Cara Therapeutics (CARA) 10-K 11 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Mar. 03, 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	2,015
Document Fiscal Period Focus	FY
Trading Symbol	CARA
Entity Registrant Name	Cara Therapeutics, Inc.
Entity Central Index Key	1,346,830
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	Accelerated Filer
Entity Common Stock, Shares Outstanding		27,254,863
Entity Public Float			$ 208,552,053

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 15,101	$ 52,663
Marketable securities	91,640
Income tax receivable	384	200
Interest receivable	80
Prepaid expenses	1,729	287
Total current assets	108,934	53,150
Property and equipment, net	1,263	2,084
Restricted cash	700	700
Total assets	110,897	55,934
Current liabilities:
Accounts payable and accrued expenses	5,268	1,946
Deferred Revenue		1,452
Total current liabilities	5,268	3,398
Deferred lease obligation	$ 585	$ 874
Commitments and contingencies (Note 21)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at December 31, 2015 and December 31, 2014; zero shares issued and outstanding at December 31, 2015 and December 31, 2014
Common stock; $0.001 par value; 100,000,000 shares authorized at December 31, 2015 and December 31, 2014; 27,254,863 shares and 22,802,039 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	$ 27	$ 23
Additional paid-in capital	209,943	131,840
Accumulated deficit	(104,891)	(80,201)
Accumulated other comprehensive loss	(35)	0
Total stockholders' equity	105,044	51,662
Total liabilities and stockholders' equity	$ 110,897	$ 55,934

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	27,254,863	22,802,039
Common stock, shares outstanding	27,254,863	22,802,039

Statements of Comprehensive Los

Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
License and milestone fees	$ 1,710	$ 302	$ 9,637
Collaborative revenue	2,093	2,201	2,225
Clinical compound revenue	0	674	102
Total revenue	3,803	3,177	11,964
Operating expenses:
Research and development	21,221	15,068	8,685
General and administrative	7,770	6,181	3,516
Total operating expenses	28,991	21,249	12,201
Operating loss	(25,188)	(18,072)	(237)
Other income (expense), net	101	126	(3,756)
Loss before benefit from income taxes	(25,087)	(17,946)	(3,993)
Benefit from income taxes	397	201	30
Net loss	(24,690)	(17,745)	(3,963)
Net loss available to common stockholders:
Basic and Diluted	$ (24,690)	$ (17,745)	$ (3,072)
Loss per share available to common stockholders:
Basic and Diluted	$ (1)	$ (0.85)	$ (0.74)
Weighted average shares:
Basic and Diluted	24,620,372	20,965,935	4,133,138
Other comprehensive loss, net of tax of $0:
Unrealized gains (losses) on available for sale marketable securities	$ (35)
Total comprehensive loss	$ (24,725)	$ (17,745)	$ (3,072)

Statements of Comprehensive Lo5

Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Other comprehensive loss, tax	$ 0	$ 0	$ 0

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Junior A Convertible Preferred Stock [Member]	Initial Public Offering [Member]	Private Placement [Member]	Follow On Public Offering [Member]	Common Stock [Member]	Common Stock [Member]Initial Public Offering [Member]	Common Stock [Member]Private Placement [Member]	Common Stock [Member]Follow On Public Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Initial Public Offering [Member]	Additional Paid-in Capital [Member]Private Placement [Member]	Additional Paid-in Capital [Member]Follow On Public Offering [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive (Loss) [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]Junior A Convertible Preferred Stock [Member]	Beneficial Conversion Feature on Convertible Promissory Notes [Member]
Balance, Value at Dec. 31, 2012	$ 58,522															$ 58,522		$ 2,050
Balance, Value at Dec. 31, 2012	$ (58,133)					$ 3				$ 1,248				$ (59,384)
Issuance of stock, Value																	$ 7,642
Balance, Shares at Dec. 31, 2012	26,636,118															26,636,118
Balance, Shares at Dec. 31, 2012						3,328,698
Issuance of stock, Shares																	2,105,263
Preferred stock converted to common shares, Value	$ 4,466					$ 1				3,574				891		$ (4,466)
Preferred stock converted to common shares, Shares						959,545										(2,246,743)
Convertible promissory notes converted to Series D preferred stock, Value																$ 3,888
Convertible promissory notes converted to Series D preferred stock, Shares																2,692,291
Beneficial conversion feature on convertible promissory notes																		1,382
Reclassification of beneficial conversion feature	3,432									3,432								(3,432)
Stock-based compensation expense	123									123
Net loss	(3,963)													(3,963)
Balance, Value at Dec. 31, 2013	65,586	$ 7,642														$ 65,586
Balance, Value at Dec. 31, 2013	$ (54,075)					$ 4				8,377				(62,456)
Balance, Shares at Dec. 31, 2013	29,186,929	2,105,263														29,186,929
Balance, Shares at Dec. 31, 2013						4,288,243
Issuance of stock, Value			$ 56,297	$ 100			$ 6				$ 56,291	$ 100
Issuance of stock, Shares							5,750,000	11,442
Preferred stock converted to common shares, Value	$ 65,586					$ 13				65,573						$ (65,586)
Preferred stock converted to common shares, Shares						12,554,171										(29,186,929)
Stock-based compensation expense	1,371									1,371
Shares issued upon exercise of stock options, Value	128									128
Shares issued upon exercise of stock options, Shares						191,800
Shares issued upon cashless exercise of warrants, Value	0					$ 0				0				0	$ 0	$ 0		$ 0
Shares issued upon cashless exercise of warrants, Shares						6,383
Net loss	(17,745)													(17,745)
Balance, Value at Dec. 31, 2014	$ 51,662					$ 23				131,840				(80,201)
Balance, Shares at Dec. 31, 2014	0
Balance, Shares at Dec. 31, 2014						22,802,039
Issuance of stock, Value					$ 75,231				$ 4				$ 75,227
Issuance of stock, Shares									4,327,956
Stock-based compensation expense	$ 2,514									2,514
Shares issued upon exercise of stock options, Value	362									362
Shares issued upon exercise of stock options, Shares						124,868
Net loss	(24,690)													(24,690)
Other comprehensive income (loss)	(35)														(35)
Balance, Value at Dec. 31, 2015	$ 105,044					$ 27				$ 209,943				$ (104,891)	$ (35)
Balance, Shares at Dec. 31, 2015	0
Balance, Shares at Dec. 31, 2015						27,254,863

Statements of Convertible Pref7

Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Initial Public Offering [Member]
Sale of common stock, per share		$ 11
Underwriting discounts and commissions and offering expenses		$ 6,953
Private Placement [Member]
Sale of common stock, per share		$ 8.74
Follow On Public Offering [Member]
Sale of common stock, per share	$ 18.60
Underwriting discounts and commissions and offering expenses	$ 5,269

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (24,690)	$ (17,745)	$ (3,963)
Adjustments to reconcile net loss to net cash (used in) provided by operations:
Stock-based compensation expense	2,514	1,371	123
Change in fair value of liability under license agreement			(35)
Accrued interest and amortization of beneficial conversion feature on promissory notes			3,605
Loss on write-off of fixed assets	2
Depreciation & amortization	839	783	789
Amortization/accretion of available-for-sale securities	(18)
Deferred rent costs	(289)	(265)	(238)
Amortization of financing costs			117
Changes in operating assets and liabilities:
Income tax receivable	(184)	(139)	(30)
Interest receivable	(80)
Prepaid expenses	(1,442)	388	(1,736)
Accounts payable and accrued expenses	3,322	(12)	722
Deferred revenue	(1,452)	(2,023)	3,475
Net cash (used in) provided by operating activities	(21,478)	(17,642)	2,829
Investing activities
Purchase of available-for-sale marketable securities	(91,657)
Purchases of property and equipment	(20)	(42)	(5)
Net cash used in investing activities	(91,677)	(42)	(5)
Financing activities
Proceeds from convertible promissory notes			1,462
Financing costs on convertible promissory notes			(70)
Repayment of convertible promissory notes			(311)
Repayment of long-term debt			(307)
Proceeds from sale of common stock		100
Proceeds from the exercise of stock options	362	128
Proceeds from initial public offering, net of issuance costs		57,762
Net cash provided by financing activities	75,593	57,990	8,416
Net cash increase (decrease) for the period	(37,562)	40,306	11,240
Cash and cash equivalents at beginning of period	52,663	12,357	1,117
Cash and cash equivalents at end of period	15,101	52,663	12,357
Supplemental disclosure of cash flow information
Cash paid for interest			37
Noncash financing activities
Conversion of convertible preferred stock to common stock		65,586
Reclassification of prepaid IPO costs paid in 2013		$ 1,465
Conversion of convertible promissory notes to Series D convertible preferred stock			3,888
Junior A Convertible Preferred Stock [Member]
Financing activities
Proceeds from sale of convertible preferred stock			$ 7,642
Follow-on Offering [Member]
Financing activities
Proceeds from follow-on offering, net of issuance costs	$ 75,231

