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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2015	Mar. 22, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
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		26,423,394
Entity Public Float			$ 21.5

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 80,042	$ 3,618
Short-term investments	31,238
Prepaid expenses and other current assets	1,086	52
Total current assets	112,366	3,670
Property and equipment, net	812
Other assets	143	1,850
Total assets	113,321	5,520
Current liabilities:
Accounts payable	1,633	1,146
Accrued expenses and other current liabilities	2,508	992
Notes payable, current portion		3,063
Convertible Bridge Notes		1,541
Convertible Bridge Notes redemption rights derivative		480
Total current liabilities	4,141	7,222
Notes payable, net of current portion		2,550
Warrant liabilities		482
Other long-term liabilities	367	24
Total liabilities	4,508	10,278
Redeemable convertible preferred stock		46,801
Commitments and Contingencies (Note 9)
Stockholders' equity (deficit):
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 and 43,509,727 shares authorized at December 31, 2015 and December 31, 2014, respectively; 26,423,394 shares and 1,020,088 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	264	10
Additional paid-in capital	304,583	76,472
Accumulated deficit	(196,023)	(128,041)
Other comprehensive loss	(11)
Total stockholders' equity (deficit)	108,813	(51,559)
Total Liabilities, Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit)	$ 113,321	5,520
Series AA Redeemable Convertible Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock		46,253
Series X Redeemable Convertible Preferred Stock [Member]
Current liabilities:
Redeemable convertible preferred stock		$ 548

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
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	43,509,727
Common stock, shares issued	26,423,394	1,020,088
Common stock, shares outstanding	26,423,394	1,020,088
Series AA Redeemable Convertible Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	0	25,757,874
Preferred stock, shares issued	0	24,057,013
Preferred stock, shares outstanding	0	24,057,013
Series X Redeemable Convertible Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	0	2,902,050
Preferred stock, shares issued	0	1,892,320
Preferred stock, shares outstanding	0	1,892,320

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating expenses:
Research and development	$ (12,554)	$ (5,592)
General and administrative	(7,842)	(2,112)
Loss from operations	(20,396)	(7,704)
Interest expense	(1,230)	(980)
Interest income	89
Loss on extinguishment of debt	(4,399)
Change in fair value of warrant liabilities	267	(845)
Change in fair value of Convertible Bridge Notes redemption rights derivative	480	(2)
Change in fair value of 2020 Convertible Notes derivative liability	(42,793)
Net loss	$ (67,982)	$ (9,531)
Net loss per share attributable to common stockholders-basic and diluted	$ (3.72)	$ (13.52)
Weighted-average number of shares outstanding-basic and diluted	18,311,333	1,020,088

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO [Member]	Secondary Public Offering [Member]	Series AA Redeemable Convertible Preferred Stock [Member]	Series AA Redeemable Convertible Preferred Stock [Member] IPO [Member]	Series X Redeemable Convertible Preferred Stock [Member]	Series X Redeemable Convertible Preferred Stock [Member] IPO [Member]	Common Stock [Member]	Common Stock [Member] IPO [Member]	Common Stock [Member] Secondary Public Offering [Member]	Common Stock [Member] Series AA Redeemable Convertible Preferred Stock [Member] IPO [Member]	Common Stock [Member] Series X Redeemable Convertible Preferred Stock [Member] IPO [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] IPO [Member]	Additional Paid-in Capital [Member] Secondary Public Offering [Member]	Additional Paid-in Capital [Member] Series AA Redeemable Convertible Preferred Stock [Member] IPO [Member]	Additional Paid-in Capital [Member] Series X Redeemable Convertible Preferred Stock [Member] IPO [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2013	$ (38,895)							$ 10					$ (176)	$ 79,781					$ (118,510)
Beginning balance, shares at Dec. 31, 2013								1,021,972					1,884
Beginning balance, shares at Dec. 31, 2013								(1,021,972)					(1,884)
Beginning Balance at Dec. 31, 2013				$ 40,685		$ 548
Beginning balance, shares at Dec. 31, 2013				23,204,783		1,892,320
Stock-based compensation	177													177
Accretion of Series AA preferred stock to redemption value	(864)			$ 864										(864)
Accrual of Series AA preferred stock dividends	(3,401)			3,401										(3,401)
Exercise of Series AA preferred stock warrants	955			$ 1,303										955
Exercise of Series AA preferred stock warrants, shares				852,230
Retirement of treasury stock	(176)												$ 176	(176)
Retirement of treasury stock, shares								1,884					1,884
Retirement of treasury stock, shares								(1,884)					(1,884)
Net loss	(9,531)																		(9,531)
Ending balance at Dec. 31, 2014	(51,559)							$ 10						76,472					(128,041)
Ending balance, shares at Dec. 31, 2014								1,020,088
Ending balance at Dec. 31, 2014	46,801			$ 46,253		$ 548
Ending balance, shares at Dec. 31, 2014				24,057,013		1,892,320
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)			$ 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, shares					(24,057,013)		(1,892,320)				7,536,331	466,319
Conversion of preferred stock into common stock, shares					(24,057,013)		(1,892,320)				7,536,331	466,319
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
Ending balance, shares at Dec. 31, 2015				0		0
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)				$ (75)	$ (5)					$ (46,309)	$ (543)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (67,982)	$ (9,531)
Adjustments to reconcile net loss to cash used by operating activities:
Noncash interest expense	1,132	238
Deferred rent and lease incentives	(20)
Loss on extinguishment of debt	4,239
Amortization of premium on marketable securities	75
Depreciation	45	0
Change in fair value of warrant liabilities	(267)	845
Change in fair value of Convertible Bridge Notes redemption rights derivative	(480)	2
Change in fair value of 2020 Convertible Notes derivative liability	42,793
Stock-based compensation	2,380	177
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,256)	(1,804)
Accounts payable	487	917
Accrued expenses and other current liabilities	1,438	(587)
Net cash used in operating activities	(17,416)	(9,743)
Cash flows from investing activities:
Purchase of short-term investments	(33,693)
Proceeds from the maturities of short-term investments	2,430
Purchase of property and equipment	(412)
Net cash provided by investing activities:	(31,675)
Cash flows from financing activities:
Net proceeds from issuance of convertible notes		1,970
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
Payments of 2020 Convertible Notes Issuance Costs	(1,841)
Net proceeds from issuance of common stock in follow-on public offering	73,965
Proceeds from the issuance of shares pursuant to stock option plans	43
Proceeds from the issuance of shares pursuant to employee stock purchase plan	63
Proceeds from exercise of warrants for Series AA Preferred Stock		8
Principal payments on notes payable	(5,800)	(1,410)
Net cash provided by financing activities:	125,515	568
Net change in cash and cash equivalents	76,424	(9,175)
Cash and cash equivalents, beginning of period	3,618	12,793
Cash and cash equivalents, end of period	80,042	3,618
Supplemental disclosure of cash flow information:
Cash paid for interest	89	738
Supplemental disclosure of noncash investing and financing activities:
Acquisition of leasehold improvements	445
Conversion of Notes into common stock	66,376
Retirement of treasury stock		176
Unrealized comprehensive loss on marketable securities	11
IPO [Member]
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]
Cash flows from financing activities:
Proceeds from exercise of warrants for Series AA Preferred Stock		8
Supplemental disclosure of noncash investing and financing activities:
Accrual of Series AA preferred stock dividends		3,401
Accretion of Series AA preferred stock to redemption value	131	864
Series AA Redeemable Convertible Preferred Stock [Member] \| IPO [Member]
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 [Member]
Supplemental disclosure of noncash investing and financing activities:
Conversion of preferred stock into common stock upon initial public offering	$ 548
Convertible Preferred Stock Warrant [Member]
Supplemental disclosure of noncash investing and financing activities:
Reclassification of fair value of warrant liability to equity		$ 2,250

Significant Accounting Policies

12 Months Ended

Dec. 31, 2015

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 subsidiary, Inotek Securities Corporation. 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.

