMENTS AND CONTINGENCIES
Future minimum rent commitments	Year Ended December 31, 2018 1,380 2019 1,959 2020 2,018 2021 2,078 2022 2,141 Thereafter 1,828 Total $ 11,404

RESTRUCTURING (Tables)

RESTRUCTURING (Tables)	12 Months Ended
	Dec. 31, 2017
RESTRUCTURING
Schedule of restructuring costs by category	Year Ended December 31, 2017 Cash Non Cash (1) Total Research and development $ 669 $ 41 $ 710 General and administrative 188 — 188 $ 857 $ 41 $ 898
Schedule of restructuring reserve	Year Ended December 31, 2017 Restructuring reserve beginning balance $ — Cash restructuring expenses incurred during the period 857 Amounts paid during the period (509) Restructuring reserve ending balance $ 348

NATURE OF OPERATIONS AND GOIN41

NATURE OF OPERATIONS AND GOING CONCERN (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
NATURE OF OPERATIONS AND GOING CONCERN
Cash and cash equivalents	$ 12,910	$ 21,464	$ 14,920	$ 13,459

SIGNIFICANT ACCOUNTING POLICI42

SIGNIFICANT ACCOUNTING POLICIES - CASH AND CASH EQUIVALENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2014
SIGNIFICANT ACCOUNTING POLICIES
Cash.	$ 111	$ 23
Money market funds	21,353	12,887
Total cash and cash equivalents	$ 21,464	$ 12,910	$ 14,920	$ 13,459
Marketable securities
Minimum period for maturity dates	90 days
Marketable securities	$ 11,577

SIGNIFICANT ACCOUNTING POLICI43

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

SIGNIFICANT ACCOUNTING POLICI44

SIGNIFICANT ACCOUNTING POLICIES, PROPERTY AND EQUIPMENT (Details)	12 Months Ended
	Dec. 31, 2017
Computer hardware | Minimum
Property and equipment
Estimated Useful Life	3 years
Computer hardware | Maximum
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 POLICI45

SIGNIFICANT ACCOUNTING POLICIES, SEGMENT (Details)	12 Months Ended
	Dec. 31, 2017segmentitem	Dec. 31, 2016item
SIGNIFICANT ACCOUNTING POLICIES
Number of operating segments | segment	1
Number of locations in the United States | item	1	1

SIGNIFICANT ACCOUNTING POLICI46

SIGNIFICANT ACCOUNTING POLICIES, INCOME TAXES (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Statutory tax rate (as a percent)		34.00%	34.00%	34.00%
Maximum
Income Taxes
Statutory tax rate (as a percent)		35.00%
Forecast
Income Taxes
Statutory tax rate (as a percent)	21.00%

SIGNIFICANT ACCOUNTING POLICI47

SIGNIFICANT ACCOUNTING POLICIES, IMPAIRMENTS (Details) - USD ($) $ in Thousands	4 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
SIGNIFICANT ACCOUNTING POLICIES
Impairment loss	$ 41	$ 41
Impairment charges on long-lived assets			$ 0

SIGNIFICANT ACCOUNTING POLICI48

SIGNIFICANT ACCOUNTING POLICIES, NET LOSS PER COMMON SHARE (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	6,035,394	6,585,224	4,410,089
Stock options
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	3,369,245	3,193,785	3,253,310
Warrants
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	2,166,149	3,391,439	1,156,779
Unvested restricted stock units
Anti-dilutive
Potentially dilutive securities not included in computation of net loss per share because effect would be anti-dilutive (in shares)	500,000

SIGNIFICANT ACCOUNTING POLICI49

SIGNIFICANT ACCOUNTING POLICIES, RECENT ACCOUNTING PRONOUNCEMENTS, ASU 2016-09 (Details) $ in Thousands	Jan. 01, 2017USD ($)
ASU 2016-09
New accounting pronouncements
Cumulative effect adjustment	$ 155

