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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Mar. 15, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	ITEK
Entity Registrant Name	Inotek Pharmaceuticals Corporation
Entity Central Index Key	0001281895
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		26,986,318
Entity Public Float			$ 43.8

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 29,798	$ 80,042
Short-term investments	96,675	31,238
Prepaid expenses and other current assets	1,876	1,086
Total current assets	128,349	112,366
Property and equipment, net	1,130	812
Other assets	168	143
Total assets	129,647	113,321
Current liabilities:
Accounts payable	1,592	1,633
Accrued expenses and other current liabilities	4,416	2,508
Accrued interest	1,204
Total current liabilities	7,212	4,141
Other long-term liabilities	307	367
Total liabilities	56,479	4,508
Commitments and Contingencies (Note 9)
Stockholders’ equity:
Preferred Stock, $0.001 par value: 5,000,000 shares authorized and no shares issued or outstanding
Common stock, $0.01 par value: 120,000,000 shares authorized at December 31, 2016 and December 31, 2015; 26,986,318 shares and 26,423,394 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	270	264
Additional paid-in capital	311,829	304,583
Accumulated deficit	(238,877)	(196,023)
Accumulated other comprehensive loss	(54)	(11)
Total stockholders’ equity	73,168	108,813
Total liabilities and stockholders’ equity	129,647	$ 113,321
2021 Convertible Notes [Member]
Current liabilities:
2021 Convertible Notes, net of issuance costs	$ 48,960

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	Secondary Public Offering [Member]	Series AA Redeemable Convertible Preferred Stock [Member]	Series AA Redeemable Convertible Preferred Stock [Member] IPO	Series X Redeemable Convertible Preferred Stock [Member]	Series X Redeemable Convertible Preferred Stock [Member] IPO	Common Stock [Member]	Common Stock [Member] IPO	Common Stock [Member] Secondary Public Offering [Member]	Common Stock [Member] Series AA Redeemable Convertible Preferred Stock [Member] IPO	Common Stock [Member] Series X Redeemable Convertible Preferred Stock [Member] IPO	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] IPO	Additional Paid-in Capital [Member] Secondary Public Offering [Member]	Additional Paid-in Capital [Member] Series AA Redeemable Convertible Preferred Stock [Member] IPO	Additional Paid-in Capital [Member] Series X Redeemable Convertible Preferred Stock [Member] IPO	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2014				$ 46,253		$ 548
Beginning balance, shares at Dec. 31, 2014				24,057,013		1,892,320
Beginning Balance at Dec. 31, 2014	$ (51,559)							$ 10					$ 76,472					$ (128,041)
Beginning balance, shares at Dec. 31, 2014								1,020,088
Stock-based compensation	2,380												2,380
Accretion of Series AA preferred stock to redemption value				$ 131
Accretion of Series AA preferred stock to redemption value	(131)												(131)
Issuance of common stock upon public offering		$ 36,495	$ 73,965						$ 70	$ 62				$ 36,425	$ 73,903
Issuance of common stock upon public offering, shares									6,966,333	6,210,000
Conversion of preferred stock into common stock, value					$ 46,384		$ 548				$ 75	$ 5				$ 46,309	$ 543
Conversion of preferred stock into common stock, value					$ (46,384)		$ (548)
Conversion of preferred stock into common stock, shares											7,536,331	466,319
Conversion of preferred stock into common stock, shares					(24,057,013)		(1,892,320)
Conversion of Convertible Bridge Notes into common stock upon initial public offering, value	2,027							$ 3					2,024
Conversion of Convertible Bridge Notes into common stock upon initial public offering, shares								337,932
Reclassification of fair value of warrant liability to equity upon initial public offering	215												215
Common stock issued pursuant to stock option plans, value	43												43
Common stock issued pursuant to stock option plans, shares								9,857
Common stock issued pursuant to employee stock purchase plan, value	63												63
Common stock issued pursuant to employee stock purchase plan, shares								13,143
Conversion of 2020 Convertible Notes into common stock, value	66,376							$ 39					66,337
Conversion of 2020 Convertible Notes into common stock, shares								3,863,391
Unrealized comprehensive loss on marketable securities	(11)																		$ (11)
Net loss	(67,982)																	(67,982)
Ending Balance at Dec. 31, 2015	108,813							$ 264					304,583					(196,023)	(11)
Ending balance, shares at Dec. 31, 2015								26,423,394
Stock-based compensation	2,909												2,909
Issuance of common stock upon public offering	3,997							$ 5					3,992
Issuance of common stock upon public offering, shares								482,689
Common stock issued pursuant to stock option plans, value	191							$ 1					190
Common stock issued pursuant to stock option plans, shares								54,310
Common stock issued pursuant to employee stock purchase plan, value	155												155
Common stock issued pursuant to employee stock purchase plan, shares								25,925
Unrealized comprehensive loss on marketable securities	(43)																		(43)
Net loss	(42,854)																	(42,854)
Ending Balance at Dec. 31, 2016	$ 73,168							$ 270					$ 311,829					$ (238,877)	$ (54)
Ending balance, shares at Dec. 31, 2016								26,986,318

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (42,854)	$ (67,982)
Adjustments to reconcile net loss to cash used in operating activities:
Noncash interest expense	222	1,132
Noncash rent expense	(60)	(20)
Loss on extinguishment of debt		4,239
Amortization of premium on marketable securities	225	75
Depreciation	169	45
Change in fair value of warrant liabilities		(267)
Change in fair value of Convertible Bridge Notes redemption rights derivative		(480)
Change in fair value of 2020 Convertible Notes derivative liability		42,793
Stock-based compensation	2,909	2,380
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(948)	(1,256)
Accounts payable	(41)	487
Accrued expenses and other current liabilities	3,112	1,438
Net cash used in operating activities	(37,266)	(17,416)
Cash flows from investing activities:
Purchases of short-term investments	(122,277)	(33,693)
Proceeds from the maturities of short-term investments	56,705	2,430
Purchase of property and equipment	(487)	(412)
Net cash used in investing activities	(66,059)	(31,675)
Cash flows from financing activities:
Net proceeds from issuance of common stock in initial public offering		38,085
Proceeds from issuance of 2020 Convertible Notes in initial public offering		21,000
Net proceeds from issuance of common stock	3,997	73,965
Principal payments on notes payable		(5,800)
Net cash provided by financing activities:	53,081	125,515
Net change in cash and cash equivalents	(50,244)	76,424
Cash and cash equivalents, beginning of period	80,042	3,618
Cash and cash equivalents, end of period	29,798	80,042
Supplemental disclosure of cash flow information:
Cash paid for interest		89
Supplemental disclosure of noncash investing and financing activities:
Acquisition of leasehold improvements		445
Conversion of Notes into common stock		66,376
Net unrealized loss on marketable securities	43	11
2021 Convertible Notes [Member]
Cash flows from financing activities:
Proceeds from issuance of 2021 Convertible Notes	52,000
Payments of Notes issuance costs	(3,262)
2020 Convertible Notes [Member]
Adjustments to reconcile net loss to cash used in operating activities:
Loss on extinguishment of debt		3,716
Cash flows from financing activities:
Payments of Notes issuance costs		(1,841)
Stock Option Plans [Member]
Cash flows from financing activities:
Proceeds from the issuance of common stock	191	43
Employee Stock Purchase Plan [Member]
Cash flows from financing activities:
Proceeds from the issuance of common stock	$ 155	63
IPO
Supplemental disclosure of noncash investing and financing activities:
Conversion of Notes into common stock		2,027
Reclassification of fair value of warrant liability to equity		215
Reclassification of deferred public offering costs to stockholders’ equity		1,590
Reclassification of deferred public offering costs to other assets		256
Series AA Redeemable Convertible Preferred Stock [Member]
Supplemental disclosure of noncash investing and financing activities:
Accretion of Series AA preferred stock to redemption value		131
Series AA Redeemable Convertible Preferred Stock [Member] \| IPO
Supplemental disclosure of noncash investing and financing activities:
Conversion of preferred stock into common stock upon initial public offering		46,384
Series X Redeemable Convertible Preferred Stock [Member] \| IPO
Supplemental disclosure of noncash investing and financing activities:
Conversion of preferred stock into common stock upon initial public offering		$ 548

Significant Accounting Policies

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Significant Accounting Policies

2. Significant Accounting Policies

Basis of Presentation—The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiaries, Inotek Securities Corporation and Inotek Ltd. All significant intercompany balances and transactions have been eliminated in consolidation.

Segment Reporting—Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment.

Use of Estimates—The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from these estimates. Significant items subject to such estimates and assumptions include the valuation of stock options used for the calculation of stock-based compensation, fair value of warrant liabilities and other derivative instruments, and determination of accruals related to research and clinical development.

Comprehensive loss—Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources, and currently consists of net loss and changes in unrealized gains and losses on short-term investments. Accumulated other comprehensive loss consists entirely of unrealized gains and losses from short-term investments as of December 31, 2016 and 2015.

Cash and Cash Equivalents—Cash and cash equivalents consist of bank deposits, certificates of deposit and money market accounts. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents.

The Company maintains its cash and cash equivalent balances in the form of money market, savings or operating accounts with financial institutions that management believes are creditworthy. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents.

Short-term investments—Short-term investments consist of investments in certificates of deposit, agency bonds and United States Treasury securities. Management determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its short-term investments as available-for-sale pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 320, Investments—Debt and Equity Securities. Short-term investments are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive loss in stockholders’ equity and a component of total comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were no realized gains or losses on short-term investments for the years ended December 31, 2016 and 2015. There was $43 and $11 of net unrealized losses on short-term investments for years ended December 31, 2016 and 2015, respectively.

The Company reviews short-term investments for other-than-temporary impairment whenever the fair value of a short-term investment is less than the amortized cost and evidence indicates that a short-term investment’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the statements of operations if the Company has experienced a credit loss, has the intent to sell the short-term investment, or if it is more likely than not that the Company will be required to sell the short-term investment before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.

Short-term investments at December 31, 2016 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	22,046	$	—	$	—		$	22,046
Agency bonds		5,917		—		(4	)		5,913
United States Treasury securities		68,766		1		(51	)		68,716
	$	96,729	$	1	$	(55	)	$	96,675

Short-term investments at December 31, 2015 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	16,160	$	—	$	—		$	16,160
Agency bonds		10,036		—		(5	)		10,031
United States Treasury securities		5,053		—		(6	)		5,047
	$	31,249	$	—	$	(11	)	$	31,238

At December 31, 2016 and 2015, all short-term investments held by the Company had contractual maturities of less than one year. The Company evaluated its securities for other-than-temporary impairment and determined that no such impairment existed at December 31, 2016 and 2015.

Property and Equipment—Property and equipment are stated at cost. Expenditures for repairs and maintenance are charged to expense as incurred. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the consolidated statement of operations. Depreciation and amortization is provided using the straight-line method over the estimated useful lives of the assets, which are as follows:

Asset Classification		Estimated Useful Life
Computer hardware and software		3 - 5 years
Laboratory equipment		5 years
Office equipment		5 years
Leasehold improvements		Shorter of useful life or remaining life of lease

Debt Issuance Costs—Debt issuance costs at December 31, 2016 consists of underwriting discounts and offering-related costs incurred by the Company in connection with the closing of the 2021 Convertible Notes and are included as a direct deduction from the carrying amount of the 2021 Convertible Notes on the Company’s consolidated balance sheet. The Company amortizes debt issuance costs to interest expense over the life of the 2021 Convertible Notes using the effective interest method. (See Note 5). Amortization of debt issuance costs was $222 for the year ended December 31, 2016.

Debt issuance costs incurred in connection with the Company’s notes payable, Convertible Bridge Notes and 2020 Convertible Notes were capitalized at the inception of the notes and amortized over the term of the respective notes using the effective interest rate method. At December 31, 2015 and 2016, the Company no longer carried the notes payable, Convertible Bridge Notes or 2020 Convertible Notes on its consolidated balance sheet (see Note 5). Amortization of deferred issuance costs was $0 and $107 for the years ended December 31, 2016 and 2015, respectively, and recorded as a component of interest expense in the accompanying consolidated statements of operations.

Deferred Public Offering Costs—Deferred public offering costs, which consist primarily of direct, incremental legal, accounting, Securities and Exchange Commission and NASDAQ Global Market fees relating to the IPO and issuance of the 2020 Convertible Notes, were capitalized as a component of other assets on the balance sheet as of December 31, 2014. At December 31, 2014, the Company had $1,846 of deferred public offering costs. In the year ended December 31, 2015, the Company incurred an additional $1,620 of public offering costs and allocated (i) $2,377 of the aggregate public offering costs to the IPO and $627 to the 2020 Convertible Notes offering, which were recorded as deferred financing costs and were amortized to interest expense from the issuance of the 2020 Convertible Notes, through the conversion of the 2020 Convertible Notes in July and August 2015; and (ii) $462 to the Follow-on Offering.