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. The Company considers all highly liquid investments with maturities of 90 days or less at the date of purchase to be cash equivalents.

The Company maintains its cash and cash equivalent balances with financial institutions that management believes are creditworthy. The Company’s cash and cash equivalent accounts and certificates of deposit, 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—Beginning in 2015, 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 income (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 for the year ended December 31, 2015, and $11 in net unrealized losses on short-term investments for the year ended December 31, 2015.

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, 2015 consist of the following (in thousands):


	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, 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, 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

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 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.

Deferred Financing Costs— Financing 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 were amortized over the term of the respective notes using the effective interest method. Amortization of deferred financing costs were $107 and $219 in the years ended December 31, 2015 and 2014, respectively (see Note 5).

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. 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).

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).

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, 2015 and 2014, 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:


	2015			2014
Numerator:
Net loss	$	(67,982	)	$	(9,531	)
Accretion and dividends on convertible preferred stock		(131	)		(4,265	)

Net loss applicable to common stockholders	$	(68,113	)	$	(13,796	)
Denominator:
Weighted average common shares outstanding—basic and diluted		18,311,333			1,020,088

Net loss per share applicable to common stockholders—basic and diluted	$	(3.72	)	$	(13.52	)

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:


	December 31, 2015		December 31, 2014
Series AA preferred stock		—		7,356,331
Series X preferred stock		—		466,319
Warrants for Series AA preferred stock		—		56,408
Warrants for common stock		56,408		—
Stock options		1,631,677		911,075

Total		1,688,085		8,790,133

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 ASU 2014-15, 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 is currently evaluating the impact of this accounting standard update on the Company’s consolidated financial statements.

Debt	12 Months Ended
Debt	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	5. Debt *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 (“Maturity Date”), 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 (the “Holder”), 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”). 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 (the “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 (the “Conversion Date”) 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 (“Fundamental Change”), as defined in the Indenture (“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 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 (“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 (“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 ASC 815, Derivatives and Hedging. 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 “2014 Convertible Bridge Notes”). The 2014 Convertible Bridge Notes were 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 IPO of common stock of at least $40,000 in gross proceeds (“a qualifying public offering”), all outstanding principal and accrued interest thereon would automatically convert into common stock at the IPO price. In addition, the 2014 Convertible Bridge Notes had the following features: (i) in the event the Company sold new notes prior to a qualifying public offering, the noteholders would convert the 2014 Convertible Bridge Notes into the new notes; (ii) if at any time prior to repayment of the 2014 Convertible Bridge Notes or a qualifying public offering the Company had a change in control transaction, the noteholders would receive either (a) cash in the amount of twice the principal and interest due as of the effective date of the change in control transaction or (b) shares of Series AA preferred stock based upon the conversion of the principal and interest due as of the effective date of the change in control transaction, whichever yields the greatest return (the ‘Change in Control Redemption Feature”); (iii) at any time after maturity, the noteholders could elect to convert all principal and accrued interest into Series AA Preferred stock at the current Series AA preferred stock conversion price; (v) the maturity date of the 2014 Convertible Bridge Notes could be extended two times for additional six-month periods; (vi) upon an event of default, as defined in the notes, the noteholders could declare the 2014 Convertible Bridge Notes immediately payable; and (vii) the Company would not prepay the 2014 Convertible Bridge Notes without the consent of noteholders owning at least two thirds of the outstanding principal. Interest accrued on the 2014 Convertible Bridge Notes was $4 at December 31, 2014 and was reflected in accrued expenses and other current liabilities. The Company determined that the automatic conversion into common stock upon an IPO was the predominant feature of the 2014 Convertible Bridge Notes. Based on this the Company deemed the 2014 Convertible Bridge Notes to be share-settled debt and accreted the debt discounts recorded (see below) to the redemption value over the term of the 2014 Convertible Bridge Notes. The Company evaluated the various features of the 2014 Convertible Bridge Notes and determined that the Change in Control Redemption Feature met the definition of a derivative and required bifurcation from the 2014 Convertible Bridge Notes. At the issuance of the 2014 Convertible Bridge Notes, the Company valued this derivative at $478 and allocated that value from the proceeds of the 2014 Convertible Bridge Notes and recorded a convertible notes redemption rights derivative liability on the balance sheet. The Company marked this liability to market at each reporting date and reflected the change in fair value in change in fair value of Convertible Bridge Notes redemption rights derivative in the statement of operations. In addition, the Company incurred $30 of costs associated with the issuance of the 2014 Convertible Bridge Notes and recorded this amount as deferred financing costs which were reflected in prepaid expenses and other current assets. The Company amortized (i) the debt discount recorded from the allocation of value to the redemption rights derivative and (ii) deferred financing costs, into interest expense using the effective interest method. During the year ended December 31, 2014, the Company reflected as interest expense related to the 2014 Convertible Bridge Notes (i) $4 related to the 8% coupon rate and (ii) $20 of amortization of the initial redemption rights derivative liability and issuance costs. In addition, the Company reflected a $2 increase in fair value of the derivative liability at December 31, 2014 as loss on change in fair value of convertible notes redemption rights derivative. At December 31, 2014, the principal balance of the 2014 Convertible Bridge Notes was $2,000. 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. For the year ended December 31, 2015, the Company reflected interest expense related to the Convertible Bridge Notes as follows: (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 the year ended December 31, 2015, in connection with the conversion of the Convertible Bridge Notes into common stock, the Company reflected (i) a $480 gain in change in fair value of the Convertible Bridge Notes redemption rights derivative on conversion 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 were to bear interest at a rate per annum of 11.0%. The Loans were to 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 were 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 granted first priority liens and the Loans were collateralized by the Company’s personal property, including cash and cash equivalents. The Loan Agreements contained representations and warranties by the Company and certain indemnification provisions, non-financial covenants and default provisions. The Loan Agreements also included certain provisions allowing for prepayment of the debt by the Company, exercisable at the Company’s option, which required payment of additional interest to the Lenders based upon a stated rate and the balance outstanding at repayment. The Company determined that the various embedded features did not require bifurcation from the Loan Agreements. 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 was the lowest effective price per share that is offered in the next round. The warrants were to 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 be classified as a liability based upon the nature of the underlying Series AA preferred stock. The Company recorded the fair value of the warrants of approximately $222 (Note 10) as a discount to the carrying value of the Loans and as a liability. The Company recognized any change in the value of the warrant liability each reporting period in the statement of operations. Additionally, the Company incurred fees related to the Loan Agreements and reimbursed Lenders for costs incurred by them aggregating $85 and reflected these fees as a discount to the carrying value of the Loan. The Company amortized these loan discounts and the Loan Termination Payment, together totaling $517, to interest expense over the term of the Loan using the effective interest rate method. For the year ended December 31, 2014, interest expense related to the Loan Agreements was $956, including $218 related to accretion of the debt discount and termination payment. At December 31, 2014, the principal balance on the Loan Agreements was $5,800, including the Loan Termination Payment and the unamortized debt discount and termination payment balance was $188. Principal payments on the Loans were $1,410 during the year ended December 31, 2014. 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, for the year ended December 31, 2015, the Company recorded a loss on extinguishment of the Loan Agreement of $323 related to the write-off of 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, 2015

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, 2015 and 2014, as the Company incurred operating losses for each of these years.