MARKETABLE SECURITIES, CASH, CA

MARKETABLE SECURITIES, CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
MARKETABLE SECURITIES.
Cash	$ 23	$ 111
Money market funds	12,887	21,353
Marketable securities		11,577
Total cash, cash equivalents and marketable securities	$ 12,910	$ 33,041
Minimum original maturity of investment portfolio	90 days

MARKETABLE SECURITIES, SHORT-TE

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

PROPERTY AND EQUIPMENT, SCHEDUL

PROPERTY AND EQUIPMENT, SCHEDULE (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property and equipment
Less accumulated depreciation and amortization	$ (1,819)	$ (3,218)
Property and equipment, net	157	510
Computer software and hardware
Property and equipment
Gross property and equipment	241	606
Research and lab equipment
Property and equipment
Gross property and equipment	508	1,895
Leasehold improvements
Property and equipment
Gross property and equipment	431	431
Office equipment
Property and equipment
Gross property and equipment	$ 796	$ 796

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	4 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation
Depreciation		$ 377	$ 536	$ 672
Disposals	$ 1,807		$ 0
Impairment loss	$ 41	$ 41

INTANGIBLE ASSETS (Details)

INTANGIBLE ASSETS (Details) - Patent licensing fee - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Intangible assets
Useful life	15 years
Intangible assets - gross	$ 200	$ 200
Accumulated amortization	(139)	(122)
Total	$ 61	$ 78

INTANGIBLE ASSETS, AMORTIZATION

INTANGIBLE ASSETS, AMORTIZATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization
Amortization expense	$ 17	$ 17	$ 17
Future amortization
2,018	17
2,019	17
2,020	17
2,021	$ 10

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ACCRUED EXPENSES
Bonus	$ 62	$ 906
Payroll	79	126
Vacation	55	91
Severance	1,160	385
Other accrued expenses	282	451
Total accrued expenses	$ 1,638	$ 1,959

FAIR VALUES OF ASSETS AND LIABI

FAIR VALUES OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets and liabilities measured at fair value on a recurring basis
Marketable securities		$ 11,577
Derivative warrant liability	$ 4	1,314
Recurring basis
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	12,887	21,353
Marketable securities		11,577
Derivative warrant liability	4	1,314
Recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents	12,887	21,353
Recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Marketable securities		11,577
Derivative warrant liability	$ 4	$ 1,314

LOAN PAYABLE (Details)

LOAN PAYABLE (Details) - USD ($) $ / shares in Units, $ in Thousands	May 01, 2015	Oct. 31, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 11, 2017	Mar. 31, 2016
Loans Payable
Interest expense			$ 74	$ 155	$ 172
Common Stock
Loans Payable
Number of shares into which a warrant may be converted			577,548		1,354,523	48,507
Common Stock | Public Offering, March 2016
Loans Payable
Number of shares into which a warrant may be converted							2,146,666
Warrants | Public Offering, March 2016
Loans Payable
Exercise price of warrant (in dollars per share)							$ 10
Fair value of warrants							$ 11,726
MassDev
Loans Payable
Line of credit, maximum		$ 2,000
Line of credit for working capital purpose		$ 200
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
Amount of monthly payment	$ 41
Future Principal payment due: 2018			$ 452
Future Principal payment due : 2019			400
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
MassDev | Warrants | Interest Expense
Loans Payable
Amortization of deferred financing costs			5	5	$ 5
MassDev | Equipment Line of Credit
Loans Payable
Interest expense			$ 71	$ 99	$ 126

LOAN PAYABLE, EQUIPMENT LOAN (D

LOAN PAYABLE, EQUIPMENT LOAN (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Summary of loans payable
MassDev Loan	$ 852	$ 1,275
Less: current portion	(452)	(423)
Noncurrent portion of equipment loan	$ 400	$ 852

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
INCOME TAXES
Provision or benefit for federal or state income taxes	$ 0	$ 0	$ 0

INCOME TAXES, CARRYFORWARDS (De

INCOME TAXES, CARRYFORWARDS (Details) $ in Thousands	Dec. 31, 2017USD ($)
U.S. federal
Net operating loss carryforwards
Net operating loss carryforwards	$ 117,298
Massachusetts
Net operating loss carryforwards
Net operating loss carryforwards	$ 109,183

