Kala Pharmaceuticals (KALA) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document and Entity Information
Entity Registrant Name	Kala Pharmaceuticals, Inc.
Entity Central Index Key	1,479,419
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		24,521,131
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash	$ 122,049	$ 45,472
Prepaid expenses and other current assets	886	154
Total current assets	122,935	45,626
Property and equipment, net	623	594
Restricted cash	133	109
Total assets	123,691	46,329
Current liabilities:
Current portion of long-term debt	6,111	556
Accounts payable	1,135	997
Accrued expenses	3,938	3,993
Total current liabilities	11,184	5,546
Long-term liabilities:
Long-term debt - less current portion	13,629	9,098
Warrant liability	0	1,039
Other long-term liabilities	15	17
Total long-term liabilities	13,644	10,154
Total liabilities	24,828	15,700
Commitments and Contingencies (Note 13)	0
Stockholders' equity (deficit):
Common stock	24	1
Additional paid-in capital	221,920	4,374
Accumulated deficit	(123,081)	(92,137)
Total stockholders’ deficit	98,863	(87,762)
Total liabilities, convertible preferred stock and stockholders' deficit	123,691	46,329
Series Seed convertible preferred stock
Long-term liabilities:
Warrant liability	0
Convertible preferred stock	11,065	11,065
Series A convertible preferred stock
Long-term liabilities:
Warrant liability	0
Convertible preferred stock	10,736	10,736
Series B convertible preferred stock
Long-term liabilities:
Warrant liability	0
Convertible preferred stock		22,185
Series B-1 convertible preferred stock
Long-term liabilities:
Convertible preferred stock		6,885
Series C convertible preferred stock
Long-term liabilities:
Warrant liability	$ 0
Convertible preferred stock		$ 67,520

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	120,000,000	110,251,951
Common stock, shares issued	24,347,150	1,181,429
Common stock, shares outstanding	24,347,150	1,181,429
Convertible preferred stock.
Convertible preferred stock, authorized	0	170,336,260
Convertible preferred stock, shares outstanding	0
Series Seed convertible preferred stock
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, authorized	0	11,323,209
Convertible preferred stock, shares issued	0	11,243,209
Convertible preferred stock, shares outstanding	0	11,243,209
Series A convertible preferred stock
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, authorized	0	9,583,432
Convertible preferred stock, shares issued	0	9,583,432
Convertible preferred stock, shares outstanding	0	9,583,432
Series B convertible preferred stock
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, authorized	0	16,597,221
Convertible preferred stock, shares issued	0	15,624,999
Convertible preferred stock, shares outstanding	0	15,624,999
Series B-1 convertible preferred stock
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, authorized	0	4,629,629
Convertible preferred stock, shares issued	0	4,629,629
Convertible preferred stock, shares outstanding	0	4,629,629
Series C convertible preferred stock
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, authorized	0	43,034,639
Convertible preferred stock, shares issued	0	42,782,688
Convertible preferred stock, shares outstanding	0	42,782,688

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating expenses:
Research and development	$ 7,018	$ 8,256	$ 23,128	$ 18,117
General and administrative	2,516	1,491	5,607	6,356
Total operating expenses	9,534	9,747	28,735	24,473
Loss from operations	(9,534)	(9,747)	(28,735)	(24,473)
Other income (expense):
Interest income	194	60	276	90
Interest expense	(212)	(186)	(618)	(566)
Change in fair value of warrant liability	(623)	206	(1,844)	177
Total other income (expense)	(641)	80	(2,186)	(299)
Net loss attributable to common stockholders—basic and diluted	$ (10,175)	$ (9,667)	$ (30,921)	$ (24,772)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.56)	$ (8.18)	$ (4.51)	$ (20.97)
Weighted average shares outstanding—basic and diluted	18,034,278	1,181,429	6,860,777	1,181,429

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (30,921)	$ (24,772)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	213	220
Change in fair value of warrant liability	1,844	(177)
Amortization of debt discount and debt issuance costs	86	83
Write-off of deferred offering costs		1,789
Stock-based compensation	2,070	1,747
Increase (decrease) in cash from:
Prepaid expenses and other current assets	(732)	(29)
Accounts payable	74	(292)
Accrued expenses	(166)	1,432
Other long-term liabilities	(2)	(22)
Net cash used in operating activities	(27,534)	(20,021)
Cash flows from investing activities:
Purchases of property and equipment	(197)	(95)
Restricted cash	(25)
Net cash used in investing activities	(222)	(95)
Cash flows from financing activities:
Proceeds from issuance of Series C convertible preferred stock		67,922
Proceeds from common stock offering, net of underwriters discounts	96,255
Proceeds from venture debt	10,000
Payment of principal on venture debt facility		(1,000)
Payment of Series C issuance costs		(402)
Payment of common stock offering costs	(2,111)
Payment of deferred offering costs		(283)
Proceeds from exercise of stock options	189
Net cash provided by financing activities	104,333	66,237
Net increase in cash	76,577	46,121
Cash at beginning of period	45,472	5,759
Cash at end of period	122,049	51,880
Supplemental disclosure of non-cash investing and financing activities:
Conversion of convertible preferred stock into common stock	118,391
Common stock offering costs included in accounts payable and accruals	131
Reclassification of warrants to additional paid-in capital	2,883	759
Purchases of property and equipment in accounts payable	45
Cash paid for interest	$ 532	$ 490

NATURE OF BUSINESS AND BASIS OF

NATURE OF BUSINESS AND BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2017
NATURE OF BUSINESS AND BASIS OF PRESENTATION
NATURE OF BUSINESS AND BASIS OF PRESENTATION	1. NATURE OF BUSINESS AND BASIS OF PRESENTATION Nature of Business —Kala Pharmaceuticals, Inc. (the “Company”) was incorporated on July 7, 2009, and is a biopharmaceutical company focused on the development and commercialization of therapies using its proprietary nanoparticle‑based Mucus Penetrating Particles, or MPP, technology, with an initial focus on the treatment of eye diseases. The Company has applied the MPP technology to lotepredol etabonate, or LE, a corticosteroid designed for ocular applications, resulting in two lead product candidates. These product candidates are INVELTYS TM (KPI-121 1.0%), for the treatment of post‑operative inflammation and pain following ocular surgery, for which the Company has submitted a New Drug Application, or NDA, and KPI-121 0.25% for the temporary relief of the signs and symptoms of dry eye disease, currently in Phase 3 clinical development. The Company is evaluating opportunities for MPP nanosuspensions of LE with less frequent daily dosing regimens for the treatment of inflammation and pain following ocular surgery, for the temporary relief of the signs and symptoms of dry eye disease and for potential chronic treatment of dry eye disease. The Company is also evaluating compounds in its topically applied MPP receptor Tyrosine Kinase Inhibitor program, or rTKI program, that inhibit the vascular endothelial growth factor, or VEGF, pathway, for the potential treatment of a number of retinal diseases. The brand name INVELTYS has been conditionally approved by the U.S. Food and Drug Administration. The Company is engaged in research and development activities, raising capital and recruiting skilled personnel. The Company is subject to a number of risks similar to those of other companies conducting high‑risk, early‑stage research and development of pharmaceutical product candidates. Principal among these risks are dependence on key individuals and intellectual property, competition from other products and companies and the technical risks associated with the successful research, development and marketing of its product candidates. The Company’s success is dependent upon its ability to raise additional capital in order to fund ongoing research and development, obtain regulatory approval of its product candidates, successfully commercialize its products, generate revenue, meet its obligations, and, ultimately, attain profitable operations. On July 25, 2017, the Company completed its initial public offering (“IPO”) of common stock pursuant to its registration statement on Form S-1, as amended (File No. 333-218936), which was declared effective by the Securities Exchange Commission (the “SEC”) on July 19, 2017. Pursuant to the registration statement, the Company issued and sold 6,900,000 shares of $0.001 par value common stock at an initial offering price of $15.00 per share, which included 900,000 shares of common stock pursuant to the underwriters’ option to purchase additional shares. The Company’s shares began trading on the NASDAQ Global Select Market under the symbol “KALA” on July 20, 2017. Proceeds from the Company’s IPO were approximately $94.1 million after deducting underwriting discounts and commissions of $7.2 million and offering costs of $2.2 million. Upon the closing of the IPO, all of the Company’s outstanding shares of convertible preferred stock automatically converted into 16,101,970 shares of common stock at the applicable conversion ratio then in effect. All of the Company’s outstanding warrants to purchase preferred stock automatically converted into warrants to purchase 202,020 shares of common stock. The Company believes that its existing cash on hand as of September 30, 2017, will enable it to fund its planned operating expenses, debt service obligations and capital expenditure requirements through the second quarter of 2019. The Company has based these estimates on assumptions that may prove to be wrong, and its operating plan may change as a result of many factors currently unknown. As a result, the Company could deplete its available capital resources sooner than it currently expects. Unaudited Interim Financial Information The condensed financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. The accompanying condensed financial statements reflect all adjustments consisting of normal, recurring adjustments, that are necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods presented. Interim results are not necessarily indicative of results for a full year. Accordingly, these financial statements should be read in conjunction with the financial statements as of and for the year ended December 31, 2016, and notes thereto, included in the Company’s final prospectus for the IPO filed with the Securities and Exchange Commission pursuant to Rule 424(b)(4) on July 20, 2017 (the “Prospectus”). Reverse Stock Split — On July 7, 2017, the Company effected a one-for-5.2083 reverse stock split of the Company ’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock. The par value per share and authorized shares of common and convertible preferred stock were not adjusted as a result of the reverse stock split. All common stock and common stock per share amounts within the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. Automatic Conversion of Preferred Stock – On July 7, 2017, the Company effected an amendment to its Amended and Restated Certificate of Incorporation, as amended. This amendment eliminated the minimum price per share of Common Stock for an underwritten public offering that would result in the automatic conversion of all outstanding shares of the Company’s Series Seed, Series A, Series B, Series B‑1 and Series C Preferred Stock.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, expense, and related disclosures. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. Estimates relied upon in preparing these financial statements relate to, but are not limited to, the fair value of common stock, preferred stock, warrants, stock compensation, accrued expenses and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Actual results may differ from these estimates under different assumptions or conditions. Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” in the Prospectus. There have been no material changes to the significant accounting policies during the period ended September 30, 2017. Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016‑09, Improvements to Employee Share‑Based Payment Accounting (“ASU 2016‑09” or “Topic 718”), which simplifies share‑based payment accounting through a variety of amendments. The standard is effective for annual periods beginning after December 15, 2016 and for interim periods within those fiscal years. The changes resulting from the adoption of this standard impact the accounting for income taxes, accounting for forfeitures, statutory tax withholding and the presentation of statutory tax withholding on the statement of cash flows. The Company adopted this standard on January 1, 2017. Under guidance within ASU 2016‑09, excess tax benefits and deficiencies are to be recognized as income tax expense or benefit in the statement of operations in the period in which they occur rather than as an increase or decrease in stockholders’ equity (deficit). Since the Company maintains a full valuation allowance on its net deferred tax asset, there was no net impact to its accumulated deficit or its net loss resulting from the adoption of this standard. Also under the guidance in ASU 2016‑09, an entity may elect to account for forfeitures as they occur or continue to estimate the total number of awards that are vested or expected to vest. The Company elected to account for forfeitures as they occur and applied the accounting change on a modified retrospective basis as a cumulative effect adjustment to accumulated deficit as of the date of adoption, January 1, 2017. The adoption of this standard did not have a material impact on the Company’s financial position, results of operations or statement of cash flows. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases (Topic 842) (“ASU 2016‑02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight‑line basis over the term of the lease, respectively. A lessee is also required to record a right‑of‑use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. ASU 2016‑02 (ASC Topic 842) supersedes the previous leases standard, ASC 840, Leases . The standard is effective for public entities for annual periods beginning after December 15, 2018 and for interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016‑02 will have on its financial statements. In August 2016, the FASB issued ASU No. 2016‑15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“ASU 2016‑15”), to address diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. In November 2016, the FASB issued ASU 2016‑18, Statement of Cash Flows Restricted Cash (“ASU 2016‑18”). This new standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning‑of‑period and end‑of‑period total amounts shown on the statement of cash flows. This guidance is effective for annual and interim reporting periods beginning after December 15, 2017, and requires retrospective application. The Company does not believe that the adoption of ASU 2016‑18 will have a material impact on its financial statements and related disclosures. In May 2017, the FASB issued ASU Update No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting (“ ASU 2017-09”), which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The amendments in ASU 2017-09 are effective f or all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company is currently evaluating the impact that ASU 2017-09 will have on the Company’s balance sheets, results of operations and statements of cash flows. In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815). The amendments in Part I of this Update change the classification analysis of certain equity-linked financial instruments (or embedded features) with down round features. The amendments also clarify existing disclosure requirements for equity-classified instruments. The amendments in Part II of this Update recharacterize the indefinite deferral of certain provisions of Topic 480 that now are presented as pending content in the Codification, to a scope exception. Those amendments do not have an accounting effect. For public business entities, the amendments in Part I of this Update are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted for, including adoption in an interim period. The Company is currently evaluating the impact of adopting this standard on its financial statements and related disclosures.