Business

Business	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	1. Business Cara Therapeutics, Inc. (the “Company”) is a clinical-stage biopharmaceutical corporation formed on July 2, 2004. The Company is focused on developing and commercializing new chemical entities designed to alleviate pain and pruritus by selectively targeting kappa opioid receptors. The Company’s primary activities to date have been organizing and staffing the Company, developing its product candidates, including conducting preclinical studies and clinical trials of CR845-based product candidates and raising capital. As of December 31, 2015, the Company has raised aggregate net proceeds of approximately $204,800 from several rounds of equity financing, including its initial public offering, or IPO, which closed in February 2014 and its follow-on offering, which closed in August 2015 (see Note 12, Stockholders’ Equity In connection with the license of rights to CR845 in Japan to Maruishi and as part of the earnings described above, in April 2013, the Company received an upfront payment of $15,000, and in August 2014 and September 2015, the Company received an additional $480 and $1,725 (net of contractual foreign currency exchange adjustments), respectively, in milestone payments. In connection with the license of rights to CR845 in South Korea to CKD and as part of the earnings described above, in 2012, the Company received aggregate upfront and milestone payments of $1,190, and in August 2015 and October 2015, the Company received an additional $209 and $417 (net of South Korean withholding taxes), respectively, in milestone payments. As of December 31, 2015, the Company had unrestricted cash and cash equivalents and marketable securities of $106,740 and an accumulated deficit of $104,891. The Company has incurred substantial net losses and negative cash flows from operating activities in nearly every fiscal period since inception and expects this trend to continue for the foreseeable future. The Company recognized a net loss of $24,690 and had net cash used in operating activities of $21,478 for the year ended December 31, 2015. The Company expects that cash and cash equivalents and marketable securities at December 31, 2015 will be sufficient to fund its operations beyond one year. The Company is subject to risks common to other life science companies including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing, and compliance with Food and Drug Administration (“FDA”) and other government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with generally-accepted accounting principles in the United States (“GAAP”) requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, as of the date of the financial statements as well as the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from the Company’s estimates and assumptions. Significant estimates include the fair value of marketable securities that are classified as level 2 of the fair value hierarchy, useful lives of fixed assets, the periods over which certain revenues will be recognized, including licensing and collaborative revenue recognized from non-refundable up-front and milestone payments, the determination of prepaid research and development clinical costs and accrued research projects, the amount of non-cash compensation costs related to share-based payments to employees and non-employees and the periods over which those costs are expensed and the likelihood of realization of deferred tax assets. Concentrations of Credit Risk Financial instruments, which potentially subject the Company to significant concentrations of credit risk consist primarily of cash equivalents and marketable securities. The Company invests its cash reserves in money market funds or high-quality marketable securities in accordance with its investment policy. The stated objectives of its investment policy is to preserve capital, provide liquidity consistent with forecasted cash flow requirements, maintain appropriate diversification and generate returns relative to these investment objectives and prevailing market conditions. The Company’s investment policy includes guidelines on acceptable investment securities, limits interest-bearing security investments to certain types of debt and money market instruments issued by the U.S. government and institutions with investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer. The Company’s cash, cash equivalents and marketable securities are held by a few major financial institutions. In accordance with the Company’s policies, the Company monitors exposure with its counterparties. The Company also maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Cash and Cash Equivalents Cash and cash equivalents include cash on hand, demand deposits, deposits with banks and highly liquid money market funds with holdings of cash. Marketable Securities The Company deems certain of its investments to be marketable securities if the investment, or in the case of money market funds, the securities underlying the money market fund, meet the definition of a debt security in Accounting Standards Codification section 320-10-20. The Company considers its marketable securities to be available-for-sale and, accordingly, these investments are recorded at fair value with unrealized gains and losses generally recorded in accumulated other comprehensive income (loss) (“AOCI”) as a separate component of stockholders’ equity. Marketable securities are reported in Marketable Securities in the Balance Sheets. Other income (expense), net, includes interest, realized gains and losses on sales of securities and other-than-temporary impairment (“OTTI”) declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company reviews its available-for-sale marketable securities for OTTI declines in fair value below its cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below its cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell, the security before recovery of its amortized cost basis. The Company’s assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. If a decline in the fair value of an available-for-sale marketable debt security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value. If the Company intends to sell the security or it is more likely than not that the Company will be forced to sell the security before recovery of the amortized cost of the security, the loss is recognized in net income. Otherwise, the loss is separated into a portion representing a credit loss, which is recorded in net income, and the remainder is recorded in Other Comprehensive Income (“OCI”), net of taxes. See Note 3, M arketable Securities Fair Value Measurement Fair Value of Financial Instruments The Company applies fair value accounting for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions and credit risks. The Company’s financial instruments consist of cash, cash equivalents, available-for-sale marketable securities, restricted cash, accounts payable and accrued liabilities. The fair values of cash and cash equivalents, restricted cash, accounts payable and accrued liabilities approximate their carrying values due to the short-term nature of these financial instruments. Marketable securities are reported on the Company’s Balance Sheets at their fair values, based upon pricing of securities with the same or similar investment characteristics as provided by pricing services, as described below. Current accounting guidance defines fair value, establishes a framework for measuring fair value in accordance with Accounting Standards Codification (“ASC”) section 820, and requires certain disclosures about fair value measurements. The valuation techniques included in the guidance are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs 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 Company classifies its investments in a fair value hierarchy that is intended to increase consistency and comparability in fair value measurements and related disclosures. The fair value hierarchy is divided into three levels based on the source of inputs as follows: • Level 1 – Observable inputs – quoted prices in active markets for identical assets and liabilities. • Level 2 – Observable inputs other than the quoted prices in active markets for identical assets and liabilities – such as quoted prices for similar instruments, quoted prices for identical or similar instruments in inactive markets, or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Unobservable inputs – includes amounts derived from valuation models where one or more significant inputs are unobservable and require the company to develop relevant assumptions. The Company records transfers between levels in the hierarchy by assuming that the transfer occurred at the end of the quarter or year-to-date period. Valuation Techniques - Level 2 Inputs The Company estimates the fair values of its financial instruments categorized as level 2 in the fair value hierarchy, including U.S. Treasury securities, other U.S. government agency obligations, corporate bonds and commercial paper by taking into consideration valuations obtained from third-party pricing services. The pricing services use industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, benchmark yields, issuer credit spreads, benchmark securities, and other observable inputs. The Company obtains a single price for each financial instrument and does not adjust the prices obtained from the pricing service. The Company validates the prices provided by its third party pricing services by reviewing their pricing methods, obtaining market values from other pricing sources and comparing them to the share prices presented by the pricing service. After completing its validation procedures, the Company did not adjust or override any fair value measurements provided by its pricing services as of December 31, 2015. The Company did not have any financial instruments categorized as level 2 as of December 31, 2014. Property and Equipment Property and equipment (consisting of computer, office and laboratory equipment, furniture and fixtures, software and leasehold improvements) are stated at cost, net of accumulated depreciation and amortization of leasehold improvements. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized over the lesser of their useful lives or the life of the lease. Asset Category Useful Lives Computer and office equipment 5 years Laboratory equipment 8 years Furniture and fixtures 7 years Software 3 years Leasehold improvements Lesser of 10 years Long-Lived Assets ASC 360, Property, Plant and Equipment Common Stock and Convertible Preferred Stock Valuation Due to the absence of an active market for the Company’s common stock and convertible preferred stock prior to its IPO, the Company utilized methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation Revenue Recognition In general, the Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; the Company’s price to the customer is fixed or determinable; collectability is reasonably assured and delivery has occurred or services have been rendered. The Company has entered into license agreements to develop, manufacture and commercialize drug products. The terms of these agreements typically contain multiple elements, including licenses and research and development services. Payments to the Company under these agreements may include nonrefundable license fees, payments for research activities, payments based upon the achievement of certain milestones and royalties on any resulting net product sales. There are no performance, cancellation, termination or refund provisions in any of the arrangements that contain material financial consequences to the Company. The Company records revenue related to these agreements in accordance with ASC 605-25, Revenue Recognition Multiple-Element Arrangements The Company determines the estimated selling price for deliverables within each agreement using vendor specific objective evidence (“VSOE”) of selling price, if available, or third party evidence (“TPE”) of selling price if VSOE is not available, or the Company’s best estimate of selling price, if neither VSOE nor TPE is available. Determining the best estimate of selling price for a deliverable requires significant judgment. Because the Company does not have VSOE or third party evidence of selling price to determine the estimated selling price of a license to its proprietary technology, it typically uses its best estimate of a selling price to estimate the selling prices for licenses to its proprietary technology. In making these estimates, the Company considers market conditions and entity-specific factors, including those contemplated in negotiating the agreements, as well as internally developed estimates that include assumptions related to the market opportunity, estimated development costs, probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating its best estimate of selling price, the Company evaluates whether changes in the key assumptions used to determine its best estimate of selling price will have a significant effect on the allocation of arrangement consideration between deliverables. The Company recognizes consideration allocated to an individual element when all other revenue recognition criteria are met for that element. Arrangement consideration allocated to license deliverables that represent separate units of accounting is recognized as revenue at the outset of the agreement assuming the general criteria for revenue recognition noted above have been met. Arrangement consideration allocated to license deliverables which do not represent separate units of accounting is deferred. The Company has determined that its license deliverables represent separate units of accounting because the counterparty has the right to sublicense and manufacture in its territory, as defined. Arrangement consideration allocated to research and development services which represent separate units of accounting is recognized as the services are performed, assuming the general criteria for revenue recognition noted above have been met. The Company has determined that its research and developments services deliverables, as applicable, represent separate units of accounting because similar services are sold separately by other vendors. The Company’s license agreements include contingent milestone payments related to specified clinical development milestones and regulatory milestones. Development milestones are payable when a product candidate initiates or advances into different clinical trial phases. Regulatory milestones are payable upon submission for marketing approval with the FDA or other countries’ regulatory authorities or on receipt of actual marketing approvals for the compound or for additional indications. At the inception of each agreement that includes milestone payments, the Company evaluates whether each such payment is a milestone payment as defined by ASC 605-28, Revenue Recognition – Milestone Method If the payment meets the criteria of a milestone payment, the Company evaluates whether such milestone is considered to be substantive. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (1) the entity’s performance to achieve the milestone, or (2) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone, (b) the consideration relates solely to past performance and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone and the level of effort and investment required to achieve the respective milestone in making this assessment. The Company recognizes substantive milestone payments as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria are met. If any milestone payment is considered not to be a substantive milestone or is considered to be a contingent payment, the Company initially defers the milestone payment, allocates it to the deliverables based on relative selling price in the same proportion as at inception of the agreement, immediately recognizes revenue to the extent of any delivered elements and recognizes the portion attributable to any undelivered elements over the remaining term of its performance obligations. If no such performance obligations exist, milestones that are considered not to be substantive or are considered to be contingent payments are generally recognized as revenue upon achievement, assuming all other revenue recognition criteria are met. Royalty revenue is recognized when earned. To date, no royalties have been earned or were otherwise due to the Company. Research and Development Expenses Research and development (“R&D”) costs are charged to expense as incurred. Costs incurred under agreements with third parties are charged to expense as incurred in accordance with the specific contractual performance terms of such agreements. Research and development expenses include, among other costs, salaries and other personnel-related costs, costs to conduct clinical trials, costs to manufacture product candidates and clinical supplies, laboratory supplies costs and facility-related costs. Non-refundable research and development advance payments are deferred and capitalized as prepaid R&D expense. The capitalized amounts are expensed as the related goods are delivered or services are performed. As of December 31, 2015 and 2014, the Company recorded $1,500 and $177 as prepaid R&D expense, respectively. Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized. The Company applies the provisions of ASC 740, Income Taxes Stock-Based Compensation The Company grants stock options to employees, non-employee members of the Company’s Board of Directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the Board of Directors’ awards of stock-based compensation are accounted for in accordance with ASC 718, Compensation Stock Compensation . Using this model, fair value is calculated based on assumptions with respect to (i) the fair value or market price of the Company’s common stock on the grant date; (ii) expected volatility of the Company’s common stock price, (iii) the periods of time over which employees and members of the Company’s Board of Directors are expected to hold their options prior to exercise (expected lives), (iv) expected dividend yield on the Company’s common stock, and (v) risk-free interest rates. Prior to the effective date of the registration statement related to the Company’s IPO in January 2014, the Company utilized methodologies in accordance with the Practice Aid to determine the fair value of the Company’s common stock on any given date. Subsequently, the stock price input to the Black-Scholes model for each stock option granted is the closing price of the Company’s common stock as quoted on The NASDAQ Global Market on the grant date. Expected volatility is based on an analysis of guideline companies in accordance with ASC 718. The expected life of stock options granted to employees and members of the Company’s Board of Directors is determined using the average of the vesting period and term, an accepted method for the Company’s option grants under the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment. The Company applies a forfeiture rate to the number of unvested awards in each reporting period in order to accrue share-based compensation expense based on an estimate of the number of awards that are expected to vest. Estimated forfeiture rates are based upon historical data of awards that were cancelled prior to vesting. The Company adjusts the total amount of compensation cost recognized for each award, in the period in which each award vests, to reflect the actual forfeitures related to that award. To the extent that the actual forfeiture rate for an award is lower than the estimated forfeiture rate, additional compensation expense is recorded in the period that the award vests. Changes in the Company’s estimated forfeiture rate will result in changes in the rate at which compensation cost for an award is recognized over its vesting period. The Company accounts for options granted to non-employee consultants under ASC 505-50, Equity-Based Payments to Non-Employees. Income (Loss) Per Share The Company computes basic net income (loss) per share by dividing net income (loss) by the weighted average number of shares of common stock outstanding. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were converted or exercised during the period, when the effect is dilutive. Common stock equivalents may include convertible preferred stock, convertible promissory notes and outstanding stock options and stock warrants, which are included under the treasury stock method when dilutive. The computation of diluted net loss per share for each of the years ended December 31, 2015, 2014 and 2013 does not include common stock equivalents since such inclusion would be antidilutive. During the year ended December 31, 2013, the Company computed basic net income (loss) per share available to common stockholders using the “two-class” method, which includes the weighted average number of shares of common stock outstanding during the period and other securities that participate in dividends (a participating security). Prior to its IPO, the Company’s shares of convertible preferred stock were participating securities as defined by ASC 260-10, Earnings Per Share Convertible Preferred Stock Under the two-class method, basic net income (loss) per share available to common stockholders is computed by dividing the net income (loss) available to common stockholders by the weighted average number of common shares outstanding for the period. The Company allocates net income on a pari passu (equal) basis to both common and preferred stockholders. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. Diluted net income (loss) per share is computed using the more dilutive of (1) the two-class method, or (2) the “if-converted” method. Refer to Note 18, Net Loss per Share Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one operating segment, which includes all activities related to the discovery and development of novel therapeutics to treat serious medical conditions, including pain and pruritus. Leases The Company recognizes rent expense for operating leases on a straight-line basis over the term of the lease, beginning on the date the Company takes possession of the property. Rent expense includes the base amounts stated in the lease agreement as well as the effect of reduced or free rent and rent escalations. At lease inception, the Company determines the lease term by assuming the exercise of those renewal options that are reasonably assured because of the significant economic penalty that exists for not exercising those options. The exercise of renewal options is at the Company’s sole discretion. The expected lease term is one of the factors used to determine whether a lease is classified operating or capital and is used to calculate the straight-line rent expense. The difference between the cash paid to the landlord and the amount recognized as rent expense on a straight-line basis is included in deferred rent and classified within long-term liabilities. Cash reimbursements received from landlords for leasehold improvements and other cash payments received from landlords as lease incentives are recorded as deferred rent and classified as long-term liabilities. Deferred rent related to landlord incentives is amortized using the straight-line method over the lease term as an offset to rent expense. Penalties paid to landlords to terminate a lease before the contractual end date of the lease are recognized on an undiscounted basis in the Statements of Comprehensive Loss. Litigation Reserves The Company may become involved in the future in various lawsuits, claims, investigations and proceedings that arise in the ordinary course of business. Accruals are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. The Company reviews these reserves at least quarterly and adjusts these reserves to reflect current law, progress of each case, opinions and views of legal counsel and other advisers, the Company’s experience in similar matters and intended response to the litigation. The Company expenses amounts for administering or litigating claims as incurred. Accruals for legal proceedings, if any, are included in Accounts payable and accrued expenses in the Balance Sheets. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update 2016-02, Leases In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740) Balance Sheet Classification of Deferred Taxes During April 2015, the FASB issued Accounting Standards Update 2015-03 (“ASU 2015-03”) Interest—Imputation of Interest (Subtopic 835-30) Simplifying the Presentation of Debt Issuance Costs Interest—Imputation of Interest (Subtopic 835-30) Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements In August 2014, the FASB issued Accounting Standards Update 2014-15 Presentation of Financial Statements – Going Concern (Subtopic 205-40), Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In May 2014, the FASB issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606)

Available-for-Sale Marketable S

Available-for-Sale Marketable Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Marketable Securities	3. Available-for-Sale Marketable Securities As of December 31, 2015, the Company’s available-for-sale marketable securities consisted of money market mutual funds and debt securities issued by the U.S. government and government-sponsored entities and by investment grade institutions. As of December 31, 2014 and for the years ended December 31, 2014 and 2013, all of the Company’s funds were held in money market savings and checking accounts that were classified as cash equivalents and not as available-for-sale marketable securities. The following table summarizes the Company’s available-for-sale marketable securities by major type of security as of December 31, 2015: Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Money market mutual funds $ 42,017 $ — $ (31 ) $ 41,986 U.S. Treasury securities 2,528 — — 2,528 Other U.S. government agency obligations 13,492 4 — 13,496 Corporate bonds 14,194 — (6 ) 14,188 Commercial paper 19,444 1 (3 ) 19,442 Total available-for-sale marketable securities $ 91,675 $ 5 $ (40 ) $ 91,640 All available-for-sale marketable securities are classified in the Balance Sheets as Marketable Securities. The Company classifies its marketable debt securities based on their contractual maturity dates. The marketable debt securities as of December 31, 2015 mature at various dates through September 2016. The fair values and amortized cost of marketable debt securities by contractual maturity were as follows. The table does not include money market funds that are classified as available-for-sale marketable securities. As of December 31, 2015 2014 Contractual maturity Fair Value Amortized Cost Fair Value Amortized Cost Less than one year $ 49,653 $ 49,657 $ — $ — For the year ended December 31, 2015, there were no sales of available-for-sale marketable securities. The following table shows the fair value of the Company’s available-for-sale marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual investments have been in a continuous unrealized loss position. Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Gross Fair Gross Fair Gross Money market mutual funds $ 30,985 $ (31 ) $ — $ — $ 30,985 $ (31 ) Corporate bonds 14,187 (6 ) — — 14,187 (6 ) Commercial paper 11,960 (3 ) — — 11,960 (3 ) Total $ 57,132 $ (40 ) $ — $ — $ 57,132 $ (40 ) As of December 31, 2015, the Company held a total of 15 positions that were in an unrealized loss position, none of which had been in an unrealized loss position for 12 months or greater. Based on the Company’s review of these securities, the Company believes that the cost basis of its available-for-sale marketable securities is recoverable and that, therefore, it had no other-than-temporary impairments on these securities as of December 31, 2015. The Company does not intend to sell these debt securities and the Company believes it is not more likely than not that it will be required to sell these securities before the recovery of their amortized cost basis, which may be maturity.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	4. Accumulated Other Comprehensive Income (Loss) The following table summarizes the changes in AOCI, net of tax, from unrealized gains (losses) on available-for-sale marketable securities, the Company’s only component of AOCI, for the year ended December 31, 2015. As of December 31, 2014 and for the years ended December 31, 2014 and 2013, all of the Company’s funds were held in money market savings and checking accounts that were classified as cash equivalents and not as available-for-sale marketable securities. For the year ended December 31, 2015, there were no reclassifications from AOCI since there were no sales of available-for-sale marketable securities. Total Accumulated Balance, December 31, 2014 $ — Other comprehensive loss before reclassifications (35 ) Amount reclassified from accumulated other comprehensive income — Net current period other comprehensive loss (35 ) Balance, December 31, 2015 $ (35 )

Prepaid Expenses

Prepaid Expenses	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Prepaid Expenses	5. Prepaid Expenses As of December 31, 2015, prepaid expenses was $1,729, consisting of $1,500 of prepaid R&D clinical costs, $98 of prepaid insurance, $96 of prepaid rent and $35 of other costs. As of December 31, 2014, prepaid expenses was $287, consisting of $92 of prepaid insurance, $177 of prepaid R&D clinical costs and $18 of other costs.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net Property and equipment, net consists of the following: December 31, 2015 2014 Computer and office equipment $ 314 $ 309 Laboratory equipment 232 233 Furniture and fixtures 155 156 Software 126 126 Leasehold improvements 7,453 7,453 $ 8,280 $ 8,276 Less accumulated depreciation and amortization 7,017 6,192 Property and equipment, net $ 1,263 $ 2,084 Depreciation and amortization expense included in research and development expense and general and administrative expense was $839, $783 and $789 for the years ended December 31, 2015, 2014 and 2013, respectively. In connection with the Company’s relocation of its operating facility from Shelton, Connecticut to Stamford, Connecticut, the Company began accelerating the amortization of the Shelton leasehold improvements from December 2015 (see Note 21, Commitments and Contingencies

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2015
Receivables [Abstract]
Restricted Cash	7. Restricted Cash The Company is required to maintain stand-by letters of credit as a security deposit under each of the Shelton Lease and the Stamford Lease (refer to Note 21, Commitments and Contingencies For the Stamford Lease, the letter of credit balance remains at $769 for the first three years following commencement of the Stamford Lease and may, upon request from the Company, thereafter be reduced to $408 through the end of the lease term in 2023. The reduction in the balance of the Letter of Credit for the Stamford Lease is contingent upon the Company not being in default of any provisions of that lease prior to request for the reduction. As of December 31, 2015, the money market account into which the Company will deposit the cash collateral for the letter of credit for the Stamford Lease had not been established and none of that cash was restricted. The restricted money market account was funded in January 2016. As of both December 31, 2015 and 2014, the Company had $700 of restricted cash in long-term assets.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	8. Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following: December 31, 2015 2014 Accounts payable $ 1,965 $ 515 Accrued research projects 1,542 549 Accrued professional fees 371 266 Accrued compensation and benefits 1,204 504 Accrued other 186 112 $ 5,268 $ 1,946