Research and Development Costs—Research and development costs are charged to expense as incurred and include, but are not limited to:

•

employee-related expenses including salaries, benefits, travel and stock-based compensation expense for research and development personnel;

•

expenses incurred under agreements with contract research organizations that conduct clinical and preclinical studies, contract manufacturing organizations and consultants;

•

costs associated with preclinical and development activities; and

•

costs associated with regulatory operations.

Costs for certain development activities, such as clinical studies, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as accrued expenses, or prepaid expenses and other current assets, if the related services have not been provided.

Stock-Based Compensation —The Company measures the cost of employee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. That cost is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the award. The fair value of options on the date of grant is calculated using the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company’s estimates of these assumptions are primarily based on historical data, peer company data and judgment regarding future trends and factors. The fair value of restricted stock awards is based on the intrinsic value of such awards on the date of grant. Compensation cost for stock purchase rights under the employee stock purchase plan is measured and recognized on the date the Company becomes obligated to issue shares of our common stock and is based on the difference between the fair value of the Company’s common stock and the purchase price on such date.

The Company accounts for stock options issued to non-employees in accordance with the provisions of ASC 505-50, Equity-Based Payments to Non-employees, which requires valuing the stock options on their grant date and remeasuring such stock options at their current fair value as they vest.

Fair Value Measurements—The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), establishes a hierarchy of inputs used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below:

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of the Company’s financial instruments, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their respective carrying values due to the short-term nature of these instruments. The Company’s assets and liabilities measured at fair value on a recurring basis include its short-term investments, warrant liabilities, convertible notes redemption rights derivative and 2020 Convertible Notes derivative liability (see Note 10). There were no material liability-classified warrants, derivatives or derivative liabilities outstanding in 2016.

Derivative Financial Instruments—All derivatives are recorded as assets or liabilities at fair value, and the changes in fair value are immediately included in earnings. The Company’s derivative financial instruments include bifurcated embedded derivatives that were identified within the 2020 Convertible Notes and the Convertible Bridge Notes (see Notes 5, 7 and 10). There were no material derivative financial instruments outstanding in 2016.

Income taxes—The Company uses the asset and liability method for accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases. Deferred tax assets and liabilities are measured using enacted rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. A valuation allowance is recorded if it is more likely than not that a deferred tax asset will not be realized. The Company has provided a full valuation allowance on its deferred tax assets.

The Company recognizes the financial statement benefit of a tax position only after determining that the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more-likely-than-not threshold, the amount recognized in the consolidated financial statements is the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement with the relevant tax authority.

The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2016 and 2015, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statements of operations.

Net loss per share—The Company calculates net loss per share in accordance with ASC 260, Earnings per Share. Basic earnings (loss) per share (“EPS”) is calculated by dividing the net income or loss applicable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration of unissued common stock equivalents. The net loss applicable to common stockholders is determined by the reported net loss for the period and deducting dividends accrued and accretion of preferred stock. Diluted EPS is calculated by adjusting the weighted average common shares outstanding for the dilutive effect of common stock options, warrants, and convertible preferred stock and accrued but unpaid convertible preferred stock dividends. In periods where a net loss is recorded, no effect is given to potentially dilutive securities, as their effect would be anti-dilutive.

The following table sets forth the computation of basic and diluted EPS attributable to the Company’s common stockholders:

	For the Years Ended December 31,
	2016			2015
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(42,854	)	$	(67,982	)
Accretion and dividends on convertible preferred stock		-			(131	)
Net loss applicable to common stockholders	$	(42,854	)	$	(68,113	)
Denominator:
Weighted average common shares outstanding—basic and diluted		26,735,175			18,311,333
Net loss per share applicable to common stockholders—basic and diluted	$	(1.60	)	$	(3.72	)

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect:

	For the Years Ended December 31,
	2016		2015
Shares issuable upon conversion of the 2021 Convertible Notes		6,483,791		—
Warrants for common stock		56,408		56,408
Stock options		2,675,458		1,631,677
Restricted Stock Units		470,000		—
Total		9,685,657		1,688,085

Subsequent Events—The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The Company has completed an evaluation of all subsequent events through the date the financial statements were issued (See Note 12).

Recent Accounting Pronouncements

In August 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements-Going Concern, which provides guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The new standard is effective for the Company for the annual period ending after December 15, 2016, and for annual and interim periods thereafter, with early adoption permitted. The Company adopted this standard for the year ended December 31, 2016. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which supersedes the current leasing guidance and upon adoption, will require lessees to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. The new standard is effective for the Company for the annual period beginning after December 15, 2018, and can be early adopted by applying a modified retrospective approach for leases existing at, and entered into after, the beginning of the earliest comparable period presented in the financial statements. The Company is currently evaluating the impact of this accounting standard update on the Company’s consolidated financial statements.

In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, which amends ASC Topic 718, Compensation – Stock Compensation, and includes provisions intended to simplify various aspects related to how share-based payments are accounted for and presented in the financial statements. The new standard is effective for the Company for the annual period beginning after December 15, 2016, and for annual and interim periods thereafter, with early adoption permitted. The adoption of this guidance is not expected to have a material impact on the Company's consolidated financial statements.

Debt

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Debt

5. Debt

2021 Convertible Notes

On August 5, 2016, the Company issued an aggregate of $50,000 of the 2021 Convertible Notes. On August 30, 2016, the Company issued an additional $2,000 of 2021 Convertible Notes pursuant to the exercise of the underwriters’ overallotment option. The 2021 Convertible Notes have a maturity date of August 1, 2021 (“Maturity Date”), are unsecured and accrue interest at a rate of 5.75% per annum, payable semi-annually on February 1 and August 1 of each year, beginning February 1, 2017. In connection with the issuance of the 2021 Convertible Notes, the Company incurred $3,262 of debt issuance costs which were recorded as a discount on the 2021 Convertible Notes.

Each holder of a 2021 Convertible Note (the “Holder”) has the option until the close of business on the second business day immediately preceding the Maturity Date to convert all, or any portion, of the 2021 Convertible Notes held by it at an initial conversion rate of 124.7505 shares of the Company’s common stock per $1 principal amount of 2021 Convertible Notes (the “Conversion Rate”). The Conversion Rate is subject to adjustment from time to time upon the occurrence of certain events, including the issuance of stock dividends and payment of cash dividends. In addition, in certain circumstances, the Conversion Rate will be increased in respect of a Holder’s conversion of 2021 Convertible Notes in connection with the occurrence of one or more corporate events specified in the indenture (as supplemented, the “Indenture”) governing the 2021 Convertible Notes (each such specified corporate event, a “Make-Whole Fundamental Change”) that occurs prior to the Maturity Date (a “Make-Whole Fundamental Change Conversion”) or in respect of a Holder’s voluntary conversion of 2021 Convertible Notes other than in connection with a Make-Whole Fundamental Change (a “Voluntary Conversion”). In connection with a Make-Whole Fundamental Change Conversion or a Voluntary Conversion, the Company will increase the Conversion Rate for the 2021 Convertible Notes surrendered for conversion by a number of additional shares of the Company’s common stock set forth in the Additional Shares Make-Whole Table in the Indenture, based on the applicable Stock Price (as defined in the Indenture) and Effective Date (as defined in the Indenture) for such conversion. The additional shares potentially issuable in connection with a Make-Whole Fundamental Change Conversion or a Voluntary Conversion range from 0 to 24.95 per $1 principal amount of 2021 Convertible Notes, subject to adjustment. If the Stock Price applicable to any conversion is greater than $40.00 per share, the Conversion Rate will not be increased. If the Stock Price applicable to any conversion is less than $6.68 per share, the Conversion Rate in connection with a Make-Whole Fundamental Change Conversion will not be increased but it will be increased by 24.95 shares in connection with a Voluntary Conversion. Upon conversion, Holders of the 2021 Convertible Notes will receive shares of the Company’s common stock and cash in lieu of fractional shares.

Upon the occurrence of a Fundamental Change, the occurrence of certain change of control transactions or delisting events (as defined in the Indenture), each Holder may require the Company to repurchase for cash all or any portion of the 2021 Convertible Notes held by such Holder at a repurchase price equal to 100% of the principal amount thereof, plus accrued and unpaid interest thereon.

The Company, at its option, may redeem for cash all or any portion of the 2021 Convertible Notes if the last reported sale price of a share of the Company’s common stock is equal to or greater than 200% of the conversion price for the 2021 Convertible Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the 2021 Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.

If an Event of Default (as defined in the Indenture), other than certain events of bankruptcy, insolvency or reorganization involving the Company, occurs and is continuing, the trustee under the Indenture (the “Trustee”) or the Holders of at least 25% in principal amount of the outstanding 2021 Convertible Notes may declare 100% of the principal of and accrued and unpaid interest, if any, on all of the 2021 Convertible Notes to be due and payable immediately. Upon the occurrence of an Event of Default relating to bankruptcy, insolvency or reorganization involving the Company, 100% of the principal of and accrued and unpaid interest, if any, on all of the 2021 Convertible Notes would become due and payable automatically.

Notwithstanding the foregoing, the Indenture provides that, to the extent the Company elects, the sole remedy for an Event of Default relating to certain failures by the Company to comply with certain reporting covenants in the Indenture, will (i) for the first 90 days after the occurrence of such an Event of Default, consist exclusively of the right to receive additional interest on the 2021 Convertible Notes at a rate equal to 0.25% per annum of the principal amount of the 2021 Convertible Notes outstanding for each day during such 90-day period on which such an Event of Default is continuing and (ii) for the period from, and including, the 91st day after the occurrence of such an Event of Default to, and including, the 180th day after the occurrence of such an Event of Default, consist exclusively of the right to receive additional interest on the 2021 Convertible Notes at a rate equal to 0.50% per annum of the principal amount of the 2021 Convertible Notes outstanding for each day during such additional 90-day period on which such an Event of Default is continuing (such additional interest, “Additional Interest”). After 180 days, if such Event of Default is not cured or waived, the 2021 Convertible Notes would be subject to acceleration in accordance with the Indenture.

The 2021 Convertible Notes are considered a hybrid financial instrument consisting of a fixed interest rate “host” and various embedded features that required evaluation as potential embedded derivatives under FASB ASC 815, Derivatives and Hedging (“ASC 815”). Based on the nature of the host instrument and the embedded features, management concluded that none of the conversion, put and redemption features required bifurcation and separate accounting from the host instrument. The Company determined that the Additional Interest was an embedded derivative that contains non-credit related events of default. As a result, the Additional Interest feature required bifurcation and separate accounting under ASC 815. Based on the amount of Additional Interest that would be owed and the likelihood of occurrence, the Company estimated the fair value of the Additional Interest feature to be insignificant upon issuance and as of December 31, 2016.

The issuance costs which were recorded as a discount on the debt are being amortized to interest expense over the life of the 2021 Convertible Notes using the effective interest method. As of December 31, 2016, the stated interest rate, was 5.75%, and the effective interest rate was 7.3%. Interest expense related to the 2021 Convertible Notes for the year ended December 31, 2016, was $1,418, including $222 related to amortization of the debt discount.

The table below summarizes the carrying value of the 2021 Convertible Notes as of December 31, 2016:

	December 31, 2016
	(in thousands)
Gross proceeds	$	52,000
Initial value of issuance costs recorded as debt discount		(3,262	)
Amortization of debt discount		222
Carrying value	$	48,960

2020 Convertible Notes

On February 23, 2015, the Company issued an aggregate of $20,000 of the 2020 Convertible Notes pursuant to its IPO. On March 24, 2015, the Company issued an additional $1,000 of 2020 Convertible Notes pursuant to the exercise of the underwriters’ overallotment option. The 2020 Convertible Notes had a maturity date of February 15, 2020, were unsecured and accrued interest at a rate of 5.0% per annum, payable semi-annually on February 15 and August 15 of each year. In connection with the issuance of the 2020 Convertible Notes, the Company incurred $2,097 of financing costs which were recorded in other assets on the balance sheet.

Each holder of a 2020 Convertible Note, had the option to convert all or any portion of such note at an initial conversion rate of 158.7302 shares of the Company’s common stock per $1 principal amount of 2020 Convertible Notes. The conversion rate was subject to adjustment from time to time upon the occurrence of certain events, including the issuance of stock dividends and payment of cash dividends. For any conversion that occurred on or after July 23, 2015, the Company would, in addition to the other consideration payable, make an interest make-whole payment to such converting holder equal to the sum of the present values of the scheduled payments of interest that would have been made on the 2020 Convertible Notes to be converted had such notes remained outstanding from the date of the conversion through the earlier of (i) the date that is three years after the conversion date and (ii) the maturity date, if the 2020 Convertible Notes had not been so converted or otherwise repurchased. Present values for the interest make-whole payment would be calculated using a discount rate equal to 2%. The Company could satisfy its obligation to pay any interest make-whole payment, at its election, in cash, shares of common stock or a combination thereof.