PREPAID EXPENSES AND OTHER CURR

PREPAID EXPENSES AND OTHER CURRENT ASSETS	9 Months Ended
	Sep. 30, 2017
PREPAID EXPENSES AND OTHER CURRENT ASSETS
PREPAID EXPENSES AND OTHER CURRENT ASSETS	3. PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, 2017 2016 Rent $ 61 $ 58 Insurance 667 55 Other 158 41 Prepaid expenses and other current assets $ 886 $ 154

ACCRUED EXPENSES

ACCRUED EXPENSES	9 Months Ended
	Sep. 30, 2017
ACCRUED EXPENSES
ACCRUED EXPENSES	4. ACCRUED EXPENSES Accrued expenses consist of the following (in thousands): September 30, December 31, 2017 2016 Development costs $ 2,350 $ 2,280 Compensation and benefits 1,140 1,480 Professional fees 194 171 Common stock offering costs 111 — Other 143 62 Accrued expenses $ 3,938 $ 3,993

DEBT

DEBT	9 Months Ended
	Sep. 30, 2017
DEBT
DEBT	5. DEBT 2014 Debt Facility In November 2014, the Company entered into a venture debt facility (“2014 Debt Facility”) for a total loan commitment of $10.0 million. On October 13, 2016, the Company entered into a First Amendment to the 2014 Debt Facility the (“First Amendment”), which reaffirmed the initial commitment to a total of $10.0 million of funding (“Term Loan A”) and increased the Company’s total borrowing capacity by an additional $10.0 million (“Term Loan B” and together with Term Loan A, “Term Loans”). On September 28, 2017, the Company drew the additional $10.0 million available under Term Loan B. Under the terms of the facility, the borrowings accrue interest at an annual rate equal to 3.00% above the Prime Rate then in effect. The interest rate was 6.50% as of December 31, 2016 and 7.25% as of September 30, 2017. The unpaid principal balance under the 2014 Debt Facility was $20.0 million and $10.0 million as of September 30, 2017 and December 31, 2016, respectively. The unamortized discount was $260,000 and $346,000 as of September 30, 2017 and December 31, 2016, respectively. During the three months ended September 30, 2017 and 2016, the Company recognized interest expense of $212,000 and $186,000, respectively, which consisted of amortization of the debt discount of $29,000 and $31,000 and the contractual coupon interest of $183,000 and $155,000, respectively. During the nine months ended September 30, 2017 and 2016, the Company recognized interest expense of $618,000 and $566,000, respectively, which consisted of amortization of the debt discount of $86,000 and $83,000 and the contractual coupon interest of $532,000 and $483,000, respectively. In connection with the 2014 Debt Facility and the initial borrowing of $5.0 million under Term Loan A, the Company issued warrants to the lender to purchase 138,889 shares of Series B Preferred Stock at an exercise price of $1.44 per share (the “2014 Warrants”). During 2015 the Company borrowed an additional $5.0 million under Term Loan A and the number of exercisable shares underlying the 2014 Warrants increased to 277,778 shares of Series B Preferred Stock or 53,333 shares of common stock at an exercise price of $7.50 per share on an as-converted basis after giving effect to the reverse stock split (see Note 1). Upon executing the First Amendment, the Company issued warrants to purchase up to 251,951 shares of Series C Preferred Stock at an exercise price of $1.59 per share (the “2016 Warrants”), or 48,374 shares of common stock at an exercise price of $8.27 per share on an as-converted basis after giving effect to the reverse stock split (see Note 1). Consistent with the warrants issued under the original 2014 Debt Facility, the number of shares of Series C Preferred Stock that become exercisable would increase in proportion to the amount of Term Loan B borrowings. Upon the September 28, 2017 draw down of Term B Loan, the 2016 Warrants became exercisable into 48,374 shares of common stock. The 2016 Warrants were not exercisable into shares as of the First Amendment date or December 31, 2016, as the Company had not borrowed under the Term B Loan during 2016. Upon issuance of the 2014 Warrants and 2016 Warrants, the Company estimated the fair value of the warrants using the Black‑Scholes option‑pricing model (see Note 6), and recorded the estimated fair value of the warrants as a liability separate from the loan balance, resulting in additional debt discount included within long‑term debt that is amortized to interest expense over the term of the loan using the effective interest method. The initial fair value of the 2014 Warrants and 2016 Warrants was $140,000 and $225,000, respectively. The warrants were subsequently re‑measured to fair value at every reporting date prior to the reporting period ending September 30, 2017 with changes in fair value recorded in the statement of operations as a component of other income (expense), as the shares underlying the warrants are exercisable into contingently redeemable shares. Upon the Company’s IPO on July 25, 2017 all of the underlying preferred stock warrants were converted into warrants for common stock, and the fair value of the warrant liability was reclassified to additional paid-in capital. As such, there was no warrant liability associated with the Term Loans as of September 30, 2017. As of December 31, 2016, the estimated fair value of the warrant liability associated with the original 2014 Debt Facility was $274,000 and the estimated fair value of the warrant liability associated with the First Amendment was $263,000. The future annual principal payments due under the Term Loans as of September 30, 2017 are as follows (in thousands): Years Ending December 31, 2017 $ 1,111 2018 6,666 2019 6,666 2020 5,557 Total $ 20,000