A reconciliation between the effective tax rates and statutory rates for the years ended December 31, 2015 and 2014 is as follows:


	2015			2014
Computed at statutory rate		34.00	%		34.00	%
State income taxes		1.20			4.93
Expiration of capital loss carryforward		(2.13	)		0.00
Expiration of state net operating loss carryforward		0.00			(9.35	)
Tax credits		0.73			2.43
Other		(3.35	)		(4.28	)
Change in value of convertible notes derivatives and warrant liabilities		(21.16	)		—
Valuation allowance		(9.29	)		(27.73	)

		—	%		—	%

The tax effect of significant temporary differences representing deferred tax assets and liabilities as of December 31, 2015 and 2014 is as follows:


	December 31,
	2015			2014
Net operating loss (“NOL”) and credit carryforwards	$	35,858		$	30,896
Capitalized research and development costs		14,406			12,041
Capital loss carryover		—			1,672
Other		927			269
Valuation allowance		(51,191	)		(44,878	)

	$	—		$	—

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, 2015 and 2014. 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, 2015 and 2014, the valuation allowance changed by $6,313 and $2,643, respectively. Realization of deferred tax assets is dependent upon the generation of future taxable income.

As of December 31, 2015, the Company had federal NOL carryforwards for income tax purposes of $88,436 that expire at various dates through 2035, and state NOL carryforwards of $47,369 that expire at various dates through 2035, available to reduce future federal and state income taxes, if any. As of December 31, 2015, the Company had federal research and development tax credits of $3,196, and state research and development tax credits of $637. 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, 2015 and 2014, the Company’s total unrecognized tax benefits totaled $333 and $284, 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. Tax years 2012 through 2015 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, 2015 and 2014 are as follows:


	2015		2014
Balance at January 1,	$	284	$	258
Additions for current year tax positions		49		26
Reductions for expirations of statute of limitations or settlements		—		—

	$	333	$	284

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

Equity

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Equity

7. Equity

Authorized Shares

As of December 31, 2015, 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 26,423,394 and 1,020,088 shares of common stock outstanding at December 31, 2015 and 2014, respectively.

Preferred Stock

The Company has evaluated the traunched nature of its Preferred Stock offerings, its investor registration rights, as well as the rights, preferences and privileges of each series of Preferred Stock and has concluded that there are 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.

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.

Rights, Preferences, and Privileges

Voting:

Series AA preferred stock voted together with all other classes and series of stock as a single class on all actions to be taken by the stockholders of the Company. Each share of Series AA preferred stock shall entitle the holder to such number of votes per share on each such action were equal the number of shares of common stock (including fractions of a share) into which each share of Series AA preferred stock was then convertible.

Dividends:

Series AA preferred stock accrued dividends quarterly at the rate of eight percent (8%) per annum, based upon the Series AA original issue price, whether or not declared, are cumulative and compounded annually. The Series AA original issue price was $1.529 per share (“Series AA Original Issue Price”).

Liquidation Preference:

Upon any liquidation, dissolution or winding up of the Company (a “Liquidation Event”), whether voluntary or involuntary, the holders of the shares of Series AA preferred stock would be paid out of the assets of the Company available for distribution to its stockholders before any payment would be made to the holders of Series X preferred stock or common stock, an amount per share equal to two times the Series AA Original Issue Price plus any accrued or declared but unpaid dividends ( the “Series AA Initial Preference”). If upon any Liquidation Event, the assets to be distributed to the holders of Series AA preferred stock would have been insufficient to permit payment to the stockholders of the Series AA Initial Preference, then the holders of the Series AA preferred stock would share ratably in any distribution of the remaining assets of the Company available for distribution in proportion to the respective amounts which would otherwise be payable in respect of the shares held by them upon such distribution if all amounts payable on or with respect to such shares were paid in full.

Upon any Liquidation Event, immediately after the holders of Series AA preferred stock have been paid in full the Series AA Initial Preference and after the holders of Series X preferred stock have been paid full the Series X preference (see Series X preferred stock below), the holders of the shares of Series AA preferred stock would be paid out of the assets of the Company available for distribution to its stockholders before any payment shall be made to the holders of common stock, a per share amount equal to one-half times the Series AA Original Issue Price (the “Series AA Secondary Preference”). If upon any Liquidation Event, the assets to be distributed to the holders of Series AA preferred stock would be insufficient to permit payment to such stockholders of the Series AA Secondary Preference, then the holders of the Series AA preferred stock would share ratably in any distribution of the remaining assets of the Company available for distribution in proportion to the respective amounts which would otherwise be payable in respect of the shares held by them upon such distribution if all amounts payable on or with respect to such shares were paid in full.

Optional Conversion:

The holder of any share or shares of Series AA preferred stock would have the right, at its option at any time, to convert any such shares of Series AA preferred stock (except that upon any liquidation of the Company the right of conversion would terminate at the close of business on the business day fixed for payment of the amounts distributable on the Series AA preferred stock), each such share of Series AA preferred stock being converted into such number of fully paid and nonassessable shares of common stock as is obtained by dividing (1) the Series AA Original Issue Price plus any accrued or declared but unpaid dividends by (2 ) the Series AA Conversion Price in effect at the date any share or shares of Series AA preferred stock are surrendered for conversion. The “Series AA Conversion Price” was $1.529 and was subject to adjustment as discussed under the section “Anti-Dilution” below.

Mandatory Conversion:

All outstanding shares of Series AA Convertible Preferred Stock (including all accrued or declared but unpaid dividends thereon) would automatically convert to shares of Common Stock (i) upon the vote or written consent of the holders of at least sixty six and two-thirds percent (66 and 2/3%) of the issued and outstanding Series AA Convertible Preferred Stock, or (ii) upon the closing of a firm commitment underwritten public offering of shares of Common Stock pursuant to an effective registration statement under the Securities Act of 1933, as amended, that is underwritten by an investment bank approved by the Board of Directors and by a vote or written consent of the holders of at least sixty six and two-thirds percent (66 and 2/3%) of the issued and outstanding Series AA Convertible Preferred Stock, with aggregate proceeds from such offering to the Corporation in excess of $40,000,000, before deduction of the underwriting discounts and commissions (a “Qualifying Public Offering”).

Special Mandatory Conversion:

In the event that any investor did not participate in a qualified financing by purchasing in the aggregate, in such qualified financing and within the time period specified by the Company its pro rata amount of the qualified financing (such Investor’s “Pro Rata Amount”), then the applicable portion of the shares of Series AA preferred stock held by such investor immediately prior to the initial closing of the qualified financing would automatically, and without any further action on the part of such Investor, be converted into common stock at a conversion ratio of one hundred-to-one (100:1) (such that every one hundred shares of Series AA preferred Stock are converted into one share of common stock), effective upon, subject to, and concurrently with, the consummation of the final closing. For purposes of determining the number of shares of Series AA preferred stock owned by an investor, and for determining the number of offered securities an investor has purchased in a qualified financing, all shares of Series AA preferred stock held by affiliates of such investor would be aggregated with such investor’s shares and all offered securities purchased by affiliates of such investor would be aggregated with the offered securities purchased by such Investor (provided that no shares or securities shall be attributed to more than one entity or person within any such group of affiliated entities or persons).

Anti-dilution:

The conversion price of the Series AA preferred stock was subject to adjustment to reduce dilution in the event that the Company issued additional equity securities at a purchase price less than the applicable conversion price. The conversion price would also be subject to proportional adjustment for events such as stock splits, stock dividends, and recapitalization. As a result of the reverse stock splits in November 2014 and January 2015, the Series AA conversion price was adjusted to $6.204.

Redemption:

Shares of Series AA preferred stock would be redeemed by the Company out of funds lawfully available there for at a price equal to the Series AA Original Issue Price per share, plus all accrued or declared but unpaid dividends thereon (the “Redemption Price”), in three annual installments commencing not more than 60 days after receipt by the Company at any time on or after the fifth anniversary of June 9, 2010, from the holders of at least sixty-six and two-thirds percent (66 and 2/3%) of the then outstanding shares of Series AA preferred stock of written notice requesting redemption of all shares of Series AA preferred stock. The date of each such installment would be referred to as a “Redemption Date.” If the Company did not have sufficient funds legally available to redeem on any Redemption Date all shares of Series AA preferred stock to be redeemed on such Redemption Date, the Company would redeem a pro rata portion of each holder’s redeemable shares of such capital stock out of funds legally available.