The 2020 Convertible Notes were convertible, at the holder’s option, upon a fundamental change, as defined in the indenture. If a holder elected to convert its notes upon a fundamental change, the Company would increase the conversion rate for the 2020 convertible notes so surrendered for conversion by a number of additional shares of common stock by which the conversion rate would have increased per $1 principal amount of notes for each stock price and make-whole fundamental change effective date as set forth in the indenture. The additional shares ranged from 7.9364 to 0.

Upon a fundamental change, each holder would have the right to require the Company to repurchase for cash all of such holder’s notes, or any portion thereof that is equal to $1 or an integral multiple of $1. The repurchase price of the 2020 Convertible Notes would equal 100% of the principal amount thereof, plus accrued and unpaid interest thereon. However, if the repurchase occurred after a regular record date for an interest payment, but before the distribution date of that interest payment, the holder would receive the regular interest payment and the repurchase price would equal 100% of the principal amount of the 2020 Convertible Notes to be repurchased.

The 2020 Convertible Notes were redeemable at the holder’s option upon an event of default. If an event of default (other than certain events of bankruptcy, insolvency or reorganization involving the Company) occurred and was continuing, the trustee by notice to the Company, or the holders of at least 25% in principal amount of the outstanding notes by written notice to the Company and the trustee, could declare 100% of the principal and accrued and unpaid interest, if any, on all of the 2020 Convertible Notes to be due and payable immediately. Upon the occurrence of certain events of default relating to bankruptcy, insolvency or reorganization involving the Company, 100% of the principal and accrued and unpaid interest, if any, on all of the 2020 Convertible Notes would become due and payable automatically.

The indenture provided that, to the extent the Company elected and for up to 180 days, the sole remedy for an event of default relating to certain failures by the Company to comply with certain reporting covenants in the indenture, consisted exclusively of the right to receive additional interest on the 2020 Convertible Notes. The additional interest consisted of interest at an additional rate of 0.25% per annum for the first 90 days after the event of default. For the 91st to 180th day after the event of default, the additional interest would consist of interest at an additional rate of 0.50% per annum. After 180 days, if the event of default was not cured or waived, the 2020 Convertible Notes were subject to acceleration as provided in Section 6.02 of the indenture.

The Company determined that the conversion option, interest make-whole payments and the additional interest were embedded derivatives that required bifurcation and separate accounting under FASB ASC 815. Based on the characteristics of the (i) conversion option including make-whole provision, (ii) the additional interest, and (iii) the 2020 Convertible Notes, the Company estimated the fair value of the conversion option including the interest make-whole provision and the additional interest using the “with” and “without” method. Using this methodology, the Company first valued the 2020 Convertible Notes with the conversion option including make-whole provision but excluding the additional interest (the “with” scenario) and subsequently valued the 2020 Convertible Notes without the conversion option including make-whole provision and excluding the additional interest (the “without” scenario). The difference between the fair values of the 2020 Convertible Notes in the “with” and “without” scenarios was the concluded fair value of the conversion option including make-whole provision as of the measurement date. The Company developed an estimate of fair value for the 2020 Convertible Notes excluding the additional interest using a binomial lattice model. The Company modeled the decision to convert or hold by considering the maximum of the conversion or hold value at every node of the lattice in which the 2020 Convertible Notes were convertible and choosing the action that would maximize the return to the 2020 Convertible Notes’ holders. The significant assumptions used in the binomial model were: the market yield and the expected volatility.

The Company estimated the fair value of the additional interest using an income approach, specifically, the risk-neutral debt valuation method that is used to derive the value of a debt instrument using the expected cash flows and the risk-free rate. The significant assumptions used in estimating the expected cash flows were: the market yield used to determine the risk-neutral probability of default and the expected recovery rate upon default.

The Company recorded $11,850 as the fair value of the combined embedded derivative liability on February 23, 2015, with a corresponding amount recorded as a discount to the 2020 Convertible Notes, related to the initial issuance of the 2020 Convertible Notes. The Company recorded approximately $573 of additional derivative liability and discount to the 2020 Convertible Notes as the fair value of the combined embedded derivative on March 24, 2015, upon the issuance of additional 2020 Convertible Notes for the exercise of the underwriters’ overallotment option. The deferred financing costs and the debt discount were recorded in other assets and were being amortized to interest expense over the life of the 2020 Convertible Notes using the effective interest method. Changes in the fair value of the combined embedded derivative liability were recorded in earnings in the period in which the changes occurred.

In July and August 2015, holders of all $21,000 principal amount of the 2020 Convertible Notes elected to convert the principal into 3,333,319 shares of common stock in accordance with the terms of the 2020 Convertible Notes. In addition, the interest make-whole payment was settled with shares of common stock, at the election of the Company, resulting in the issuance of 530,072 additional shares of common stock. As of the conversion dates, the fair value of the combined embedded derivative liability was determined to be $55,216. The change in the estimated fair value of the combined embedded derivative liability from the recognition dates to the conversion dates and for the year ended December 31, 2015, was $42,793. In addition, the Company recorded a charge of $3,716 in the year ended December 31, 2015, related to extinguishment of the 2020 Convertible Notes. As of December 31, 2015, all $21,000 of the 2020 Convertible Notes were extinguished.

Interest expense related to the 2020 Convertible Notes for the year ended December 31, 2015, was $963, including $74 related to amortization of the issuance costs and $440 related to amortization of the debt discount.

Convertible Bridge Notes

In December 2014, the Company sold an aggregate of $2,000 of subordinated convertible promissory notes to existing stockholders (the “Convertible Bridge Notes”). The Convertible Bridge Notes were scheduled to mature on June 30, 2015 and accrued interest at the rate of 8% per annum and were subordinate to all other senior indebtedness of the Company. Upon the closing of an initial public offering of common stock of at least $40,000 in gross proceeds, all outstanding principal and accrued interest thereon would automatically convert into common stock at the initial public offering price.

Pursuant to the IPO in February 2015, the Convertible Bridge Notes were converted into 337,932 shares of common stock based upon the IPO common share offering price of $6.00 per share. During the year ended December 31, 2015, the Company reflected as interest expense related to the Convertible Bridge Notes (i) $23 related to the 8% coupon rate and (ii) $128 of amortization of the initial fair value of the redemption rights derivative and issuance costs. In connection with the conversion of the Convertible Bridge Notes into common stock, the Company recorded a (i) a $480 gain in change in fair value of the of the Convertible Bridge Notes redemption rights derivative from the write off of the derivative and (ii) a loss on extinguishment of debt of $360 from the acceleration of the unamortized balance of the debt discount and issuance costs.

Notes Payable

On June 28, 2013, the Company entered into two Loan and Security Agreements (the “Loan Agreements” or “Loans”) with two financial entities (the “Lenders”) pursuant to which the Company issued Loans for $3,500 to each lender and received proceeds of $6,915 net of costs and fees payable to the lenders. The Loans bore interest at a rate per annum of 11.0%. The Loans would mature on October 1, 2016 and required interest-only payments for the initial 12 months and thereafter required repayment of the principal balance with interest in 27 monthly installments. Also, upon full repayment or maturity of the Loans, the Lenders would be due a termination payment of 3.0% of the initial principal amount of the Loans, or $210 (the “Loan Termination Payment”).

In connection with the Loan Agreements, the Company issued to the Lenders fully-vested warrants to purchase either, at the election of the warrant holder, (i) 228,906 shares of the Company’s Series AA preferred stock at an exercise price of $1.529 per share, or (ii) $350 of stock in the next round stock, as defined in the Loan Agreements, at a price that is the lowest effective price per share that is offered in the next round. The warrants expire on the earlier of (i) ten years after the date of grant, or (ii) immediately prior to an acquisition transaction, as defined in the warrants. The Company determined that the warrants should initially be classified as a liability based upon the nature of the underlying Series AA preferred stock.

In connection with the Company’s IPO in February 2015, the Company exercised its right to terminate the Loan Agreements by paying the $5,347 principal balance due, the $210 Loan Termination Payment, a $160 prepayment fee calculated as 3% of the principal balance due at the time of the termination, plus $23 of interest accrued from February 1, 2015 through the payoff date. The Company made a scheduled principal payment of $243 in January 2015.

For the year ended December 31, 2015, interest expense related to the Loan Agreements was $115, including $26 related to accretion of the debt discount and termination payment. Additionally, in the year ended December 31, 2015, the Company recorded a charge for loss on extinguishment of debt of $323 related to the write-off of the unamortized debt discount.

Subsequent to the Company’s IPO, the warrants issued to the lenders became exercisable for 56,408 shares of common stock at $6.204 per share. The Company calculated the fair value of the warrants at the IPO date using a Black Scholes model using the following assumptions: a fair value of $6.00 per share (the IPO price of the Company’s common stock), 8.4 years to maturity, 1.70% risk-free rate, and 60% volatility. The Company determined the fair value of the warrant liability at the IPO date to be $215 and recorded a gain on change in fair value of warrant liabilities of $267 in the statement of operations for the year ended December 31, 2015. The Company determined that subsequent to this change, the warrants were exercisable at a fixed price for a fixed number of shares of common stock and qualified for equity classification under the accounting guidance, and the fair value of $215 was reclassified to additional paid-in capital as of the IPO date in the year ended December 31, 2015.

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

6. Income Taxes

No provision for federal or state income taxes was recorded during the years ended December 31, 2016 and 2015, as the Company incurred operating losses for each of these years.

The following table reconciles the statutory rate to the effective tax rates for each of the years ended December 31, 2016 and 2015:

	For the Years Ended December 31,
	2016				2015
Computed at statutory rate		34.00		%		34.00		%
State income taxes		4.76				1.20
Expiration of capital loss carryforward		—				(2.13	)
Tax credits		3.38				0.73
Other		(1.74	)			(3.35	)
Change in value of convertible notes derivatives and warrant liabilities		—				(21.16	)
Valuation allowance		(40.40	)			(9.29	)
		—		%		—		%

The tax effect of significant temporary differences representing deferred tax assets and liabilities as of December 31, 2016 and 2015 is as follows:

	December 31,
	2016			2015
	(in thousands)
Net operating loss (“NOL”) and credit carryforwards	$	43,765		$	35,858
Capitalized research and development costs		22,775			14,406
Other		1,963			927
Valuation allowance		(68,503	)		(51,191	)
	$	—		$	—

As required by ASC 740, Income Taxes, management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of NOL carryforwards and capitalized research and development costs. As a result of the fact that the Company has incurred tax losses from inception, management has determined that it is more likely than not that the Company will not recognize the benefits of federal and state net deferred tax assets and, as a result, a full valuation allowance has been established against its net deferred tax assets as of December 31, 2016 and 2015. The Company has offset certain deferred tax liabilities with deferred tax assets that are expected to generate offsetting deductions within the same period. During the years ended December 31, 2016 and 2015, the valuation allowance changed by $17,312 and $6,313, respectively. Realization of deferred tax assets is dependent upon the generation of future taxable income.

As of December 31, 2016, the Company had federal NOL carryforwards for income tax purposes of $105,336 that expire at various dates through 2036, and state NOL carryforwards of $62,653 that expire at various dates through 2036, available to reduce future federal and state income taxes, if any. As of December 31, 2016, the Company had federal research and development tax credits of $4,654, and state research and development tax credits of $717. If substantial changes in the Company’s ownership should occur, as defined in Section 382 of the Internal Revenue Code of 1986, as amended, (the “Code”), there could be annual limitations on the amount of loss carryforwards which can be realized in future periods. The Company has determined that it has experienced prior ownership changes occurring in 2005, 2007 and 2015. The pre-change NOLs, although subject to an annual limitation, can be utilized in future years as well as any post change NOLs, provided that sufficient income is generated and no future ownership changes occur that may limit the Company’s NOLs.

As of December 31, 2016 and 2015, the Company’s total unrecognized tax benefits totaled $488 and $333, respectively, which if recognized would affect the effective tax rate prior to the adjustment for the Company’s valuation allowance. The Company files income tax returns in the U.S. federal and Massachusetts tax jurisdictions. Starting in tax year 2016, the Company will file tax returns in the New Jersey tax jurisdiction. Tax years 2013 through 2016 remain open to examination by the tax jurisdictions in which the Company is subject to tax. Since the Company is in a loss carryforward position, the Internal Revenue Service (“IRS”) and state taxing authorities are permitted to audit the earlier tax years and propose adjustments up to the amount of the NOLs generated. The Company is not currently under examination by the IRS or any other jurisdiction for any tax years.

The change in unrecognized tax benefits for each of the years ended December 31, 2016 and 2015 is as follows:

	For the Years Ended December 31,
	2016		2015
	(in thousands)
Balance at January 1,	$	333	$	284
Additions for prior year tax positions		6		—
Additions for current year tax positions		149		49
	$	488	$	333

The Company does not expect significant changes in its unrecognized tax benefits over the next twelve months.