PREFERRED STOCK WARRANTS

PREFERRED STOCK WARRANTS	9 Months Ended
	Sep. 30, 2017
PREFERRED STOCK WARRANTS
PREFERRED STOCK WARRANTS	6. PREFERRED STOCK WARRANTS The Company has issued warrants in connection with debt transactions that were completed prior to 2014, all of which were classified as liabilities as of December 31, 2016. The warrants were remeasured at fair value at each reporting period prior to the reporting period ending September 30, 2017, as the warrants were exercisable into contingently redeemable shares. As of December 31, 2016, warrants outstanding to acquire Series C Preferred Stock were not exercisable into shares of Series C Preferred Stock. As part of the draw down of Term Loan B on September 28, 2017, warrants to acquire 48,374 shares of common stock became exercisable. The following table summarizes the warrants outstanding at each of the dates identified: Shares Exercisable at Exercise Expiration September 30, December 31, Issued Exercisable for Price Date 2017 2016 2011 and 2012 Series Seed Preferred Stock $ 1.00 July 2019 — 80,000 (1) 2013 Series B Preferred Stock $ 1.44 April 2021 — 694,444 (1) 2014 Series B Preferred Stock $ 1.44 November 2024 — 277,778 (1) 2016 Series C Preferred Stock $ 1.59 October 2026 — (2) — (2) (1) As of December 31, 2016, the preferred stock warrants to purchase Series Seed Preferred Stock issued in 2011 and 2012, Series B Preferred Stock issued in 2013 and Series B Preferred Stock issued in 2014 were exercisable, and on a converted basis would have represented warrants to purchase common stock of 15,360, 133,334 and 53,333 shares, respectively. As of September 30, 2017 there were no preferred stock warrants outstanding (See Note 1). As of September 30, 2017 all of the underlying preferred stock warrants were converted into warrants for common stock, of which 149,327 were outstanding. (2) As of December 31, 2016, the preferred stock warrants to purchase Series C Preferred Stock were not exercisable and as of September 30, 2017, there were no preferred stock warrants outstanding (See Note 1). Upon the September 2017 $10.0 million draw down of the Term B Loan, the warrants became exercisable for 48,374 shares of common stock, which for comparative purposes represents 251,951 shares of Series C Preferred Stock on a pre-converted basis. As of September 30, 2017, all 48,374 warrants were outstanding.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2017
FAIR VALUE OF FINANCIAL INSTRUMENTS
FAIR VALUE OF FINANCIAL INSTRUMENTS	7. FAIR VALUE OF FINANCIAL INSTRUMENTS Certain assets and liabilities are carried at fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • • • The Company’s preferred stock warrant liability is carried at fair value determined according to the fair value hierarchy and classified as a Level 3 measurement. The carrying value of accounts payable and accrued expenses approximate their fair value due to the short‑term nature of these assets and liabilities. Management believes that the Company’s long‑term debt (See Note 5) bears interest at the prevailing market rate for instruments with similar characteristics and, accordingly, the carrying value of long‑term debt, including the current portion, also approximates its fair value. The fair value of the outstanding debt was estimated using a discounted cash flow analysis based on current market interest rates for debt issuances with similar remaining years to maturity, adjusted for credit risk, which represents a Level 3 measurement. Upon the Company’s IPO on July 25, 2017, all of the underlying preferred stock warrants became exercisable for common stock instead of preferred stock and the $2,883,000 fair value of the warrant liability as measured immediately prior to the IPO was charged to additional paid in capital with the reclassification of the warrants as equity, not a liability. There was no warrant liability as of September 30, 2017 and, as such, there were no assets and liabilities measured at fair value on a recurring basis of September 30, 2017. As of December 31, 2016, the Company’s preferred stock warrants associated with the issuances of the 2014 Debt Facility and the First Amendment, as well as debt transactions entered into prior to 2014, were recorded at fair value. The assets and liabilities measured at fair value on a recurring basis as of December 31, 2016, and the input categories associated with those assets and liabilities are as follows (in thousands): Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs Carrying Value (Level 1) (Level 2) (Level 3) December 31, 2016 2011 and 2012 Series Seed Warrants $ 39 $ — $ — $ 39 2013 Series B Warrants 463 — — 463 2014 Series B Warrants 274 — — 274 2016 Series C Warrants 263 — — 263 Total warrant liability $ 1,039 $ — $ — $ 1,039 The Company has historically classified the value of the warrants as Level 3 measurements within the fair value hierarchy because the fair value is derived using significant unobservable inputs, which included the estimated volatility, the estimated fair value of the underlying preferred stock, and to the extent that the number of exercisable shares underlying the warrants were adjustable based on the amount of the Term Loans drawn down or the probability that the Company would draw down on the debt facility. The following table provides a summary of changes in the fair value of the Company’s derivative liability, which is included as a component of other (income) expense (in thousands): Three Months Ended September 30, 2017 2016 Warrant Warrant Liability Liability Fair value - June 30, $ 2,260 $ 965 Change in fair value of warrant liability 623 (206) Reclassification of preferred warrant liability (2,883) — Fair value - September 30, $ — $ 759 Nine Months Ended September 30, 2017 2016 Warrant Warrant Liability Liability Fair value - December 31, $ 1,039 $ 936 Change in fair value of warrant liability 1,844 (177) Reclassification of preferred warrant liability (2,883) — Fair value - September 30, $ — $ 759 The Company determined the fair values of the warrants at December 31, 2016 and on an interim basis on July 19, 2017, using the Black‑Scholes option‑pricing model. The July 19, 2017 valuation was performed as a basis for the anticipated reclassification of the preferred warrant liability to equity in connection with the IPO and conversion of the preferred stock and warrants. The following assumptions were used for the respective measurement date (1) : 2011 and 2012 Series 2013 2014 Seed Series B Series B Series C Warrants Warrants Warrants Warrants December 31, 2016 Volatility 100.00 % 87.00 % 114.00 % 58.30 % Risk-free interest rate 1.30 % 1.80 % 2.30 % 2.40 % Estimated fair value of underlying shares $ 0.89 $ 1.11 $ 1.11 1.54 Remaining contractual term (years) 2.6 4.3 7.9 9.8 Expected dividend yield — % — % — % — % July 19, 2017 Volatility 119.00 % 112.00 % 114.00 % 116.00 % Risk-free interest rate 1.40 % 1.60 % 2.10 % 2.20 % Estimated fair value of underlying shares $ 13.50 $ 13.50 $ 13.50 $ 13.50 Remaining contractual term (years) 2.0 3.7 7.3 9.2 Expected dividend yield — % — % — % — % (1) For purposes of determining the fair value of the warrants to purchase Series C Preferred Stock as of December 31, 2016 and July 19, 2017, the Company estimated that there was a 100% probability that it would draw down on the remaining $10.0 million available under the 2014 Debt Facility as of the measurement date, and as such, assumed that the warrants would be exercisable into the maximum number of shares stipulated in the First Amendment.

CONVERTIBLE PREFERRED STOCK

CONVERTIBLE PREFERRED STOCK	9 Months Ended
	Sep. 30, 2017
CONVERTIBLE PREFERRED STOCK
CONVERTIBLE PREFERRED STOCK	8. CONVERTIBLE PREFERRED STOCK Upon the closing of the Company’s IPO on July 25, 2017, all outstanding shares of convertible preferred stock converted into 16,101,970 shares of the Company’s common stock. As such, there were no outstanding shares of convertible preferred stock as of September 30, 2017. Convertible preferred stock consisted of the following as of December 31, 2016 (in thousands, except share amounts): Common Stock Shares Issued Issuable Designated and Liquidation Carrying Upon Shares Issuance Dates Outstanding Value Value Conversion (1) Series Seed 11,323,209 December 2009 2,000,001 October 2010 2,000,003 February 2012 7,243,205 11,243,209 $ 11,243 $ 11,065 Series A 9,583,432 February 2013 4,791,716 July 2013 4,791,716 9,583,432 $ 11,500 $ 10,736 Series B 16,597,221 April 2014 15,624,999 $ 22,500 $ 22,185 Series B-1 4,629,629 August 2015 4,629,629 $ 7,000 $ 6,885 Series C 43,034,639 April 2016 42,782,688 $ 67,922 $ 67,520 (1) No fractional shares of Common Stock were issuable upon conversion of the Preferred Stock. In lieu of any fractional shares to which the holder would otherwise be entitled, the Company paid cash equal to such fraction multiplied by the fair market value of a share of Common Stock as determined in good faith by the Board of Directors of the Company. Whether or not fractional shares would be issuable upon such conversion shall be determined on the basis of the total number of shares of Preferred Stock the holder is at the time converting into Common Stock and the aggregate number of shares of Common Stock issuable upon such conversion. Series Seed Convertible Preferred Stock In December 2009, the Company issued an aggregate of 2,000,001 shares of Series Seed Preferred Stock for gross proceeds of $2.0 million or $1.00 per share. In October 2010, the Company issued an aggregate of 2,000,003 shares of Series Seed Preferred Stock to existing investors for gross proceeds of $2.0 million or $1.00 per share. In February 2012, the Company issued an aggregate of 7,243,205 shares of Series Seed Preferred Stock to existing and new investors, which included 6,150,000 shares for gross proceeds of $6.2 million and 1,093,205 shares converted from convertible debt of $1.0 million principal and $93,000 accrued interest. Costs incurred in connection with each of the individual issuances of Series Seed Preferred Stock were $124,000, $39,000 and $15,000 respectively, which have been recorded as a reduction to the carrying amount of the Series Seed Preferred Stock. On July 25, 2017, upon the closing of the Company’s IPO, all outstanding shares of Series Seed Convertible Stock converted into 2,158,708 shares of the Company’s common stock. As such, there were no outstanding shares of Series Seed Convertible Preferred Stock as of September 30, 2017. Series A Convertible Preferred Stock In February 2013, the Company issued 4,791,716 shares of Series A Preferred Stock, at a purchase price of $1.20 per share for gross proceeds of $5.8 million. Additionally, in accordance with the terms of the Series A Preferred Stock Purchase Agreement, investors were granted the right to purchase up to an additional 4,791,716 shares of Series A Preferred Stock, at a price of $1.20 per share, upon the Company meeting certain milestone criteria by December 31, 2013, approval of the Board and approval of the investors holding a majority of the outstanding shares of Series A Preferred Stock. In June 2013, the Board approved waiving one of the milestone events provided for in the Series A Preferred Stock Purchase Agreement. Accordingly, the second tranche of Series A Preferred Stock closed on July 15, 2013 and the Company issued 4,791,716 shares of Series A Preferred Stock for gross proceeds of $5.8 million, or $1.20 per share. Costs incurred in connection with the issuance of the Series A Preferred Stock were $93,000, which have been recorded as a reduction in the carrying amount of the Series A Preferred Stock. On July 25, 2017, upon the closing of the Company’s IPO, all outstanding shares of Series A Convertible Stock converted into 1,840,029 shares of the Company’s common stock. As such, there were no outstanding shares of Series A Convertible Preferred Stock as of September 30, 2017. Series B Convertible Preferred Stock In April 2014, the Company issued 15,624,999 shares of Series B Preferred Stock for gross proceeds of $22.5 million or $1.44 per share which included conversion of the outstanding principal and interest on the 2013 Notes (See Note 7) of $5.1 million, which converted into 3,562,785 shares of Series B Preferred Stock pursuant to the terms of the Notes. Costs incurred in connection with the issuance of the Series B Preferred Stock were $315,000, which have been recorded as a reduction in the carrying amount of the Series B Preferred Stock. On July 25, 2017, upon the closing of the Company’s IPO, all outstanding shares of Series B Convertible Stock converted into 3,000,017 shares of the Company’s common stock. As such, there were no outstanding shares of Series B Convertible Preferred Stock as of September 30, 2017. Series B‑1 Convertible Preferred Stock On August 17, 2015, the Company issued 4,629,629 shares of Series B‑1 Senior Convertible Preferred Stock (“Series B‑1 Preferred Stock”) for gross proceeds of $7.0 million or $1.512 per share. Costs incurred in connection with the issuance of the Series B‑1 Preferred Stock were $115,000, which have been recorded as a reduction in the carrying amount of the Series B‑1 Preferred Stock. On July 25, 2017, upon the closing of the Company’s IPO, all outstanding shares of Series B-1 Convertible Stock converted into 888,894 shares of the Company’s common stock. As such, there were no outstanding shares of Series B-1 Convertible Preferred Stock as of September 30, 2017. Series C Convertible Preferred Stock On April 5, 2016, the Company issued 42,782,688 shares of Series C Preferred Stock for gross proceeds of $67.9 million or $1.5876 per share. Costs incurred in connection with the issuance of the Series C Preferred Stock were $402,000, which have been recorded as a reduction in the carrying amount of the Series C Preferred Stock. On July 25, 2017, upon the closing of the Company’s IPO, all outstanding shares of Series C Convertible Stock converted into 8,214,322 shares of the Company’s common stock. As such, there were no outstanding shares of Series C Convertible Preferred Stock as of September 30, 2017. Treatment of Preferred Stock Generally The rights, preferences, and privileges of the Series Seed, Series A, Series B, Series B-1 and Series C (collectively the “Preferred Stock”) are included in the Prospectus. As described in Note 1, on July 7, 2017, the Company effected an amendment to its Amended and Restated Certificated of the Incorporation, as amended. This amendment eliminated the minimum price per share of Common Stock for an underwritten public offering that would result in the automatic conversion of all outstanding shares of the Company’s Series Seed, Series A, Series B, Series B‑1 and Series C Preferred Stock. As described in Note 1, on July 7, 2017, the Company effected a one-for-5.2083 reverse stock split of the Company’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock.