INCOME TAXES, CREDITS (Details)

INCOME TAXES, CREDITS (Details) - Research Tax Credit Carryforward $ in Thousands	Dec. 31, 2017USD ($)
U.S. federal
Tax credit carryforwards
Research and development tax credit carryforwards	$ 991
Massachusetts
Tax credit carryforwards
Research and development tax credit carryforwards	$ 230

INCOME TAXES, Tax Act (Details)

INCOME TAXES, Tax Act (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Statutory tax rate (as a percent)			34.00%	34.00%	34.00%
Decrease in deferred tax relating to tax reform Act	$ 15,521
Maximum
Income Taxes
Statutory tax rate (as a percent)			35.00%
Forecast
Income Taxes
Statutory tax rate (as a percent)		21.00%

INCOME TAXES, NET DEFERRED TAX

INCOME TAXES, NET DEFERRED TAX ASSET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Significant components of net deferred tax asset
Net operating loss carryforward	$ 31,533	$ 37,245
Research and development credit carryforward	1,173	1,065
Stock-based compensation	2,828	5,235
Depreciation and amortization	71	31
Accrued expenses	357	264
Charitable contributions	27	63
Subtotal	35,989	43,903
Valuation allowance	(35,989)	(43,903)
Increase (decrease) in valuation allowance	(7,914)	9,406
Uncertain tax positions that would affect its effective tax rate	0	$ 0
ASU 2016-09
Significant components of net deferred tax asset
Effect on retained earnings of recording additional deferred tax assets	642
Net deferred tax assets	$ 0

INCOME TAXES, STATUTORY INCOME

INCOME TAXES, STATUTORY INCOME TAX RATES (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax benefits computed using the federal statutory income tax rate
Statutory rate	(34.00%)	(34.00%)	(34.00%)
State taxes, net of benefit	(4.70%)	(5.40%)	(3.50%)
Permanent differences:
Derivative losses	2.90%	(0.90%)	11.00%
Other	1.10%	0.20%	0.30%
Research and development tax credit	(0.20%)	(0.50%)	(0.40%)
Other	1.40%	0.50%	0.40%
Adoption of ASU 2016-09	7.40%
Increase / (decrease) in valuation reserve	(32.00%)	40.10%	26.20%
Change in federal tax rate	58.10%
Effective tax rate	0.00%	0.00%	0.00%

COMMON STOCK, PAR VALUE (Detail

COMMON STOCK, PAR VALUE (Details) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common stock, number of shares, par value and other disclosures
Common stock, authorized	100,000,000	100,000,000
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, issued	34,274,776	32,044,087
Common stock, outstanding	34,274,776	32,044,087