Equity

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Equity

7. Equity

Authorized Shares

As of December 31, 2016, the Company’s authorized capital stock consisted of 120,000,000 shares of common stock, par value $0.01 per share, and 5,000,000 shares of undesignated preferred stock, par value $0.001 per share.

Reverse Stock Splits

In November 2014, the board of directors and the stockholders of the Company approved a 1-for-3.39 reverse stock split of the Company’s outstanding common stock and in January 2015, the board of directors and the stockholders of the Company approved a 1-for-1.197 reverse stock split of the Company’s outstanding common stock. Shares of common stock underlying outstanding stock options were proportionally reduced and the respective exercise prices were proportionally increased in accordance with the terms of the option agreements. The Company’s historical share and per share information has been retroactively adjusted in the financial statements presented to give effect to these reverse stock splits, including reclassifying an amount equal to the reduction in par value to additional paid-in capital.

Common Stock

All preferences, voting powers, relative, participating, optional, or other specific rights and privileges, limitations, or restrictions of the common stock are expressly subject to those that may be fixed with respect to any shares of preferred stock. Common stockholders are entitled to one vote per share, and to receive dividends, when and if declared by the Board. There were 26,986,318 and 26,423,394 shares of common stock outstanding at December 31, 2016 and 2015, respectively.

Preferred Stock

The Company has evaluated the tranched nature of its Preferred Stock offerings described below, its investor registration rights, as well as the rights, preferences and privileges of each series of Preferred Stock and concluded that there were no freestanding derivative instruments or any embedded derivatives requiring bifurcation. Additionally, the Company assessed the conversion terms associated with its Preferred Stock and concluded that there were no beneficial conversion features. As of December 31, 2016 and 2015, there were no shares of preferred stock issued and outstanding.

Series AA Redeemable Convertible Preferred Stock

In connection with the sale of Series AA preferred stock in 2013, the Company issued warrants to purchase 852,230 shares of Series AA preferred stock at a price of $0.01 per share, with an expiration date on the earliest of (i) July 11, 2023, (ii) the closing of the Company’s IPO, or (iii) the closing of a sale event, as defined in the warrant. The Company allocated $1,585 of the proceeds received to the warrants issued, representing the grant date fair value of the warrants, and accounts for these warrants as liabilities. The Company recognized any change in the fair value of the warrant liabilities each reporting period in the consolidated statements of operations (Note 10). These warrants were exercised in full during the year ended December 31, 2014 for total proceeds of $8 which was recorded as Series AA preferred carrying value. The aggregate $2,250 fair value of the warrants as of the date of each exercise was reclassified partially to Series AA preferred stock carrying value and the remainder to accumulated paid-in capital.

Due to the optional redemption feature of the Series AA preferred stock, the Company classified the Series AA preferred stock as temporary equity in the mezzanine section of the balance sheet and accreted the value to the redemption amount. The carrying amount of the Series AA preferred stock at December 31, 2014 was $46,253, including $9,976 of accrued but unpaid and undeclared dividends. All shares of Series AA preferred stock converted to shares of common stock upon the IPO in February 2015. Pursuant to these conversions, the $46,384 carrying value of the Series AA preferred stock at the time of the IPO was reclassified as $75 to common stock par value and $46,309 additional paid-in capital.

Series X Redeemable Convertible Preferred Stock

In June 2010, the Company sold 2,451,184 shares of Series X redeemable convertible preferred stock (“Series X preferred stock”) to employees and consultants to the Company at a purchase price of $0.001 per share, subject to stock purchase and restriction agreements, which included repurchase rights by the Company.

Two employees that purchased Series X preferred stock were terminated by the Company in May 2013. Upon termination, the Company repurchased an aggregate of 558,864 shares of Series X preferred stock and modified the vesting terms on the remaining 558,862 shares of Series X preferred stock held by these employees such that the Company’s repurchase rights would expire upon consummation of an IPO of its common stock occurring prior to June 30, 2015. The Company estimated the fair value of the modified award at the modification date to be $950 and recognized this amount as stock-based compensation expense in 2015 as a result of the Company’s February 2015 IPO.

The following table is a rollforward of unvested Series X preferred stock shares:

Unvested—December 31, 2014	558,862
Vested	(558,862	)
Repurchased	—
Unvested—December 31, 2015	—

Due to the redemption feature of the Series X preferred stock, the Company classified the Series X preferred stock as temporary equity in the mezzanine section of the balance sheet at December 31, 2014. Pursuant to the IPO, all Series X preferred stock became vested and converted into common stock. Pursuant to these conversions, the $548 carrying value of the Series X preferred stock at the time of the IPO was reclassified as $5 to common stock par value and $543 additional paid-in capital.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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+ Details

Stock Plans

12 Months Ended

Dec. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Plans

8. Stock Plans

The Company has granted common stock options pursuant to the 2004 and 2014 Plans (as defined below) at an exercise price that is not less than the fair market value of the Company’s stock as determined by the board of directors, with input from management. Prior to the Company’s IPO, the board of directors had determined the estimated fair value of the Company’s common stock on the date of grant based on a number of objective and subjective factors, including external market conditions, rights and preferences of securities senior to the common stock at the time of each grant, the likelihood of achieving a liquidity event such as an IPO or the sale of the Company, and third party valuations. For stock option grants prior to the IPO, the computation of expected volatility was based on the historical volatilities of peer companies. The peer companies include organizations that are in the same industry, with similar size and stage of growth. The Company estimates that the expected life of the options granted using the simplified method allowable under Staff Accounting Bulletin No. 107, Share Based Payments. The expected life is applied to the stock option grant group as a whole, as the Company does not expect substantially different exercise or post vesting termination behavior among its employee population. The interest rate for grants pursuant to the 2004 and 2014 Plans are based on the U.S. treasury bills rate for U.S. treasury bills with terms commensurate with the expected term of the option grants on the grant date of the option.

2004 Stock Option and Incentive Plan

In July 2004, the Company’s board of directors adopted the 2004 Stock Option and Incentive Plan (the “2004 Plan”) for the issuance of incentive stock options, restricted stock, and other equity awards, all for common stock, as determined by the board of directors to employees, officers, directors, consultants, and advisors of the Company and its subsidiaries. Only stock options were granted under the 2004 Plan. The 2004 Plan expired in February 2014 but remains effective for all outstanding options.

The following table summarizes the option activity for each of the years ended December 31, 2016 and 2015 under the 2004 Plan:

	Number of Shares			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
						(in thousands)
Outstanding as of December 31, 2014		10,958		$	40.58
Exercised		—		$	—
Expired		(41	)	$	40.58
Outstanding as of December 31, 2015		10,917		$	40.58
Exercised		—		$	—
Expired		—		$	—
Cancelled		(291	)	$	40.58
Outstanding as of December 31, 2016		10,626		$	40.58	$	—
Vested and exercisable as of December 31, 2016		10,626		$	40.58	$	—
Weighted-average years remaining on contractual life		1.25
Unrecognized compensation cost related to non-vested stock options	$	—

The Company recorded no stock compensation expense in the years ended December 31, 2016 and 2015 relating to stock options granted pursuant to the 2004 Plan. At December 31, 2016, all 2004 Plan options were fully vested and there was no unrecognized stock-based compensation expense relating to stock options granted pursuant to the 2004 Plan. Options outstanding as of December 31, 2016 had no intrinsic value, as the option price exceeded the fair value of the underlying shares.

2014 Stock Option and Incentive Plan

In August 2014, the Company’s board of directors adopted the 2014 Stock Option and Incentive Plan (the “2014 Plan”) for the issuance of incentive and non-qualified stock options, restricted stock, and other equity awards, all for common stock, as determined by the board of directors to employees, officers, directors, consultants, and advisors of the Company and its subsidiaries. Pursuant to the provisions of the 2014 Plan and approval by the board of directors, on January 1, 2017 an additional 1,079,453 shares were added to the 2014 Plan representing 4% of total common shares issued and outstanding at December 31, 2016. There were 3,034 shares available for issuance under the 2014 Plan as of December 31, 2016. The 2014 Plan expires in August 2024.

For the year ended December 31, 2016, the Company recorded aggregate stock-based compensation expense of $2,843 for stock options under the 2014 Plan: $1,521 in general and administrative expense and $1,322 in research and development expense. For the year ended December 31, 2015, the Company recorded aggregate stock-based compensation expense of $1,389 for stock options under the 2014 Plan: $795 in general and administrative expense and $594 in research and development expense.

During the year ended December 31, 2016, the board of directors granted a total of 1,156,500 ten-year term stock options to employees and directors of the Company. The fair value of each stock option granted was estimated on the grant date using a Black-Scholes stock option pricing model based on the following assumptions: an expected term of 5.31 to 6.08 years; expected stock price volatility of 76.9% to 82.4%, a risk free rate of 1.20% to 2.08%, and a dividend yield of 0%. The Company will recognize $5,950 (net of any forfeitures) of stock-based compensation expense for these stock options on a straight-line basis commencing upon the grant dates through the final vesting dates.

During 2015, the Board of Directors granted a total of 730,500 ten-year term stock options to employees and directors of the Company. The fair value of each stock option granted was estimated on the grant date using a Black-Scholes stock option pricing model based on the following assumptions: an expected term of 5.31 to 6.08 years; expected stock price volatility of 80.9% to 101.1%, a risk free rate of 1.55% to 1.85%, and a dividend yield of 0%. The Company will recognize $3,209 (net of any forfeitures) of stock-based compensation expense for these stock options on a straight-line basis commencing upon the grant dates through the final vesting dates.

On August 28, 2014, the Board of Directors granted 840,975, ten-year term, stock options to officers of the Company at an exercise price of $4.342 per share, the fair market value of the common stock as determined by the Board of Directors, on the condition that the options would be of no further force and effect if the Company did not consummate an IPO prior to the one-year anniversary of the grant date (the “IPO Condition”). The IPO Condition was met upon the Company’s February 2015 IPO. These stock options vested 25% on the one-year anniversary of the grant date and the remaining 75% will vest in equal monthly installments over the following 36 months.

The fair value of the stock options granted during 2014 was estimated on the grant date using a Black-Scholes stock option pricing model based on the following assumptions: an expected term of 5 to 6.25 years; expected stock price volatility of 83.3% to 92.5%; a risk free rate of 1.63% to 1.84%; and a dividend yield of 0%. The Company is recognizing $2,798 of stock-based compensation expense for these stock options on a straight-line basis commencing upon the grant date in August 2014 through the final vesting date in August 2018. As a result of the resolution of the IPO Condition, the year ended December 31, 2015 reflects stock compensation expense calculated from the grant date in August 2014 through December 31, 2015.

The following table summarizes the option activity for each of the years ended December 31, 2016 and 2015 under the 2014 Plan:

	Number of Shares			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
						(in thousands)
Outstanding as of December 31, 2014		900,117		$	4.34
Granted		730,500		$	5.69
Exercised		(9,857	)	$	4.34
Cancelled		—		$	—
Outstanding as of December 31, 2015		1,620,760		$	4.95
Granted		1,156,500		$	7.77
Exercised		(84,428	)	$	4.71
Cancelled		(28,000	)	$	6.79
Outstanding as of December 31, 2016		2,664,832		$	6.16	$	2,064
Vested and exercisable as of December 31, 2016		820,884		$	4.97	$	930
Weighted-average years remaining on contractual life		8.59
Unrecognized compensation cost related to non-vested stock options	$	7,692

The weighted-average fair value of all stock options granted for the years ending December 31, 2016 and 2015 was $5.23 and $4.39, respectively. Intrinsic value at December 31, 2016 and 2015 is based on the closing price of the Company’s common stock of $6.10 and $11.33 per share, respectively. As of December 31, 2016, all options granted are expected to vest.

In 2016, 30,118 shares of the 84,428 total options exercised were surrendered to the Company pursuant to a net exercise right.

In December 2016, the board granted to certain executive officers an aggregate of 470,000 Restricted Stock Units (“RSU’s”) pursuant to the 2014 Plan. Each restricted stock unit represents a contingent right to receive one share of Company common stock. Vesting for these RSU’s was based equally on the achievement of two performance-based conditions, subject to continued service through such achievement dates. The intrinsic fair value of these RSU’s as of the date of grant was $3,055 and no stock-based compensation expense was recorded in 2016 as the Company determined that the vesting conditions were not probable of occurring. As of December 31, 2016, there were 470,000 RSU’s outstanding and an aggregate of 3,134,832 RSU’s and stock options for shares of Company common stock pursuant to the 2014 Plan. In January 2017, these RSU’s were modified such that instead of vesting based on the achievement of certain performance-based conditions, they will vest in equal annual installments over four years from the December 2016 date of grant, subject to continued service through such dates.