Convertible Promissory Notes

Convertible Promissory Notes	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Convertible Promissory Notes	9. Convertible Promissory Notes In December 2012 and February 2013, the Company issued an aggregate of $4,000 principal amount of Convertible Promissory Notes (“Notes”) due August 28, 2013 (“Maturity Date”). The sale was consummated through two closings. The initial closing was on December 28, 2012 for $2,538 principal amount. The final closing was on February 28, 2013 for $1,462 principal amount. All of the Notes were purchased by current stockholders, all of whom were given the opportunity to buy their pro rata share of the Notes. The holders of preferred stock who did not participate in the Note financing had their shares of preferred stock converted into common stock at their respective then applicable conversion rates. As a result, as of February 2013, 2,246,743 shares of preferred stock were converted into 959,545 shares of common stock. Because the original terms of the preferred stock were modified to reflect this mandatory conversion, the Company determined that the preferred stock had been extinguished. Accordingly, the conversion date difference between the carrying value of the preferred stock converted ($4,466) and the fair value of the common stock issued ($3,575) has been recorded as a gain ($891) within accumulated deficit. The Notes bore interest at 8% per annum and had a Maturity Date of August 28, 2013. The Notes were not eligible to be repaid prior to the maturity date without the consent of the holders of a majority in interest of the outstanding aggregate principal amount of the Notes. The Notes included an optional conversion feature and a mandatory conversion feature. The optional conversion feature allowed the Note holder, any time prior to the Maturity Date, to elect to convert the balance of the note plus accrued interest into Series D convertible preferred stock at a conversion price of $1.444244 per share. In accordance with ASC 470-20, Debt with Conversion and Other Options The mandatory conversion of the Notes would have occurred in the event the Company issued or sold equity securities on or before August 28, 2013 of not less than $10,000. In this event, the Notes plus all accrued interest would have automatically converted into the issued class of equity securities at a price per share equal to 90% of the cash price paid by the investors in the new equity securities. In accordance with ASC 815-15, Derivatives and Hedging The Company estimated the fair value of the contingent call option by estimating the accreted value of the Notes upon conversion, with consideration provided for the 10% price discount and the probability of the Company closing an equity offering in excess of $10,000 before August 28, 2013. The Company classified the liability within Level 3 of the fair value hierarchy as the probability factor is an unobservable input and significant to the valuation model. Increases in the probability of an equity offering closing before August 28, 2013 in excess of $10,000 would increase the fair value of the liability. In April 2013, the estimated fair value of the contingent call option of $41 was reduced to zero with an equal reduction in interest expense, since the Company estimated the probability of closing a $10,000 equity offering before August 28, 2013 as zero, following the receipt of $23,000 in connection with the Maruishi transaction in April 2013, which removed the need for a $10,000 financing prior to August 28, 2013. Prior to the Maturity Date, the Company received notice from Note holders to convert Notes in the aggregate amount of $3,888 in principal plus accrued interest, into 2,692,291 shares of Series D convertible preferred stock, and the remaining Notes, in the aggregate amount of $311 in principal and accrued interest, were repaid during October 2013. Deferred financing costs related to the convertible promissory notes were amortized over the life of the related debt using the effective interest method. For the year ended December 31, 2013, deferred financing cost of $117 was amortized and included in interest expense, within other income (expense), net.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Long-Term Debt	10. Long-Term Debt In September 2007, the Company entered into a $4,000 term loan (“Loan”) with Connecticut Innovations Inc. (“CII”). The Loan carried a 7% interest rate and was payable in monthly installments over five years. The Loan was collateralized by property and equipment which was owned by the Company that was located in Shelton, Connecticut. The CII Loan contained certain non-financial covenants, including the requirement that the Company maintain its principal place of business and conduct the majority of its operations in Connecticut. If the Company failed to maintain its Connecticut presence, all amounts due under the Loan would be immediately due and payable with the cumulative interest rate increasing to 25%. On September 4, 2012, the Company and CII amended the Loan to defer all payments due between July 1, 2012 and December 31, 2012 until January 2, 2013 and to increase the interest rate to 8.5%. The Company repaid the remaining principal balance of $307 plus accrued interest outstanding under the Loan in April 2013. In connection with the Loan, the Company issued to CII a warrant to purchase 19,851 shares of common stock at an exercise price of $10.08. The fair value of such warrant at the date of issuance was determined not to be material. The warrant also incorporated the non-financial covenants of the Loan described above. If the Company failed to maintain its Connecticut presence, it would be required to pay CII the excess of the market price of the common stock over the warrant exercise price for all unexercised shares represented by the warrant and/or the exercise price paid plus the market price on any shares acquired through a previous exercise of the warrants. On July 31, 2014, CII exercised its outstanding warrant in a cashless exercise, resulting in the issuance of 6,383 shares of the Company’s common stock.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Convertible Preferred Stock	11. Convertible Preferred Stock In connection with the Notes (refer to Note 9, Convertible Promissory Notes In April 2013, the Company issued to Maruishi (refer to Note, 14, Collaborations In September 2013, the Company issued an aggregate of 2,692,291 shares of Series D convertible preferred stock upon the conversion of the Notes (refer to Note 9, Convertible Promissory Notes The following tables summarize the outstanding Preferred Stock as of December 31, 2013 and December 31, 2012: As of December 31, 2013 Preferred Preferred Liquidation Carrying Common Stock Junior 173,611 173,611 $ 500 $ 354 69,444 Junior A 2,105,263 2,105,263 8,000 7,642 842,105 Series A 1,677,118 1,677,118 1,677 1,677 670,830 Series B 2,254,417 2,254,417 4,509 4,509 980,163 Series C 10,930,946 10,930,946 33,886 33,886 5,173,413 Series D 12,260,845 12,045,574 17,397 17,518 4,818,216 29,402,200 29,186,929 $ 65,969 $ 65,586 12,554,171 As of December 31, 2012 Preferred Preferred Liquidation Carrying Common Stock Junior 173,611 173,611 $ 500 $ 354 69,444 Junior A — — — — — Series A 2,000,000 2,000,000 2,000 2,000 800,000 Series B 2,370,000 2,370,000 4,740 4,740 1,030,434 Series C 11,706,450 11,706,450 36,290 36,290 5,540,457 Series D 10,386,057 10,386,057 15,000 15,138 4,154,422 26,636,118 26,636,118 $ 58,530 $ 58,522 11,594,757 Upon the closing of the Company’s IPO on February 5, 2014, all 29,186,929 shares of the Company’s Preferred Stock that were issued and outstanding on that date were automatically converted into an aggregate of 12,554,171 shares of its common stock. As of December 31, 2015 and 2014, there were no shares of Preferred Stock issued or outstanding. Prior to automatic conversion of the Preferred Stock to common stock upon the closing of the Company’s IPO, the following terms and conditions applied to the Preferred Stock: Liquidation Preferences In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the Company, including a deemed liquidation event, as defined in the Company’s amended and restated certificate of incorporation, the following liquidation preferences as of December 31, 2013 were payable to the holders of Preferred Stock: Series D Preferred Stock, aggregate liquidation preference of $17,397, plus declared, but unpaid dividends; Series C Preferred Stock, aggregate liquidation preference of $33,886, plus declared, but unpaid dividends; Series B Preferred Stock, aggregate liquidation preference of $4,509, plus declared, but unpaid dividends; Series A Preferred Stock, aggregate liquidation preference of $1,677 plus declared, but unpaid dividends; Junior A Preferred Stock, aggregate liquidation preference of $8,000 plus declared, but unpaid dividends; and Junior Preferred Stock, aggregate liquidation preference of $500 plus declared, but unpaid dividends. The Series D Preferred Stock liquidation preferences are senior to Series C Preferred Stock liquidation preferences, the Series C Preferred Stock liquidation preferences are senior to the Series B Preferred Stock liquidation preferences, the Series B Preferred Stock liquidation preferences are senior to the Series A Preferred Stock liquidation preferences, the Series A Preferred Stock liquidation preferences are senior to the Junior A Preferred Stock liquidation preferences, and the Junior A Preferred Stock liquidation preferences are senior to the Junior Preferred Stock liquidation preferences. If all amounts would have been paid to the holders of the Preferred Stock in respect of their liquidation preferences, then the remaining assets of the Company would have been distributed pro rata to the holders of Series D Preferred Stock and the common stockholders, subject to a maximum of an additional $4.332732 per share for the holders of Series D Preferred Stock. As a result, the Series D Preferred Stock’s total liquidation preference could have been up to $70,000, exclusive of any declared, but unpaid dividends. The amount that each holder of Preferred Stock would have received upon liquidation, dissolution or winding up of the Company would have been the greater of the cumulative amounts described above or the amount that such holder of Preferred Stock would have received if the shares of Preferred Stock converted into common stock immediately prior to the liquidation, dissolution or winding up of the Company. Conversion Each holder of Preferred Stock had the right to convert any or all of such holder’s Preferred Stock into common stock at any time. As of December 31, 2013, Junior Preferred Stock, Junior A Preferred Stock, Series A Preferred Stock and Series D Preferred Stock were convertible into common stock at a conversion ratio of one to 0.4 and Series B and Series C were convertible into common stock at a conversion ratio of one to 0.434782 and one to 0.473282, respectively. The conversion ratio for all Preferred Stock was subject to adjustment based on certain events specified in the Company’s amended and restated certificate of incorporation, including a stock split, if the Company pays a dividend to common stockholders without a corresponding dividend to the Preferred Stockholders or if the Company sells, or is deemed to sell, common stock at a price per share that is less than the then effective conversion prices of each class of Preferred Stock. Pursuant to these provisions, the conversion ratio for the Series B Preferred Stock and Series C Preferred Stock was adjusted upon the issuance of the Series D Preferred Stock. Automatic Conversion Contemporaneously with the closing of a qualified public offering of common stock, as defined in the Company’s amended and restated certificate of incorporation, or upon a vote of the holders of a majority of the Preferred Stock, voting together as a single class, and holders of at least 67% of the Series D Preferred Stock, all outstanding shares of Preferred Stock would automatically convert into common stock at the then effective applicable conversion rates for such shares. Contemporaneously with the closing of the Company’s IPO, all outstanding shares of Preferred Stock were automatically converted into common stock at the then effective applicable conversion rates for such shares (see above). Dividends Dividends on all series of outstanding Preferred Stock were payable when and if declared by the Company’s Board of Directors. No dividends shall be paid to the holders of the Company’s common stock unless equivalent dividends have been declared and paid on each series of outstanding Preferred Stock. No dividends were declared or paid by the Company for any period during which the Preferred Stock was outstanding through the date of the closing of the Company’s IPO. Voting Rights As set forth in the Company’s amended and restated certificate of incorporation, the holders of Series A, Series B, Series C and Series D Preferred Stock (“Senior Preferred Stock”) were entitled to vote as one class, with common stockholders, based on the number of shares of common stock each holder would receive upon conversion of their Senior Preferred Stock into shares of common stock, for all matters except for the approval of certain major actions by the Company and the election of directors. Subject to certain ownership thresholds and certain nomination and approval rights set forth in the Company’s amended and restated certificate of incorporation and an amended and restated voting agreement by and among the Company and certain stockholders of the Company, directors are elected as follows: common stockholders vote as a separate class for the election of two directors; the holders of Series D Preferred Stock vote as a separate class for the election of one director; the holders of Series C Preferred Stock vote as a separate class for the election of three directors; and the holders of Senior Preferred Stock vote as a combined class for the election of one director. Upon the closing of the Company’s initial public offering on February 5, 2014, the voting agreement terminated and the Company’s stockholders no longer have any special rights regarding the election or designation of members of its Board of Directors. Registration Rights The former holders of shares of Preferred Stock have certain registration rights as set forth in an amended and restated investors’ rights agreement by and among the Company and certain of its stockholders.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity The Company’s Board of Directors has authorized 100,000,000 shares of the Company’s common stock, par value $0.001 per share, and 5,000,000 shares of undesignated preferred stock, par value $0.001 per share, that may be issued from time to time by the Board of Directors of the Company in one or more series. As of December 31, 2015, there were 27,254,863 shares of common stock and no shares of preferred stock issued and outstanding. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to dividends when and if declared by the Board of Directors, subject to the preferential rights of the holders of preferred stock, if any. On January 30, 2014, the Company’s registration statement on Form S-1 relating to its IPO was declared effective, providing for the sale of 5,750,000 shares of the Company’s common stock at a public offering price of $11.00 per share, for an aggregate offering price of $63,250. As a result of the IPO, the Company received net proceeds of $56,297 after deducting $6,953 of underwriting discounts and commissions and offering expenses paid by the Company. On December 1, 2014, the Company sold 11,442 shares of common stock to its Chief Medical Officer at $8.74 per share (which was the closing price of the Company’s common stock on the NASDAQ Global Market on that date) for gross proceeds of $100. The shares of common stock have not been registered under the Securities Act of 1933, as amended (the “Securities Act”), and have been sold pursuant to an exemption from registration contained in the Securities Act based in part upon the purchaser’s representations contained in the purchase agreement. On July 29, 2015, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Stifel, Nicolaus & Company, Incorporated and Piper Jaffray & Co., as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 3,763,440 shares of its common stock (the “Offering”). The Offering was made pursuant to the Company’s Registration Statement on Form S-3 (File No. 333-203072), filed with the SEC on March 27, 2015 and declared effective on May 13, 2015, and a related prospectus supplement dated July 29, 2015, which was filed with the SEC on July 30, 2015. As part of the Offering, the Company granted the underwriters an option to purchase 564,516 additional shares of common stock. On August 4, 2015, the Company closed the Offering, including the full exercise of the underwriters’ option to purchase 564,516 additional shares of common stock, at a public offering price of $18.60 per share. The Company received net proceeds of approximately $75,231, after deducting the underwriting discounts and commissions and offering expenses paid by the Company.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	13. Fair Value Measurements The following table summarizes the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2015 and 2014 and by level within the fair value hierarchy: Fair value measurement as of December 31, 2015: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash and cash equivalents: Money market mutual funds, savings account and checking account $ 15,101 $ 15,101 $ — $ — Available-for-sale marketable securities: Money market mutual funds 41,986 41,986 — U.S. Treasury securities 2,528 2,528 — Other U.S. government agency obligations 13,496 13,496 — Corporate bonds 14,188 14,188 — Commercial paper 19,442 19,442 — Restricted cash: Bank Certificate of Deposit 700 700 — — Total financial assets $ 107,441 $ 15,801 $ 91,640 $ — Fair value measurement as of December 31, 2014: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash equivalents: Money market savings account and checking account $ 52,663 $ 52,663 $ — $ — Restricted cash: Bank Certificate of Deposit 700 700 — — $ 53,363 $ 53,363 $ — $ — There were no purchases, sales or maturities of Level 3 financial assets and no unrealized gains or losses related to Level 3 available-for-sale marketable securities for the years ended December 31, 2015, 2014 and 2013. There were no transfers of financial assets between Levels 1, 2, or 3 classifications during the years ended December 31, 2015, 2014 and 2013.