COMMON STOCK, TRANSACTIONS (Det

COMMON STOCK, TRANSACTIONS (Details) $ / shares in Units, $ in Thousands	Mar. 12, 2018USD ($)	Jan. 25, 2018USD ($)$ / sharesshares	Apr. 08, 2015shares	Mar. 31, 2016USD ($)$ / sharesshares	Jul. 31, 2015USD ($)shares	Jan. 31, 2015USD ($)shares	Mar. 12, 2018shares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)shares	Aug. 11, 2017shares
Common stock disclosures
Proceeds from exercise of stock options | $								$ 26	$ 191	$ 1,068
Proceeds from exercise of warrants | $								3		7,789
Issuance of common stock to 401(k) plan | $								183	208	201
Proceeds from issuance of stock under ESPP | $								$ 51	$ 91
Common stock, par value (in dollars per share) | $ / shares								$ 0.00001	$ 0.00001
Proceeds from issuance of common stock and warrants | $									$ 29,905	$ 14,480
Common Stock
Common stock disclosures
Issuance of common stock upon exercise of stock options (in shares)								89,387	135,205	316,177
Proceeds from exercise of stock options | $								$ 26	$ 191	$ 1,068
Issuance of common stock upon exercise of warrants (in shares)								3,464		1,379,575
Proceeds from exercise of warrants | $								$ 3		$ 7,789
Issuance of common stock upon cashless exercise of warrants (in shares)									4,979	25,052
Issuance of common stock to 401(k) plan (in shares)								98,319	37,528	17,437
Issuance of common stock to 401(k) plan | $								$ 183	$ 208	$ 201
Stock issued under ESPP (in shares)								17,750	16,729
Proceeds from issuance of stock under ESPP | $								$ 51	$ 91
Issuance of stock in exchange for warrants (in shares)								2,021,419
Number of shares into which a warrant may be converted								577,548		1,354,523	48,507
Issuance of stock in public offering (in shares)										2,388,245
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
Number of warrants to purchase common stock (in shares)										40,955
Reverse stock split ratio			0.25
Stock issued during period, shares, reverse stock splits			1,514
Issuance of common stock for services (in shares)								350	365
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
Common Stock | Sales Agreement
Common stock disclosures
Issuance of stock in public offering (in shares)					388,245
Aggregate proceeds from sale agreement of shares of common stock | $					$ 50,000
Percentage of Commission on the gross proceeds from sales agreement of shares of common stock					3.00%
Net proceeds from issuance of equity (in dollars) | $										$ 3,442
Common Stock | Public Offering, March 2016
Common stock disclosures
Number of shares into which a warrant may be converted				2,146,666
Equity issuance (in price per unit) | $ / shares				$ 7.49
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%
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 | $				$ 29,905
Subsequent event | Common Stock | Purchase and registration rights agreement
Common stock disclosures
Aggregate proceeds | $		$ 15,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.00001
Term		24 months
Issuance of stock in public offering (in shares)		429,800					3,344,769
Net proceeds from issuance of equity (in dollars) | $	$ 2,252

COMMON STOCK, RESERVES (Details

COMMON STOCK, RESERVES (Details)	Dec. 31, 2017shares
Summary of common stock reserves
Total Reserves	6,035,394
Warrants
Summary of common stock reserves
Total Reserves	2,166,149
Restricted Stock Units (RSUs)
Summary of common stock reserves
Total Reserves	500,000
Stock options
Summary of common stock reserves
Total Reserves	3,369,245

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 11, 2017	Dec. 31, 2014
Derivative instruments
Derivatives (gain) loss	$ 2,267	$ (593)	$ 10,804
Derivative instruments, fair value	$ 4	1,314
Common Stock
Derivative instruments
Number of shares into which a warrant may be converted	577,548		1,354,523	48,507
Common Stock | Public Offering, May 2014
Derivative instruments
Number of shares into which a warrant may be converted	1,750,156
Warrants
Derivative instruments
Derivative instruments, fair value	$ 4	1,314	$ 1,907		$ 7,224
Warrants | Other Income (Expense)
Derivative instruments
Derivatives (gain) loss	$ 2,267	$ (593)	$ 10,804

DERIVATIVE INSTRUMENTS, FAIR VA

DERIVATIVE INSTRUMENTS, FAIR VALUE OF WARRANTS (Details) - Warrants	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair value of warrants
Risk-free interest rate (as a percent)	1.91%	1.20%	0.65%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Expected term (in years)	1 year 4 months 6 days	2 years 4 months 24 days	3 years 4 months 24 days
Expected volatility (as a percent)	82.00%	89.00%	100.00%

DERIVATIVE INSTRUMENTS, CHANGES

DERIVATIVE INSTRUMENTS, CHANGES IN DERIVATIVE WARRANT LIABILITY (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in Derivative Warrant Liability
Balance at beginning of year		$ 1,314
Repurchase of warrants		(40)
Fair value of derivative warrant liability reclassified to additional paid in capital				$ (16,121)
Balance at end of period	$ 4	4	$ 1,314
Warrants
Changes in Derivative Warrant Liability
Balance at beginning of year		1,314	1,907	7,224
Increase in derivative liability prior to warrant exchange		3,029
Reduction in derivative liability due to warrant exchange		(3,537)
Repurchase of warrants	(40)	(40)
Fair value of derivative warrant liability reclassified to additional paid in capital				(16,121)
Increase (decrease) in the fair value of warrants		(762)	(593)	10,804
Balance at end of period	$ 4	$ 4	$ 1,314	$ 1,907