In January 2017, an additional 916,000 RSU’s were granted to employees of the Company. These RSU’s will vest at various times over the four years following the date of grant.

Employee Stock Purchase Plan

In November 2014, the Company’s board of directors adopted and the stockholders approved the 2014 Employee Stock Purchase Plan (the “ESPP”). The ESPP provides that the number of shares reserved and available for issuance under the ESPP shall be cumulatively increased each January 1, beginning on January 1, 2016, by the lesser of (i) 600,000 shares of common stock or (ii) the number of shares necessary to set the number of shares of Common Stock under the Plan at 1% percent of the outstanding number of shares as of January 1 of the applicable year. However, the board of directors reserves the right to determine that there will be no increase for any year or that any increase will be for a lesser number of shares. As of January 1, 2017, 31,555 shares were added to the ESPP. As of December 31, 2016, there were 238,308 shares available for issuance under the ESPP.

All employees who are whose customary employment is for more than 20 hours a week are eligible to participate in the ESPP. Any employee who owns 5% or more of the voting power or value of the Company’s shares of common stock is not eligible to purchase shares under the ESPP. Each employee who is a participant in the ESPP may purchase shares by authorizing payroll deductions of up to 10% of his or her base compensation during an offering period. Unless the participating employee has previously withdrawn from the offering, his or her accumulated payroll deductions will be used to purchase shares of common stock on the last business day of the offering period at a price equal to 85% of the fair market value of the ordinary shares on the first business day or the last business day of the offering period, whichever is lower, provided that no more than 5,000 shares of common stock may be purchased by any one employee during each offering period. Under applicable tax rules, an employee may purchase no more than $25,000 worth of stock, valued at the start of the purchase period, under the ESPP in any calendar year.

In 2015, $63 was withheld and used to purchase 13,143 shares of common stock and the Company recorded $41 of stock-based compensation expense pursuant to the ESPP. In 2016, $155 was withheld and used to purchase 25,925 shares of common stock and the Company recorded $66 of stock-based compensation expense pursuant to the ESPP.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Fair Value of Financial Measurements

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value of Financial Measurements

10. Fair Value of Financial Measurements

Items measured at fair value on a recurring basis include short term investments, derivative instruments and warrant liabilities.

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy:

	Fair Value Measurements at
	December 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Money market mutual funds (included in cash and cash equivalents)	$	20,698	$	20,698	$	—	$	—

Certificates of deposit	$	22,046	$	—	$	22,046	$	—
Agency bonds		5,913		—		5,913		—
United States Treasury securities		68,716		68,716		—		—
Short-term investments	$	96,675	$	68,716	$	27,959	$	—

	Fair Value Measurements at
	December 31, 2015
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Certificates of deposit	$	16,160	$	—	$	16,160	$	—
Agency bonds		10,031		—		10,031		—
United States Treasury securities		5,047		5,047		—		—
Short-term investments	$	31,238	$	5,047	$	26,191	$	—

Money market mutual funds

The Company classifies its money market mutual funds as Level 1 assets under the fair value hierarchy as these assets have been valued using quoted market prices in active markets without any valuation adjustment.

Short-term investments

The Company classifies its United States Treasury securities as Level 1 assets under the fair value hierarchy as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its certificates of deposit as Level 2 assets under the fair value hierarchy, as there are no quoted market prices in active markets, and its agency bonds as Level 2 assets under the fair value hierarchy, as these assets are not always valued daily using quoted market prices in active markets.

Convertible preferred stock warrant liability

As previously discussed (see Notes 5 and 7), the Company issued warrants to purchase Series AA preferred stock in connection with the 2013 Series AA preferred stock issuance, which were exercised in full in 2014, and Loan Agreements.

The following table details the assumptions used in the Black-Scholes option pricing model used to estimate the fair value of the Series AA preferred stock warrants as of February 17, 2015, the date upon which the Series AA preferred stock warrants became exercisable for common stock:

	February 17,
	2015
Volatility		60%
Expected term (years)	8.4
Expected dividend yield		0.0%
Risk-free rate		1.7%

Convertible debt redemption rights derivative

The 2014 Convertible Bridge Notes redemption rights derivative required separate accounting and was valued using a single income valuation approach. Pursuant to the IPO, the Convertible Bridge Notes were converted into 337,932 shares of common stock.

2020 Convertible Notes derivative liability

The fair value methodologies related to the 2020 Convertible Notes derivative liability are discussed in Note 5.

During the periods presented, the Company did not change the manner in which it values liabilities that are measured at fair value using Level 3 inputs. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during any of the years presented.

The following table reflects the change in the Company’s Level 3 liabilities for the year ended December 31, 2015:

	Convertible preferred stock warrant liabilities			Convertible Bridge Notes redemption rights derivative			2020 Convertible Notes derivative liability
	(in thousands)
Balance at December 31, 2014	$	482		$	480		$	—
Issuance of 2020 Convertible Notes		—			—			12,423
Change in fair value		(267	)		(480	)		42,793
Reclassification to stockholders’ equity		(215	)		—			—
Conversion to common stock		—			—			(55,216	)
Balance at December 31, 2015	$	—		$	—		$	—

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Basis of Presentation

Segment Reporting

Use of Estimates

Comprehensive loss

Cash and Cash Equivalents

Short-term investments

Short-term investments at December 31, 2016 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	22,046	$	—	$	—		$	22,046
Agency bonds		5,917		—		(4	)		5,913
United States Treasury securities		68,766		1		(51	)		68,716
	$	96,729	$	1	$	(55	)	$	96,675

Short-term investments at December 31, 2015 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	16,160	$	—	$	—		$	16,160
Agency bonds		10,036		—		(5	)		10,031
United States Treasury securities		5,053		—		(6	)		5,047
	$	31,249	$	—	$	(11	)	$	31,238

Property and Equipment

Asset Classification		Estimated Useful Life
Computer hardware and software		3 - 5 years
Laboratory equipment		5 years
Office equipment		5 years
Leasehold improvements		Shorter of useful life or remaining life of lease

Debt Issuance Costs

Deferred Public Offering Costs

Research and Development Costs

Research and Development Costs—Research and development costs are charged to expense as incurred and include, but are not limited to:

•

employee-related expenses including salaries, benefits, travel and stock-based compensation expense for research and development personnel;

•

expenses incurred under agreements with contract research organizations that conduct clinical and preclinical studies, contract manufacturing organizations and consultants;

•

costs associated with preclinical and development activities; and

•

costs associated with regulatory operations.

Stock-Based Compensation

Fair Value Measurements

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

Derivative Financial Instruments

Income taxes

Net loss per share

The following table sets forth the computation of basic and diluted EPS attributable to the Company’s common stockholders:

	For the Years Ended December 31,
	2016			2015
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(42,854	)	$	(67,982	)
Accretion and dividends on convertible preferred stock		-			(131	)
Net loss applicable to common stockholders	$	(42,854	)	$	(68,113	)
Denominator:
Weighted average common shares outstanding—basic and diluted		26,735,175			18,311,333
Net loss per share applicable to common stockholders—basic and diluted	$	(1.60	)	$	(3.72	)

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect:

	For the Years Ended December 31,
	2016		2015
Shares issuable upon conversion of the 2021 Convertible Notes		6,483,791		—
Warrants for common stock		56,408		56,408
Stock options		2,675,458		1,631,677
Restricted Stock Units		470,000		—
Total		9,685,657		1,688,085

Subsequent Events

Recent Accounting Pronouncements

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Short-term Investment

Short-term investments at December 31, 2016 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	22,046	$	—	$	—		$	22,046
Agency bonds		5,917		—		(4	)		5,913
United States Treasury securities		68,766		1		(51	)		68,716
	$	96,729	$	1	$	(55	)	$	96,675

Short-term investments at December 31, 2015 consist of the following:

	Cost Basis		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Current:
Certificates of deposit	$	16,160	$	—	$	—		$	16,160
Agency bonds		10,036		—		(5	)		10,031
United States Treasury securities		5,053		—		(6	)		5,047
	$	31,249	$	—	$	(11	)	$	31,238

Schedule of Estimated Useful Life of Asset Classification

Depreciation and amortization is provided using the straight-line method over the estimated useful lives of the assets, which are as follows:

Asset Classification		Estimated Useful Life
Computer hardware and software		3 - 5 years
Laboratory equipment		5 years
Office equipment		5 years
Leasehold improvements		Shorter of useful life or remaining life of lease

Schedule of Computation of Basic and Diluted EPS

The following table sets forth the computation of basic and diluted EPS attributable to the Company’s common stockholders:

	For the Years Ended December 31,
	2016			2015
	(in thousands, except share and per share amounts)
Numerator:
Net loss	$	(42,854	)	$	(67,982	)
Accretion and dividends on convertible preferred stock		-			(131	)
Net loss applicable to common stockholders	$	(42,854	)	$	(68,113	)
Denominator:
Weighted average common shares outstanding—basic and diluted		26,735,175			18,311,333
Net loss per share applicable to common stockholders—basic and diluted	$	(1.60	)	$	(3.72	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect:

	For the Years Ended December 31,
	2016		2015
Shares issuable upon conversion of the 2021 Convertible Notes		6,483,791		—
Warrants for common stock		56,408		56,408
Stock options		2,675,458		1,631,677
Restricted Stock Units		470,000		—
Total		9,685,657		1,688,085

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of Reconciliation Between Statutory to Effective Tax Rates

The following table reconciles the statutory rate to the effective tax rates for each of the years ended December 31, 2016 and 2015:

	For the Years Ended December 31,
	2016				2015
Computed at statutory rate		34.00		%		34.00		%
State income taxes		4.76				1.20
Expiration of capital loss carryforward		—				(2.13	)
Tax credits		3.38				0.73
Other		(1.74	)			(3.35	)
Change in value of convertible notes derivatives and warrant liabilities		—				(21.16	)
Valuation allowance		(40.40	)			(9.29	)
		—		%		—		%

Schedule of Tax Effect of Significant Temporary Differences Representing Deferred Tax Assets and Liabilities

The tax effect of significant temporary differences representing deferred tax assets and liabilities as of December 31, 2016 and 2015 is as follows:

	December 31,
	2016			2015
	(in thousands)
Net operating loss (“NOL”) and credit carryforwards	$	43,765		$	35,858
Capitalized research and development costs		22,775			14,406
Other		1,963			927
Valuation allowance		(68,503	)		(51,191	)
	$	—		$	—

Schedule of Change in Unrecognized Tax Benefits

The change in unrecognized tax benefits for each of the years ended December 31, 2016 and 2015 is as follows:

	For the Years Ended December 31,
	2016		2015
	(in thousands)
Balance at January 1,	$	333	$	284
Additions for prior year tax positions		6		—
Additions for current year tax positions		149		49
	$	488	$	333

Stock Plans (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes the option activity for each of the years ended December 31, 2016 and 2015 under the 2004 Plan:

	Number of Shares			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
						(in thousands)
Outstanding as of December 31, 2014		10,958		$	40.58
Exercised		—		$	—
Expired		(41	)	$	40.58
Outstanding as of December 31, 2015		10,917		$	40.58
Exercised		—		$	—
Expired		—		$	—
Cancelled		(291	)	$	40.58
Outstanding as of December 31, 2016		10,626		$	40.58	$	—
Vested and exercisable as of December 31, 2016		10,626		$	40.58	$	—
Weighted-average years remaining on contractual life		1.25
Unrecognized compensation cost related to non-vested stock options	$	—

The following table summarizes the option activity for each of the years ended December 31, 2016 and 2015 under the 2014 Plan:

	Number of Shares			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
						(in thousands)
Outstanding as of December 31, 2014		900,117		$	4.34
Granted		730,500		$	5.69
Exercised		(9,857	)	$	4.34
Cancelled		—		$	—
Outstanding as of December 31, 2015		1,620,760		$	4.95
Granted		1,156,500		$	7.77
Exercised		(84,428	)	$	4.71
Cancelled		(28,000	)	$	6.79
Outstanding as of December 31, 2016		2,664,832		$	6.16	$	2,064
Vested and exercisable as of December 31, 2016		820,884		$	4.97	$	930
Weighted-average years remaining on contractual life		8.59
Unrecognized compensation cost related to non-vested stock options	$	7,692

Fair Value of Financial Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value of Assets and Liabilities Measured on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy:

	Fair Value Measurements at
	December 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Money market mutual funds (included in cash and cash equivalents)	$	20,698	$	20,698	$	—	$	—

Certificates of deposit	$	22,046	$	—	$	22,046	$	—
Agency bonds		5,913		—		5,913		—
United States Treasury securities		68,716		68,716		—		—
Short-term investments	$	96,675	$	68,716	$	27,959	$	—