Collaborations

Collaborations	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	14. Collaborations Chong Kun Dang Pharmaceutical Corporation In April, 2012, the Company entered into a license agreement with CKD (the “CKD Agreement”) that provides CKD with the exclusive rights to develop, manufacture and commercialize products containing CR845 in South Korea. Under the CKD Agreement, the Company received a non-refundable and non-creditable amount of $1,000 and is eligible to receive milestone payments totaling $3,750, relating to pre-defined clinical development ($2,250) and regulatory events ($1,500), as well as royalties on sales of any marketed products containing CR845. The Company has accounted for the milestones under ASC 605 Revenue Recognition – Milestone Method In exchange for the $1,000, the Company provided CKD with the license for CR845 and issued CKD 173,611 shares of Junior Preferred Stock. The Company recorded the issuance of the 173,611 shares of Junior Preferred Stock as a capital transaction for $354, which represented the shares’ estimated fair value as of the transaction date. The remaining proceeds of $646 were recorded as license revenue as the license was the only deliverable within the agreement that had stand-alone value and was determined to be a separate unit of accounting under ASC 605-25, Revenue Recognition Multiple – Element Arrangements In July 2015, the Company met the milestone criteria, as set forth in the CKD Agreement, for completion of a Phase 1b trial of Oral CR845 in the United States. As a result, in August 2015, the Company received a milestone payment of $209 (net of South Korean withholding tax of $41) from CKD. In September 2015, the Company met the milestone criteria, as set forth in the CKD Agreement, for completion of a Phase 2 trial of CR845 in uremic pruritus patients in the United States. As a result, in October 2015, the Company received a milestone payment of $417 (net of South Korean withholding tax of $83) from CKD. Both milestones were considered to be substantive and the full amount of the milestone payments was recognized as milestone revenue when the milestones were achieved. The next potential milestone that the Company could be entitled to receive under the CKD Agreement will be a clinical development milestone for completion of a Phase 3 trial of CR845 in uremic pruritus in the United States. If achieved, this milestone will result in a payment of $750, before South Korean withholding taxes, being due to the Company. Maruishi Pharmaceutical Co., Ltd In April 2013, the Company entered into a license agreement with Maruishi (the “Maruishi Agreement”) under which the Company granted Maruishi an exclusive license to develop, manufacture, and commercialize drug products containing CR845 for acute pain and uremic pruritus in Japan. Under the Maruishi Agreement, the Company and Maruishi are required to use commercially reasonable efforts, at their own expense, to develop, obtain regulatory approval for and commercialize CR845 in the United States and Japan, respectively. In addition, the Company provided Maruishi specific clinical development services for CR845 used in Maruishi’s field of use. Under the terms of the agreement, the Company received an upfront non-refundable, non-creditable license fee of $15,000. As indicated in Note 2, Summary of Significant Accounting Policies – Revenue Recognition Revenue Recognition - Multiple Element Arrangements. As a result, the total value of the arrangement of $15,337 (consisting of the $15,000 upfront payment, plus the additional amount assigned to these deliverables as a result of the Junior A Preferred Stock premium, see below) was allocated between the two units of accounting. The Company used its best estimate of the selling price of these units of accounting, since, as described in Note 2 Summary of Significant Accounting Policies – Revenue Recognition Under the terms of the Maruishi Agreement, the Company is also entitled to receive aggregate milestone payments of $8,000 for events performed by Maruishi in Japan and $2,500 for events performed by the Company in the United States. At the time of execution of the Maruishi Agreement, there was significant uncertainty as to whether the stated milestones would be achieved. In conjunction with this uncertainty, the Company has determined that the milestones achieved in the United States are substantive in nature as they are commensurate with the enhancement of value of the delivered license as they relate to clinical success and advancement within the FDA drug development platform. The Company accounts for those milestone payments under ASC 605-28 Revenue Recognition – Milestone Method During June 2014, Maruishi completed a Phase 1 clinical trial in Japan related to CR845 in acute post-operative pain, which constituted achievement of one of the milestones specified in the license agreement and was considered not to be substantive. Accordingly, the Company allocated the non-refundable payment of $480, net of a contractual foreign currency exchange adjustment, to the two deliverables in the same proportion as the initial upfront payment had been allocated. The portion of the payment allocated to the previously delivered license deliverable ($302) was recognized as license revenue entirely at the time of achievement of the milestone. A portion of the payment allocated to the R&D services deliverable ($88) was recognized as collaborative revenue at the time of achievement of the milestone to the extent of R&D services provided through that date and the remainder ($90) was deferred and was recognized as collaborative revenue through July 2015, which was the period during which the Company provided R&D services to Maruishi. In September 2015, Maruishi initiated a Phase 2 clinical trial of CR845 in Japan for uremic pruritus, which triggered a $1,725 milestone payment (net of contractual foreign currency exchange adjustments of $275) to the Company. At the time of achievement of the milestone, the Company had delivered all deliverables under the Maruishi Agreement. Since the milestone was achieved in Japan, it was deemed not to be substantive. Accordingly, the Company recognized $1,084 as milestone revenue and $641 as collaborative revenue in connection with achievement of this milestone. The next potential milestone that the Company could be entitled to receive under the Maruishi Agreement will be a clinical development milestone for the completion of the first Phase 3 pivotal trial of CR845 in acute pain in the United States. If achieved, this milestone will result in a payment of $1,000, before contractual foreign currency exchange adjustments, being due to the Company. Along with the R&D services performed by the Company for Maruishi, the Company supplied Maruishi with CR845 clinical material as an accommodation. The Company had previously entered into manufacturing and service agreements with third parties to manufacture CR845. Payments made by the Company to third parties based on firm and fixed commitments by Maruishi to purchase CR845 from the Company were capitalized as prepaid expense. During the manufacturing process, title and risk of loss remained with the third party until the Company paid in full for the material. Once the Company had title to the CR845 and had delivered it to Maruishi, prepaid expense related to that CR845 was reduced with an offset to R&D expense. At that time, Maruishi reimbursed the Company for its external and internal costs for purchasing CR845 and processing the sale to Maruishi and the Company recognized clinical compound revenue for the reimbursement amount. During the years ended December 31, 2015, 2014 and 2013, the Company recognized clinical compound revenue of $0, $674 and $102, respectively. Deposits received from Maruishi prior to delivery of CR845 were recorded as deferred revenue. The Company is also eligible to receive tiered, low double digit royalties with respect to any sales of the licensed product sold in Japan by Maruishi. Additionally, the Company can receive sublicense fees (subject to certain credits for milestone payments already made) if Maruishi enters into a sublicense agreement regarding the product candidates. Also, in conjunction with entering into this arrangement, Maruishi purchased 2,105,263 shares of Junior A Preferred Stock of the Company pursuant to a stock purchase agreement for a purchase price of $3.80 per share, for total consideration of $8,000. These shares have been recorded at their fair value of $7,663 or $3.64 per share. As a result, the premium of $337 was allocated to the arrangement consideration (see above). The Company incurred R&D expense related to the Maruishi Agreement of $1,583 (consisting of clinical trial costs related to the R&D services deliverable), $3,558 (consisting of $3,000 of clinical trial costs related to the R&D services deliverable and $558 related to cost of clinical compound sold to Maruishi) and $2,452 (consisting of $2,420 of clinical trial costs related to the R&D services deliverable and $32 related to cost of clinical compound sold to Maruishi) during years ended December 31, 2015, 2014 and 2013, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	15. Stock-Based Compensation 2014 Equity Incentive Plan The Company’s 2014 Equity Incentive Plan, or 2014 Plan, is administered by the Company’s Board of Directors or a duly authorized committee thereof (the “Plan Administrator”). The 2014 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, performance stock awards and other forms of equity compensation (collectively, “Stock Awards”). Additionally, the 2014 Plan provides for the grant of performance cash awards. Incentive stock options may be granted only to employees. All other awards may be granted to employees, including officers, non-employee directors, and non-employee consultants. No incentive stock options may be granted under the 2014 Plan after the tenth anniversary of the effective date of the 2014 Plan. Stock Awards granted under the 2014 Plan vest at the rate specified by the Plan Administrator, which, to date, has been 25% on the first anniversary of the date of grant and the balance ratably over the next 36 months. The Plan Administrator determines the term of Stock Awards granted under the 2014 Plan up to a maximum of ten years. Initially, the aggregate number of shares of the Company’s common stock that may be issued pursuant to Stock Awards under the 2014 Plan was 1,600,000 shares. Additionally, the number of shares of the Company’s common stock reserved for issuance under the 2014 Plan will automatically increase on January 1 of each year, beginning on January 1, 2015 and continuing through and including January 1, 2024, by 3% of the total number of shares of the Company’s capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s Board of Directors. The maximum number of shares that may be issued pursuant to the exercise of incentive stock options under the 2014 Plan is 30,000,000 shares. On January 1, 2015 and January 1, 2016, the aggregate number of shares of common stock that may be issued pursuant to stock awards under the Company’s 2014 Equity Incentive Plan automatically increased to 2,284,061 and 3,101,707, respectively. 2004 Stock Incentive Plan The Company’s 2004 Stock Incentive Plan (the “2004 Plan”), as amended, was adopted by the Company’s Board of Directors and stockholders. Under the 2004 Plan, the Company has granted stock options to selected officers, employees and consultants of the Company. The Company’s Board of Directors administers the 2004 Plan. Options granted under the 2004 Plan have a maximum term of ten years. Options issued generally vest 25% on the first anniversary date of grant and the balance ratably over the next 36 months. Following the effectiveness of the 2014 Plan in January 2014, no additional options or restricted share awards were granted under the 2004 Plan. As of September 30, 2014, the 2004 Plan has expired and no further grants of stock options or restricted stock are allowed. The Company accounts for stock options granted to employees and non-employee members of the Board of Directors in accordance with ASC 718, Compensation – Stock Compensation Equity-Based Payments to Non-Employees Summary of Significant Accounting Policies - Stock-Based Compensation A summary of the Company’s stock option activity related to employees, non-employee members of the Board of Directors and non-employee consultants as of December 31, 2015 and changes during the year then ended is as follows: Number of Weighted- Aggregate Outstanding at December 31, 2014 1,022,360 $ 8.16 Granted 774,000 11.77 Exercised (124,868 ) 2.89 Expired (8,000 ) 0.25 Forfeited (5,084 ) 10.45 Outstanding at December 31, 2015 1,658,408 $ 10.27 $ 11,058 Weighted average remaining contractual life as of December 31, 2015 (yrs) 8.31 510,298 $ 7.78 $ 4,634 Weighted average remaining contractual life as of December 31, 2015 (yrs) 6.59 Options vested and expected to vest at December 31, 2015 1,574,746 $ 10.14 $ 10,693 Weighted average remaining contractual life as of December 31, 2015 (yrs) 8.26 The total fair value of options vested during the years ended December 31, 2015, 2014 and 2013 was $2,489, $393 and $75, respectively. The intrinsic value of options exercised during the years ended December 31, 2015, 2014 and 2013 was $1,748, $2,055 and $0, respectively. During the years ended December 31, 2015 and 2014, the Company granted 774,000 and 884,000 stock options, respectively, to employees, non-employee members of the Board of Directors or non-employee consultants. The Company did not grant any stock options during the year ended December 31, 2013. The fair values of the stock options granted to those groups were estimated using the Black-Scholes option valuation model with the following ranges of assumptions (see Note 2, Summary of Significant Accounting Policies - Stock-Based Compensation Year Ended December 31, 2015 2014 Risk-free interest rate 1.43% - 1.89% 1.64% - 2.72% Expected volatility 64.0% - 67.4% 64.9% - 71.3% Expected dividend yield 0% 0% Expected life of employee and Board of Directors’ options (in years) 6.25 6.25 Expected life of non-employee options (in years) 10 10 The weighted average grant date fair value of options granted to employees, non-employee members of the Board of Directors for their Board service and non-employee consultants during the years ended December 31, 2015 and 2014 was $7.17 and $7.09, respectively. At the end of each fiscal quarter during the years ended December 31, 2015, 2014 and 2013, the Company used the Black-Scholes option valuation model with the following ranges of assumptions to re-measure the fair value of all outstanding unvested options that had been granted to non-employee consultants until each option grant was fully vested. Year Ended December 31, 2015 2014 2013 Risk-free interest rate 1.81% - 2.15% 1.96% - 2.72% 2.5% - 3.2% Expected volatility 70.6% - 72.2% 69% - 71% 71% - 72% Expected dividend yield 0% 0% 0% Expected life of non-employee options (in years) 8.1 - 8.8 6 - 10 1.5 – 7 Under ASC 505-50, upon re-measurement of each award, income or expense is recognized during its vesting term. The weighted average fair values of outstanding unvested options that had been granted to non-employee consultants as re-measured during the years ended December 31, 2015, 2014 and 2013 were $10.05, $10.77 and $6.54, respectively. During the years ended December 31, 2015, 2014 and 2013, the Company recognized compensation expense in the accompanying Statements of Comprehensive Loss relating to stock options, as follows: Year Ended December 31, 2015 2014 2013 Research and development $ 1,073 $ 349 $ 71 General and administrative 1,441 1,022 52 Total stock option expense $ 2,514 $ 1,371 $ 123 As of December 31, 2015, the total compensation expense relating to unvested options granted to employees, non-employee members of the Board of Directors and non-employee consultants that had not yet been recognized was $7,036, which is expected to be realized over a weighted average period of 2.98 years. The Company will issue shares upon exercise of options from common stock reserved.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	16. Income Taxes The Company’s benefit from income taxes is as follows: December 31, 2015 2014 2013 Current: Federal $ — $ — $ — State (397 ) (201 ) (30 ) (397 ) (201 ) (30 ) Deferred: Federal — — — State — — — — — — Benefit from income taxes $ (397 ) $ (201 ) $ (30 ) The Company’s tax benefits relate to state research and development tax credits exchanged for cash. The State of Connecticut provides companies with the opportunity to exchange certain research and development credit carryforwards for cash in exchange for foregoing the carryforward of the research and development credit. The program provides for such exchange of the research and development credits at a rate of 65% of the annual research and development credit, as defined. A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations is as follows: December 31, 2015 2014 2013 Income taxes using U.S. federal statutory rate 34.00 % 34.00 % 34.00 % State income taxes, net of federal benefit 5.95 % 5.23 % 6.03 % Impact of R&D tax credit on effective tax rate 3.14 % 3.03 % 12.04 % Stock option shortfalls and cancellations -0.03 % -0.69 % 0.00 % Permanent items and other -0.41 % -0.57 % -1.42 % Change in valuation allowance -41.07 % -39.88 % -49.90 % 1.58 % 1.12 % 0.75 % Significant components of the Company’s deferred tax assets are as follows: December 31, 2015 2014 Net operating loss carryforwards $ 36,217 $ 27,094 Federal and state tax credits 4,315 3,508 Accelerated depreciation 1,206 1,018 Deferred revenue — 566 Stock-based compensation expense 1,106 333 Other 189 197 43,033 32,716 Valuation allowance (43,033 ) (32,716 ) Net deferred tax asset $ — $ — A 100% valuation allowance has been recorded on the deferred tax asset as of December 31, 2015 and 2014 because management believes it is more likely than not that the asset will not be realized. The change in the valuation allowance during 2015 and 2014 was $10,317 and $7,156, respectively. The Company has a tax benefit of approximately $839 related to the exercise of non-qualified stock options and the disqualified disposition of incentive stock options. Pursuant to ASC 718, the benefit will be recognized and recorded to additional paid-in-capital when the benefit is realized through the reduction of taxes payable. The Company applies the provisions of ASC 740, Income Taxe As of December 31, 2015, the Company’s U.S. federal tax return for 2014 is under examination by the Internal Revenue Service. At December 31, 2015, the Company had federal and state net operating loss carryforwards of approximately $95,900 and $89,899, respectively. The federal and state tax loss carryforwards will begin to expire in 2026 and 2027, respectively, unless previously utilized. The losses may also be subject to limitation pursuant to Internal Revenue Code 382. The Company also had federal and state research and development tax credit carryforwards of approximately $3,642 and $707, respectively. The federal credits will begin expiring in 2025 unless previously utilized. The Connecticut credit carryforwards have no expiration period. Because of the net operating loss and research credit carryforwards, tax years 2007 through 2015 remain open to U.S. federal and state tax examinations.