COMMON STOCK

COMMON STOCK	9 Months Ended
	Sep. 30, 2017
COMMON STOCK AND PREFERRED STOCK
COMMON STOCK	9. COMMON STOCK AND PREFERRED STOCK COMMON STOCK The Company was authorized to issue up to 120,000,000 and 110,251,951 shares of common stock with a $0.001 par value per share as of September 30, 2017 and December 31, 2016, respectively. As of September 30, 2017 and December 31, 2016, the Company had 24,347,150 and 1,181,429 shares of common stock issued and outstanding, respectively. The rights, preferences, and privileges of the Company’s common stock are included in the Prospectus. There were no changes to the rights, preferences, and privileges of the common stock during the nine months ended September 30, 2017. PREFERRED STOCK Upon completion of the Company’s IPO, all outstanding shares of the Company’s preferred stock automatically converted into an aggregate of 16.1 million shares of the Company’s common stock. The Company also is authorized to issue 5.0 million shares of undesignated preferred stock in one or more series. As of September 30, 2017, no shares of preferred stock were issued or outstanding. Reserved Shares —As of September 30, 2017, the Company had reserved the following shares of common stock issuable upon exercise of rights under warrants and exercise of stock options, and as of December 31, 2016, the Company had reserved the following shares of common stock issuable upon conversion of then outstanding convertible preferred stock, convertible preferred stock issuable upon exercise of rights under warrants and exercise of stock options (See Note 8): September 30, December 31, 2017 2016 Convertible preferred stock — 16,101,970 2013 Warrant rights to acquire Series B Preferred Stock — 133,327 2014 Warrant rights to acquire Series B Preferred Stock — 53,333 2016 Warrant rights to acquire Series C Preferred Stock — 48,374 2011 Warrant rights to acquire Series Seed Preferred Stock — 15,360 Warrant rights to acquire Common Stock 197,701 — 2009 stock option plan 3,001,752 3,533,726 2017 stock option plan 2,011,203 Total 5,210,656 19,886,090

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2017
STOCK-BASED COMPENSATION
STOCK-BASED COMPENSATION	10. STOCK‑BASED COMPENSATION Stock Incentive Plan —On December 11, 2009, the Board adopted the 2009 Employee, Director and Consultant Equity Incentive Plan (the “2009 Plan”) for the issuance of common stock and stock options to employees, officers, directors, consultants, and advisors. Under the 2009 Plan, the Board determined the number of shares of common stock to be granted pursuant to the awards, as well as the exercise price and terms of such awards. The exercise price of incentive stock options could not be less than the fair value of the common stock on the date of grant. Stock options awarded under the 2009 Plan expire 10 years after the grant date, unless the Board sets a shorter term. Options granted under the plan generally vest over a four‑year period. As of December 31, 2016, there were 338,256 shares of common stock available for future grant under the 2009 Plan. On July 19, 2017, the Company’s 2017 Prior to the IPO, the Company had granted 86,056 stock options which contain performance‑based vesting criteria. These criteria were milestone events that were specific to the Company’s corporate goals. Stock‑based compensation expense associated with performance‑based stock options is recognized if the achievement of the performance condition is considered probable using management’s best estimates. The milestones were not deemed probable as of December 31, 2016 and were not met and had expired as of September 30, 2017. The Company granted 0 stock options to non‑employee consultants for the three months ended September 30, 2017 and 2016, and 4,224 and 0 stock options for the nine months ended September 30, 2017 and 2016, respectively. During the three months ended September 30, 2017 and 2016, the Company recognized $46,000 and $6,000, respectively, in stock compensation expense related to non‑employee consultants. During the nine months ended September 30, 2017 and 2016, the Company recognized $83,000, and $34,000, respectively, in stock compensation expense related to non‑employee consultants. A portion of the unvested stock options will vest upon the sale of all or substantially all of the stock or assets of the Company. A summary of option activity for employee and non‑employee awards under the 2009 Plan and the 2017 Plan for the nine months ended September 30, 2017 is as follows (in thousands, except share and per share amounts): Weighted Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Term Value (Years) Outstanding at January 1,2017 $ 3.26 $ 1,200 Granted 16.06 Exercised 1.46 Forfeited 2.72 Outstanding at September 30, 2017 $ 5.97 $ 61,572 Vested and expected to vest at September 30, 2017 3,645,645 $ 5.97 $ 61,552 Options exercisable at September 30, 2017 1,590,655 $ 3.43 $ 30,882 The Company records stock‑based compensation related to stock options granted at fair value. The Company utilizes the Black‑Scholes option‑pricing model to estimate the fair value of stock option grants and to determine the related compensation expense. The assumptions used in calculating the fair value of stock‑based payment awards represent management’s best estimates. The assumptions used in determining fair value of the stock options granted in the nine months ended September 30, 2017 and 2016 are as follows: Nine Months Ended September 30, 2017 2016 Expected volatility 103% - 122% 108% - 110% Risk-free interest rate 1.81% - 2.29% 1.21% - 1.33% Expected dividend yield 0% 0% Expected term (in years) 5.04 - 9.82 5.62 - 6.18 The Company derived the risk‑free interest rate assumption from the U.S. Treasury rates for U.S. Treasury zero‑coupon bonds with maturities similar to those of the expected term of the awards being valued. The Company based the assumed dividend yield on its expectation of not paying dividends in the foreseeable future. The Company calculated the weighted‑average expected term of options using the simplified method, as the Company lacks relevant historical data due to the Company’s limited operating experience. The estimated volatility is based upon the historical volatility of comparable companies with publicly available share prices. The impact of forfeitures on compensation expense are recorded as they occur. The weighted average grant‑date fair value of options granted was $14.74 and $2.77, respectively, during the three months ended September 30, 2017 and 2016, and $13.19 and $2.73, respectively, during the nine months ended September 30, 2017 and 2016. There were 747,892 and 1,516,894 options granted during the nine months ended September 30, 2017 and 2016, respectively. The fair value is being expensed over the vesting period of the options on a straight‑line basis as the services are being provided. The Company has recorded aggregate stock‑based compensation expense related to the issuance of stock option awards of $981,000 and $554,000, respectively, during the three months ended September 30, 2017 and 2016, and $2.1 million and $1.7 million during the nine months ended September 30, 2017 and 2016, respectively. As of September 30, 2017, there was $13.2 million of unrecognized compensation cost related to the stock options granted, which is expected to be expensed over a weighted‑average period of 3.07 years. Stock-based Compensation Expenses —Stock‑based compensation expense was classified in the statements of operations as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Research and development $ 357 $ 180 $ 749 $ 309 General and administrative 624 374 1,321 1,438 Total $ 981 $ 554 $ 2,070 $ 1,747

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2017
INCOME TAXES
INCOME TAXES	11. INCOME TAXES The Company did not record a provision or benefit for income taxes during the three and nine months ended September 30, 2017 and 2016. The Company continues to maintain a valuation allowance for its U.S. federal and state deferred tax assets. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Management reevaluates the positive and negative evidence at each reporting period. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. Under the provisions of Section 382 of the Internal Revenue Code of 1986, certain substantial changes in the Company’s ownership, including a sale of the Company, or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of net operating loss carryforwards, which could be used annually to offset future taxable income. The Company files its corporate income tax returns in the United States and Massachusetts, California, Kentucky, Pennsylvania, New Hampshire, New York, North Carolina and Texas. All tax years since the date of incorporation remain open to examination by the major taxing jurisdictions (state and federal) to which the Company is subject, as carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service (“IRS”) or other authorities if they have or will be used in a future period. The Company is not currently under examination by the IRS or any other jurisdictions for any tax year. As of September 30, 2017 and 2016, the Company had no uncertain tax positions. The Company’s policy is to recognize interest and penalties related to income tax matters as a component of income tax expense, of which no interest or penalties were recorded for the nine months ended September 30, 2017 and 2016.

NET LOSS PER COMMON SHARE

NET LOSS PER COMMON SHARE	9 Months Ended
	Sep. 30, 2017
NET LOSS PER COMMON SHARE
NET LOSS PER COMMON SHARE	12. NET LOSS PER COMMON SHARE Net Loss per Share —Basic and diluted net loss per share attributable to common stockholders were calculated as follows (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Numerator: Net loss attributable to common stockholders $ (10,175) $ (9,667) $ (30,921) $ (24,772) Denominator: Weighted average shares outstanding—basic and diluted 18,034,278 1,181,429 6,860,777 1,181,429 Net loss per share attributable to common stockholders—basic and diluted $ (0.56) $ (8.18) $ (4.51) $ (20.97) The Company’s potential dilutive securities, which include stock options and warrants to purchase common stock as of September 30, 2017 and stock options, warrants to purchase preferred stock and convertible preferred stock as of December 31, 2016, have been excluded from the computation of diluted net loss per share, for each respective period, as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders are the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti‑dilutive effect: September 30, 2017 2016 Convertible preferred stock (as converted to common stock) - 16,101,970 Options to purchase common stock 3,646,631 3,063,049 Common stock warrants 197,701 250,394 3,844,332 19,415,413

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2017
COMMITMENTS AND CONTINGENCIES.
COMMITMENTS AND CONTINGENCIES.	13. COMMITMENTS AND CONTINGENCIES Leases —The Company entered into a three‑year lease agreement for its new headquarters on September 30, 2013, with a commencement date of February 1, 2014. As part of the terms of the lease agreement, the landlord agreed to fund certain improvements to the Company’s facility. The amount funded by the landlord was $78,000 and has been recorded as a liability which is being amortized as a reduction of rent expense over the term of the lease. On June 30, 2016, the lease was amended to extend the term from January 31, 2017 to January 31, 2019. In connection with the lease agreement, the Company issued a letter of credit to the landlord for $84,000. The Company secured the letter of credit using restricted cash for the full amount of the letter. The restricted cash as of September 30, 2017 is included in other noncurrent assets in the accompanying balance sheets. Total rent expense for the lease, which is recorded on a straight‑line basis, for the three months ended September 30, 2017 and 2016 was $97,000 and $85,000, respectively and for the nine months ended September 30, 2017 and 2016 was $290,000 and $244,000, respectively. Future minimum commitments due under these non-cancelable operating lease agreements as of September 30, 2017 are as follows (in thousands): Years Ending December 31, 2017 (remaining three months) $ 99 2018 410 2019 34 Total minimum lease payments $ 543 License Agreement —In 2009, the Company entered into an exclusive license agreement with The Johns Hopkins University (“JHU”), as amended in November 2012, May 2014, August 2014 and October 2014, which licensed to the Company a portfolio of specified patent rights and remains in full force and effect. Pursuant to the terms of the agreement, as amended, the Company agreed to pay an initial license fee, minimum annual payments beginning in 2017, certain development and commercial milestone payments, royalties on product sales and reimburse all or a portion of the costs associated with the preparation, filing, prosecution and maintenance of the agreed‑upon patents and patent applications to JHU (“Prosecution Costs”). After 2016 and until the first commercial sale of product, the minimum annual payment will be $38,000. If the Company achieves the first commercial sale of the product in the United States, European Union, or Japan, the annual minimum payment will increase to $113,000. The Company is obligated to pay JHU low single‑digit running royalties based upon a percentage of net sales of the licensed products. The Company also has an obligation to pay JHU certain one‑time development and commercial milestone payments. The Company recorded research and development expenses related to the JHU agreement of $97,000 and $50,000, respectively, for the three months ended September 30, 2017 and 2016 and $108,000 and $99,000, respectively, for the nine months ended September 30, 2017 and 2016. In 2015, the Company entered into a non‑exclusive license agreement with Massachusetts Eye and Ear Infirmary (“MEEI”), which licensed to the Company a certain questionnaire called “Symptom Assessment in Dry Eye” for use in clinical trials. Pursuant to the terms of the agreement, the Company agreed to pay an initial license fee of $10,000. Beginning in 2016, the Company was also obligated to pay an annual payment of $5,000. The agreement terminates in 2018. Litigation —The Company is not currently subject to any material legal proceedings. Guarantees and Indemnifications —The Company’s Certificate of Incorporation authorizes the Company to indemnify and advance expenses to its officers and directors and agents to the fullest extent permitted by law. The Company leases office space under a non‑cancelable operating lease. Under the lease the Company is required to indemnify the landlord against claims, actions, or damages incurred in connection with, among other items, the Company’s occupancy and use of the premises. The Company’s equity agreements and certain other arrangements include standard indemnifications against claims, actions, or other matters that may arise in connection with these arrangements. As of September 30, 2017, the Company had not experienced any losses related to these indemnification obligations, and no claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and has no amount accrued related to these contingencies. The Company does not expect these indemnifications to have a material adverse effect on these financial statements.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2017
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	14. SUBSEQUENT EVENTS The Company has evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its financial statements or disclosures.