STOCK OPTIONS (Details)

STOCK OPTIONS (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended	12 Months Ended			18 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Jun. 16, 2016	Apr. 30, 2015	Mar. 31, 2015
Stock options
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan		6,035,394	6,035,394			6,035,394
Stock-based compensation (in dollars)			$ 4,106	$ 5,063	$ 4,666
Stock Options
Stock options
Options to purchase common stock outstanding (in shares)		3,369,245	3,369,245	3,193,785		3,369,245
Granted (in shares)			1,439,463
Expected term			10 years
Vesting period			48 months
2007 Plan
Stock options
Options to purchase common stock outstanding (in shares)		46,476	46,476			46,476
Shares available for future grants		0	0			0
Expected term			10 years
2010 Plan
Stock options
Options to purchase common stock outstanding (in shares)		1,444,644	1,444,644			1,444,644
Shares available for future grants							322,355
Granted (in shares)						0
Expected term			10 years
2015 Plan
Stock options
Options to purchase common stock outstanding (in shares)		1,878,125	1,878,125			1,878,125
Shares authorized for issuance		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%
Increase in shares of common stock reserved for issuance (in shares)			50,000
Maximum aggregate number of shares reserved for issuance during term of employee stock purchase plan		1,250,000	1,250,000			1,250,000
Offering Period			6 months
Stock issued under ESPP (in shares)	4,691
Stock-based compensation (in dollars)			$ 14	$ 46
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 (in dollars)		$ 3

STOCK OPTIONS, ASSUMPTIONS USED

STOCK OPTIONS, ASSUMPTIONS USED IN DETERMINING THE FAIR VALUE (Details) - Stock Options	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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)	6 years 2 months 19 days	5 years 11 months 27 days	6 years
Expected volatility (as a percent)	104.00%	111.00%	116.00%
Minimum
Assumptions used principally in determining the fair value of options granted
Risk-free interest rate (as a percent)	1.69%	1.20%	1.53%
Maximum
Assumptions used principally in determining the fair value of options granted
Risk-free interest rate (as a percent)	2.36%	1.52%	1.89%

STOCK OPTIONS, SUMMARY OF OPTIO

STOCK OPTIONS, SUMMARY OF OPTION ACTIVITY - (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of option activity - Shares
Outstanding at the beginning of year (in shares)	3,193,785
Granted (in shares)	1,439,463
Forfeited (in shares)	(1,174,616)
Exercised (in shares)	(89,387)
Outstanding at the end of period (in shares)	3,369,245	3,193,785
Vested at the end of period (in shares)	2,224,246
Vested and expected to vest at the end of period (in shares)	3,369,245
Summary of option activity - Weighted Average Exercise Price
Outstanding at the beginning of year (in dollars per shares)	$ 7.52
Granted (in dollars per shares)	3.94
Forfeited (in dollars per shares)	6.40
Exercised (in dollars per shares)	0.29
Outstanding at the end of period (in dollars per shares)	6.57	$ 7.52
Vested at the end of period (in dollars per share)	7.54
Vested and expected to vest at the end of period (in dollars per share)	$ 6.57
Option activity disclosures
Weighted Average Remaining Contractual Term - Outstanding	7 years 1 month 21 days
Weighted Average Remaining Contractual Term - Vested	6 years 2 months 19 days
Weighted Average Remaining Contractual Term - Vested and expected to vest	7 years 1 month 21 days
Aggregate Intrinsic Value - Outstanding (in dollars)	$ 22
Aggregate Intrinsic Value - Vested (in dollars)	22
Aggregate Intrinsic Value - Vested and expected to vest (in dollars)	$ 22
Stock Option
Weighted average grant-date fair value of options granted	$ 2.54	$ 5.23	$ 7.37
Total fair value of options vested	$ 3,837	$ 5,179	$ 5,144
Total unrecognized compensation expense	$ 3,516
Period for unrecognized compensation expense is estimated to be recognized	2 years 4 months 17 days