Certain “change in control” events, as defined in the Company’s certificate of incorporation, were considered to be liquidation events upon which the holders of Series AA preferred stock have had the option to require the Company redeem the shares held, at their liquidation value, as discussed above.

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. Pursuant to these agreements, the shares vest upon the third anniversary of the issuance if the purchaser of the Series X preferred shares remained an employee or maintained a business relationship with the Company. The Series X preferred stockholder could not sell, assign, transfer, pledge, encumber or dispose of all or any of the unvested shares except to the Company. The Company determined that the issuance of these restricted shares was compensatory in nature and accounted for the issuance as stock-based compensation. The excess grant date value, over the proceeds received from each purchase was determined to be compensation expense.

Simultaneous with the issuance of Series X preferred stock, the Company entered into termination and separation agreements with certain employees and consultants who purchased 392,189 shares of Series X preferred stock. The Company determined that there was no substantive future services required of these employees and consultants and recognized all of the associated compensation expense upon issuance.

The remaining 2,058,995 shares were issued to continuing employees of the Company and the Company recognized the compensation expense on a straight-line basis over the requisite service period, net of an estimated forfeiture rate which concluded in 2013.

Two of the 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. The modified vesting terms provide that the shares will vest upon the occurrence of a liquidation event, if such liquidation event occurs within two years of the date of the modifications. The Company retains the right to repurchase the unvested shares at the purchase price of $0.01 per share if a liquidation event does not occur within two years of the date of the modification. During the year ended December 31, 2014, the Company further modified the vesting terms of these 558,862 shares of Series X preferred stock such that the Company’s repurchase right will 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 and at December 31, 2014 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, discussed further below, 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.

Rights, Preferences, and Privileges

Voting Rights:

The Series X preferred stock did not have any voting rights, except as related to the election of certain directors. When the Series X preferred stock had voting rights, each share of Series X preferred stock entitled the holder to such number of votes per share on each such action as shall equal the number of shares of common stock into which each share of Series X preferred stock was then convertible.

Liquidation Preference:

Upon any liquidation event, such as a liquidation, dissolution or winding up of the Company, immediately after the holders of Series AA preferred stock would have been paid in full, the Series AA preferred stock initial preference as described above and before any payment is made to the holders of common stock, the holders of the shares of Series X preferred stock would be paid out of assets of the Company available for distribution to its stockholders a per share amount determined by taking the product of (1) the percentage calculated as (i) the total number of issued and outstanding shares of common stock owned by the holders of Series X preferred stock determined on an as converted fully-diluted basis divided by (ii) the total number of issued and outstanding shares of common stock of the Company on an as-converted fully diluted basis, and (2) the remaining assets of the Company available for distribution to its stockholders, and dividing such product by the number of issued and outstanding shares of Series X preferred stock (the “Series X Preference”).

Certain change in control events, as defined in the Company’s certificate of incorporation, were to be considered to be liquidation events upon which the holders of Series X preferred stock had the option to require the Company redeem the shares held, at their liquidation value, as discussed above.

Right to Convert:

The holder of any share of Series X preferred stock had the right, at any time to convert any such share (except that upon any liquidation of the Company the right of conversion shall terminate at the close of business on the business day fixed for payment of the amounts distributable on the Series X preferred stock), into fully paid and nonassessable shares of common stock based on the Series X Conversion Ratio. The Series X Conversion Ratio was initially 1:1, and subject to adjustment as discussed under the section “Anti-Dilution” below.

Mandatory Conversion:

The Series X preferred stock would be automatically converted into common stock, at the then applicable conversion price (i) in the event that the holders of at least two-thirds of the outstanding Series AA preferred stock, voting as a single class, consent to such conversion, or (ii) upon the closing of a qualified public offering, as defined.

Anti-Dilution:

The conversion price of the Series X preferred stock was subject to adjustment to reduce dilution in the event that the Company issues additional equity securities at a price less than the applicable conversion price. The conversion price would also be subject to proportional adjustment for events such as stock splits, stock dividends, and recapitalization. As a result of the reverse stock splits in November 2014 and January 2015, the Series X conversion ratio was adjusted to approximately 1-for-4.06.

- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Stock Plans

12 Months Ended

Dec. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Plans

8. Stock Plans

The Company has historically 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. The board of directors has historically 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 the years ended December 31, 2015 and 2014 under the 2004 Plan:


	Number of Shares			Weighted-Average Exercise Price Per Share		Aggregate Intrinsic Value
Options outstanding at December 31, 2013		11,835		$	40.58		—
Granted		—			—		—
Exercised		—			—		—
Expired		(877	)		40.58		—

Options outstanding at December 31, 2014		10,958			40.58		—
Granted		—			—		—
Exercised		—			—		—
Expired		(41	)		40.58		—

Options outstanding at December 31, 2015		10,917		$	40.58		—

Options exercisable at December 31, 2015		10,917		$	40.58		—

Weighted-average years remaining on contractual life		2.50
Unrecognized compensation cost related to non-vested stock options	$	—

The Company recorded no stock compensation expense in the years ended December 31, 2015 and 2014, respectively relating to stock options granted pursuant to the 2004 Plan. At December 31, 2015, all 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, 2015 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. Subsequent to the IPO in February 2015, there were 2,175,216 shares available for grant under the 2014 Plan. There were 544,599 shares issuable under the 2014 Plan as of December 31, 2015. Pursuant to the provisions of the 2014 Plan and approval by the board of directors, on January 1, 2016 an additional 1,056,936 shares were added to the 2014 Plan representing 4% of total common shares issued and outstanding at December 31, 2015. The 2014 Plan expires in August 2024.

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. Additionally on August 28, 2014, the Board of Directors granted an aggregate of 59,142 stock options to the directors that were fully vested on the date of the grant.

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 Company recorded stock compensation expense of $170 in general and administrative expense in the year ended December 31, 2014 related to the 59,142 stock options that were granted pursuant to the 2014 Plan and fully vested as of the date of grant. The Company is recognizing $2,798 of stock compensation expense related to the remaining 840,975 stock options on a straight-line basis over the vesting period commencing upon the consummation of the IPO in February 2015.

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 of stock-based compensation expense for these stock options on a straight-line basis commencing upon the grant dates through the final vesting dates.

As of December 31, 2015, the Company had $4,621 of unrecognized compensation expense related to options granted under its 2014 Equity Plan. This cost is expected to be recognized over a weighted average period of 2.9 years from December 31, 2015.

The Company recognizes compensation expense based on the estimated grant date fair value method using the Black-Scholes valuation model. The Company reduces compensation expense for expected forfeitures, as estimated by management.

The following table summarizes the 2014 Plan option activity for the two years ended December 31, 2015:


	Number of Shares			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
Options outstanding at December 31, 2013		—		$	—		—
Granted		900,117			4.34		—
Exercised		—			—		—
Expired		—			—		—

Options outstanding at December 31, 2014		900,117			4.34		—
Granted		730,500			5.69		—
Exercised		(9,857	)		4.34		—
Expired		—			—		—

Options outstanding at December 31, 2015		1,620,760		$	4.95	$	10,339

Options exercisable at December 31, 2015		359,610		$	4.40	$	2,492

Weighted-average years remaining on contractual life		9.05
Unrecognized compensation cost related to non-vested stock options	$	4,621

The weighted-average fair value of all stock options granted for the years ending December 31, 2015 and 2014 was $4.39 and $3.30, respectively. Intrinsic value at December 31, 2015 is based on the closing price of the Company’s common stock of $11.33 per share.