	Fair Value Measurements at
	December 31, 2015
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Certificates of deposit	$	16,160	$	—	$	16,160	$	—
Agency bonds		10,031		—		10,031		—
United States Treasury securities		5,047		5,047		—		—
Short-term investments	$	31,238	$	5,047	$	26,191	$	—

Schedule of Assumptions Used to Estimate Fair Value of Series AA Preferred Stock Warrants

	February 17,
	2015
Volatility		60%
Expected term (years)	8.4
Expected dividend yield		0.0%
Risk-free rate		1.7%

Schedule of Change in Company's Level 3 Liabilities

The following table reflects the change in the Company’s Level 3 liabilities for the year ended December 31, 2015:

	Convertible preferred stock warrant liabilities			Convertible Bridge Notes redemption rights derivative			2020 Convertible Notes derivative liability
	(in thousands)
Balance at December 31, 2014	$	482		$	480		$	—
Issuance of 2020 Convertible Notes		—			—			12,423
Change in fair value		(267	)		(480	)		42,793
Reclassification to stockholders’ equity		(215	)		—			—
Conversion to common stock		—			—			(55,216	)
Balance at December 31, 2015	$	—		$	—		$	—

Organization and Operations - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended	12 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	Jul. 31, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Aug. 30, 2016	Aug. 05, 2016	Apr. 30, 2016	Mar. 24, 2015	Feb. 23, 2015	Jun. 28, 2013
Schedule Of Description Of Business [Line Items]
Net proceeds from issuance of equity		$ 73,965,000		$ 36,495,000	$ 3,997,000	$ 73,965,000
Net proceeds from issuance of debts				18,903,000
Accumulated deficit					(238,877,000)	$ (196,023,000)
Aggregate cash and cash equivalents and marketable securities					126,473,000
Cowen and Company, LLC [Member]
Schedule Of Description Of Business [Line Items]
Net proceeds from issuance of equity					$ 3,997,000
Number of shares of common stock sold					482,689
Available for sale of common stock					$ 45,599,000
Maximum [Member] \| Cowen and Company, LLC [Member]
Schedule Of Description Of Business [Line Items]
Amount of stock transactions									$ 200,000,000
Amount of common stock transactions									$ 50,000,000
Over-Allotment Option [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount	$ 2,000,000			$ 1,000,000
Initial public offering common stock, shares		810,000		299,333
Initial public offering common stock, per shares				$ 6.00
IPO
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares				6,966,333
IPO \| Affiliated Entity [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares				3,005,000
Secondary Public Offering [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares		6,210,000
Initial public offering common stock, per shares		$ 12.75
2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount		$ 21,000,000	$ 21,000,000							$ 1,000,000	$ 20,000,000
Convertible senior notes, interest rate, stated percentage					5.00%
Convertible Notes converted into shares		3,333,319	3,333,319
Additional shares of common stock		530,072	530,072
Senior Notes [Member] \| 2021 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount	$ 52,000,000							$ 50,000,000
Convertible senior notes, interest rate, stated percentage	5.75%				5.75%
Net proceeds from issuance of equity	$ 48,738,000
Senior Notes [Member] \| 2021 Convertible Notes [Member] \| Over-Allotment Option [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount							$ 2,000,000
Senior Notes [Member] \| 2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount				$ 21,000,000
Convertible senior notes, interest rate, stated percentage				5.00%
Notes Payable [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount		$ 21,000,000	$ 21,000,000									$ 3,500,000
Convertible Notes converted into shares		3,333,319	3,333,319
Additional shares of common stock		530,072	530,072

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)	Aug. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Number of operating segments \| Segment	1
Realized gains or losses on short-term investment	$ 0	$ 0
Unrealized losses on short-term investment	43,000	11,000
Other than temporary impairment evaluated	0	0
Amortization of deferred financing costs	$ 0	107,000
Deferred public offering costs		1,620,000		$ 1,846,000
Tax benefits recognized likelihood of being realized upon ultimate settlement	greater than 50 percent
Accrued interest or penalties	$ 0	0
Accrued interest or penalties recognized	0	0
Equity Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Deferred public offering costs		2,377,000
2021 Convertible Notes [Member] \| Senior Notes [Member]
Summary Of Significant Accounting Policy [Line Items]
Amortization of debt issuance costs	$ 222,000
2020 Convertible Notes Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Deferred public offering costs		$ 627,000
2020 Convertible Notes Offering [Member] \| Follow-on Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Deferred public offering costs			$ 462,000

Debt - 2021 Convertible Notes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) d $ / shares	Dec. 31, 2015 USD ($)	Aug. 31, 2016 USD ($)	Aug. 30, 2016 USD ($)	Aug. 05, 2016 USD ($)	Mar. 31, 2015 USD ($)
Debt Instrument [Line Items]
Interest expense	$ 1,418,000	$ 1,230,000
Over-Allotment Option [Member]
Debt Instrument [Line Items]
Debt instrument principal amount			$ 2,000,000			$ 1,000,000
2021 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt issuance costs incurred	$ 3,262,000
2021 Convertible Notes [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal amount			$ 52,000,000		$ 50,000,000
Debt instrument maturity date	Aug. 01, 2021
Debt instrument payment terms	Semi-annually
Convertible senior notes, interest rate, stated percentage	5.75%		5.75%
Debt instrument payment start date	Feb. 01, 2017
Debt issuance costs incurred	$ 3,262,000
Number of shares, note gets converted into	124.7505
Principal amount	$ 1
Debt instrument redemption description	The Company, at its option, may redeem for cash all or any portion of the 2021 Convertible Notes if the last reported sale price of a share of the Company’s common stock is equal to or greater than 200% of the conversion price for the 2021 Convertible Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the 2021 Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.
Percentage of common stock conversion price	200.00%
Number of minimum trading days \| d	20
Number of consecutive trading days	30 days
Holdings in debt outstanding	25.00%
Number of days after default	180 days
Effective interest rate	7.30%
Interest expense	$ 1,418,000
Amortization of debt discount	$ 222,000
2021 Convertible Notes [Member] \| Senior Notes [Member] \| First 90 Days [Member]
Debt Instrument [Line Items]
Effective interest rate	0.25%
2021 Convertible Notes [Member] \| Senior Notes [Member] \| 91 to 180 Days [Member]
Debt Instrument [Line Items]
Effective interest rate	0.50%
2021 Convertible Notes [Member] \| Senior Notes [Member] \| Over-Allotment Option [Member]
Debt Instrument [Line Items]
Debt instrument principal amount				$ 2,000,000
2021 Convertible Notes [Member] \| Fundamental Change [Member]
Debt Instrument [Line Items]
Principal amount	$ 1
Conversion of stock, description	If the Stock Price applicable to any conversion is greater than $40.00 per share, the Conversion Rate will not be increased. If the Stock Price applicable to any conversion is less than $6.68 per share, the Conversion Rate in connection with a Make-Whole Fundamental Change Conversion will not be increased but it will be increased by 24.95 shares in connection with a Voluntary Conversion.
Debt instrument repurchase description	Upon the occurrence of a Fundamental Change, the occurrence of certain change of control transactions or delisting events (as defined in the Indenture), each Holder may require the Company to repurchase for cash all or any portion of the 2021 Convertible Notes held by such Holder at a repurchase price equal to 100% of the principal amount thereof, plus accrued and unpaid interest thereon.
Percentage of principal amount of notes to be purchased	100.00%
2021 Convertible Notes [Member] \| Fundamental Change [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into	0
Debt Instrument, conversion rate \| $ / shares	$ 40.00
2021 Convertible Notes [Member] \| Fundamental Change [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into	24.95
Debt Instrument, conversion rate \| $ / shares	$ 6.68

Debt - 2020 Convertible Notes - Additional Information (Detail)	1 Months Ended		12 Months Ended
	Aug. 31, 2015 USD ($) shares	Jul. 31, 2015 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Mar. 24, 2015 USD ($)	Feb. 23, 2015 USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt				$ 4,239,000
Interest expense			$ 1,418,000	1,230,000
2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	$ 21,000,000	$ 21,000,000			$ 1,000,000	$ 20,000,000
Debt instrument maturity date			Feb. 15, 2020
Convertible notes, interest rate, stated percentage			5.00%
Financing costs incurred by the company			$ 2,097,000
Number of shares, note gets converted into			158.7302
Principal amount			$ 1
Discount rate			2.00%
Holdings in debt outstanding			25.00%
Number of days after default			180 days
Fair value of combined embedded derivative liability			$ 55,216,000			$ 11,850,000
Derivative liabilities and discount recorded					$ 573,000
Convertible Notes converted into shares \| shares	3,333,319	3,333,319
Additional shares of common stock \| shares	530,072	530,072
Change in estimated fair value of combined embedded derivative liability				42,793,000
Loss on extinguishment of debt				3,716,000
Extinguishment of debt				21,000,000
Interest expense				963,000
Amortization of financing costs and discounts				74,000
Amortization of debt discount				$ 440,000
2020 Convertible Notes [Member] \| First 90 Days [Member]
Debt Instrument [Line Items]
Additional interest rate			0.25%
2020 Convertible Notes [Member] \| 91 to 180 Days [Member]
Debt Instrument [Line Items]
Additional interest rate			0.50%
2020 Convertible Notes [Member] \| Fundamental Change [Member]
Debt Instrument [Line Items]
Percentage of principal amount of notes to be purchased			100.00%
Repurchase price description			Upon a fundamental change, each holder would have the right to require the Company to repurchase for cash all of such holder’s notes, or any portion thereof that is equal to $1 or an integral multiple of $1.
Repurchase price \| $ / shares			$ 1
2020 Convertible Notes [Member] \| Fundamental Change [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			7.9364
2020 Convertible Notes [Member] \| Fundamental Change [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			0

Debt - Notes Payable - Additional Information (Detail)		1 Months Ended	12 Months Ended
Debt - Notes Payable - Additional Information (Detail)	Jun. 28, 2013 USD ($) Agreement Entity	Feb. 28, 2015 USD ($)	Dec. 31, 2016 USD ($) Installment $ / shares shares	Dec. 31, 2015 USD ($)	Aug. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jan. 31, 2015 USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt				$ 4,239,000
Change in fair value of warrant liabilities				(267,000)
Notes Payable [Member]
Debt Instrument [Line Items]
Number of loan and security agreements \| Agreement	2
Number of financial entities \| Entity	2
Debt instrument principal balance	$ 3,500,000				$ 21,000,000	$ 21,000,000
Proceeds from loans issued	$ 6,915,000
Interest rate			11.00%
Loan maturity date			Oct. 01, 2016
Interest only payments for initial			12 months
Number of installments \| Installment			27
Termination payment percentage		3.00%	3.00%
Loan termination payment		$ 210,000	$ 210,000
Warrant or right securities called by warrants, amount			$ 350,000
Warrant expiration date			The warrants expire on the earlier of (i) ten years after the date of grant, or (ii) immediately prior to an acquisition transaction, as defined in the warrants.
Repaying principal amount		5,347,000
Prepayment fee		160,000
Interest accrued		$ 23,000
Debt instrument, principal payments							$ 243,000
Interest expense related to loan agreements				115,000
Accretion of debt discounts and loan termination payment				26,000
Loss on extinguishment of debt				323,000
Warrants issued to lenders exercisable to common shares \| shares			56,408
Warrants issued to lenders exercisable to common shares, price per share \| $ / shares			$ 6.204
Change in fair value of warrant liabilities				267,000
Reclassification of fair value of warrant liability to equity upon initial public offering				$ 215,000
Notes Payable [Member] \| Warrants Exercisable for Common Stock [Member]
Debt Instrument [Line Items]
IPO price of the Company's common stock \| $ / shares			$ 6.00
Fair value assumptions, expected term			8 years 4 months 24 days
Fair value assumptions, risk free interest rate			1.70%
Fair value assumptions, expected volatility rate			60.00%
Fair value of the warrant liability			$ 215,000
Notes Payable [Member] \| Series AA Preferred Stock [Member]
Debt Instrument [Line Items]
Preferred stock issued to lenders \| shares			228,906
Preferred stock issued to lenders, price per share \| $ / shares			$ 1.529

Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Jan. 31, 2015	Nov. 30, 2014	Jun. 30, 2010 $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 shares
Stockholders Equity [Line Items]
Common stock, shares authorized \| shares				120,000,000	120,000,000
Common stock, par value \| $ / shares				$ 0.01	$ 0.01
Preferred stock, shares authorized \| shares				5,000,000	5,000,000
Preferred stock, par value \| $ / shares				$ 0.001	$ 0.001
Reverse stock split, conversion ratio	0.835422	0.294985
Reverse stock split, description				In November 2014, the board of directors and the stockholders of the Company approved a 1-for-3.39 reverse stock split of the Company’s outstanding common stock and in January 2015, the board of directors and the stockholders of the Company approved a 1-for-1.197 reverse stock split of the Company’s outstanding common stock.
Common stock voting rights description				One vote per share
Common stock, shares outstanding \| shares				26,986,318	26,423,394
Preferred stock issued \| shares				0	0
Preferred stock outstanding \| shares				0	0
Accretion of Series AA preferred stock to redemption value					$ (131)
Series AA Redeemable Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Warrants issued to purchase stock \| shares				852,230
Warrant price per share \| $ / shares				$ 0.01
Warrant expiration date				Expiration date on the earliest of (i) July 11, 2023, (ii) the closing of the Company’s IPO, or (iii) the closing of a sale event, as defined in the warrant.
Proceeds received allocated to warrant issued				$ 1,585
Proceed from warrant exercise						$ 8
Accretion of Series AA preferred stock to redemption value						2,250
Redeemable convertible preferred stock						46,253
Accrued but unpaid and undeclared dividends						$ 9,976
Series AA Redeemable Convertible Preferred Stock [Member] \| Conversion of Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Common stock, par value \| $ / shares						$ 75
Redeemable convertible preferred stock						$ 46,384
Preferred stock, additional paid in capital						46,309
Series X Redeemable Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Redeemable convertible preferred stock						$ 548
Preferred stock repurchased \| shares							558,864
Preferred stock shares vested \| shares							558,862
Series X Redeemable Convertible Preferred Stock [Member] \| Employees And Consultants [Member]
Stockholders Equity [Line Items]
Shares sold \| shares			2,451,184
Share Price \| $ / shares			$ 0.001
Series X Redeemable Convertible Preferred Stock [Member] \| Conversion of Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Common stock, par value \| $ / shares						$ 5
Redeemable convertible preferred stock						$ 548
Preferred stock, additional paid in capital						$ 543
Series X Redeemable Convertible Preferred Stock [Member] \| IPO
Stockholders Equity [Line Items]
Stock based compensation expense				$ 950

Stock Plans - Summary of Stock Option Activity (Detail) - USD ($)		12 Months Ended
	Aug. 28, 2014	Dec. 31, 2016	Dec. 31, 2015
2004 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance		10,917	10,958
Number of Shares , Expired			(41)
Number of Shares , Cancelled		(291)
Number of Shares Outstanding, Ending Balance		10,626	10,917
Number of Shares, Vested and exercisable		10,626
Weighted-average years remaining on contractual life		1 year 3 months
Unrecognized compensation cost related to non-vested stock options		$ 0
Weighted Average Exercise Price Per Share, Beginning Balance		$ 40.58	$ 40.58
Weighted Average Exercise Price Per Share, Expired			40.58
Weighted Average Exercise Price Per Share, Cancelled		40.58
Weighted Average Exercise Price Per Share, Ending Balance		40.58	$ 40.58
Weighted Average Exercise Price Per Share, Vested and exercisable		$ 40.58
Aggregate Intrinsic Value, Outstanding Ending Balance		$ 0
2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance		1,620,760	900,117
Stock options granted	840,975	1,156,500	730,500
Number of Shares , Exercised		(84,428)	(9,857)
Number of Shares , Cancelled		(28,000)
Number of Shares Outstanding, Ending Balance		2,664,832	1,620,760
Number of Shares, Vested and exercisable		820,884
Weighted-average years remaining on contractual life		8 years 7 months 2 days
Unrecognized compensation cost related to non-vested stock options		$ 7,692,000
Weighted Average Exercise Price Per Share, Beginning Balance		$ 4.95	$ 4.34
Weighted Average Exercise Price Per Share, Granted	$ 4.342	7.77	5.69
Weighted Average Exercise Price Per Share, Exercised		4.71	4.34
Weighted Average Exercise Price Per Share, Cancelled		6.79
Weighted Average Exercise Price Per Share, Ending Balance		6.16	4.95
Weighted Average Exercise Price Per Share, Vested and exercisable		$ 4.97
Aggregate Intrinsic Value, Outstanding Ending Balance		$ 2,064,000
Aggregate Intrinsic Value, Vested and exercisable		$ 930,000
Weighted Average Exercise Price Per Share, Granted	$ 4.342	$ 7.77	$ 5.69

Stock Plans - Additional Information (Detail)		1 Months Ended		12 Months Ended
Stock Plans - Additional Information (Detail)	Aug. 28, 2014 $ / shares shares	Jan. 31, 2017 shares	Aug. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) Milestone $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014	Jan. 01, 2017 shares
Stockholders Equity [Line Items]
Common stock withheld pursuant to employee stock purchase plan \| $				$ 155,000	$ 63,000
Subsequent Event [Member] \| Restricted Stock Units [Member]
Stockholders Equity [Line Items]
Number of shares granted by board \| shares		916,000
Vesting period		4 years
2004 Stock Option Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				0	0
Unrecognized compensation cost related to non-vested stock options \| $				0
Stock options, intrinsic value \| $				0
2014 Stock Option and Incentive Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				2,843,000	$ 1,389,000
Unrecognized compensation cost related to non-vested stock options \| $				7,692,000
Stock options, intrinsic value \| $				$ 2,064,000
Number of shares reserved for future issuance \| shares				3,034
Percentage of outstanding common stock increased to shares available for grant				4.00%
Stock options granted \| shares	840,975			1,156,500	730,500
Expiration period of stock options	10 years			10 years	10 years
Stock options, dividend yield				0.00%	0.00%	0.00%
Weighted Average Exercise Price Per Share, Granted \| $ / shares	$ 4.342			$ 7.77	$ 5.69
Stock options, terms of vesting				These stock options vested 25% on the one-year anniversary of the grant date and the remaining 75% will vest in equal monthly installments over the following 36 months.
Weighted-average fair value of stock option granted \| $ / shares				$ 5.23	4.39
Closing price of common stock \| $ / shares				$ 6.10	$ 11.33
Total options exercised \| shares				84,428	9,857
Number of shares surrendered pursuant to net exercise right \| shares				30,118
2014 Stock Option and Incentive Plan [Member] \| Restricted Stock Units [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				$ 0
Stock options, terms of vesting				Vesting for these RSU’s was based equally on the achievement of two performance-based conditions, subject to continued service through such achievement dates.
Number of common stock received for contingent right \| shares				1
Number of vesting achievement of performance-based conditions \| Milestone				2
Intrinsic fair value, date of grant \| $				$ 3,055
Number of shares outstanding \| shares				470,000
Aggregate number of outstanding shares \| shares				3,134,832
2014 Stock Option and Incentive Plan [Member] \| Restricted Stock Units [Member] \| Executive Officers [Member]
Stockholders Equity [Line Items]
Number of shares granted by board \| shares				470,000
2014 Stock Option and Incentive Plan [Member] \| Share-based Compensation Award, Tranche One [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $			$ 2,798,000	$ 5,950,000	$ 3,209,000
Stock options, vesting percentage	25.00%
2014 Stock Option and Incentive Plan [Member] \| Vest Equally Over 36 Months [Member]
Stockholders Equity [Line Items]
Stock options, vesting percentage	75.00%
2014 Stock Option and Incentive Plan [Member] \| Minimum [Member]
Stockholders Equity [Line Items]
Stock options, expected term				5 years 3 months 22 days	5 years 3 months 22 days	5 years
Stock options, expected stock price volatility				76.90%	80.90%	83.30%
Stock options, risk free rate				1.20%	1.55%	1.63%
2014 Stock Option and Incentive Plan [Member] \| Maximum [Member]
Stockholders Equity [Line Items]
Stock options, expected term				6 years 29 days	6 years 29 days	6 years 3 months
Stock options, expected stock price volatility				82.40%	101.10%	92.50%
Stock options, risk free rate				2.08%	1.85%	1.84%
2014 Stock Option and Incentive Plan [Member] \| General and Administrative Expense [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				$ 1,521,000	$ 795,000
2014 Stock Option and Incentive Plan [Member] \| Research and Development Expense [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				1,322,000	594,000
2014 Stock Option and Incentive Plan [Member] \| Subsequent Event [Member]
Stockholders Equity [Line Items]
Number of shares reserved for future issuance \| shares							1,079,453
Employee Stock Purchase Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense \| $				$ 66,000	41,000
Number of shares reserved for future issuance \| shares				600,000
Percentage of outstanding common stock increased to shares available for grant				1.00%
Number of shares available for issuance \| shares				238,308
Percentage of minimum voting power of common stock not eligible to purchase shares				5.00%
Maximum payroll deduction of employee compensation, percentage				10.00%
Discount rate employees purchase shares on offering period				85.00%
Maximum number of shares purchased by an employee \| shares				5,000
Maximum worth of stock an employee purchases \| $				$ 25,000,000
Common stock withheld pursuant to employee stock purchase plan \| $				$ 155,000	$ 63,000
Number of shares issued \| shares				25,925	13,143
Employee Stock Purchase Plan [Member] \| Subsequent Event [Member]
Stockholders Equity [Line Items]
Number of shares reserved for future issuance \| shares							31,555

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating expenses:
Research and development	$ (31,985)	$ (12,554)
General and administrative	(9,894)	(7,842)
Loss from operations	(41,879)	(20,396)
Interest expense	(1,418)	(1,230)
Interest income	443	89
Loss on extinguishment of debt		(4,399)
Change in fair value of warrant liabilities		267
Change in fair value of Convertible Bridge Notes redemption rights derivative		480
Change in fair value of 2020 Convertible Notes derivative liability		(42,793)
Net loss	$ (42,854)	$ (67,982)
Net loss per share attributable to common stockholders—basic and diluted	$ (1.60)	$ (3.72)
Weighted-average number of shares outstanding—basic and diluted	26,735,175	18,311,333

Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2016
Compensation Related Costs [Abstract]
Benefit Plans	11. Benefit Plans Retirement Plan The Company sponsors a 401(k) savings plan (the “Savings Plan”) for all eligible U.S. employees. The Company reserves the right to modify, amend, or terminate the Savings Plan. Employees may contribute up to the maximum allowed by the IRS, while the Company contributes to the plan at the discretion of the board of directors. The Company’s contributions to the plan for the years ended December 31, 2016 and 2015 were $168 and $35, respectively. Management Incentive Plan In August 2014, the Company adopted the Amended and Restated 2014 Management Incentive Plan (the “MIP”) in which certain of our named executive officers participated. Pursuant to the MIP, upon a “change in control” (as defined in the MIP), a bonus pool will be created from the proceeds received in connection with such change in control (ranging from 7 percent to 9.75 percent of transaction proceeds, depending upon the level of transaction proceeds received in the transaction), and each participant is entitled to receive a bonus equal to a certain percentage of such bonus pool. The MIP terminates automatically upon the earliest of (i) March 31, 2015 (unless a change in control has occurred prior to such date), (ii) the closing of our IPO, (iii) the closing of a qualified financing, as defined in the MIP, and (iv) the date all amounts to be paid under the MIP following a change in control have been paid. The MIP terminated upon the closing of our IPO in February 2015.

Subsequent Event	12 Months Ended
Subsequent Event	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Event	12. Subsequent Event On January 6, 2017, a purported stockholder of the Company filed a putative class action in the U.S. District Court for the District of Massachusetts, against the Company, David Southwell, Rudolf Baumgartner, Dale Ritter, and William McVicar, captioned Whitehead v. Inotek Pharmaceuticals Corporation, et al., No. 1:17-cv-10025. The complaint alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and SEC Rule 10b-5 based on allegedly false and misleading statements and omissions regarding our MATrX-1 phase 3 clinical trial of trabodenoson. The lawsuit seeks among other things, unspecified compensatory damages, interest, attorneys’ fees and costs, and unspecified equitable/injunctive relief. The Company intends to vigorously defend itself against this claim.