License and Research Agreement

License and Research Agreement	12 Months Ended
	Dec. 31, 2015
Research and Development [Abstract]
License and Research Agreement	17. License and Research Agreement Effective April 2005, the Company entered into a semi-exclusive worldwide royalty-free license agreement (the “Glasgow License Agreement”) for a certain G protein-coupled receptor (“GPCR”) assay technology with the University of Glasgow (“Glasgow”). The Company issued 200,000 shares of its common stock to Glasgow as compensation for this license. Upon an exit event, including an IPO or as otherwise defined in the Glasgow License Agreement, Glasgow had the option to require the Company to guarantee a return of $1,000 on its 200,000 shares of common stock. If the proceeds from the exit event resulted in a return of less than $1,000, the Company was required to make an additional license payment by giving Glasgow cash or through the issuance of additional shares (at the Company’s option), as specified in the Glasgow License Agreement. In accordance with ASC 480, Distinguishing Liabilities from Equity Collaborations

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss per Share	18. Net Loss per Share The Company computes net loss per share available to common stockholders in accordance with ASC 260-10, Earnings per Share Significant Accounting Policies – Income (Loss) per Share The denominators used in the net loss per share available to common stockholders computations are as follows: Year Ended December 31, 2015 2014 2013 Basic: Weighted average shares outstanding 24,620,372 20,965,935 4,133,138 Diluted: Weighted average shares outstanding - Basic 24,620,372 20,965,935 4,133,138 Convertible preferred stock* — — — Common stock options* — — — Common stock warrants* — — — Convertible promissory notes (as converted)* — — — Demoninator for diluted net loss per share available to common stockholders 24,620,372 20,965,935 4,133,138 * No amounts were considered as their effects would be anti-dilutive. Basic and diluted net loss per share available to common stockholders are computed as follows: Year Ended December 31, 2015 2014 2013 Net loss $ (24,690 ) $ (17,745 ) $ (3,963 ) Add back: extinguishment of preferred shares — — 891 Net loss available to common stockholders - Basic and Diluted $ (24,690 ) $ (17,745 ) $ (3,072 ) Weighted-average common shares outstanding available to common stockholders Basic and Diluted 24,620,372 20,965,935 4,133,138 Net loss per share available to common stockholders: Basic and Diluted $ (1.00 ) $ (0.85 ) $ (0.74 ) Securities outstanding at the end of the respective periods presented below, that could potentially dilute basic earnings per share in the future, that were not included in the computation of diluted net loss per share because to do so would have been antidilutive are as follows: Year Ended December 31, 2015 2014 2013 Convertible preferred stock — — 12,554,171 Common stock options 1,658,408 1,022,360 490,160 Common stock warrants — — 19,851 All shares of the Company’s convertible preferred stock were automatically converted to shares of the Company’s common stock upon the closing of the IPO on February 5, 2014 (see Note 11, Convertible Preferred Stock Long-Term Debt

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	19. Related Party Transactions The Company is party to a consulting agreement with a founder and a common stockholder of the Company who provides scientific advisory services. Total expenses under this agreement were $164, $169 and $134 for the years ended December 31, 2015, 2014 and 2013, respectively. Included in accounts payable and accrued expenses as of December 31, 2015 and 2014, respectively, was $21 and $35 for amounts due to this stockholder.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
Employee Benefit Plan	20. Employee Benefit Plan In February 2006, the Company adopted a defined contribution retirement plan that complies with Section 401(k) of the Internal Revenue Code. All employees over the age of 21 are eligible to participate in the plan after three consecutive months of service. Employees are able to defer a portion of their pay into the plan on the first day of the quarter on or after the day all age and service requirements have been met. The plan allows the Company to match employee contributions; however, there were no matching contributions paid through December 31, 2014. Effective January 1, 2015, all eligible employees receive an employer contribution equal to 3% of their salary up to the annual IRS limit. During the year ended December 31, 2015, employer contributions to the plan were $80.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	21. Commitments and Contingencies Shelton Operating Lease As of December 31, 2015, the Company leases its operating facility located in Shelton, Connecticut. The lease agreement, as amended, requires monthly lease payments through October 13, 2017. At inception of the lease, the Company received an incentive allowance from the landlord of $2,127. The Company recorded the incentive allowance as leasehold improvements and deferred lease obligation. The Company is recording monthly rent expense associated with the lease on a straight-line basis over the ten-year minimum term of the lease reduced by the amortization of the deferred lease obligation over the same time period. As a result of this straight-line basis, deferred lease obligation includes $374 and $582 of unamortized incentive allowance plus $211 and $292 of accrued rent at December 31, 2015 and 2014, respectively. Total rent expense under the operating lease was $665, $643 and $616 for the years ended December 31, 2015, 2014 and 2013, respectively. Future minimum rental payments under the Shelton operating lease at December 31, 2015 are as follows: 2016 $ 913 2017 740 Total $ 1,653 In conjunction with the signing of the Shelton, Connecticut lease, the Company entered into a standby letter of credit agreement for $2,170, which expires on May 31, 2017 as a security deposit for the premises. In accordance with the terms of the lease, because no drawing was made against the standby letter of credit nor has any default under the operating lease occurred, the amount of the letter of credit was automatically reduced by $294 annually starting March 1, 2008 until the stated amount reached a balance of $700, which occurred in 2012. This standby letter of credit is secured with restricted cash (refer to Note 7, Restricted Cash In connection with the relocation of the Company’s operating facility from Shelton to Stamford, Connecticut (see below), as of December 31, 2015, the Company was negotiating with the Shelton landlord regarding the Company’s future obligations under the Shelton lease. The Company is accelerating the amortization of the Shelton leasehold improvements from the date of signing of the Stamford lease through the expected date that the Company will vacate the Shelton facility. Additional amortization expense as a result of such acceleration amounted to $67 during the year ended December 31, 2015 and will be $899 for the period from January through May 2016. Stamford Operating Lease In December 2015, the Company entered into a lease agreement (the “Stamford Lease”) with Four Stamford Plaza Owner LLC (the “Landlord”) for office space in Stamford, Connecticut (the “Premises”). The purpose of the Stamford Lease is to relocate the Company’s corporate headquarters. The Stamford Lease commences upon completion of renovations to the Premises, which is expected to be in May 2016 (the “Commencement Date”), and ends 90 months thereafter. The Stamford Lease requires monthly lease payments, including rent escalations and rent holidays, during the initial lease term. The Company will begin to make rental payments from the Commencement Date. The Stamford Lease is renewable for one five-year term. In connection with the signing of the Stamford Lease, the Company entered into a standby letter of credit agreement for $769, which serves as a security deposit for the Premises. The standby letter of credit expires on December 16, 2016 and is automatically renewed annually through November 1, 2023. This standby letter of credit will be secured with restricted cash in a money market account, although the restricted money market account was not established until January 2016 (refer to Note 7, Restricted Cash Future minimum rental payments under the Stamford Lease at December 31, 2015 are as follows: 2016 $ 288 2017 875 2018 1,093 2019 1,217 2020 1,241 Thereafter 3,650 Total $ 8,364 Under the Stamford Lease, the Landlord will contribute approximately $1,021 toward the cost of tenant improvements to the Premises as an incentive allowance. At the Commencement Date, the Company will record the incentive allowance as a leasehold improvements asset and a deferred lease obligation liability. The Company will record monthly rent expense associated with the Stamford Lease on a straight-line basis from the Commencement Date through the 7.5-year minimum term of the Stamford Lease, reduced by the amortization of the deferred lease obligation over the same time period.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Legal Matters	22. Legal Matters From time to time, the Company may become involved in arbitrations or legal proceedings that arise in the ordinary course of its business. The Company cannot predict the timing or outcome of these claims and proceedings. Currently, the Company is not involved in any such arbitration and/or legal proceeding that it expects to have a material effect on its financial condition, results of operations or business.

Quarterly Results of Operations

Quarterly Results of Operations	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations	23. Quarterly Results of Operations (Unaudited) The following tables contain selected financial data for each quarter of the years ended December 31, 2015 and 2014. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair presentation of the information for each quarter of the years ended December 31, 2015 and 2014. The operating results for any period are not necessarily indicative of results for any future periods. Year Ended December 31, 2015 First Second Third Fourth Revenues $ 489 $ 874 $ 2,440 $ — Net loss - Basic and Diluted (4,689 ) (5,684 ) (4,787 ) (9,530 ) Loss per share - Basic and Diluted $ (0.21 ) $ (0.25 ) $ (0.19 ) $ (0.35 ) Year Ended December 31, 2014 First Second Third Fourth Revenues $ 178 $ 960 $ 1,125 $ 914 Net loss - Basic and Diluted (3,383 ) (3,645 ) (6,545 ) (4,172 ) Loss per share - Basic and Diluted $ (0.22 ) $ (0.16 ) $ (0.29 ) $ (0.18 )

Summary of Significant Accoun32

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally-accepted accounting principles in the United States (“GAAP”) requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, as of the date of the financial statements as well as the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from the Company’s estimates and assumptions. Significant estimates include the fair value of marketable securities that are classified as level 2 of the fair value hierarchy, useful lives of fixed assets, the periods over which certain revenues will be recognized, including licensing and collaborative revenue recognized from non-refundable up-front and milestone payments, the determination of prepaid research and development clinical costs and accrued research projects, the amount of non-cash compensation costs related to share-based payments to employees and non-employees and the periods over which those costs are expensed and the likelihood of realization of deferred tax assets.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments, which potentially subject the Company to significant concentrations of credit risk consist primarily of cash equivalents and marketable securities. The Company invests its cash reserves in money market funds or high-quality marketable securities in accordance with its investment policy. The stated objectives of its investment policy is to preserve capital, provide liquidity consistent with forecasted cash flow requirements, maintain appropriate diversification and generate returns relative to these investment objectives and prevailing market conditions. The Company’s investment policy includes guidelines on acceptable investment securities, limits interest-bearing security investments to certain types of debt and money market instruments issued by the U.S. government and institutions with investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer. The Company’s cash, cash equivalents and marketable securities are held by a few major financial institutions. In accordance with the Company’s policies, the Company monitors exposure with its counterparties. The Company also maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand, demand deposits, deposits with banks and highly liquid money market funds with holdings of cash.
Marketable Securities	Marketable Securities The Company deems certain of its investments to be marketable securities if the investment, or in the case of money market funds, the securities underlying the money market fund, meet the definition of a debt security in Accounting Standards Codification section 320-10-20. The Company considers its marketable securities to be available-for-sale and, accordingly, these investments are recorded at fair value with unrealized gains and losses generally recorded in accumulated other comprehensive income (loss) (“AOCI”) as a separate component of stockholders’ equity. Marketable securities are reported in Marketable Securities in the Balance Sheets. Other income (expense), net, includes interest, realized gains and losses on sales of securities and other-than-temporary impairment (“OTTI”) declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method. The Company reviews its available-for-sale marketable securities for OTTI declines in fair value below its cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below its cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell, the security before recovery of its amortized cost basis. The Company’s assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. If a decline in the fair value of an available-for-sale marketable debt security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value. If the Company intends to sell the security or it is more likely than not that the Company will be forced to sell the security before recovery of the amortized cost of the security, the loss is recognized in net income. Otherwise, the loss is separated into a portion representing a credit loss, which is recorded in net income, and the remainder is recorded in Other Comprehensive Income (“OCI”), net of taxes. See Note 3, M arketable Securities Fair Value Measurement
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company applies fair value accounting for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions and credit risks. The Company’s financial instruments consist of cash, cash equivalents, available-for-sale marketable securities, restricted cash, accounts payable and accrued liabilities. The fair values of cash and cash equivalents, restricted cash, accounts payable and accrued liabilities approximate their carrying values due to the short-term nature of these financial instruments. Marketable securities are reported on the Company’s Balance Sheets at their fair values, based upon pricing of securities with the same or similar investment characteristics as provided by pricing services, as described below. Current accounting guidance defines fair value, establishes a framework for measuring fair value in accordance with Accounting Standards Codification (“ASC”) section 820, and requires certain disclosures about fair value measurements. The valuation techniques included in the guidance are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs 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 Company classifies its investments in a fair value hierarchy that is intended to increase consistency and comparability in fair value measurements and related disclosures. The fair value hierarchy is divided into three levels based on the source of inputs as follows: • Level 1 – Observable inputs – quoted prices in active markets for identical assets and liabilities. • Level 2 – Observable inputs other than the quoted prices in active markets for identical assets and liabilities – such as quoted prices for similar instruments, quoted prices for identical or similar instruments in inactive markets, or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Unobservable inputs – includes amounts derived from valuation models where one or more significant inputs are unobservable and require the company to develop relevant assumptions. The Company records transfers between levels in the hierarchy by assuming that the transfer occurred at the end of the quarter or year-to-date period. Valuation Techniques - Level 2 Inputs The Company estimates the fair values of its financial instruments categorized as level 2 in the fair value hierarchy, including U.S. Treasury securities, other U.S. government agency obligations, corporate bonds and commercial paper by taking into consideration valuations obtained from third-party pricing services. The pricing services use industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, benchmark yields, issuer credit spreads, benchmark securities, and other observable inputs. The Company obtains a single price for each financial instrument and does not adjust the prices obtained from the pricing service. The Company validates the prices provided by its third party pricing services by reviewing their pricing methods, obtaining market values from other pricing sources and comparing them to the share prices presented by the pricing service. After completing its validation procedures, the Company did not adjust or override any fair value measurements provided by its pricing services as of December 31, 2015. The Company did not have any financial instruments categorized as level 2 as of December 31, 2014.
Property and Equipment	Property and Equipment Property and equipment (consisting of computer, office and laboratory equipment, furniture and fixtures, software and leasehold improvements) are stated at cost, net of accumulated depreciation and amortization of leasehold improvements. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized over the lesser of their useful lives or the life of the lease. Asset Category Useful Lives Computer and office equipment 5 years Laboratory equipment 8 years Furniture and fixtures 7 years Software 3 years Leasehold improvements 10 years
Long-Lived Assets	Long-Lived Assets ASC 360, Property, Plant and Equipment
Common Stock and Convertible Preferred Stock Valuation	Common Stock and Convertible Preferred Stock Valuation Due to the absence of an active market for the Company’s common stock and convertible preferred stock prior to its IPO, the Company utilized methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation
Revenue Recognition	Revenue Recognition In general, the Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; the Company’s price to the customer is fixed or determinable; collectability is reasonably assured and delivery has occurred or services have been rendered. The Company has entered into license agreements to develop, manufacture and commercialize drug products. The terms of these agreements typically contain multiple elements, including licenses and research and development services. Payments to the Company under these agreements may include nonrefundable license fees, payments for research activities, payments based upon the achievement of certain milestones and royalties on any resulting net product sales. There are no performance, cancellation, termination or refund provisions in any of the arrangements that contain material financial consequences to the Company. The Company records revenue related to these agreements in accordance with ASC 605-25, Revenue Recognition Multiple-Element Arrangements The Company determines the estimated selling price for deliverables within each agreement using vendor specific objective evidence (“VSOE”) of selling price, if available, or third party evidence (“TPE”) of selling price if VSOE is not available, or the Company’s best estimate of selling price, if neither VSOE nor TPE is available. Determining the best estimate of selling price for a deliverable requires significant judgment. Because the Company does not have VSOE or third party evidence of selling price to determine the estimated selling price of a license to its proprietary technology, it typically uses its best estimate of a selling price to estimate the selling prices for licenses to its proprietary technology. In making these estimates, the Company considers market conditions and entity-specific factors, including those contemplated in negotiating the agreements, as well as internally developed estimates that include assumptions related to the market opportunity, estimated development costs, probability of success and the time needed to commercialize a product candidate pursuant to the license. In validating its best estimate of selling price, the Company evaluates whether changes in the key assumptions used to determine its best estimate of selling price will have a significant effect on the allocation of arrangement consideration between deliverables. The Company recognizes consideration allocated to an individual element when all other revenue recognition criteria are met for that element. Arrangement consideration allocated to license deliverables that represent separate units of accounting is recognized as revenue at the outset of the agreement assuming the general criteria for revenue recognition noted above have been met. Arrangement consideration allocated to license deliverables which do not represent separate units of accounting is deferred. The Company has determined that its license deliverables represent separate units of accounting because the counterparty has the right to sublicense and manufacture in its territory, as defined. Arrangement consideration allocated to research and development services which represent separate units of accounting is recognized as the services are performed, assuming the general criteria for revenue recognition noted above have been met. The Company has determined that its research and developments services deliverables, as applicable, represent separate units of accounting because similar services are sold separately by other vendors. The Company’s license agreements include contingent milestone payments related to specified clinical development milestones and regulatory milestones. Development milestones are payable when a product candidate initiates or advances into different clinical trial phases. Regulatory milestones are payable upon submission for marketing approval with the FDA or other countries’ regulatory authorities or on receipt of actual marketing approvals for the compound or for additional indications. At the inception of each agreement that includes milestone payments, the Company evaluates whether each such payment is a milestone payment as defined by ASC 605-28, Revenue Recognition – Milestone Method If the payment meets the criteria of a milestone payment, the Company evaluates whether such milestone is considered to be substantive. This evaluation includes an assessment of whether (a) the consideration is commensurate with either (1) the entity’s performance to achieve the milestone, or (2) the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone, (b) the consideration relates solely to past performance and (c) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, regulatory, commercial and other risks that must be overcome to achieve the respective milestone and the level of effort and investment required to achieve the respective milestone in making this assessment. The Company recognizes substantive milestone payments as revenue upon the achievement of the milestone, assuming all other revenue recognition criteria are met. If any milestone payment is considered not to be a substantive milestone or is considered to be a contingent payment, the Company initially defers the milestone payment, allocates it to the deliverables based on relative selling price in the same proportion as at inception of the agreement, immediately recognizes revenue to the extent of any delivered elements and recognizes the portion attributable to any undelivered elements over the remaining term of its performance obligations. If no such performance obligations exist, milestones that are considered not to be substantive or are considered to be contingent payments are generally recognized as revenue upon achievement, assuming all other revenue recognition criteria are met. Royalty revenue is recognized when earned. To date, no royalties have been earned or were otherwise due to the Company.
Research and Development Expenses	Research and Development Expenses Research and development (“R&D”) costs are charged to expense as incurred. Costs incurred under agreements with third parties are charged to expense as incurred in accordance with the specific contractual performance terms of such agreements. Research and development expenses include, among other costs, salaries and other personnel-related costs, costs to conduct clinical trials, costs to manufacture product candidates and clinical supplies, laboratory supplies costs and facility-related costs. Non-refundable research and development advance payments are deferred and capitalized as prepaid R&D expense. The capitalized amounts are expensed as the related goods are delivered or services are performed. As of December 31, 2015 and 2014, the Company recorded $1,500 and $177 as prepaid R&D expense, respectively.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized. The Company applies the provisions of ASC 740, Income Taxes
Stock-Based Compensation	Stock-Based Compensation The Company grants stock options to employees, non-employee members of the Company’s Board of Directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the Board of Directors’ awards of stock-based compensation are accounted for in accordance with ASC 718, Compensation Stock Compensation . Using this model, fair value is calculated based on assumptions with respect to (i) the fair value or market price of the Company’s common stock on the grant date; (ii) expected volatility of the Company’s common stock price, (iii) the periods of time over which employees and members of the Company’s Board of Directors are expected to hold their options prior to exercise (expected lives), (iv) expected dividend yield on the Company’s common stock, and (v) risk-free interest rates. Prior to the effective date of the registration statement related to the Company’s IPO in January 2014, the Company utilized methodologies in accordance with the Practice Aid to determine the fair value of the Company’s common stock on any given date. Subsequently, the stock price input to the Black-Scholes model for each stock option granted is the closing price of the Company’s common stock as quoted on The NASDAQ Global Market on the grant date. Expected volatility is based on an analysis of guideline companies in accordance with ASC 718. The expected life of stock options granted to employees and members of the Company’s Board of Directors is determined using the average of the vesting period and term, an accepted method for the Company’s option grants under the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment. The Company applies a forfeiture rate to the number of unvested awards in each reporting period in order to accrue share-based compensation expense based on an estimate of the number of awards that are expected to vest. Estimated forfeiture rates are based upon historical data of awards that were cancelled prior to vesting. The Company adjusts the total amount of compensation cost recognized for each award, in the period in which each award vests, to reflect the actual forfeitures related to that award. To the extent that the actual forfeiture rate for an award is lower than the estimated forfeiture rate, additional compensation expense is recorded in the period that the award vests. Changes in the Company’s estimated forfeiture rate will result in changes in the rate at which compensation cost for an award is recognized over its vesting period. The Company accounts for options granted to non-employee consultants under ASC 505-50, Equity-Based Payments to Non-Employees.
Income (Loss) Per Share	Income (Loss) Per Share The Company computes basic net income (loss) per share by dividing net income (loss) by the weighted average number of shares of common stock outstanding. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were converted or exercised during the period, when the effect is dilutive. Common stock equivalents may include convertible preferred stock, convertible promissory notes and outstanding stock options and stock warrants, which are included under the treasury stock method when dilutive. The computation of diluted net loss per share for each of the years ended December 31, 2015, 2014 and 2013 does not include common stock equivalents since such inclusion would be antidilutive. During the year ended December 31, 2013, the Company computed basic net income (loss) per share available to common stockholders using the “two-class” method, which includes the weighted average number of shares of common stock outstanding during the period and other securities that participate in dividends (a participating security). Prior to its IPO, the Company’s shares of convertible preferred stock were participating securities as defined by ASC 260-10, Earnings Per Share Convertible Preferred Stock Under the two-class method, basic net income (loss) per share available to common stockholders is computed by dividing the net income (loss) available to common stockholders by the weighted average number of common shares outstanding for the period. The Company allocates net income on a pari passu (equal) basis to both common and preferred stockholders. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. Diluted net income (loss) per share is computed using the more dilutive of (1) the two-class method, or (2) the “if-converted” method. Refer to Note 18, Net Loss per Share
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one operating segment, which includes all activities related to the discovery and development of novel therapeutics to treat serious medical conditions, including pain and pruritus.
Leases	Leases The Company recognizes rent expense for operating leases on a straight-line basis over the term of the lease, beginning on the date the Company takes possession of the property. Rent expense includes the base amounts stated in the lease agreement as well as the effect of reduced or free rent and rent escalations. At lease inception, the Company determines the lease term by assuming the exercise of those renewal options that are reasonably assured because of the significant economic penalty that exists for not exercising those options. The exercise of renewal options is at the Company’s sole discretion. The expected lease term is one of the factors used to determine whether a lease is classified operating or capital and is used to calculate the straight-line rent expense. The difference between the cash paid to the landlord and the amount recognized as rent expense on a straight-line basis is included in deferred rent and classified within long-term liabilities. Cash reimbursements received from landlords for leasehold improvements and other cash payments received from landlords as lease incentives are recorded as deferred rent and classified as long-term liabilities. Deferred rent related to landlord incentives is amortized using the straight-line method over the lease term as an offset to rent expense. Penalties paid to landlords to terminate a lease before the contractual end date of the lease are recognized on an undiscounted basis in the Statements of Comprehensive Loss.
Litigation Reserves	Litigation Reserves The Company may become involved in the future in various lawsuits, claims, investigations and proceedings that arise in the ordinary course of business. Accruals are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. The Company reviews these reserves at least quarterly and adjusts these reserves to reflect current law, progress of each case, opinions and views of legal counsel and other advisers, the Company’s experience in similar matters and intended response to the litigation. The Company expenses amounts for administering or litigating claims as incurred. Accruals for legal proceedings, if any, are included in Accounts payable and accrued expenses in the Balance Sheets.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update 2016-02, Leases In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740) Balance Sheet Classification of Deferred Taxes During April 2015, the FASB issued Accounting Standards Update 2015-03 (“ASU 2015-03”) Interest—Imputation of Interest (Subtopic 835-30) Simplifying the Presentation of Debt Issuance Costs Interest—Imputation of Interest (Subtopic 835-30) Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements In August 2014, the FASB issued Accounting Standards Update 2014-15 Presentation of Financial Statements – Going Concern (Subtopic 205-40), Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In May 2014, the FASB issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606)