Employee Stock Purchase Plan

In November 2014 the Company’s board of directors adopted and the stockholders approved the 2014 Employee Stock Purchase Plan (“ESPP”). The Company’s board of directors has authorized the issuance of a number of shares of common stock issuable under the ESPP to the number that represents 1% of our outstanding common stock outstanding after the IPO, or 160,276 shares. 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. The number of shares reserved and available for issuance under the ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. The ESPP may be terminated or amended by the board of directors at any time, but will automatically terminate upon the tenth anniversary of the date the ESPP is approved by the stockholders. An amendment that increases the number of shares of common stock that are authorized under the ESPP and certain other amendments require the approval of the stockholders.

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.

No offerings of the ESPP commenced as of December 31, 2014. In 2015, $63 was withheld and used to purchase 13,143 shares of common stock and the Company recorded $43 of stock-based compensation expense pursuant to the ESPP.

Restricted Common Stock

In 2011, the Company issued 24,280 restricted common shares pursuant to a stock purchase and restriction agreement for a price of $0.0406 per share. The Company received $1 from the grantee. These shares vested 25% on each of the first four anniversaries of the date of grant. During the year ended December 31, 2014, the board of directors accelerated the vesting of the last tranche resulting in 12,140 shares vesting in such period. The Company recorded the excess grant date fair value over the proceeds received as compensation expense. The Company recorded $7 of stock-based compensation expense related to this award in the year ended December 31, 2014. At December 31, 2015 there were no restricted common shares outstanding.

Fair Value of Financial Measurements

12 Months Ended

Dec. 31, 2015

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, 2015
	Total		Level 1		Level 2		Level 3
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	$	—


	Fair Value Measurements at December 31, 2014
	Total		Level 1		Level 2		Level 3
Liabilities
Convertible preferred stock warrant liability	$	482	$	—	$	—	$	482

Convertible notes redemption rights derivative	$	480	$	—	$	—	$	480

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 and Loan Agreements. The Series AA warrant liabilities were recorded at their fair value on the date of issuance and were remeasured on each subsequent balance sheet date and as of the warrant exercise date, with fair value changes recognized as income (decrease in fair value) or expense (increase in fair value) in other income (expense) in the statements of operations.

Prior to the IPO, in addition to the assumptions above, the Company’s estimated fair value of the Series AA preferred stock warrant liabilities is calculated using other key assumptions including the probability of an exit event, the enterprise value as determined on an income approach, and a discount for lack of marketability. Management, with the assistance of an independent valuation firm, made these subjective determinations based on available current information.

The Company used a hybrid valuation model in which a Monte Carlo simulation was used to calculate the fair value of the Company’s equity securities under three scenarios including: i) an IPO scenario, ii) a merger or acquisition scenario or iii) a stay private scenario. The Company then probability-weighted each equity value derived from the Monte Carlo simulation based upon the Company’s estimate of the likelihood of the exit scenario occurring.

The assumptions used in calculating the estimated fair value of the warrants represent the Company’s best estimates and include probabilities of settlement scenarios, enterprise value, time to liquidity, risk-free interest rates, discount for lack of marketability and volatility. The estimates are based, in part, on subjective assumptions and could differ materially in the future. Generally, increases or decreases in the fair value of the underlying convertible preferred stock would result in a directionally similar impact in the fair value measurement of the warrant liability. 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, and the Monte Carlo simulation model used to estimate the fair value of the Series AA preferred stock warrants at December 31, 2014:


	February 17,			December 31,
	2015			2014
Volatility		60	%		65% –70	%
Expected term (years)		8.4			0.17 – 0.50
Expected dividend yield		0.0	%		0.0	%
Risk-free rate		1.7	%		0.02% –0.03	%

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. The Company estimated the fair value of the redemption rights derivative using a ‘‘with and without’’ income valuation approach. Under this approach, the Company estimated the present value of the fixed interest rate debt based on the fair value of similar debt instruments excluding the embedded feature. This amount was then compared to the fair value of the debt instrument including the embedded feature using a probability weighted approach by assigning each embedded derivative feature a probability of occurrence, with consideration provided for the settlement amount including conversion discounts, prepayment penalties, the expected life of the liability and the applicable discount rate.

As of the issuance of the 2014 Convertible Bridge Notes on December 22, 2014 and on December 31, 2014, the Company ascribed a probability of occurrence to the Change in Control Redemption Feature of 25%. The expected life of the feature was the remaining term of the debt and the discount rate was 18.9%. The Company classified the liability within Level 3 of the fair value hierarchy as the probability factor and the discount rate are unobservable inputs and significant to the valuation model. As of December 31, 2014, the fair value of the embedded derivative was $480, respectively. 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 has not changed 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 years ended December 31, 2015 and 2014:


	Convertible preferred stock warrant liabilities			Convertible Bridge Notes redemption rights derivative			2020 Convertible Notes derivative liability
Balance at December 31, 2013	$	1,888		$	—		$	—
Issuance of 2014 Convertible Bridge Notes		—			478			—
Change in fair value		844			2			—
Warrant exercises		(2,250	)		—			—

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, 2015

Accounting Policies [Abstract]

Basis of Presentation

Segment Reporting

Use of Estimates

Cash and Cash Equivalents

Short-term investments

Short-term investments at December 31, 2015 consist of the following (in thousands):


	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

Deferred Public Offering Costs

Deferred Financing 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:


	2015			2014
Numerator:
Net loss	$	(67,982	)	$	(9,531	)
Accretion and dividends on convertible preferred stock		(131	)		(4,265	)

Net loss applicable to common stockholders	$	(68,113	)	$	(13,796	)
Denominator:
Weighted average common shares outstanding—basic and diluted		18,311,333			1,020,088

Net loss per share applicable to common stockholders—basic and diluted	$	(3.72	)	$	(13.52	)

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:


	December 31, 2015		December 31, 2014
Series AA preferred stock		—		7,356,331
Series X preferred stock		—		466,319
Warrants for Series AA preferred stock		—		56,408
Warrants for common stock		56,408		—
Stock options		1,631,677		911,075

Total		1,688,085		8,790,133

Subsequent Events

Recent Accounting Pronouncements

Recent Accounting Pronouncements

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Schedule of Short-term Investment

Short-term investments at December 31, 2015 consist of the following (in thousands):


	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:


	2015			2014
Numerator:
Net loss	$	(67,982	)	$	(9,531	)
Accretion and dividends on convertible preferred stock		(131	)		(4,265	)

Net loss applicable to common stockholders	$	(68,113	)	$	(13,796	)
Denominator:
Weighted average common shares outstanding—basic and diluted		18,311,333			1,020,088

Net loss per share applicable to common stockholders—basic and diluted	$	(3.72	)	$	(13.52	)

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:


	December 31, 2015		December 31, 2014
Series AA preferred stock		—		7,356,331
Series X preferred stock		—		466,319
Warrants for Series AA preferred stock		—		56,408
Warrants for common stock		56,408		—
Stock options		1,631,677		911,075

Total		1,688,085		8,790,133

- 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

Fair Value of Financial Measurements (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015
	Total		Level 1		Level 2		Level 3
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	$	—


	Fair Value Measurements at December 31, 2014
	Total		Level 1		Level 2		Level 3
Liabilities
Convertible preferred stock warrant liability	$	482	$	—	$	—	$	482

Convertible notes redemption rights derivative	$	480	$	—	$	—	$	480

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

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, and the Monte Carlo simulation model used to estimate the fair value of the Series AA preferred stock warrants at December 31, 2014:


	February 17,			December 31,
	2015			2014
Volatility		60	%		65% –70	%
Expected term (years)		8.4			0.17 – 0.50
Expected dividend yield		0.0	%		0.0	%
Risk-free rate		1.7	%		0.02% –0.03	%

Schedule of Change in Company's Level 3 Liabilities

The following table reflects the change in the Company’s Level 3 liabilities for the years ended December 31, 2015 and 2014:


	Convertible preferred stock warrant liabilities			Convertible Bridge Notes redemption rights derivative			2020 Convertible Notes derivative liability
Balance at December 31, 2013	$	1,888		$	—		$	—
Issuance of 2014 Convertible Bridge Notes		—			478			—
Change in fair value		844			2			—
Warrant exercises		(2,250	)		—			—

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
	Aug. 31, 2015	Jul. 31, 2015	Feb. 28, 2015	Mar. 31, 2015	Dec. 31, 2015	Mar. 24, 2015	Feb. 23, 2015	Dec. 31, 2014	Jun. 28, 2013
Schedule Of Description Of Business [Line Items]
Net proceeds from issuance of equity	$ 73,965,000			$ 36,495,000
Net proceeds from issuance of debts				$ 18,903,000
Accumulated deficit					$ (196,023,000)			$ (128,041,000)
Aggregate cash and cash equivalents and marketable securities					$ 111,280,000
2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Convertible senior notes, interest rate, stated percentage					5.00%
Aggregate principal amount	$ 21,000,000	$ 21,000,000				$ 1,000,000	$ 20,000,000
Convertible Notes converted into shares	3,333,319	3,333,319
Additional shares of common stock	530,072	530,072
Senior Notes [Member] \| 2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Convertible senior notes, interest rate, stated percentage			5.00%
Aggregate principal amount			$ 20,000,000
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
IPO [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares			6,667,000
Initial public offering common stock, per shares			$ 6.00
IPO [Member] \| Affiliated Entity [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares			3,005,000
Over-Allotment Option [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares	810,000			299,333
Initial public offering common stock, per shares				$ 6.00
Over-Allotment Option [Member] \| Senior Notes [Member] \| 2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount				$ 1,000,000
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

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, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Mar. 24, 2015 USD ($)	Feb. 23, 2015 USD ($)
Debt Instrument [Line Items]
Interest expense			$ 1,230,000	$ 980,000
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
Charges related to 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] \| Maximum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			0
2020 Convertible Notes [Member] \| Fundamental Change [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			7.9364

Debt - Convertible Bridge Notes - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Feb. 28, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Amortization of financing costs			$ 107,000	$ 219,000
Losses on extinguishment of debt			$ (4,239,000)
2014 Convertible Bridge Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal balance		$ 2,000,000		$ 2,000,000
Debt instrument maturity date			Jun. 30, 2015
Debt instrument annual interest rate		8.00%	8.00%	8.00%
Interest accrued				$ 4,000
Value of derivative		$ 478,000		478,000
Deferred financing costs		30,000		30,000
Debt instrument, interest expense to coupon rate			$ 23,000	4,000
Amortization of financing costs			128,000	20,000
Gain in change in fair value			480,000	$ 2,000
Losses on extinguishment of debt			$ (360,000)
Debt converted into shares of common stock	337,932
Share offering price	$ 6.00
2014 Convertible Bridge Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Gross proceeds		$ 40,000,000

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, 2015 USD ($) Installment $ / shares shares	Dec. 31, 2014 USD ($)	Aug. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jan. 31, 2015 USD ($)
Debt Instrument [Line Items]
Amortized loan discounts and loan termination payment			$ 107,000	$ 219,000
Principal payments on loan			5,800,000	1,410,000
Losses on extinguishment of debt			(4,239,000)
Change in fair value of warrant liabilities			$ (267,000)	845,000
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	188,000
Warrant or right securities called by warrants, amount			$ 350,000
Warrant expiration date			The warrants were to 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.
Fair value of the warrant liability				222,000
Debt issuance costs				85,000
Amortized loan discounts and loan termination payment				517,000
Interest expense related to loan agreements			$ 115,000	956,000
Accretion of debt discounts and loan termination payment			26,000	218,000
Debt instrument, principal payments				5,800,000			$ 243,000
Principal payments on loan				$ 1,410,000
Repaying principal amount		5,347,000
Prepayment fee		160,000
Interest accrued		$ 23,000
Losses 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 Series AA Preferred Stock [Member]
Debt Instrument [Line Items]
Fair value of the warrant liability			$ 215,000
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%
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

Income Taxes - Schedule of Reconciliation Between Effective and Statutory Rates (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Computed at statutory rate	34.00%	34.00%
State income taxes	1.20%	4.93%
Expiration of capital loss carryforward	(2.13%)	(0.00%)
Expiration of state net operating loss carryforward	0.00%	(9.35%)
Tax credits	0.73%	2.43%
Other	(3.35%)	(4.28%)
Change in value of convertible notes derivatives and warrant liabilities	(21.16%)
Valuation allowance	(9.29%)	(27.73%)
Effective Income Tax Rate Reconciliation,Total	0.00%	0.00%

Equity - Additional Information (Detail)	1 Months Ended			12 Months Ended
Equity - Additional Information (Detail)	Jan. 31, 2015	Nov. 30, 2014	Jun. 30, 2010 $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) shares
Stockholders Equity [Line Items]
Common stock, shares authorized \| shares				120,000,000	43,509,727
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				26,423,394	1,020,088
Proceed from warrant exercise					$ 8,000
Redeemable convertible preferred stock					46,801,000
Proceeds from public offering				$ 38,085,000
Stock based compensation expense					7
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				$ 1,585,000
Proceed from warrant exercise					8,000
Carrying value of converted stock reclassified to additional paid-in capital					2,250,000
Redeemable convertible preferred stock					46,253,000	$ 40,685,000
Accrued but unpaid and undeclared dividends					$ 9,976,000
Preferred stock dividends quarterly rate				8.00%
Preferred stock issued , price per share \| $ / shares				$ 1.529
Preferred stock conversion price \| $ / shares				$ 1.529
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					$ 46,384,000
Preferred stock, additional paid in capital					46,309,000
Series AA Redeemable Convertible Preferred Stock [Member] \| Mandatory Convertible [Member]
Stockholders Equity [Line Items]
Automatic conversion of preferred stock to common stock, description				All outstanding shares of Series AA Convertible Preferred Stock (including all accrued or declared but unpaid dividends thereon) would automatically convert to shares of Common Stock (i) upon the vote or written consent of the holders of at least sixty six and two-thirds percent (66 and 2/3%) of the issued and outstanding Series AA Convertible Preferred Stock, or (ii) upon the closing of a firm commitment underwritten public offering of shares of Common Stock pursuant to an effective registration statement under the Securities Act of 1933, as amended, that is underwritten by an investment bank approved by the Board of Directors and by a vote or written consent of the holders of at least sixty six and two-thirds percent (66 and 2/3%) of the issued and outstanding Series AA Convertible Preferred Stock, with aggregate proceeds from such offering to the Corporation in excess of $40,000,000, before deduction of the underwriting discounts and commissions (a “Qualifying Public Offering”).
Series AA Preferred Stock [Member]
Stockholders Equity [Line Items]
Reverse stock split, description				As a result of the reverse stock splits in November 2014 and January 2015, the Series AA conversion price was adjusted to $6.204.
Special mandatory conversion description				In the event that any investor did not participate in a qualified financing by purchasing in the aggregate, in such qualified financing and within the time period specified by the Company its pro rata amount of the qualified financing (such Investor’s “Pro Rata Amount”), then the applicable portion of the shares of Series AA preferred stock held by such investor immediately prior to the initial closing of the qualified financing would automatically, and without any further action on the part of such Investor, be converted into common stock at a conversion ratio of one hundred-to-one (100:1) (such that every one hundred shares of Series AA preferred Stock are converted into one share of common stock), effective upon, subject to, and concurrently with, the consummation of the final closing
Reverse stock split, conversion price \| $ / shares				$ 6.204
Series AA Preferred Stock, Redemption Terms				Shares of Series AA preferred stock would be redeemed by the Company out of funds lawfully available there for at a price equal to the Series AA Original Issue Price per share, plus all accrued or declared but unpaid dividends thereon (the “Redemption Price”), in three annual installments commencing not more than 60 days after receipt by the Company at any time on or after the fifth anniversary of June 9, 2010, from the holders of at least sixty-six and two-thirds percent (66 and 2/3%) of the then outstanding shares of Series AA preferred stock of written notice requesting redemption of all shares of Series AA preferred stock. The date of each such installment would be referred to as a “Redemption Date.” If the Company did not have sufficient funds legally available to redeem on any Redemption Date all shares of Series AA preferred stock to be redeemed on such Redemption Date, the Company would redeem a pro rata portion of each holder’s redeemable shares of such capital stock out of funds legally available.
Series X Redeemable Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Redeemable convertible preferred stock					$ 548,000	$ 548,000
Preferred stock repurchased \| shares						558,864
Preferred stock shares vested \| shares						558,862
Stock options, terms of vesting				The modified vesting terms provide that the shares will vest upon the occurrence of a liquidation event, if such liquidation event occurs within two years of the date of the modifications. The Company retains the right to repurchase the unvested shares at the purchase price of $0.01 per share if a liquidation event does not occur within two years of the date of the modification.
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					$ 548,000
Preferred stock, additional paid in capital					$ 543,000
Series X Redeemable Convertible Preferred Stock [Member] \| IPO [Member]
Stockholders Equity [Line Items]
Stock based compensation expense				$ 950,000
Series X Redeemable Convertible Preferred Stock [Member] \| Employees And Consultants [Member]
Stockholders Equity [Line Items]
Shares sold \| shares			2,451,184	2,058,995
Share Price \| $ / shares			$ 0.001
Number of shares forfeited \| shares				392,189
Series X Preferred Stock [Member]
Stockholders Equity [Line Items]
Reverse stock split, conversion ratio				0.246305
Reverse stock split, description				As a result of the reverse stock splits in November 2014 and January 2015, the Series X conversion ratio was adjusted to approximately 1-for-4.06.
Preferred stock shares vested \| shares				558,862
Minimum [Member] \| Series AA Redeemable Convertible Preferred Stock [Member] \| Mandatory Convertible [Member]
Stockholders Equity [Line Items]
Percentage of issued and outstanding preferred stock required to vote for conversion				66.67%
Proceeds from public offering				$ 40,000,000