SUMMARY OF SIGNIFICANT ACCOUN20

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, expense, and related disclosures. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. Estimates relied upon in preparing these financial statements relate to, but are not limited to, the fair value of common stock, preferred stock, warrants, stock compensation, accrued expenses and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Actual results may differ from these estimates under different assumptions or conditions.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016‑09, Improvements to Employee Share‑Based Payment Accounting (“ASU 2016‑09” or “Topic 718”), which simplifies share‑based payment accounting through a variety of amendments. The standard is effective for annual periods beginning after December 15, 2016 and for interim periods within those fiscal years. The changes resulting from the adoption of this standard impact the accounting for income taxes, accounting for forfeitures, statutory tax withholding and the presentation of statutory tax withholding on the statement of cash flows. The Company adopted this standard on January 1, 2017. Under guidance within ASU 2016‑09, excess tax benefits and deficiencies are to be recognized as income tax expense or benefit in the statement of operations in the period in which they occur rather than as an increase or decrease in stockholders’ equity (deficit). Since the Company maintains a full valuation allowance on its net deferred tax asset, there was no net impact to its accumulated deficit or its net loss resulting from the adoption of this standard. Also under the guidance in ASU 2016‑09, an entity may elect to account for forfeitures as they occur or continue to estimate the total number of awards that are vested or expected to vest. The Company elected to account for forfeitures as they occur and applied the accounting change on a modified retrospective basis as a cumulative effect adjustment to accumulated deficit as of the date of adoption, January 1, 2017. The adoption of this standard did not have a material impact on the Company’s financial position, results of operations or statement of cash flows. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases (Topic 842) (“ASU 2016‑02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight‑line basis over the term of the lease, respectively. A lessee is also required to record a right‑of‑use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. ASU 2016‑02 (ASC Topic 842) supersedes the previous leases standard, ASC 840, Leases . The standard is effective for public entities for annual periods beginning after December 15, 2018 and for interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016‑02 will have on its financial statements. In August 2016, the FASB issued ASU No. 2016‑15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“ASU 2016‑15”), to address diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. In November 2016, the FASB issued ASU 2016‑18, Statement of Cash Flows Restricted Cash (“ASU 2016‑18”). This new standard requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning‑of‑period and end‑of‑period total amounts shown on the statement of cash flows. This guidance is effective for annual and interim reporting periods beginning after December 15, 2017, and requires retrospective application. The Company does not believe that the adoption of ASU 2016‑18 will have a material impact on its financial statements and related disclosures. In May 2017, the FASB issued ASU Update No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting (“ ASU 2017-09”), which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The amendments in ASU 2017-09 are effective f or all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2017, with early adoption permitted. The Company is currently evaluating the impact that ASU 2017-09 will have on the Company’s balance sheets, results of operations and statements of cash flows. In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815). The amendments in Part I of this Update change the classification analysis of certain equity-linked financial instruments (or embedded features) with down round features. The amendments also clarify existing disclosure requirements for equity-classified instruments. The amendments in Part II of this Update recharacterize the indefinite deferral of certain provisions of Topic 480 that now are presented as pending content in the Codification, to a scope exception. Those amendments do not have an accounting effect. For public business entities, the amendments in Part I of this Update are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted for, including adoption in an interim period. The Company is currently evaluating the impact of adopting this standard on its financial statements and related disclosures.

PREPAID EXPENSES AND OTHER CU21

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Tables)	9 Months Ended
	Sep. 30, 2017
PREPAID EXPENSES AND OTHER CURRENT ASSETS
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, 2017 2016 Rent $ 61 $ 58 Insurance 667 55 Other 158 41 Prepaid expenses and other current assets $ 886 $ 154

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	9 Months Ended
	Sep. 30, 2017
ACCRUED EXPENSES
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): September 30, December 31, 2017 2016 Development costs $ 2,350 $ 2,280 Compensation and benefits 1,140 1,480 Professional fees 194 171 Common stock offering costs 111 — Other 143 62 Accrued expenses $ 3,938 $ 3,993

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2017
DEBT
Schedule of maturities of long-term debt	The future annual principal payments due under the Term Loans as of September 30, 2017 are as follows (in thousands): Years Ending December 31, 2017 $ 1,111 2018 6,666 2019 6,666 2020 5,557 Total $ 20,000

PREFERRED STOCK WARRANTS (Table

PREFERRED STOCK WARRANTS (Tables)	9 Months Ended
	Sep. 30, 2017
PREFERRED STOCK WARRANTS
Schedule of outstanding warrants	Shares Exercisable at Exercise Expiration September 30, December 31, Issued Exercisable for Price Date 2017 2016 2011 and 2012 Series Seed Preferred Stock $ 1.00 July 2019 — 80,000 (1) 2013 Series B Preferred Stock $ 1.44 April 2021 — 694,444 (1) 2014 Series B Preferred Stock $ 1.44 November 2024 — 277,778 (1) 2016 Series C Preferred Stock $ 1.59 October 2026 — (2) — (2) (1) As of December 31, 2016, the preferred stock warrants to purchase Series Seed Preferred Stock issued in 2011 and 2012, Series B Preferred Stock issued in 2013 and Series B Preferred Stock issued in 2014 were exercisable, and on a converted basis would have represented warrants to purchase common stock of 15,360, 133,334 and 53,333 shares, respectively. As of September 30, 2017 there were no preferred stock warrants outstanding (See Note 1). As of September 30, 2017 all of the underlying preferred stock warrants were converted into warrants for common stock, of which 149,327 were outstanding. (2) As of December 31, 2016, the preferred stock warrants to purchase Series C Preferred Stock were not exercisable and as of September 30, 2017, there were no preferred stock warrants outstanding (See Note 1). Upon the September 2017 $10.0 million draw down of the Term B Loan, the warrants became exercisable for 48,374 shares of common stock, which for comparative purposes represents 251,951 shares of Series C Preferred Stock on a pre-converted basis. As of September 30, 2017, all 48,374 warrants were outstanding.

FAIR VALUE OF FINANCIAL INSTR25

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2017
FAIR VALUE OF FINANCIAL INSTRUMENTS
Schedule of assets and liabilities measured at fair value on a recurring basis	The assets and liabilities measured at fair value on a recurring basis as of December 31, 2016, and the input categories associated with those assets and liabilities are as follows (in thousands): Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs Carrying Value (Level 1) (Level 2) (Level 3) December 31, 2016 2011 and 2012 Series Seed Warrants $ 39 $ — $ — $ 39 2013 Series B Warrants 463 — — 463 2014 Series B Warrants 274 — — 274 2016 Series C Warrants 263 — — 263 Total warrant liability $ 1,039 $ — $ — $ 1,039
Schedule of changes in Level 3 fair value measurements	The following table provides a summary of changes in the fair value of the Company’s derivative liability, which is included as a component of other (income) expense (in thousands): Three Months Ended September 30, 2017 2016 Warrant Warrant Liability Liability Fair value - June 30, $ 2,260 $ 965 Change in fair value of warrant liability 623 (206) Reclassification of preferred warrant liability (2,883) — Fair value - September 30, $ — $ 759 Nine Months Ended September 30, 2017 2016 Warrant Warrant Liability Liability Fair value - December 31, $ 1,039 $ 936 Change in fair value of warrant liability 1,844 (177) Reclassification of preferred warrant liability (2,883) — Fair value - September 30, $ — $ 759
Schedule of fair values of warrants, using the Black Scholes option pricing model	2011 and 2012 Series 2013 2014 Seed Series B Series B Series C Warrants Warrants Warrants Warrants December 31, 2016 Volatility 100.00 % 87.00 % 114.00 % 58.30 % Risk-free interest rate 1.30 % 1.80 % 2.30 % 2.40 % Estimated fair value of underlying shares $ 0.89 $ 1.11 $ 1.11 1.54 Remaining contractual term (years) 2.6 4.3 7.9 9.8 Expected dividend yield — % — % — % — % July 19, 2017 Volatility 119.00 % 112.00 % 114.00 % 116.00 % Risk-free interest rate 1.40 % 1.60 % 2.10 % 2.20 % Estimated fair value of underlying shares $ 13.50 $ 13.50 $ 13.50 $ 13.50 Remaining contractual term (years) 2.0 3.7 7.3 9.2 Expected dividend yield — % — % — % — % For purposes of determining the fair value of the warrants to purchase Series C Preferred Stock as of December 31, 2016 and July 19, 2017, the Company estimated that there was a 100% probability that it would draw down on the remaining $10.0 million available under the 2014 Debt Facility as of the measurement date, and as such, assumed that the warrants would be exercisable into the maximum number of shares stipulated in the First Amendment.