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Useful Lives of Property and Equipment	Property and equipment (consisting of computer, office and laboratory equipment, furniture and fixtures, software and leasehold improvements) are stated at cost, net of accumulated depreciation and amortization of leasehold improvements. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized over the lesser of their useful lives or the life of the lease. Asset Category Useful Lives Computer and office equipment 5 years Laboratory equipment 8 years Furniture and fixtures 7 years Software 3 years Leasehold improvements Lesser of 10 years

Available-for-Sale Marketable34

Available-for-Sale Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Marketable Securities by Major Type of Security	The following table summarizes the Company’s available-for-sale marketable securities by major type of security as of December 31, 2015: Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Money market mutual funds $ 42,017 $ — $ (31 ) $ 41,986 U.S. Treasury securities 2,528 — — 2,528 Other U.S. government agency obligations 13,492 4 — 13,496 Corporate bonds 14,194 — (6 ) 14,188 Commercial paper 19,444 1 (3 ) 19,442 Total available-for-sale marketable securities $ 91,675 $ 5 $ (40 ) $ 91,640
Schedule of Fair Values and Amortized Cost of Marketable Debt Securities by Contractual Maturity	The Company classifies its marketable debt securities based on their contractual maturity dates. The marketable debt securities as of December 31, 2015 mature at various dates through September 2016. The fair values and amortized cost of marketable debt securities by contractual maturity were as follows. The table does not include money market funds that are classified as available-for-sale marketable securities. As of December 31, 2015 2014 Contractual maturity Fair Value Amortized Cost Fair Value Amortized Cost Less than one year $ 49,653 $ 49,657 $ — $ —
Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities	The following table shows the fair value of the Company’s available-for-sale marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual investments have been in a continuous unrealized loss position. Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Gross Fair Gross Fair Gross Money market mutual funds $ 30,985 $ (31 ) $ — $ — $ 30,985 $ (31 ) Corporate bonds 14,187 (6 ) — — 14,187 (6 ) Commercial paper 11,960 (3 ) — — 11,960 (3 ) Total $ 57,132 $ (40 ) $ — $ — $ 57,132 $ (40 )

Accumulated Other Comprehensi35

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Summary of Changes in AOCI, Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities	The following table summarizes the changes in AOCI, net of tax, from unrealized gains (losses) on available-for-sale marketable securities, the Company’s only component of AOCI, for the year ended December 31, 2015. As of December 31, 2014 and for the years ended December 31, 2014 and 2013, all of the Company’s funds were held in money market savings and checking accounts that were classified as cash equivalents and not as available-for-sale marketable securities. For the year ended December 31, 2015, there were no reclassifications from AOCI since there were no sales of available-for-sale marketable securities. Total Accumulated Balance, December 31, 2014 $ — Other comprehensive loss before reclassifications (35 ) Amount reclassified from accumulated other comprehensive income — Net current period other comprehensive loss (35 ) Balance, December 31, 2015 $ (35 )

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and equipment, net consists of the following: December 31, 2015 2014 Computer and office equipment $ 314 $ 309 Laboratory equipment 232 233 Furniture and fixtures 155 156 Software 126 126 Leasehold improvements 7,453 7,453 $ 8,280 $ 8,276 Less accumulated depreciation and amortization 7,017 6,192 Property and equipment, net $ 1,263 $ 2,084

Accounts Payable and Accrued 37

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following: December 31, 2015 2014 Accounts payable $ 1,965 $ 515 Accrued research projects 1,542 549 Accrued professional fees 371 266 Accrued compensation and benefits 1,204 504 Accrued other 186 112 $ 5,268 $ 1,946

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Schedule of Convertible Preferred Stock	The following tables summarize the outstanding Preferred Stock as of December 31, 2013 and December 31, 2012: As of December 31, 2013 Preferred Preferred Liquidation Carrying Common Stock Junior 173,611 173,611 $ 500 $ 354 69,444 Junior A 2,105,263 2,105,263 8,000 7,642 842,105 Series A 1,677,118 1,677,118 1,677 1,677 670,830 Series B 2,254,417 2,254,417 4,509 4,509 980,163 Series C 10,930,946 10,930,946 33,886 33,886 5,173,413 Series D 12,260,845 12,045,574 17,397 17,518 4,818,216 29,402,200 29,186,929 $ 65,969 $ 65,586 12,554,171 As of December 31, 2012 Preferred Preferred Liquidation Carrying Common Stock Junior 173,611 173,611 $ 500 $ 354 69,444 Junior A — — — — — Series A 2,000,000 2,000,000 2,000 2,000 800,000 Series B 2,370,000 2,370,000 4,740 4,740 1,030,434 Series C 11,706,450 11,706,450 36,290 36,290 5,540,457 Series D 10,386,057 10,386,057 15,000 15,138 4,154,422 26,636,118 26,636,118 $ 58,530 $ 58,522 11,594,757

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following table summarizes the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2015 and 2014 and by level within the fair value hierarchy: Fair value measurement as of December 31, 2015: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash and cash equivalents: Money market mutual funds, savings account and checking account $ 15,101 $ 15,101 $ — $ — Available-for-sale marketable securities: Money market mutual funds 41,986 41,986 — U.S. Treasury securities 2,528 2,528 — Other U.S. government agency obligations 13,496 13,496 — Corporate bonds 14,188 14,188 — Commercial paper 19,442 19,442 — Restricted cash: Bank Certificate of Deposit 700 700 — — Total financial assets $ 107,441 $ 15,801 $ 91,640 $ — Fair value measurement as of December 31, 2014: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash equivalents: Money market savings account and checking account $ 52,663 $ 52,663 $ — $ — Restricted cash: Bank Certificate of Deposit 700 700 — — $ 53,363 $ 53,363 $ — $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Summary of Stock Option Activity	A summary of the Company’s stock option activity related to employees, non-employee members of the Board of Directors and non-employee consultants as of December 31, 2015 and changes during the year then ended is as follows: Number of Weighted- Aggregate Outstanding at December 31, 2014 1,022,360 $ 8.16 Granted 774,000 11.77 Exercised (124,868 ) 2.89 Expired (8,000 ) 0.25 Forfeited (5,084 ) 10.45 Outstanding at December 31, 2015 1,658,408 $ 10.27 $ 11,058 Weighted average remaining contractual life as of December 31, 2015 (yrs) 8.31 510,298 $ 7.78 $ 4,634 Weighted average remaining contractual life as of December 31, 2015 (yrs) 6.59 Options vested and expected to vest at December 31, 2015 1,574,746 $ 10.14 $ 10,693 Weighted average remaining contractual life as of December 31, 2015 (yrs) 8.26
Summary of Assumptions Used in Black-Scholes Option Pricing Model	The fair values of the stock options granted to those groups were estimated using the Black-Scholes option valuation model with the following ranges of assumptions (see Note 2, Summary of Significant Accounting Policies - Stock-Based Compensation Year Ended December 31, 2015 2014 Risk-free interest rate 1.43% - 1.89% 1.64% - 2.72% Expected volatility 64.0% - 67.4% 64.9% - 71.3% Expected dividend yield 0% 0% Expected life of employee and Board of Directors’ options (in years) 6.25 6.25 Expected life of non-employee options (in years) 10 10
Summary of Compensation Expense Relating to Stock Options	During the years ended December 31, 2015, 2014 and 2013, the Company recognized compensation expense in the accompanying Statements of Comprehensive Loss relating to stock options, as follows: Year Ended December 31, 2015 2014 2013 Research and development $ 1,073 $ 349 $ 71 General and administrative 1,441 1,022 52 Total stock option expense $ 2,514 $ 1,371 $ 123
Re-Measurement [Member]
Summary of Assumptions Used in Black-Scholes Option Pricing Model	At the end of each fiscal quarter during the years ended December 31, 2015, 2014 and 2013, the Company used the Black-Scholes option valuation model with the following ranges of assumptions to re-measure the fair value of all outstanding unvested options that had been granted to non-employee consultants until each option grant was fully vested. Year Ended December 31, 2015 2014 2013 Risk-free interest rate 1.81% - 2.15% 1.96% - 2.72% 2.5% - 3.2% Expected volatility 70.6% - 72.2% 69% - 71% 71% - 72% Expected dividend yield 0% 0% 0% Expected life of non-employee options (in years) 8.1 - 8.8 6 - 10 1.5 – 7