Stock Plans - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 28, 2014	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares , Granted		730,500
Unrecognized compensation cost related to non-vested stock options		$ 4,621
2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance		900,117
Number of Shares , Granted	840,975	730,500	900,117
Number of Shares , Exercised		(9,857)
Number of Shares Outstanding, Ending Balance		1,620,760	900,117
Weighted Average Exercise Price Per Share, Beginning Balance		$ 4.34
Number of Shares, Options Exercisable		359,610
Weighted Average Exercise Price Per Share, Granted	$ 4.342	$ 5.69	$ 4.34
Weighted-average years remaining on contractual life		9 years 18 days
Weighted Average Exercise Price Per Share, Exercised		$ 4.34
Unrecognized compensation cost related to non-vested stock options		$ 4,621
Weighted Average Exercise Price Per Share, Ending Balance		$ 4.95	$ 4.34
Weighted Average Exercise Price Per Share, Options Exercisable		$ 4.40
Aggregate Intrinsic Value, Granted		$ 0	$ 0
Aggregate Intrinsic Value, Exercised		0	0
Aggregate Intrinsic Value, Expired		0	$ 0
Aggregate Intrinsic Value, Outstanding Ending Balance		10,339
Aggregate Intrinsic Value, Options Exercisable		$ 2,492
2004 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance		10,958	11,835
Number of Shares , Expired		(41)	(877)
Number of Shares Outstanding, Ending Balance		10,917	10,958
Weighted Average Exercise Price Per Share, Beginning Balance		$ 40.58	$ 40.58
Number of Shares, Options Exercisable		10,917
Weighted-average years remaining on contractual life		2 years 6 months
Unrecognized compensation cost related to non-vested stock options		$ 0
Weighted Average Exercise Price Per Share, Expired		$ 40.58	40.58
Weighted Average Exercise Price Per Share, Ending Balance		40.58	$ 40.58
Weighted Average Exercise Price Per Share, Options Exercisable		$ 40.58
Aggregate Intrinsic Value, Granted		$ 0	$ 0
Aggregate Intrinsic Value, Exercised		0	0
Aggregate Intrinsic Value, Expired		0	$ 0
Aggregate Intrinsic Value, Outstanding Ending Balance		$ 0

Stock Plans - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended
Stock Plans - Additional Information (Detail) - USD ($)	Aug. 28, 2014	Feb. 28, 2015	Aug. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2011	Jan. 01, 2016
Stockholders Equity [Line Items]
Stock-based compensation expense					$ 7
Unrecognized compensation cost related to non-vested stock options				$ 4,621,000
Stock options granted				730,500
Expiration period of stock options				10 years
Common stock withheld pursuant to employee stock purchase plan				$ 63,000
Common shares outstanding				26,423,394	1,020,088
Restricted Stock [Member]
Stockholders Equity [Line Items]
Closing price of common stock						$ 0.0406
Stock issued during the period						24,280
Amount received from option granted				$ 1,000
Percentage of option grant for shares vested				25.00%
Shares vesting in the period				12,140
Common shares outstanding				0
Black-Scholes Stock Option Pricing Model [Member] \| Directors and Employees [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense				$ 3,209,000
Stock options, dividend yield				0.00%
Minimum [Member] \| Black-Scholes Stock Option Pricing Model [Member] \| Directors and Employees [Member]
Stockholders Equity [Line Items]
Expiration period of stock options				5 years 3 months 22 days
Stock options, expected stock price volatility				80.90%
Stock options, risk free rate				1.55%
Maximum [Member] \| Black-Scholes Stock Option Pricing Model [Member] \| Directors and Employees [Member]
Stockholders Equity [Line Items]
Expiration period of stock options				6 years 29 days
Stock options, expected stock price volatility				101.10%
Stock options, risk free rate				1.85%
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			$ 2,798,000
Unrecognized compensation cost related to non-vested stock options				4,621,000
Stock options, intrinsic value				$ 10,339,000
Number of shares available for grant				2,175,216
Number of shares reserved for future issuance				544,599
Percentage of outstanding common stock increased to shares available for grant				4.00%
Stock options granted	840,975			730,500	900,117
Expiration period of stock options	10 years
Exercise price of stock options granted	$ 4.342			$ 5.69	$ 4.34
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.
Additional stock options granted	59,142
Stock options vested	59,142
Stock options, dividend yield				0.00%
Weighted-average years remaining on non-vested compensation cost				2 years 10 months 25 days
Closing price of common stock				$ 11.33
Weighted-average fair value of stock option granted				$ 4.39	$ 3.30
2014 Stock Option and Incentive Plan [Member] \| General and Administrative Expense [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense		$ 2,798,000			$ 170,000
2014 Stock Option and Incentive Plan [Member] \| Minimum [Member]
Stockholders Equity [Line Items]
Stock options, expected term				5 years
Stock options, expected stock price volatility				83.30%
Stock options, risk free rate				1.63%
2014 Stock Option and Incentive Plan [Member] \| Maximum [Member]
Stockholders Equity [Line Items]
Stock options, expected term				6 years 3 months
Stock options, expected stock price volatility				92.50%
Stock options, risk free rate				1.84%
2014 Stock Option and Incentive Plan [Member] \| Vest on One-Year Anniversary [Member]
Stockholders Equity [Line Items]
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] \| Subsequent Event [Member]
Stockholders Equity [Line Items]
Number of shares reserved for future issuance							1,056,936
Employee Stock Purchase Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense				$ 43,000
Number of shares available for grant				160,276
Percentage of outstanding common stock increased to shares available for grant				1.00%
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				5,000
Maximum worth of stock an employee purchases				$ 25,000
Number of shares issued				13,143	0
Common stock withheld pursuant to employee stock purchase plan				$ 63,000
Employee Stock Purchase Plan [Member] \| Maximum [Member]
Stockholders Equity [Line Items]
Number of shares reserved for future issuance				600,000

Subsequent Event - Schedule of Annual Cash Commitments Pursuant to Operating Lease Amendment (Detail) - USD ($) $ in Thousands	Jul. 01, 2016	Dec. 31, 2015
Operating Leased Assets [Line Items]
2016		$ 209
2017		289
2018		298
2019		306
2020		314
Thereafter		706
Total		$ 2,122
Lease Amendment [Member] \| Subsequent Event [Member]
Operating Leased Assets [Line Items]
2016	$ 28
2017	113
2018	113
2019	115
2020	115
Thereafter	254
Total	$ 738

Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2015
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, 2015 and 2014 were $35 and $16, 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.