CONVERTIBLE PREFERRED STOCK (Ta

CONVERTIBLE PREFERRED STOCK (Tables)	9 Months Ended
	Sep. 30, 2017
CONVERTIBLE PREFERRED STOCK
Schedule of preferred stock	Convertible preferred stock consisted of the following as of December 31, 2016 (in thousands, except share amounts): Common Stock Shares Issued Issuable Designated and Liquidation Carrying Upon Shares Issuance Dates Outstanding Value Value Conversion (1) Series Seed 11,323,209 December 2009 2,000,001 October 2010 2,000,003 February 2012 7,243,205 11,243,209 $ 11,243 $ 11,065 Series A 9,583,432 February 2013 4,791,716 July 2013 4,791,716 9,583,432 $ 11,500 $ 10,736 Series B 16,597,221 April 2014 15,624,999 $ 22,500 $ 22,185 Series B-1 4,629,629 August 2015 4,629,629 $ 7,000 $ 6,885 Series C 43,034,639 April 2016 42,782,688 $ 67,922 $ 67,520 (1) No fractional shares of Common Stock were issuable upon conversion of the Preferred Stock. In lieu of any fractional shares to which the holder would otherwise be entitled, the Company paid cash equal to such fraction multiplied by the fair market value of a share of Common Stock as determined in good faith by the Board of Directors of the Company. Whether or not fractional shares would be issuable upon such conversion shall be determined on the basis of the total number of shares of Preferred Stock the holder is at the time converting into Common Stock and the aggregate number of shares of Common Stock issuable upon such conversion.

COMMON STOCK (Tables)

COMMON STOCK (Tables)	9 Months Ended
	Sep. 30, 2017
COMMON STOCK AND PREFERRED STOCK
Schedule of reserved common stock shares for potential conversion of outstanding convertible preferred stock	September 30, December 31, 2017 2016 Convertible preferred stock — 16,101,970 2013 Warrant rights to acquire Series B Preferred Stock — 133,327 2014 Warrant rights to acquire Series B Preferred Stock — 53,333 2016 Warrant rights to acquire Series C Preferred Stock — 48,374 2011 Warrant rights to acquire Series Seed Preferred Stock — 15,360 Warrant rights to acquire Common Stock 197,701 — 2009 stock option plan 3,001,752 3,533,726 2017 stock option plan 2,011,203 Total 5,210,656 19,886,090

STOCK_BASED COMPENSATION (Table

STOCK‑BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2017
STOCK-BASED COMPENSATION
Summary of option activity for employee and non employee awards	A summary of option activity for employee and non‑employee awards under the 2009 Plan and the 2017 Plan for the nine months ended September 30, 2017 is as follows (in thousands, except share and per share amounts): Weighted Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Term Value (Years) Outstanding at January 1,2017 $ 3.26 $ 1,200 Granted 16.06 Exercised 1.46 Forfeited 2.72 Outstanding at September 30, 2017 $ 5.97 $ 61,572 Vested and expected to vest at September 30, 2017 3,645,645 $ 5.97 $ 61,552 Options exercisable at September 30, 2017 1,590,655 $ 3.43 $ 30,882
Schedule of assumptions used in determining fair value of the stock options granted	Nine Months Ended September 30, 2017 2016 Expected volatility 103% - 122% 108% - 110% Risk-free interest rate 1.81% - 2.29% 1.21% - 1.33% Expected dividend yield 0% 0% Expected term (in years) 5.04 - 9.82 5.62 - 6.18
Schedule of stock based compensation expense	Stock-based Compensation Expenses —Stock‑based compensation expense was classified in the statements of operations as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Research and development $ 357 $ 180 $ 749 $ 309 General and administrative 624 374 1,321 1,438 Total $ 981 $ 554 $ 2,070 $ 1,747

NET LOSS PER COMMON SHARE (Tabl

NET LOSS PER COMMON SHARE (Tables)	9 Months Ended
	Sep. 30, 2017
NET LOSS PER COMMON SHARE
Schedule of computation of basic and diluted net loss per share	Net Loss per Share —Basic and diluted net loss per share attributable to common stockholders were calculated as follows (in thousands, except share and per share amounts): Three Months Ended Nine Months Ended September 30, September 30, 2017 2016 2017 2016 Numerator: Net loss attributable to common stockholders $ (10,175) $ (9,667) $ (30,921) $ (24,772) Denominator: Weighted average shares outstanding—basic and diluted 18,034,278 1,181,429 6,860,777 1,181,429 Net loss per share attributable to common stockholders—basic and diluted $ (0.56) $ (8.18) $ (4.51) $ (20.97)
Schedule of outstanding securities excluded from the computation of diluted weighted average shares outstanding as they would have been anti-dilutive	September 30, 2017 2016 Convertible preferred stock (as converted to common stock) - 16,101,970 Options to purchase common stock 3,646,631 3,063,049 Common stock warrants 197,701 250,394 3,844,332 19,415,413

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2017
COMMITMENTS AND CONTINGENCIES.
Schedule of future minimum commitments	Future minimum commitments due under these non-cancelable operating lease agreements as of September 30, 2017 are as follows (in thousands): Years Ending December 31, 2017 (remaining three months) $ 99 2018 410 2019 34 Total minimum lease payments $ 543

NATURE OF BUSINESS AND BASIS 31

NATURE OF BUSINESS AND BASIS OF PRESENTATION - Nature of Business (Details) $ / shares in Units, $ in Thousands	Jul. 25, 2017USD ($)$ / sharesshares	Jul. 07, 2017	Jul. 25, 2017USD ($)$ / sharesshares	Sep. 30, 2017USD ($)$ / shares	Dec. 31, 2016$ / shares
Initial Public Offering
Common stock, par value | $ / shares				$ 0.001	$ 0.001
Net proceeds | $				$ 96,255
Common stock shares issued | shares	16,101,970
Reverse Stock Split
Reverse stock split		0.1920
IPO
Initial Public Offering
Issuance of common stock upon IPO, net $96.3M (in shares) | shares	6,900,000
Share price (in dollars per share) | $ / shares	$ 15		$ 15
Net proceeds | $	$ 94,100
Underwriter's option
Initial Public Offering
Issuance of common stock upon IPO, net $96.3M (in shares) | shares	900,000
Share price (in dollars per share) | $ / shares	$ 15		$ 15
Underwriting discounts and commissions | $	$ 7,200
Offering costs | $			$ 2,200
Common stock.
Initial Public Offering
Shares warrants may purchase | shares	202,020		202,020
Common stock. | IPO
Initial Public Offering
Common stock, par value | $ / shares	$ 0.001		$ 0.001

PREPAID EXPENSES AND OTHER CU32

PREPAID EXPENSES AND OTHER CURRENT ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
PREPAID EXPENSES AND OTHER CURRENT ASSETS
Rent	$ 61	$ 58
Insurance	667	55
Other	158	41
Prepaid expenses and other current assets	$ 886	$ 154

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
ACCRUED EXPENSES
Development costs	$ 2,350	$ 2,280
Compensation and benefits	1,140	1,480
Professional fees	194	171
Deferred offering costs	111
Other	143	62
Accrued expenses	$ 3,938	$ 3,993

DEBT (Details)

DEBT (Details) - USD ($)	Sep. 28, 2017	Dec. 31, 2016	Oct. 13, 2016	Dec. 31, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2014
Debt instruments
Total loan commitment	$ 10,000,000
Interest expense					$ 212,000	$ 186,000	$ 618,000	$ 566,000
Term loan							10,000,000
Unpaid balance					20,000,000		20,000,000
Warrant Liability		$ 1,039,000			$ 0		$ 0		$ 1,039,000
2014 Series B Warrants
Debt instruments
Fair value of warrants		274,000							274,000		$ 140,000
2016 Series C Warrants
Debt instruments
Fair value of warrants		$ 263,000	$ 225,000						$ 263,000
2014 Debt Facility
Debt instruments
Total loan commitment											$ 10,000,000
Additional borrowing capacity			$ 10,000,000
Interest rate (as a percent)		6.50%			7.25%		7.25%		6.50%
Unpaid principal balance		$ 10,000,000			$ 20,000,000		$ 20,000,000		$ 10,000,000
Unamortized discount		346,000			260,000		260,000		346,000
Interest expense					212,000	186,000	618,000	566,000
Amortization of debt discount					29,000	31,000	86,000	83,000
Contractual coupon interest					183,000	$ 155,000	532,000	$ 483,000
2014 Debt Facility | Prime Rate
Debt instruments
Variable rate of interest			3.00%
Term Loan A
Debt instruments
Total loan commitment			$ 10,000,000
Proceeds from borrowing				$ 5,000,000						$ 5,000,000
Term Loan B
Debt instruments
Term loan	$ 10,000,000
Series B convertible preferred stock
Debt instruments
Warrant Liability					$ 0		$ 0
Shares Exercisable		133,334
Series B convertible preferred stock | 2014 Series B Warrants
Debt instruments
Exercise Price					$ 1.44		$ 1.44
Shares Exercisable									$ 277,778
Series B convertible preferred stock | Term Loan A | 2014 Series B Warrants
Debt instruments
Shares warrants may purchase				138,889						277,778
Exercise Price				$ 1.44
Series C convertible preferred stock
Debt instruments
Warrant Liability					$ 0		$ 0
Shares warrants may purchase	48,374
Shares Exercisable		$ 53,333
Series C convertible preferred stock | 2016 Series C Warrants
Debt instruments
Exercise Price					$ 1.59		$ 1.59
Series C convertible preferred stock | Term Loan B | 2016 Series C Warrants
Debt instruments
Exercise Price			$ 1.59
Series C convertible preferred stock | Term Loan B | 2016 Series C Warrants | Maximum
Debt instruments
Shares warrants may purchase	48,374		251,951
Common Stock
Debt instruments
Shares warrants may purchase	251,951
Common Stock | Term Loan A | 2014 Series B Warrants
Debt instruments
Shares warrants may purchase										53,333
Exercise Price										$ 7.50
Common Stock | Term Loan B | 2016 Series C Warrants
Debt instruments
Exercise Price			$ 8.27
Common Stock | Term Loan B | 2016 Series C Warrants | Maximum
Debt instruments
Shares warrants may purchase			48,374
Shares Exercisable							$ 48,374

DEBT - Future annual principal

DEBT - Future annual principal payments (Details) $ in Thousands	Sep. 30, 2017USD ($)
Maturities of long-term debt
2,017	$ 1,111
2,018	6,666
2,019	6,666
2,020	5,557
Total	$ 20,000