STOCK OPTIONS, RESTRICTED STOCK

STOCK OPTIONS, RESTRICTED STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based compensation
Stock-based compensation (in dollars)	$ 4,106	$ 5,063	$ 4,666
Restricted Stock Units (RSUs)
Number of Grants
Granted (in shares)	595,000
Forfeited (in shares)	(95,000)
Unvested balance at	500,000
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)	$ 1.06
Forfeited (in dollars per share)	1.25
Unvested balance at (in dollars per share)	$ 1.03
Restricted stock units issued
Number of shares issued to employees (in shares)	595,000
Share-based compensation
Stock-based compensation (in dollars)	$ 40
Unrecognized compensation
Total unrecognized compensation expense	$ 474
Period for unrecognized compensation expense is estimated to be recognized	2 years 11 months 12 days

WARRANTS (Details)

WARRANTS (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Mar. 31, 2016	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 11, 2017	Aug. 10, 2017
Warrants to purchase common stock issued and outstanding
Number of Warrants			2,166,149
Weighted average exercise price			$ 9.93
Weighted average life in years			3 years 2 months 12 days
Proceeds from issuance of common stock and warrants				$ 29,905	$ 14,480
Common Stock
Warrants to purchase common stock issued and outstanding
Number of shares issued (in shares)					2,388,245
Warrants for purchase of common stock (in shares)			577,548		1,354,523	48,507
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
Common Stock | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrants for purchase of common stock (in shares)			13,429
Warrants
Fair value of warrants
Expected volatility (as a percent)			82.00%	89.00%	100.00%
Risk-free interest rate (as a percent)			1.91%	1.20%	0.65%
Expected term (in years)			1 year 4 months 6 days	2 years 4 months 24 days	3 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	$ 11,726
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%
Warrants | Derivative with Exercise Price Two
Warrants to purchase common stock issued and outstanding
Warrant Exercise Price						$ 0.83	$ 3.87
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
Proceeds from issuance of common stock and warrants	$ 29,905
Equity | Derivative with Exercise Price One
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 Three
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 Two
Warrants to purchase common stock issued and outstanding
Warrants Issued Year			2,014
Number of Warrants			13,429
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	Dec. 31, 2017USD ($)shares	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)shares	Aug. 11, 2017$ / sharesshares
Warrants
Derivatives gain (loss) | $				$ (2,267)	$ 593	$ (10,804)
Issuance of common stock on warrant exchange | $				3,537
Repurchase of warrants | $				40
Warrants
Warrants
Repurchase of warrants | $			$ 40	$ 40
Warrants | Derivative with Exercise Price Two
Warrants
Exercise price (in dollars per unit) | $ / shares	$ 3.87						$ 0.83
Common Stock
Warrants
Issuance of stock in exchange for warrants (in shares) | shares				2,021,419
Number of shares into which a warrant may be converted | shares			577,548	577,548		1,354,523	48,507
Common Stock | Derivative with Exercise Price Two
Warrants
Number of shares into which a warrant may be converted | shares			13,429	13,429
Warrant Exchange Agreement
Warrants
Number of times for exchange of warrants | item	3.5
Exercise price (in dollars per unit) | $ / shares	$ 3.87
Derivatives gain (loss) | $		$ (3,029)
Issuance of common stock on warrant exchange | $	$ 3,537
Warrant Exchange Agreement | Common Stock
Warrants
Issuance of stock in exchange for warrants (in shares) | shares	2,021,419
Number of shares into which a warrant may be converted | shares	577,548
Stock price (in dollars per share) | $ / shares		$ 1.75
Warrant Exchange Agreement | Fair Value | Common Stock
Warrants
Issuance of stock in exchange for warrants (in shares) | shares		2,021,419

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee benefit plan disclosures
Eligibility criteria for participation in the Plan	21 years
Expense portion of fair value of stock	$ 183	$ 208	$ 201
Common Stock
Employee benefit plan disclosures
Issuance of common stock to 401(k) plan (in shares)	98,319	37,528	17,437
Expense portion of fair value of stock	$ 183	$ 208	$ 201