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Aug. 31, 2015 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Number of operating segments \| Segment	1
Realized gains or losses on short-term investment	$ 0
Unrealized losses on short-term investment	11,000
Other than temporary impairment evaluated	0
Deferred public offering costs	1,620,000	$ 1,846,000
Amortization of deferred financing costs	107,000	$ 219,000
Equity Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Deferred public offering costs	2,377,000
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

Significant Accounting Policies - Schedule of Short-term Investment (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	$ 31,249
Available-for-sale securities, Unrealized Gains	0
Available-for-sale securities, Unrealized Losses	(11)
Available-for-sale securities, Fair Value	31,238
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	16,160
Available-for-sale securities, Unrealized Gains	0
Available-for-sale securities, Fair Value	16,160
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	10,036
Available-for-sale securities, Unrealized Gains	0
Available-for-sale securities, Unrealized Losses	(5)
Available-for-sale securities, Fair Value	10,031
United States Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	5,053
Available-for-sale securities, Unrealized Gains	0
Available-for-sale securities, Unrealized Losses	(6)
Available-for-sale securities, Fair Value	$ 5,047

Significant Accounting Policies - Schedule of Estimated Useful Life of Asset Classification (Detail)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Leasehold improvements	Shorter of useful life or remaining life of lease
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Office Equipment and Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years
Minimum [Member] \| Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	3 years
Maximum [Member] \| Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated Useful Life	5 years

Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1,688,085	8,790,133
Series AA Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		7,356,331
Series X Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		466,319
Warrants Exercisable for Series AA Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		56,408
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
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1,631,677	911,075

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (67,982)	$ (9,531)
Other comprehensive loss :
Net unrealized loss on marketable securities	(11)
Total comprehensive loss	$ (67,993)	$ (9,531)

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

Organization and Operations	12 Months Ended
Organization and Operations	Dec. 31, 2015
Accounting Policies [Abstract]
Organization and Operations	1. Organization and Operations Inotek Pharmaceuticals Corporation (the “Company”) is a clinical-stage biopharmaceutical company advancing 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 February 2015, the Company completed its initial public offering (the “IPO”) of (i) 6,667,000 shares of common stock at a price of $6.00 per share and (ii) $20,000 aggregate principal amount of 5% Convertible Senior Notes due 2020 (the “2020 Convertible Notes”). Existing stockholders and their affiliated entities purchased approximately 3,005,000 shares of common stock issued in the IPO at the same terms previously described. In March 2015 the underwriters purchased 299,333 shares of common stock at $6.00 per share and $1,000 of the 2020 Convertible Notes pursuant to exercises of their overallotment options. 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 (See Note 7). 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 (as defined below) 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, 2015, the Company had an accumulated deficit of $196,023 and $111,280 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 expects operating expenses will substantially increase in the future related to additional clinical testing and to support an increased infrastructure to support expanded operations and being a public company 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, 2015	Dec. 31, 2014
Numerator:
Net loss	$ (67,982)	$ (9,531)
Accretion and dividends on convertible preferred stock	(131)	(4,265)
Net loss applicable to common stockholders	$ (68,113)	$ (13,796)
Denominator:
Weighted average common shares outstanding - basic and diluted	18,311,333	1,020,088
Net loss per share applicable to common stockholders - basic and diluted	$ (3.72)	$ (13.52)

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,074	$ 217
Less: accumulated depreciation	(262)	(217)
Property and equipment, net	812
Office Equipment and Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	334	50
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	252	$ 167
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	43
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 445

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Depreciation expense	$ 45	$ 0

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Research and development	$ 375	$ 116
Government payable	450	421
Compensation and benefits	999	293
Professional fees	347	155
Other	337	7
Total	$ 2,508	$ 992

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Valuation allowance, deferred tax asset, increase (decrease)	$ 6,313,000	$ 2,643,000
Operating loss carryforwards, federal	88,436,000
Operating loss carryforwards, state	47,369,000
Unrecognized tax benefits	333,000	284,000	$ 258,000
Federal [Member]
Income Taxes [Line Items]
Provision for income taxes	$ 0	0
Operating loss carryforwards, expiration year	2035
Tax credit carryforwards, research and development	$ 3,196,000
State [Member]
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0
Operating loss carryforwards, expiration year	2035
Tax credit carryforwards, research and development	$ 637,000

Income Taxes - Schedule of Tax Effect of Significant Temporary Differences Representing Deferred Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Components of Deferred Tax Assets and Liabilities [Abstract]
Net operating loss ("NOL") and credit carryforwards	$ 35,858	$ 30,896
Capitalized research and development costs	14,406	12,041
Capital loss carryover		1,672
Other	927	269
Valuation allowance	(51,191)	(44,878)
Deferred Tax Assets, Net	$ 0	$ 0

Income Taxes - Schedule of Change In Unrecognized Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized Tax Benefits, Beginning Balance	$ 284	$ 258
Additions for current year tax positions	49	26
Reductions for expirations of statute of limitations or settlements	0	0
Unrecognized Tax Benefits, Ending Balance	$ 333	$ 284

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) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Operating Leased Assets [Line Items]
Commencement date of lease	2015-09
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.
Lease term	90 months
Acquisition of leasehold improvements	$ 445	$ 445
Operating leases, rent expenses		143	$ 54
Leased Office Building [Member]
Operating Leased Assets [Line Items]
Operating leases, rent expenses		$ 85

Commitments and Contingencies - Schedule of Remaining Annual Cash Commitments Pursuant to Operating Lease (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2016	$ 209
2017	289
2018	298
2019	306
2020	314
Thereafter	706
Total	$ 2,122

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, 2015	Dec. 31, 2014
Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	$ 16,160
Agency Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	10,031
United States Treasury Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	5,047
Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	31,238
Convertible Preferred Stock Warrant Liability [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total liability fair value disclosure		$ 482
Convertible Notes Redemption Rights Derivative [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total liability fair value disclosure		480
Level 1 [Member] \| United States Treasury Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	5,047
Level 1 [Member] \| Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	5,047
Level 2 [Member] \| Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	16,160
Level 2 [Member] \| Agency Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	10,031
Level 2 [Member] \| Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	$ 26,191
Level 3 [Member] \| Convertible Preferred Stock Warrant Liability [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total liability fair value disclosure		482
Level 3 [Member] \| Convertible Notes Redemption Rights Derivative [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total liability fair value disclosure		$ 480

Fair Value of Financial Measurements - Schedule of Assumptions Used to Estimate Fair Value of Series AA Preferred Stock Warrants (Detail) - Convertible Preferred Stock Warrant Liability [Member]		12 Months Ended
	Feb. 17, 2015	Dec. 31, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Volatility	60.00%
Expected term (years)	8 years 4 months 24 days
Expected dividend yield	0.00%	0.00%
Risk-free rate	1.70%
Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Volatility		65.00%
Expected term (years)		2 months 1 day
Risk-free rate		0.02%
Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Volatility		70.00%
Expected term (years)		6 months
Risk-free rate		0.03%