PREFERRED STOCK WARRANTS (Detai

PREFERRED STOCK WARRANTS (Details) - USD ($)	Dec. 31, 2016	Sep. 30, 2017	Dec. 31, 2016	Sep. 28, 2017	Oct. 13, 2016
Preferred stock warrants
Warrant Liability	$ 1,039,000	$ 0	$ 1,039,000
Total loan commitment				$ 10,000,000
Series Seed convertible preferred stock
Preferred stock warrants
Shares Exercisable	15,360
Warrant Liability		$ 0
Series Seed convertible preferred stock | 2011 and 2012 Series Seed Warrants
Preferred stock warrants
Exercise Price		$ 1
Shares Exercisable			80,000
Series B convertible preferred stock
Preferred stock warrants
Shares Exercisable	133,334
Warrant Liability		$ 0
Series B convertible preferred stock | 2013 Series B Warrants
Preferred stock warrants
Exercise Price		$ 1.44
Shares Exercisable			694,444
Series B convertible preferred stock | 2014 Series B Warrants
Preferred stock warrants
Exercise Price		$ 1.44
Shares Exercisable			$ 277,778
Series C convertible preferred stock
Preferred stock warrants
Shares Exercisable	$ 53,333
Warrant Liability		$ 0
Shares warrants may purchase				48,374
Series C convertible preferred stock | 2016 Series C Warrants
Preferred stock warrants
Exercise Price		$ 1.59
Series C convertible preferred stock | 2016 Series C Warrants | Term Loan B
Preferred stock warrants
Exercise Price					$ 1.59
Preferred stock warrants outstanding		48,374
Series C convertible preferred stock | 2016 Series C Warrants | Term Loan B | Maximum
Preferred stock warrants
Shares warrants may purchase				48,374	251,951
Common Stock
Preferred stock warrants
Preferred stock warrants outstanding		149,327
Shares warrants may purchase				251,951
Common Stock | 2016 Series C Warrants | Term Loan B
Preferred stock warrants
Exercise Price					$ 8.27
Common Stock | 2016 Series C Warrants | Term Loan B | Maximum
Preferred stock warrants
Shares Exercisable		$ 48,374
Shares warrants may purchase					48,374
Preferred stock
Preferred stock warrants
Preferred stock warrants outstanding		0

FAIR VALUE OF FINANCIAL INSTR37

FAIR VALUE OF FINANCIAL INSTRUMENTS - Assets and Liabilities measured at fair value (Details) (Imported) - Recurring $ in Thousands	Dec. 31, 2016USD ($)
Significant Unobservable Inputs
Warrant Liability	$ 1,039
Carrying Value
Warrant Liability	1,039
2011 and 2012 Series Seed Warrants | Significant Unobservable Inputs
Warrant Liability	39
2011 and 2012 Series Seed Warrants | Carrying Value
Warrant Liability	39
2013 Series B Warrants | Significant Unobservable Inputs
Warrant Liability	463
2013 Series B Warrants | Carrying Value
Warrant Liability	463
2014 Series B Warrants | Significant Unobservable Inputs
Warrant Liability	274
2014 Series B Warrants | Carrying Value
Warrant Liability	274
2016 Series C Warrants | Significant Unobservable Inputs
Warrant Liability	263
2016 Series C Warrants | Carrying Value
Warrant Liability	$ 263

FAIR VALUE OF FINANCIAL INSTR38

FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair values of the warrants, using the Black‑Scholes option‑pricing model (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 19, 2017	Dec. 31, 2016
Fair Value Measurements
Percentage of probability	100.00%	100.00%
Remaining borrowing capacity	$ 10	$ 10
2011 and 2012 Series Seed Warrants
Fair Value Measurements
Volatility	119.00%	100.00%
Risk-free interest rate	1.40%	1.30%
Estimated fair value of underlying shares	$ 13.50	$ 0.89
Remaining contractual term	2 years	2 years 7 months 6 days
2013 Series B Warrants
Fair Value Measurements
Volatility	112.00%	87.00%
Risk-free interest rate	1.60%	1.80%
Estimated fair value of underlying shares	$ 13.50	$ 1.11
Remaining contractual term	3 years 8 months 12 days	4 years 3 months 18 days
2014 Series B Warrants
Fair Value Measurements
Volatility	114.00%	114.00%
Risk-free interest rate	2.10%	2.30%
Estimated fair value of underlying shares	$ 13.50	$ 1.11
Remaining contractual term	7 years 3 months 18 days	7 years 10 months 24 days
2016 Series C Warrants
Fair Value Measurements
Volatility	116.00%	58.30%
Risk-free interest rate	2.20%	2.40%
Estimated fair value of underlying shares	$ 13.50	$ 1.54
Remaining contractual term	9 years 2 months 12 days	9 years 9 months 18 days

FAIR VALUE OF FINANCIAL INSTR39

FAIR VALUE OF FINANCIAL INSTRUMENTS - Derivative liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)
Balance at beginning of period			$ 1,039	$ 936
Change in fair value of warrant liability	$ 623	$ (206)	1,844	(177)
Reclassification of preferred warrant liability	(2,883)		(2,883)
Balance at end of period	$ 2,883	$ 759	$ 2,883	$ 759

CONVERTIBLE PREFERRED STOCK - S

CONVERTIBLE PREFERRED STOCK - Shares issued (Details) - USD ($) $ in Thousands	Jul. 25, 2017	Sep. 30, 2017	Dec. 31, 2016	Apr. 05, 2016	Aug. 17, 2015	Apr. 30, 2014	Jul. 15, 2013	Feb. 28, 2013	Feb. 29, 2012	Oct. 31, 2010	Dec. 31, 2009
Temporary Equity
Common stock shares issued	16,101,970
Convertible preferred stock.
Temporary Equity
Designated Shares		0	170,336,260
Shares Outstanding		0
Series Seed convertible preferred stock
Temporary Equity
Designated Shares		0	11,323,209
Shares Issued		0	11,243,209
Shares Outstanding		0	11,243,209
Liquidation Value		$ 11,243	$ 11,243
Carrying Value		$ 11,065	$ 11,065
Common Stock Issuable Upon Conversion		2,158,708	2,158,708
Common stock shares issued	2,158,708
Series Seed convertible preferred stock | December 2009
Temporary Equity
Shares Issued		2,000,001	2,000,001								2,000,001
Shares Outstanding		2,000,001	2,000,001
Series Seed convertible preferred stock | October 2010
Temporary Equity
Shares Issued		2,000,003	2,000,003							2,000,003
Shares Outstanding		2,000,003	2,000,003
Series Seed convertible preferred stock | February 2012
Temporary Equity
Shares Issued		7,243,205	7,243,205						7,243,205
Shares Outstanding		7,243,205	7,243,205
Series A convertible preferred stock
Temporary Equity
Designated Shares		0	9,583,432
Shares Issued		0	9,583,432
Shares Outstanding		0	9,583,432
Liquidation Value		$ 11,500	$ 11,500
Carrying Value		$ 10,736	$ 10,736
Common Stock Issuable Upon Conversion		1,840,029	1,840,029
Common stock shares issued	1,840,029
Series A convertible preferred stock | February 2013
Temporary Equity
Shares Issued		4,791,716	4,791,716					4,791,716
Shares Outstanding		4,791,716	4,791,716
Series A convertible preferred stock | July 2013
Temporary Equity
Shares Issued		4,791,716	4,791,716				4,791,716
Shares Outstanding		4,791,716	4,791,716
Series B convertible preferred stock
Temporary Equity
Designated Shares		0	16,597,221
Shares Issued		0	15,624,999
Shares Outstanding		0	15,624,999
Carrying Value			$ 22,185
Common stock shares issued	3,000,017
Series B convertible preferred stock | April 2014
Temporary Equity
Designated Shares		16,597,221	16,597,221
Shares Issued		15,624,999	15,624,999			15,624,999
Shares Outstanding		15,624,999	15,624,999
Liquidation Value		$ 22,500	$ 22,500
Carrying Value		$ 22,185	$ 22,185
Common Stock Issuable Upon Conversion		3,000,017	3,000,017
Series B-1 convertible preferred stock
Temporary Equity
Common stock shares issued	888,894
Series B-1 convertible preferred stock | August 2015
Temporary Equity
Designated Shares		4,629,629	4,629,629
Shares Issued		4,629,629	4,629,629		4,629,629
Shares Outstanding		4,629,629	4,629,629
Liquidation Value		$ 7,000	$ 7,000
Carrying Value		$ 6,885	$ 6,885
Common Stock Issuable Upon Conversion		888,894	888,894
Series C convertible preferred stock
Temporary Equity
Designated Shares		0	43,034,639
Shares Issued		0	42,782,688
Shares Outstanding		0	42,782,688
Carrying Value			$ 67,520
Common stock shares issued	8,214,322
Series C convertible preferred stock | April 2016
Temporary Equity
Designated Shares		43,034,639	43,034,639
Shares Issued		42,782,688	42,782,688	42,782,688
Shares Outstanding		42,782,688	42,782,688
Liquidation Value		$ 67,922	$ 67,922
Carrying Value		$ 67,520	$ 67,520
Common Stock Issuable Upon Conversion		8,214,322	8,214,322

CONVERTIBLE PREFERRED STOCK -41

CONVERTIBLE PREFERRED STOCK - Shares converted (Details)	Jul. 25, 2017shares	Jul. 07, 2017	Apr. 05, 2016USD ($)$ / sharesshares	Aug. 17, 2015USD ($)$ / sharesshares	Jul. 15, 2013USD ($)$ / sharesshares	Apr. 30, 2014USD ($)$ / sharesshares	Jun. 30, 2013item	Feb. 28, 2013USD ($)$ / sharesshares	Feb. 29, 2012USD ($)shares	Oct. 31, 2010USD ($)$ / sharesshares	Dec. 31, 2009USD ($)$ / sharesshares	Dec. 31, 2013$ / sharesshares	Sep. 30, 2017USD ($)shares	Dec. 31, 2016USD ($)shares
Temporary equity
Common stock shares issued | shares	16,101,970
Warrant Liability | $													$ 0	$ 1,039,000
Reverse stock split		0.1920
Series Seed convertible preferred stock
Temporary equity
Shares Issued | shares													0	11,243,209
Issuance cost | $									$ 15,000	$ 39,000	$ 124,000
Common stock shares issued | shares	2,158,708
Warrant Liability | $													$ 0
Series A convertible preferred stock
Temporary equity
Shares Issued | shares													0	9,583,432
Share price (in dollars per share) | $ / shares												$ 1.20
Additional shares available for purchase | shares												4,791,716
Issuance cost | $					$ 93,000
Number of milestones approved by the board | item							1
Common stock shares issued | shares	1,840,029
Warrant Liability | $													$ 0
Series B convertible preferred stock
Temporary equity
Shares Issued | shares													0	15,624,999
Common stock shares issued | shares	3,000,017
Warrant Liability | $													$ 0
Series B-1 convertible preferred stock
Temporary equity
Common stock shares issued | shares	888,894
Warrant Liability | $													$ 0
Series C convertible preferred stock
Temporary equity
Shares Issued | shares													0	42,782,688
Common stock shares issued | shares	8,214,322
Warrant Liability | $													$ 0
December 2009 | Series Seed convertible preferred stock
Temporary equity
Shares Issued | shares											2,000,001		2,000,001	2,000,001
Gross proceeds | $											$ 2,000,000
Share price (in dollars per share) | $ / shares											$ 1
October 2010 | Series Seed convertible preferred stock
Temporary equity
Shares Issued | shares										2,000,003			2,000,003	2,000,003
Gross proceeds | $										$ 2,000,000
Share price (in dollars per share) | $ / shares										$ 1
February 2012 | Series Seed convertible preferred stock
Temporary equity
Shares Issued | shares									7,243,205				7,243,205	7,243,205
Gross proceeds | $									$ 6,200,000
Shares issued upon conversion (in shares) | shares									6,150,000
Shares issued upon conversion of convertible debt (in shares) | shares									1,093,205
Face amount | $									$ 1,000,000
Accrued interest | $									$ 93,000
February 2013 | Series A convertible preferred stock
Temporary equity
Shares Issued | shares								4,791,716					4,791,716	4,791,716
Gross proceeds | $								$ 5,800,000
Share price (in dollars per share) | $ / shares								$ 1.20
July 2013 | Series A convertible preferred stock
Temporary equity
Shares Issued | shares					4,791,716								4,791,716	4,791,716
Gross proceeds | $					$ 5,800,000
Share price (in dollars per share) | $ / shares					$ 1.20
April 2014 | Series B convertible preferred stock
Temporary equity
Shares Issued | shares						15,624,999							15,624,999	15,624,999
Gross proceeds | $						$ 22,500,000
Share price (in dollars per share) | $ / shares						$ 1.44
Shares issued upon conversion (in shares) | shares						3,562,785
Shares issued upon conversion of convertible debt | $						$ 5,100,000
Issuance cost | $						$ 315,000,000
August 2015 | Series B-1 convertible preferred stock
Temporary equity
Shares Issued | shares				4,629,629									4,629,629	4,629,629
Gross proceeds | $				$ 7,000,000
Share price (in dollars per share) | $ / shares				$ 1.512
Issuance cost | $				$ 115,000
April 2016 | Series C convertible preferred stock
Temporary equity
Shares Issued | shares			42,782,688										42,782,688	42,782,688
Gross proceeds | $			$ 67,900,000
Share price (in dollars per share) | $ / shares			$ 1.5876
Issuance cost | $			$ 402,000,000