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Components of Income Taxes (Benefit)	The Company’s benefit from income taxes is as follows: December 31, 2015 2014 2013 Current: Federal $ — $ — $ — State (397 ) (201 ) (30 ) (397 ) (201 ) (30 ) Deferred: Federal — — — State — — — — — — Benefit from income taxes $ (397 ) $ (201 ) $ (30 )
Schedule of Reconciliation of Income Taxes Computed Using U.S. Federal Statutory Rate to that Reflected in Operations	A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations is as follows: December 31, 2015 2014 2013 Income taxes using U.S. federal statutory rate 34.00 % 34.00 % 34.00 % State income taxes, net of federal benefit 5.95 % 5.23 % 6.03 % Impact of R&D tax credit on effective tax rate 3.14 % 3.03 % 12.04 % Stock option shortfalls and cancellations -0.03 % -0.69 % 0.00 % Permanent items and other -0.41 % -0.57 % -1.42 % Change in valuation allowance -41.07 % -39.88 % -49.90 % 1.58 % 1.12 % 0.75 %
Schedule of Significant Components of Company's Deferred Tax Assets	Significant components of the Company’s deferred tax assets are as follows: December 31, 2015 2014 Net operating loss carryforwards $ 36,217 $ 27,094 Federal and state tax credits 4,315 3,508 Accelerated depreciation 1,206 1,018 Deferred revenue — 566 Stock-based compensation expense 1,106 333 Other 189 197 43,033 32,716 Valuation allowance (43,033 ) (32,716 ) Net deferred tax asset $ — $ —

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Computation of Denominators Used in Net Loss per Share Available to Common Stockholders	The denominators used in the net loss per share available to common stockholders computations are as follows: Year Ended December 31, 2015 2014 2013 Basic: Weighted average shares outstanding 24,620,372 20,965,935 4,133,138 Diluted: Weighted average shares outstanding - Basic 24,620,372 20,965,935 4,133,138 Convertible preferred stock* — — — Common stock options* — — — Common stock warrants* — — — Convertible promissory notes (as converted)* — — — Demoninator for diluted net loss per share available to common stockholders 24,620,372 20,965,935 4,133,138 * No amounts were considered as their effects would be anti-dilutive.
Computation of Basic and Diluted Net Loss per Share Available to Common Stockholders	Basic and diluted net loss per share available to common stockholders are computed as follows: Year Ended December 31, 2015 2014 2013 Net loss $ (24,690 ) $ (17,745 ) $ (3,963 ) Add back: extinguishment of preferred shares — — 891 Net loss available to common stockholders - Basic and Diluted $ (24,690 ) $ (17,745 ) $ (3,072 ) Weighted-average common shares outstanding available to common stockholders Basic and Diluted 24,620,372 20,965,935 4,133,138 Net loss per share available to common stockholders: Basic and Diluted $ (1.00 ) $ (0.85 ) $ (0.74 )
Schedule of Anti-Dilutive Common Stock Equivalents Excluded from Calculations of Diluted Net Loss per Share	Securities outstanding at the end of the respective periods presented below, that could potentially dilute basic earnings per share in the future, that were not included in the computation of diluted net loss per share because to do so would have been antidilutive are as follows: Year Ended December 31, 2015 2014 2013 Convertible preferred stock — — 12,554,171 Common stock options 1,658,408 1,022,360 490,160 Common stock warrants — — 19,851

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Shelton Operating Lease [Member]
Schedule of Future Minimum Rental Payments Under Operating Leases	Future minimum rental payments under the Shelton operating lease at December 31, 2015 are as follows: 2016 $ 913 2017 740 Total $ 1,653
Stamford Operating Lease [Member]
Schedule of Future Minimum Rental Payments Under Operating Leases	Future minimum rental payments under the Stamford Lease at December 31, 2015 are as follows: 2016 $ 288 2017 875 2018 1,093 2019 1,217 2020 1,241 Thereafter 3,650 Total $ 8,364

Quarterly Results of Operatio44

Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Selected Financial Data for Each Quarter	The following tables contain selected financial data for each quarter of the years ended December 31, 2015 and 2014. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair presentation of the information for each quarter of the years ended December 31, 2015 and 2014. The operating results for any period are not necessarily indicative of results for any future periods. Year Ended December 31, 2015 First Second Third Fourth Revenues $ 489 $ 874 $ 2,440 $ — Net loss - Basic and Diluted (4,689 ) (5,684 ) (4,787 ) (9,530 ) Loss per share - Basic and Diluted $ (0.21 ) $ (0.25 ) $ (0.19 ) $ (0.35 ) Year Ended December 31, 2014 First Second Third Fourth Revenues $ 178 $ 960 $ 1,125 $ 914 Net loss - Basic and Diluted (3,383 ) (3,645 ) (6,545 ) (4,172 ) Loss per share - Basic and Diluted $ (0.22 ) $ (0.16 ) $ (0.29 ) $ (0.18 )

Business - Additional Informati

Business - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Oct. 31, 2015	Sep. 30, 2015	Aug. 31, 2015	Aug. 31, 2014	Apr. 30, 2013	Apr. 30, 2012	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Nature Of Business [Line Items]
Date of formation																Jul. 2, 2004
Proceeds from equity and debt financing	$ 204,800
Upfront and milestone payments earned in connection with license agreements	32,500
Upfront and milestone payments related to license agreement																$ 1,710	$ 302	$ 9,637
Unrestricted cash and cash equivalents and marketable securities	106,740							$ 106,740								106,740
Accumulated deficit	$ 104,891							104,891				$ 80,201				104,891	80,201
Net loss								$ 9,530	$ 4,787	$ 5,684	$ 4,689	$ 4,172	$ 6,545	$ 3,645	$ 3,383	24,690	17,745	3,963
Net cash used in operating activities																$ (21,478)	$ (17,642)	$ 2,829
Minimum [Member]
Nature Of Business [Line Items]
Expected period to fund operations																1 year
Maruishi Pharmaceutical Co., Ltd. [Member]
Nature Of Business [Line Items]
Upfront license fee received						$ 15,000
Milestone payment received					$ 480
Amount due from milestone payments net of contractual foreign currency exchange adjustments			$ 1,725
Upfront and milestone payments related to license agreement																$ 1,084
Chong Kun Dang Pharmaceutical Corporation [Member]
Nature Of Business [Line Items]
Milestone payment received		$ 417		$ 209
Upfront and milestone payments related to license agreement							$ 646												$ 1,190

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2015
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	8 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	7 years
Software [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	3 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, description	Lesser of 10 years or life of lease

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)Segments	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policies [Line Items]
Royalty revenue	$ 0
Prepaid R&D expense	$ 1,500,000	$ 177,000
Expected dividend yield	0.00%	0.00%
Number of operating segments | Segments	1
Nonemployee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Maximum contractual life	10 years	10 years
Nonemployee Options [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Maximum contractual life	10 years

Available-for-Sale Marketable48

Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 91,675
Gross Unrealized Gains	5
Gross Unrealized Losses	(40)
Estimated Fair Value	91,640
Money Market Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,017
Gross Unrealized Losses	(31)
Estimated Fair Value	41,986
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,528
Estimated Fair Value	2,528
Other U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,492
Gross Unrealized Gains	4
Estimated Fair Value	13,496
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,194
Gross Unrealized Losses	(6)
Estimated Fair Value	14,188
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,444
Gross Unrealized Gains	1
Gross Unrealized Losses	(3)
Estimated Fair Value	$ 19,442

Available-for-Sale Marketable49

Available-for-Sale Marketable Securities - Schedule of Fair Values and Amortized Cost of Marketable Debt Securities by Contractual Maturity (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Investments, Debt and Equity Securities [Abstract]
Fair value of marketable debt securities, contractual maturity, Less than one year	$ 49,653
Amortized Cost of marketable debt securities, contractual maturity, Less than one year	$ 49,657

Available-for-Sale Marketable50

Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	$ 57,132
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(40)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	57,132
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(40)
Money Market Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	30,985
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(31)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	30,985
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(31)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	14,187
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(6)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	14,187
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(6)
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	11,960
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(3)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	11,960
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (3)

Available-for-Sale Marketable51

Available-for-Sale Marketable Securities - Additional Information (Detail)	Dec. 31, 2015Position
Investments, Debt and Equity Securities [Abstract]
Number of available-for-sale marketable securities in unrealized loss positions	15

Accumulated Other Comprehensi52

Accumulated Other Comprehensive Income (Loss) - Summary of Changes in AOCI, Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Total Accumulated Other Comprehensive (Loss), Beginning Balance	$ 0
Other comprehensive loss before reclassifications	(35)
Amount reclassified from accumulated other comprehensive income	0
Net current period other comprehensive loss	(35)
Total Accumulated Other Comprehensive (Loss), Ending Balance	$ (35)

Prepaid Expenses - Additional I

Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 1,729	$ 287
Prepaid insurance	98	92
Prepaid R&D clinical costs	1,500	177
Other costs	35	$ 18
Prepaid rent	$ 96

Property and Equipment, Net - P

Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,280	$ 8,276
Less accumulated depreciation and amortization	7,017	6,192
Property and equipment, net	1,263	2,084
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	314	309
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	232	233
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	155	156
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	126	126
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,453	$ 7,453

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 839	$ 783	$ 789

Restricted Cash - Additional In

Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash balance	$ 700	$ 700
Shelton Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash balance	$ 700
Lease term	2,017
Stamford Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Lease term	2,023
Letter of credit, remaining amount	$ 769
Letter of credit, remaining amount after three years	$ 408

Accounts Payable and Accrued 57

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts payable	$ 1,965	$ 515
Accrued research projects	1,542	549
Accrued professional fees	371	266
Accrued compensation and benefits	1,204	504
Accrued other	186	112
Total	$ 5,268	$ 1,946

Convertible Promissory Notes -

Convertible Promissory Notes - Additional Information (Detail)	Aug. 28, 2013USD ($)shares	Feb. 28, 2013USD ($)shares	Dec. 31, 2012USD ($)$ / shares	Oct. 31, 2013USD ($)	Apr. 30, 2013USD ($)	Feb. 28, 2013USD ($)shares	Dec. 31, 2015Closings	Dec. 31, 2014shares	Dec. 31, 2013USD ($)shares	Dec. 31, 2012USD ($)$ / shares	Dec. 28, 2012USD ($)
Debt Instrument [Line Items]
Percentage of discount on conversion price	10.00%
Probability of closing a $10,000 equity offering before August 28, 2013					0.00%
Convertible promissory notes converted to Series D convertible preferred stock, Value									$ 3,888,000
Repayment of convertible promissory notes				$ 311,000					311,000
Deferred financing costs									117,000
Series D Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Convertible promissory notes converted to Series D convertible preferred stock, Shares | shares	2,692,291
Convertible promissory notes converted to Series D convertible preferred stock, Value	$ 3,888,000
Maruishi License Agreement [Member]
Debt Instrument [Line Items]
Amount received in connection with Maruishi transaction					$ 23,000,000
Optional Conversion Feature [Member]
Debt Instrument [Line Items]
Debt conversion feature, description							The optional conversion feature allowed the Note holder, any time prior to the Maturity Date, to elect to convert the balance of the note plus accrued interest into Series D convertible preferred stock at a conversion price of $1.444244 per share.
Amortization of debt discount to interest expense									3,407,000	$ 25,000
Optional Conversion Feature [Member] | Series D Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Conversion price per share | $ / shares			$ 1.444244							$ 1.444244
Estimated fair value of preferred stock | $ / shares			$ 2.61
Mandatory Conversion Feature [Member]
Debt Instrument [Line Items]
Debt conversion feature, description							The mandatory conversion of the Notes would have occurred in the event the Company issued or sold equity securities on or before August 28, 2013 of not less than $10,000. In this event, the Notes plus all accrued interest would have automatically converted into the issued class of equity securities at a price per share equal to 90% of the cash price paid by the investors in the new equity securities.
Latest date equity securities issued for mandatory conversion							Aug. 28, 2013
Conversion condition, value of shares issued	$ 10,000,000
Amount in which promissory notes are converted as a percentage of the price paid by new investors	90.00%
Beneficial Conversion Feature on Convertible Promissory Notes [Member]
Debt Instrument [Line Items]
Debt, face amount		$ 1,462,000				$ 1,462,000			$ 4,000,000		$ 2,538,000
Number of closings | Closings							2
Debt, maturity date							Aug. 28, 2013
Debt, initial closing date							Dec. 28, 2012
Debt, final closing date							Feb. 28, 2013
Debt, interest rate		8.00%				8.00%
Fair value of liability					$ 0
Beneficial Conversion Feature on Convertible Promissory Notes [Member] | Optional Conversion Feature [Member]
Debt Instrument [Line Items]
Beneficial conversion feature		$ 1,382,000								$ 2,050,000
Beneficial Conversion Feature on Convertible Promissory Notes [Member] | Mandatory Conversion Feature [Member]
Debt Instrument [Line Items]
Fair value of liability			$ 41,000							$ 41,000
Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Preferred stock converted to common shares | shares		2,246,743				2,246,743		(29,186,929)	(2,246,743)
Carrying value of convertible preferred stock									$ 4,466,000
Common Stock [Member]
Debt Instrument [Line Items]
Preferred stock converted to common shares | shares		959,545				959,545		12,554,171	959,545
Fair value of common stock issued									$ 3,575,000
Accumulated Deficit [Member]
Debt Instrument [Line Items]
Gain on conversion of preferred stock to common stock									$ 891,000

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jul. 31, 2014	Apr. 30, 2013	Sep. 30, 2007	Dec. 31, 2015	Dec. 31, 2013	Sep. 04, 2012
Debt Instrument [Line Items]
Repayment of long-term debt					$ 307
Exercise price, per share			$ 10.08
Number of shares to be purchased under warrant			19,851
Warrant exercise date				Jul. 31, 2014
Common stock issued in result of warrants exercise	6,383
Term Loan [Member]
Debt Instrument [Line Items]
Debt, face amount			$ 4,000
Debt, interest rate			7.00%			8.50%
Debt, frequency of periodic payments				Monthly installments over five years
Debt, payment period			5 years
Debt, default description				If the Company failed to maintain its Connecticut presence, all amounts due under the Loan would be immediately due and payable with the cumulative interest rate increasing to 25%.
Debt, cumulative interest rate			25.00%
Repayment of long-term debt		$ 307

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail)	Feb. 28, 2013shares	Feb. 05, 2014shares	Sep. 30, 2013shares	Feb. 28, 2013shares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014shares	Dec. 31, 2013USD ($)$ / sharesshares	Apr. 30, 2013USD ($)shares	Dec. 31, 2012USD ($)shares
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued		29,186,929			0	0	29,186,929		26,636,118
Convertible Preferred stock, shares outstanding		29,186,929			0	0	29,186,929		26,636,118
Conversion of stock, shares issued		12,554,171
IPO closing date					Feb. 5, 2014
Liquidation preference | $							$ 65,969,000		$ 58,530,000
Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred stock converted to common shares	2,246,743			2,246,743		(29,186,929)	(2,246,743)
Convertible promissory notes converted to Series D convertible preferred stock, Shares							2,692,291
Convertible Preferred stock, shares outstanding							29,186,929		26,636,118
Dividends declared or paid | $					$ 0
Common Stock [Member]
Temporary Equity [Line Items]
Preferred stock converted to common shares	959,545			959,545		12,554,171	959,545
Junior Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							173,611		173,611
Convertible Preferred stock, shares outstanding							173,611		173,611
Liquidation preference | $							$ 500,000		$ 500,000
Preferred stock to common stock conversion ratio							0.4
Junior A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							2,105,263
Convertible Preferred stock, shares outstanding							2,105,263
Liquidation preference | $							$ 8,000,000
Preferred stock to common stock conversion ratio							0.4
Junior A Convertible Preferred Stock [Member] | Maruishi Pharmaceutical Co., Ltd. [Member] | Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued								2,105,263
Convertible Preferred stock, estimated fair value | $								$ 7,663,000
Series D Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							12,045,574		10,386,057
Convertible promissory notes converted to Series D convertible preferred stock, Shares			2,692,291
Convertible Preferred stock, shares outstanding							12,045,574		10,386,057
Liquidation preference | $							$ 17,397,000		$ 15,000,000
Preferred stock to common stock conversion ratio							0.4
Minimum percentage of stock required for conversion of outstanding Preferred Stock to common stock					67.00%
Series D Convertible Preferred Stock [Member] | Maximum [Member]
Temporary Equity [Line Items]
Liquidation preference | $							$ 70,000,000
Liquidation preference per share | $ / shares							$ 4.332732
Series C Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							10,930,946		11,706,450
Convertible Preferred stock, shares outstanding							10,930,946		11,706,450
Liquidation preference | $							$ 33,886,000		$ 36,290,000
Preferred stock to common stock conversion ratio							0.473282
Series B Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							2,254,417		2,370,000
Convertible Preferred stock, shares outstanding							2,254,417		2,370,000
Liquidation preference | $							$ 4,509,000		$ 4,740,000
Preferred stock to common stock conversion ratio							0.434782
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible Preferred stock, shares issued							1,677,118		2,000,000
Convertible Preferred stock, shares outstanding							1,677,118		2,000,000
Liquidation preference | $							$ 1,677,000		$ 2,000,000
Preferred stock to common stock conversion ratio							0.4