Significant Accounting Policies - Schedule of Short-term Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	$ 96,729	$ 31,249
Available-for-sale securities, Unrealized Gains	1
Available-for-sale securities, Unrealized Losses	(55)	(11)
Available-for-sale securities, Fair Value	96,675	31,238
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	22,046	16,160
Available-for-sale securities, Fair Value	22,046	16,160
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	5,917	10,036
Available-for-sale securities, Unrealized Losses	(4)	(5)
Available-for-sale securities, Fair Value	5,913	10,031
United States Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	68,766	5,053
Available-for-sale securities, Unrealized Gains	1
Available-for-sale securities, Unrealized Losses	(51)	(6)
Available-for-sale securities, Fair Value	$ 68,716	$ 5,047

Significant Accounting Policies - Schedule of Estimated Useful Lives of Asset Classification (Detail)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Leasehold improvements	Shorter of useful life or remaining life of lease
Computer Hardware and Software [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	3 years
Computer Hardware and Software [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	26,986,318	26,423,394
Common stock, shares outstanding	26,986,318	26,423,394

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (42,854)	$ (67,982)
Other comprehensive loss:
Net unrealized loss on marketable securities	(43)	(11)
Total comprehensive loss	$ (42,897)	$ (67,993)

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
IPO
Issuance of common stock upon initial public offering, offering costs	$ 403	$ 5,303

Organization and Operations	12 Months Ended
Organization and Operations	Dec. 31, 2016
Accounting Policies [Abstract]
Organization and Operations	1. Organization and Operations Inotek Pharmaceuticals Corporation (the “Company”) is a clinical-stage biopharmaceutical company developing molecules with novel mechanisms of action to address significant diseases of the eye. The Company’s business strategy is to develop and progress its product candidates through human clinical trials. The Company’s headquarters are located in Lexington, Massachusetts. The Company has devoted substantially all of its efforts to research and development, including clinical trials of its product candidates. The Company has not completed the development of any product candidates. The Company has no current source of revenue to sustain present activities and does not expect to generate revenue until and unless the Company receives regulatory approval of and successfully commercializes its product candidates. The Company is subject to a number of risks and uncertainties similar to those of other life science companies developing new products, including, among others, the risks related to the necessity to obtain adequate additional financing, to successfully develop product candidates, to obtain regulatory approval of products candidates, to comply with government regulations, to successfully commercialize its potential products, to the protection of proprietary technology and to the dependence on key individuals. In August 2016, the Company closed an underwritten public offering of $52,000 aggregate principal amount of 5.75% Convertible Senior Notes due 2021, including $2,000 from an exercise of the underwriters’ overallotment option, (the “2021 Convertible Notes”), and received net proceeds of $48,738 after deducting underwriting discounts and offering-related costs (see Note 5). In April 2016, the Company filed a registration statement on Form S-3 containing two prospectuses: (i) a base prospectus which covers the offering, issuance and sale of up to $200,000 in the aggregate of an indeterminate number of shares of common stock and preferred stock, such indeterminate principal amount of debt securities and such indeterminate number of warrants and units; and (ii) a sales agreement prospectus covering the offering, issuance and sale of up to a maximum aggregate offering price of $50,000 of the Company’s common stock that may be issued and sold under an at-the-market sales agreement with Cowen and Company, LLC (the “ATM”). The $50,000 of common stock that may be issued and sold under the ATM reduces the available balance under the base prospectus by the amount issued. During the year ended December 31, 2016, the Company sold 482,689 shares of common stock and received net proceeds of $3,997, pursuant to the ATM. At December 31, 2016, $45,599 was available for sale of common stock under the ATM. In the first quarter of 2015, the Company completed its initial public offering (the “IPO”) of (i) 6,966,333 shares of common stock, including 299,333 shares from an exercise of the underwriters’ overallotment option at a price of $6.00 per share and (ii) $21,000 aggregate principal amount of 5.0% Convertible Senior Notes due 2020 (the “2020 Convertible Notes”), including $1,000 from an exercise of the underwriters’ overallotment option. Existing stockholders and their affiliated entities purchased approximately 3,005,000 shares of common stock issued in the IPO at the same terms. The Company received net proceeds of $36,495, after deducting underwriting discounts and offering-related costs, from its equity issuances and $18,903 in net proceeds, after deducting underwriting discounts and offering-related costs, from its debt issuances. In July and August 2015, holders of $21,000 principal amount of the 2020 Convertible Notes elected to convert the principal into 3,333,319 shares of common stock. In addition, the Interest Make-Whole Payment (see Note 5) was settled with shares of common stock, at the election of the Company, resulting in the issuance of 530,072 additional shares of common stock. In August 2015, the Company completed an underwritten public offering of its common stock (the “Follow-on Offering”). The Company issued 6,210,000 shares of its common stock at a price of $12.75 per share, including 810,000 shares from the underwriters’ full exercise of their overallotment option, and received net proceeds of $73,965, after deducting underwriting discounts and offering-related costs. Prior to this the Company has funded its operations primarily through the sale of preferred stock and issuance of convertible promissory notes and notes payable. As of December 31, 2016, the Company had an accumulated deficit of $238,877 and $126,473 of cash, cash equivalents and short-term investments. The Company will need to expend substantial resources for research and development, including costs associated with the clinical testing of its product candidates and will need to obtain additional financing to fund its operations and to conduct trials for its product candidates. If such products were to receive regulatory approval, the Company would need to prepare for the potential commercialization of its product candidates and fund the commercial launch and continued marketing of its products. The Company will require additional funding in the future and may not be able to raise such additional funds. The Company expects losses will continue as it conducts research and development activities. The Company will seek to finance future cash needs through public or private equity offerings, license agreements, debt financings, collaborations, strategic alliances, or any combination thereof. The incurrence of indebtedness would result in increased fixed payment obligations and could also result in restrictive covenants, such as limitations on our ability to incur additional debt, limitations on the Company’s ability to acquire, sell or license intellectual property rights and other operating restrictions that could adversely impact the ability of the Company to conduct its business. If adequate funds are not available, the Company would delay, reduce or eliminate research and development programs and reduce administrative expenses. The Company may seek to access the public or private capital markets whenever conditions are favorable, even if it does not have an immediate need for additional capital at that time. In addition, if the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, it may have to relinquish valuable rights to its technologies, future revenue streams or product candidates or to grant licenses on terms that may not be favorable to it. If the Company is unable to raise sufficient funding, it may be unable to continue to operate. There is no assurance that the Company will be successful in obtaining sufficient financing on acceptable terms and conditions to fund continuing operations, if at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations and financial condition.

Significant Accounting Policies - Schedule of Computation of Basic and Diluted EPS(Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss	$ (42,854)	$ (67,982)
Accretion and dividends on convertible preferred stock		(131)
Net loss applicable to common stockholders	$ (42,854)	$ (68,113)
Denominator:
Weighted average common shares outstanding—basic and diluted	26,735,175	18,311,333
Net loss per share applicable to common stockholders—basic and diluted	$ (1.60)	$ (3.72)

Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	9,685,657	1,688,085
Shares Issuable Upon Conversion of the 2021 Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	6,483,791
Warrants for Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	56,408	56,408
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,675,458	1,631,677
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	470,000

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,561	$ 1,074
Less: accumulated depreciation	(431)	(262)
Property and equipment, net	1,130	812
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	407	334
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	263	252
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	446	43
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 445	$ 445

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment Net [Abstract]
Depreciation expense	$ 169	$ 45

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Compensation and benefits	$ 2,171	$ 999
Research and development	1,148	375
Government payable	478	450
Professional fees	311	347
Other	308	337
Total	$ 4,416	$ 2,508

Debt - Convertible Bridge Notes - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Feb. 28, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Amortization of financing costs			$ 0	$ 107,000
Loss on extinguishment of debt				$ 4,239,000
2014 Convertible Bridge Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 2,000,000
Debt instrument maturity date			Jun. 30, 2015
Debt instrument annual interest rate		8.00%		8.00%
Debt converted into shares of common stock	337,932
Share offering price	$ 6.00
Debt instrument, interest expense to coupon rate				$ 23,000
Amortization of financing costs				128,000
Gain in change in fair value				480,000
Loss on extinguishment of debt				$ 360,000
2014 Convertible Bridge Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Gross proceeds		$ 40,000,000

Income Taxes - Schedule of Reconciliation Between Statutory to Effective Tax Rates (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed at statutory rate	34.00%	34.00%
State income taxes	4.76%	1.20%
Expiration of capital loss carryforward		(2.13%)
Tax credits	3.38%	0.73%
Other	(1.74%)	(3.35%)
Change in value of convertible notes derivatives and warrant liabilities		(21.16%)
Valuation allowance	(40.40%)	(9.29%)
Effective Income Tax Rate Reconciliation,Total	0.00%	0.00%

Income Taxes - Schedule of Tax Effect of Significant Temporary Differences Representing Deferred Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Components of Deferred Tax Assets and Liabilities [Abstract]
Net operating loss (“NOL”) and credit carryforwards	$ 43,765	$ 35,858
Capitalized research and development costs	22,775	14,406
Other	1,963	927
Valuation allowance	(68,503)	(51,191)
Deferred Tax Assets, Net	$ 0	$ 0

Income Taxes - Schedule of Change In Unrecognized Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized Tax Benefits, Beginning Balance	$ 333	$ 284
Additions for prior year tax positions	6
Additions for current year tax positions	149	49
Unrecognized Tax Benefits, Ending Balance	$ 488	$ 333

Equity - Schedule of Rollforward of Unvested Stock Shares (Detail) - Series X Preferred Stock [Member]	12 Months Ended
	Dec. 31, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested—December 31, 2014	558,862
Vested	(558,862)
Repurchased	0

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 29, 2016 $ / ft²	May 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Operating Leased Assets [Line Items]
Commencement date of lease		2015-09
Acquisition of leasehold improvements		$ 445		$ 445
Lease amendment commencement date	Jul. 01, 2016
Lease term	90 months
Lease extension term	5 years
Lease description			The lease term is 90 months and the Company has the right to extend the term for one period of five years.
Annual lease rate per square foot in first year of lease \| $ / ft²	25
Annual lease rate per square foot in last year of lease \| $ / ft²	30.50
Operating leases, rent expenses			$ 275	143
Research and development expense			$ 31,985	$ 12,554
Transition Agreement [Member]
Operating Leased Assets [Line Items]
Description of Transition Agreement			Pursuant to the terms of the Transition Agreement, Dr. McVicar will remain an employee of the Company as a Senior Advisor for a six-month period ending April 4, 2017 (the “Transition Period”) and for twelve months thereafter will receive his salary and medical benefits at the same rate in effect as of the date of the Transition Agreement.
Former Chief Scientific Officer [Member] \| Transition Agreement [Member]
Operating Leased Assets [Line Items]
Research and development expense			$ 900
Former Chief Scientific Officer [Member] \| Transition Agreement [Member] \| Stock Options [Member]
Operating Leased Assets [Line Items]
Stock based compensation expense			$ 200

Commitments and Contingencies - Schedule of Remaining Aggregate Annual Commitments Pursuant to Office Lease and Lease Amendment (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2017	$ 402
2018	411
2019	421
2020	429
2021	439
Thereafter	520
Total	$ 2,622

Fair Value of Financial Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Money Market Mutual Funds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Money market mutual funds (included in cash and cash equivalents)	$ 20,698
Money Market Mutual Funds [Member] \| Level 1 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Money market mutual funds (included in cash and cash equivalents)	20,698
Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	22,046	$ 16,160
Certificates of Deposit [Member] \| Level 2 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	22,046	16,160
Agency Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	5,913	10,031
Agency Bonds [Member] \| Level 2 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	5,913	10,031
United States Treasury Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	68,716	5,047
United States Treasury Securities [Member] \| Level 1 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	68,716	5,047
Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	96,675	31,238
Short-term Investments [Member] \| Level 1 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	68,716	5,047
Short-term Investments [Member] \| Level 2 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	$ 27,959	$ 26,191

Fair Value of Financial Measurements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014 shares
Convertible Notes Redemption Rights Derivative [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Notes converted in to shares	337,932

Fair Value of Financial Measurements - Schedule of Change in Company's Level 3 Liabilities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Beginning Balance	$ 482
Change in fair value	(267)
Reclassification to stockholders' equity	(215)
Convertible Notes Redemption Rights Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Beginning Balance	480
Change in fair value	(480)
2020 Convertible Notes Derivative Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Change in fair value	42,793
Conversion to common stock	(55,216)
2020 Convertible Notes Derivative Liability [Member] \| 2020 Convertible Notes [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Gains and Losses [Line Items]
Issuance of Notes	$ 12,423

Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Compensation Related Costs Disclosure [Line Items]
Contribution to savings plan		$ 168	$ 35
Minimum [Member] \| 2014 Management Incentive Plan [Member]
Compensation Related Costs Disclosure [Line Items]
Portion of transaction proceeds, bonus for each participants under bonus pool	7.00%
Maximum [Member] \| 2014 Management Incentive Plan [Member]
Compensation Related Costs Disclosure [Line Items]
Portion of transaction proceeds, bonus for each participants under bonus pool	9.75%

Subsequent Event - Additional Information (Detail) - Whitehead v. Inotek Pharmaceuticals Corporation [Member] - Pending Litigation [Member]	12 Months Ended
	Dec. 31, 2016
Subsequent Event [Line Items]
Lawsuit filing date	January 6, 2017
Name of plaintiff	purported stockholder of the Company
Lawsuit action domicile	U.S. District Court for the District of Massachusetts
Name of defendant	David Southwell, Rudolf Baumgartner, Dale Ritter, and William McVicar, captioned Whitehead v. Inotek Pharmaceuticals Corporation
Lawsuit allegation, description	The complaint alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and SEC Rule 10b-5 based on allegedly false and misleading statements and omissions regarding our MATrX-1 phase 3 clinical trial of trabodenoson.
Lawsuit management action, description	The lawsuit seeks among other things, unspecified compensatory damages, interest, attorneys’ fees and costs, and unspecified equitable/injunctive relief. The Company intends to vigorously defend itself against this claim.