COMMON STOCK AND PREFERRED STOC

COMMON STOCK AND PREFERRED STOCK (Details) - $ / shares	Sep. 30, 2017	Jul. 25, 2017	Dec. 31, 2016
Common stock and preferred stock
Common stock, authorized	120,000,000		110,251,951
Common stock, par value	$ 0.001		$ 0.001
Common stock, shares issued	24,347,150	16,100,000	1,181,429
Common stock, shares outstanding	24,347,150		1,181,429
Preferred stock, authorized	5,000,000	5,000,000	0
Preferred stock, shares issued	0		0
Preferred stock, shares outstanding	0		0
Common stock shares reserved for future issuance	5,210,656		19,886,090
2009 stock option plan
Common stock and preferred stock
Common stock shares reserved for future issuance	3,001,752		3,533,726
2017 stock option plan
Common stock and preferred stock
Common stock shares reserved for future issuance	2,011,203
2013 Series B Warrants
Common stock and preferred stock
Common stock shares reserved for future issuance			133,327
2014 Series B Warrants
Common stock and preferred stock
Common stock shares reserved for future issuance			53,333
2016 Series C Warrants
Common stock and preferred stock
Common stock shares reserved for future issuance			48,374
Common Stock
Common stock and preferred stock
Common stock shares reserved for future issuance	197,701
Convertible preferred stock.
Common stock and preferred stock
Common stock shares reserved for future issuance			16,101,970
Common stock. | 2011 Warrant rights to acquire Series Seed Preferred Stock
Common stock and preferred stock
Common stock shares reserved for future issuance			15,360

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($)	3 Months Ended		9 Months Ended		18 Months Ended	21 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Share-based compensation
Common stock available for future grant	5,210,656		5,210,656			5,210,656	19,886,090
Options granted			747,892	1,516,894
Stock based compensation expense	$ 981,000	$ 554,000	$ 2,070,000	$ 1,747,000
Cash proceeds from the exercise of stock options			$ 189,000
Employee and Non-Employee Stock Options | Non-employees
Share-based compensation
Options granted	0		4,224	0
Stock based compensation expense	$ 46,000	$ 6,000	$ 83,000	$ 34,000
Performance Stock Options
Share-based compensation
Options granted					86,056
2009 Plan
Share-based compensation
Common stock available for future grant							338,256
Options granted			747,892
Unrecognized compensation expense	$ 13,200,000		$ 13,200,000			$ 13,200,000
2009 Plan | Employee and Non-Employee Stock Options
Share-based compensation
Options Expiry Term						10 years
Vesting Period			4 years
2017 Equity Incentive Plan
Share-based compensation
Common stock available for future grant	1,366,324		1,366,324			1,366,324
Common Stock Capital Shares Reserved For Future Issuance Percent Of Outstanding Shares			4.00%
2017 Equity Incentive Plan | Minimum
Share-based compensation
Common stock available for future grant	3,573,766		3,573,766			3,573,766
2017 Equity Incentive Plan | Maximum
Share-based compensation
Common stock available for future grant	3,533,757		3,533,757			3,533,757

STOCK_BASED COMPENSATION - Stoc

STOCK‑BASED COMPENSATION - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Number of Shares
Granted (in shares)	747,892	1,516,894
2009 Plan
Number of Shares
Outstanding at the beginning of the period (in shares)	3,195,469
Granted (in shares)	747,892
Exercised (in shares)	(129,461)
Forfeited	(167,269)
Outstanding at the end of the period (in shares)	3,646,631		3,195,469
Vested and expected to vest (in shares)	3,645,645
Options exercisable (in shares)	1,590,655
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 3.26
Granted (in dollars per share)	16.06
Exercised (in dollars per share)	1.46
Forfeited	2.72
Outstanding at the end of the period (in dollars per share)	5.97		$ 3.26
Vested and expected to vest (in dollars per share )	5.97
Options exercisable (in dollars per shares)	$ 3.43
Weighted Average Remaining Contractual Term
Weighted average period	8 years 4 months 24 days		8 years 7 months 6 days
Vested and expected to vest	8 years 4 months 24 days
Options exercisable	7 years 9 months 18 days
Aggregate Intrinsic Value
Outstanding at the beginning of the period (in dollars)	$ 1,200
Outstanding at the end of the period (in dollars)	61,572		$ 1,200
Vested and expected to vest (in dollars)	61,552
Options exercisable (in dollars)	$ 30,882

STOCK_BASED COMPENSATION - Fair

STOCK‑BASED COMPENSATION - Fair Value Assumptions (Details)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected volatility (maximum)	122.00%
Employee and Non-Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected volatility (minimum)	103.00%	108.00%
Expected volatility (maximum)		110.00%
Risk-free interest rate (minimum)	1.81%	1.21%
Risk-free interest rate (maximum)	2.29%	1.33%
Expected dividend yield	0.00%	0.00%
Minimum | Employee and Non-Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	5 years 15 days	5 years 7 months 13 days
Maximum | Employee and Non-Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	9 years 9 months 26 days	6 years 2 months 5 days

STOCK-BASED COMPENSATION - Othe

STOCK-BASED COMPENSATION - Other (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based compensation
Weighted average grant date fair value of options granted	$ 14.74	$ 2.77	$ 13.19	$ 2.73
Options granted			747,892	1,516,894
Stock based compensation expense	$ 981	$ 554	$ 2,070	$ 1,747
2009 Plan
Share-based compensation
Options granted			747,892
Unrecognized compensation expense	$ 13,200		$ 13,200
Weighted average expense recognition period			3 years 26 days

STOCK_BASED COMPENSATION - St47

STOCK‑BASED COMPENSATION - Stock‑based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based compensation
Stock based compensation expense	$ 981	$ 554	$ 2,070	$ 1,747
Research and development
Share-based compensation
Stock based compensation expense	357	180	749	309
General and administrative
Share-based compensation
Stock based compensation expense	$ 624	$ 374	$ 1,321	$ 1,438

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
INCOME TAXES
Uncertain tax positions	$ 0	$ 0
Interest or penalties recorded	$ 0	$ 0

NET LOSS PER COMMON SHARE (Deta

NET LOSS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net loss attributable to common stockholders	$ (10,175)	$ (9,667)	$ (30,921)	$ (24,772)
Denominator:
Weighted average shares outstanding—basic and diluted	18,034,278	1,181,429	6,860,777	1,181,429
Net loss per share attributable to common stockholders—basic and diluted	$ (0.56)	$ (8.18)	$ (4.51)	$ (20.97)

NET LOSS PER COMMON SHARE - Ant

NET LOSS PER COMMON SHARE - Antidilutive securities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 28, 2017
Outstanding securities excluded from the computation of diluted weighted average shares outstanding as they would have been anti dilutive:
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)	3,844,332	19,415,413
Total loan commitment			$ 10,000
Convertible preferred stock.
Outstanding securities excluded from the computation of diluted weighted average shares outstanding as they would have been anti dilutive:
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)		16,101,970
Stock Options
Outstanding securities excluded from the computation of diluted weighted average shares outstanding as they would have been anti dilutive:
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)	3,646,631	3,063,049
Preferred stock warrants.
Outstanding securities excluded from the computation of diluted weighted average shares outstanding as they would have been anti dilutive:
Outstanding securities excluded from the computation of diluted weighted average shares outstanding (in shares)	197,701	250,394

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Leases (Details) - USD ($)	Sep. 30, 2013	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Leases
Lease term	3 years
Amount funded by landlord	$ 78,000
Total rent expense		$ 97,000	$ 85,000	$ 290,000	$ 244,000
Letter of Credit
Leases
Face amount			$ 84,000		$ 84,000

COMMITMENTS AND CONTINGENCIES52

COMMITMENTS AND CONTINGENCIES - Future minimum obligations (Details) $ in Thousands	Sep. 30, 2017USD ($)
Minimum obligations due under its license agreements
2017 (remaining three months)	$ 99
2,018	410
2,019	34
Total minimum license payments	$ 543

COMMITMENTS AND CONTINGENCIES53

COMMITMENTS AND CONTINGENCIES - License Agreement (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Contingencies
Research and development expenses	$ 7,018,000	$ 8,256,000	$ 23,128,000	$ 18,117,000
The Johns Hopkins University (“JHU”)
Contingencies
Minimum annual payment			38,000
License fee , if the company achieves the first commercial sale			113,000
Research and development expenses	$ 97,000	$ 50,000	$ 108,000	$ 99,000
Massachusetts Eye and Ear Infirmary (“MEEI”)
Contingencies
Initial payment of license fee						$ 10,000
Annual license fee					$ 5,000

COMMITMENTS AND CONTINGENCIES54

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications (Details)	Sep. 30, 2017USD ($)
Indemnification obligations
Indemnification obligations	$ 0
Accrued Contingencies	$ 0