INTELLECTUAL PROPERTY LICENSE (

INTELLECTUAL PROPERTY LICENSE (Details) - Boston Childrens Hospital Bch License - USD ($) $ in Thousands	Dec. 31, 2011	Dec. 31, 2017	Dec. 31, 2016
Intellectual Property License
Useful life	15 years
Initial license fee paid	$ 75
Capitalized license fees, gross		$ 200	$ 200
Milestone payments expensed		$ 175

COMMITMENTS AND CONTINGENCIES,

COMMITMENTS AND CONTINGENCIES, LEASES (Details) - Cambridge Lease $ in Thousands	Nov. 01, 2018	Oct. 31, 2017USD ($)ft²item	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Commitments
Lease space (in square feet) | ft²		26,342
Term of commercial lease	5 years	6 years 3 months
Number of options to extend lease | item		1
Term of lease extension option		5 years
Standby letter of credit		$ 311
Deferred rent liability			$ 397	$ 276
Leasehold improvements, net			$ 61	$ 143

COMMITMENTS AND CONTINGENCIES81

COMMITMENTS AND CONTINGENCIES, FUTURE MINIMUM RENT COMMITMENTS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jun. 19, 2017USD ($)	Jun. 13, 2017ft²	Mar. 31, 2016USD ($)ft²
Future minimum rent commitments
2,018	$ 1,380
2,019	1,959
2,020	2,018
2,021	2,078
2,022	2,141
Thereafter	1,828
Total	11,404
Commitments
Total rent expense	1,231	$ 918	$ 1,123
Sublease
Commitments
Lease space (in square feet) | ft²						5,233
Tenant security deposit and first month's rent						$ 51
Tenant security deposit						$ 26
Sublease income recorded as offset to rent expense	26	$ 230
Moderna Sublease
Commitments
Lease space (in square feet) | ft²					5,233
Tenant security deposit				$ 55
Sublease income recorded as offset to rent expense	$ 164

COMMITMENTS AND CONTINGENCIES82

COMMITMENTS AND CONTINGENCIES, COMPENSATION (Details) - Executive - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016
Compensation Arrangement
Term of award	1 year
Compensation expense		$ 174	$ 101

COMMITMENTS AND CONTINGENCIES83

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

RESTRUCTURING (Details)

RESTRUCTURING (Details) - USD ($) $ in Thousands	Aug. 28, 2017	Dec. 31, 2017
RESTRUCTURING
Percentage of reduction in headcount	39.00%
Restructuring costs		$ 898

RESTRUCTURING, COSTS BY CATEGOR

RESTRUCTURING, COSTS BY CATEGORY (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Restructuring costs by category
Restructuring costs, cash	$ 857
Restructuring costs, non cash	41
Restructuring costs	898
Research and development
Restructuring costs by category
Restructuring costs, cash	669
Restructuring costs, non cash	41
Restructuring costs	710
General and administrative
Restructuring costs by category
Restructuring costs, cash	188
Restructuring costs	$ 188

RESTRUCTURING, RESERVE (Details

RESTRUCTURING, RESERVE (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Restructuring reserve
Cash restructuring expenses incurred during the period	$ 857
Amounts paid during the period	(509)
Restructuring reserve, ending balance	$ 348

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - Dr. Robert Langer - Consulting agreement - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2017
Related Party Transactions
Holding percentage of common stock			5.00%
Consulting fees per year	$ 100	$ 250
Consulting fees paid			$ 204

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 12, 2018	Jan. 25, 2018	Mar. 12, 2018	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Subsequent events
Common stock, par value (in dollars per share)					$ 0.00001	$ 0.00001
Common Stock
Subsequent events
Issuance of stock in public offering (in shares)				2,388,245
Subsequent event | Common Stock | Purchase and registration rights agreement
Subsequent events
Aggregate proceeds		$ 15,000
Term		24 months
Common stock, par value (in dollars per share)		$ 0.00001
Drawn	$ 2,252
Issuance of stock in public offering (in shares)		429,800	3,344,769