Convertible Preferred Stock - S

Convertible Preferred Stock - Schedule of Convertible Preferred Stock (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Feb. 05, 2014	Dec. 31, 2013	Dec. 31, 2012
Temporary Equity [Line Items]
Preferred Shares Authorized				29,402,200	26,636,118
Preferred Shares Issued	0	0	29,186,929	29,186,929	26,636,118
Preferred Shares Outstanding	0	0	29,186,929	29,186,929	26,636,118
Liquidation preference				$ 65,969	$ 58,530
Carrying Value				$ 65,586	$ 58,522
Common Stock Issuable Upon Conversion				12,554,171	11,594,757
Junior Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				173,611	173,611
Preferred Shares Issued				173,611	173,611
Preferred Shares Outstanding				173,611	173,611
Liquidation preference				$ 500	$ 500
Carrying Value				$ 354	$ 354
Common Stock Issuable Upon Conversion				69,444	69,444
Junior A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				2,105,263
Preferred Shares Issued				2,105,263
Preferred Shares Outstanding				2,105,263
Liquidation preference				$ 8,000
Carrying Value				$ 7,642
Common Stock Issuable Upon Conversion				842,105
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				1,677,118	2,000,000
Preferred Shares Issued				1,677,118	2,000,000
Preferred Shares Outstanding				1,677,118	2,000,000
Liquidation preference				$ 1,677	$ 2,000
Carrying Value				$ 1,677	$ 2,000
Common Stock Issuable Upon Conversion				670,830	800,000
Series B Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				2,254,417	2,370,000
Preferred Shares Issued				2,254,417	2,370,000
Preferred Shares Outstanding				2,254,417	2,370,000
Liquidation preference				$ 4,509	$ 4,740
Carrying Value				$ 4,509	$ 4,740
Common Stock Issuable Upon Conversion				980,163	1,030,434
Series C Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				10,930,946	11,706,450
Preferred Shares Issued				10,930,946	11,706,450
Preferred Shares Outstanding				10,930,946	11,706,450
Liquidation preference				$ 33,886	$ 36,290
Carrying Value				$ 33,886	$ 36,290
Common Stock Issuable Upon Conversion				5,173,413	5,540,457
Series D Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized				12,260,845	10,386,057
Preferred Shares Issued				12,045,574	10,386,057
Preferred Shares Outstanding				12,045,574	10,386,057
Liquidation preference				$ 17,397	$ 15,000
Carrying Value				$ 17,518	$ 15,138
Common Stock Issuable Upon Conversion				4,818,216	4,154,422

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 04, 2015	Dec. 01, 2014	Jan. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Jul. 29, 2015
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized				100,000,000	100,000,000
Common stock, par value				$ 0.001	$ 0.001
Preferred stock, shares authorized				5,000,000	5,000,000
Preferred stock, par value				$ 0.001	$ 0.001
Common stock, shares outstanding				27,254,863	22,802,039
Preferred stock, shares issued				0	0
Preferred stock, shares outstanding				0	0
Common stock, shares issued			5,750,000
Aggregate gross offering proceeds			$ 63,250
Net proceeds as a result of IPO			56,297		$ 57,762
Underwriting discounts and commissions			$ 6,953
Common stock, shares issued				27,254,863	22,802,039
Chief Medical Officer [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued		11,442
Public offering price per share		$ 8.74
Gross proceeds of common stock		$ 100
Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued						3,763,440
Follow On Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share				$ 18.60
Net proceeds from offering of common stock	$ 75,231			$ 75,231
Follow On Public Offering [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	3,763,440			4,327,956
Public offering price per share	$ 18.60
Net proceeds from offering of common stock				$ 4
Underwriters [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	564,516
Initial Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share			$ 11		$ 11
Net proceeds from offering of common stock					$ 56,297
Initial Public Offering [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued					5,750,000
Net proceeds from offering of common stock					$ 6

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial assets
Available-for-sale marketable securities	$ 91,640
Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	14,188
Recurring [Member]
Financial assets
Total financial assets	107,441	$ 53,363
Recurring [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	14,188
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Total financial assets	15,801	53,363
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Total financial assets	91,640
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	14,188
Recurring [Member] | Money Market Mutual Funds [Member]
Financial assets
Cash and cash equivalents	15,101	52,663
Available-for-sale marketable securities	41,986
Recurring [Member] | Money Market Mutual Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Cash and cash equivalents	15,101	52,663
Recurring [Member] | Money Market Mutual Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	41,986
Recurring [Member] | Commercial Paper [Member]
Financial assets
Available-for-sale marketable securities	19,442
Recurring [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	19,442
Recurring [Member] | Other U.S. Government Agency Obligations [Member]
Financial assets
Available-for-sale marketable securities	13,496
Recurring [Member] | Other U.S. Government Agency Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	13,496
Recurring [Member] | U.S. Treasury Securities [Member]
Financial assets
Available-for-sale marketable securities	2,528
Recurring [Member] | U.S. Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	2,528
Recurring [Member] | Bank Certificate of Deposit [Member]
Financial assets
Restricted cash	700	700
Recurring [Member] | Bank Certificate of Deposit [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Restricted cash	$ 700	$ 700

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)Securities	Dec. 31, 2014USD ($)Securities	Dec. 31, 2013USD ($)Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases of financial assets	$ 0	$ 0	$ 0
Sales of financial assets	0	0	0
Maturities of financial assets	$ 0	$ 0	$ 0
Transfers of financial assets between Levels 1, 2, or 3 classifications | Securities	0	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains	$ 0	$ 0	$ 0
Unrealized losses	$ 0	$ 0	$ 0

Collaborations - Additional Inf

Collaborations - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended							12 Months Ended
	Oct. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Aug. 31, 2015USD ($)	Aug. 31, 2014USD ($)	Jun. 30, 2014USD ($)	Apr. 30, 2013USD ($)$ / sharesshares	Apr. 30, 2012USD ($)shares	Dec. 31, 2015USD ($)Deliverablesshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)shares	Dec. 31, 2012USD ($)shares	Feb. 05, 2014shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and milestone fee revenue								$ 1,710	$ 302	$ 9,637
Deferred R&D service revenue									1,452
Collaborative revenue								2,093	2,201	2,225
Clinical compound revenue								$ 0	$ 674	$ 102
Issuance of convertible preferred stock | shares								0	0	29,186,929	26,636,118	29,186,929
Research and development expense								$ 21,221	$ 15,068	$ 8,685
Junior Convertible Preferred Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of convertible preferred stock | shares										173,611	173,611
Junior A Convertible Preferred Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of convertible preferred stock | shares										2,105,263
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront non-refundable, non-creditable license fee						$ 15,000
License and milestone fee revenue								$ 1,084
Milestone payment received				$ 480
Number of deliverables for revenue recognized | Deliverables								2
Value of arrangement						15,337
Deferred R&D service revenue								$ 0	1,452
Revenue recognized from nonsubstantive milestones								8,000
Revenue recognized from substantive milestones								2,500
Non-refundable contingent payment					$ 480
Collaborative revenue								641
Amount due from milestone payments net of contractual foreign currency exchange adjustments		$ 1,725
Contractual foreign currency exchange adjustments		$ 275
Stock purchase agreement, purchase price of preferred stock						8,000
Stock purchase agreement, purchase price fair value of preferred stock						$ 7,663
Stock purchase agreement, purchase price fair value of preferred stock per share | $ / shares						$ 3.64
Stock purchase agreement, purchase price premium of preferred stock						$ 337
Clinical trial costs related to the R&D services deliverable								1,583	3,000	$ 2,420
Research and development expense									3,558	2,452
Cost of clinical compound sold to Maruishi									$ 558	$ 32
Maruishi Pharmaceutical Co., Ltd. [Member] | Junior A Convertible Preferred Stock [Member] | Convertible Preferred Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of convertible preferred stock | shares						2,105,263
Stock purchase agreement, purchase price of preferred stock per share | $ / shares						$ 3.80
Maruishi Pharmaceutical Co., Ltd. [Member] | Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Next potential milestone that could be received								1,000
Maruishi Pharmaceutical Co., Ltd. [Member] | License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and milestone fee revenue					302	$ 9,637
Estimated selling price						10,200
Maruishi Pharmaceutical Co., Ltd. [Member] | R & D Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Estimated selling price						6,200
Deferred R&D service revenue					90	$ 5,700
Collaborative revenue					$ 88
Chong Kun Dang Pharmaceutical Corporation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront non-refundable, non-creditable license fee							$ 1,000
Milestone payments receivable							3,750
License and milestone fee revenue							$ 646				$ 1,190
Milestone payment received	$ 417		$ 209
South Korean Withholding tax	$ 83		$ 41
Next potential milestone that could be received								$ 750
Chong Kun Dang Pharmaceutical Corporation [Member] | Junior Convertible Preferred Stock [Member] | Convertible Preferred Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of convertible preferred stock, Shares | shares							173,611
Issuance of convertible preferred stock, Value							$ 354
Chong Kun Dang Pharmaceutical Corporation [Member] | Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable							2,250
Chong Kun Dang Pharmaceutical Corporation [Member] | Regulatory Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable							$ 1,500

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 01, 2016	Jan. 01, 2015	Sep. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options vested	$ 2,489	$ 393	$ 75
Intrinsic value of options exercised	$ 1,748	$ 2,055	$ 0
Options granted	774,000	884,000	0
Compensation expense not yet recognized	$ 7,036
Weighted average period of compensation expense not yet recognized	2 years 11 months 23 days
Employees, Non-employee Members of Board of Directors and Non-employee consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options granted	$ 7.17	$ 7.09
Nonemployee Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair values of outstanding unvested options	$ 10.05	$ 10.77	$ 6.54
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options that may be granted after the tenth anniversary of the 2014 Plan	0
Annual increases in number of shares reserved for issuance as a percentage of shares of capital stock outstanding through January 1, 2024	3.00%
Share-based compensation arrangement by share-based payment award, number of shares authorized		1,600,000			2,284,061
Options granted	774,000
2014 Equity Incentive Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized				3,101,707
2014 Equity Incentive Plan [Member] | Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date	25.00%
2014 Equity Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted	36 months
2014 Equity Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards granted	10 years
2014 Equity Incentive Plan [Member] | Incentive Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized	30,000,000
2004 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance						0	0
2004 Stock Incentive Plan [Member] | Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date	25.00%
2004 Stock Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted	36 months
2004 Stock Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards granted	10 years

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Granted	774,000	884,000	0
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding at December 31, 2014	1,022,360
Number of Options, Granted	774,000
Number of Options, Exercised	(124,868)
Number of Options, Expired	(8,000)
Number of Options, Forfeited	(5,084)
Number of Options, Outstanding at December 31, 2015	1,658,408	1,022,360
Number of Options, Outstanding, Weighted average remaining contractual life as of December 31, 2015	8 years 3 months 22 days
Number of Options, Options exercisable at December 31, 2015	510,298
Number of Options, Exercisable, Weighted average remaining contractual life as of December 31, 2015	6 years 7 months 2 days
Number of Options, Options vested and expected to vest at December 31, 2015	1,574,746
Number of Options, Vested and expected to vest, Weighted average remaining contractual life as of December 31, 2015	8 years 3 months 4 days
Weighted-Average Exercise Price, Outstanding at December 31, 2014	$ 8.16
Weighted-Average Exercise Price, Granted	11.77
Weighted-Average Exercise Price, Exercised	2.89
Weighted-Average Exercise Price, Expired	0.25
Weighted-Average Exercise Price, Forfeited	10.45
Weighted-Average Exercise Price, Outstanding at December 31, 2015	10.27	$ 8.16
Weighted-Average Exercise Price, Options exercisable at December 31, 2015	7.78
Weighted-Average Exercise Price, Options vested and expected to vest at December 31, 2015	$ 10.14
Aggregate Intrinsic Value, Outstanding at December 31, 2015	$ 11,058
Aggregate Intrinsic Value, Options exercisable at December 31, 2015	4,634
Aggregate Intrinsic Value, Options vested and expected to vest at December 31, 2015	$ 10,693

Stock-Based Compensation - Su68

Stock-Based Compensation - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.43%	1.64%
Risk-free interest rate, maximum	1.89%	2.72%
Expected volatility, minimum	64.00%	64.90%
Expected volatility, maximum	67.40%	71.30%
Expected dividend yield	0.00%	0.00%
Employee and Board of Directors Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	6 years 3 months	6 years 3 months
Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	10 years	10 years

Stock-Based Compensation - Su69

Stock-Based Compensation - Summary of Re-measurement of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.43%	1.64%
Risk-free interest rate, maximum	1.89%	2.72%
Expected volatility, minimum	64.00%	64.90%
Expected volatility, maximum	67.40%	71.30%
Expected dividend yield	0.00%	0.00%
Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	10 years	10 years
Maximum [Member] | Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	10 years
Re-Measurement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.81%	1.96%	2.50%
Risk-free interest rate, maximum	2.15%	2.72%	3.20%
Expected volatility, minimum	70.60%	69.00%	71.00%
Expected volatility, maximum	72.20%	71.00%	72.00%
Expected dividend yield	0.00%	0.00%	0.00%
Re-Measurement [Member] | Minimum [Member] | Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	8 years 1 month 6 days	6 years	1 year 6 months
Re-Measurement [Member] | Maximum [Member] | Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	8 years 9 months 18 days	10 years	7 years

Stock-Based Compensation - Su70

Stock-Based Compensation - Summary of Compensation Expense Relating to Stock Options (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 2,514	$ 1,371	$ 123
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	1,073	349	71
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 1,441	$ 1,022	$ 52

Income Taxes - Components of In

Income Taxes - Components of Income Taxes (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 0	$ 0	$ 0
State	(397)	(201)	(30)
Total Current	(397)	(201)	(30)
Deferred:
Federal	0	0	0
State	0	0	0
Total Deferred	0	0	0
Benefit from income taxes	$ (397)	$ (201)	$ (30)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Percentage of annual research and development credit for cash			65.00%
Valuation allowance on the deferred tax asset	100.00%	100.00%
Change in valuation allowance			$ 10,317,000	$ 7,156,000
Tax benefit on exercise of non-qualified stock options and disqualified disposition of incentive stock options			839,000
Unrecognized tax benefits	$ 0	$ 0	$ 0	$ 0
Unrecognized tax benefits, related interest and penalties	0	$ 0
Tax examinations, description			Tax years 2007 through 2015 remain open to U.S. federal and state tax examinations.
Earliest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2,007
Latest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2,015
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	95,900,000		$ 95,900,000
Federal [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2,026
Federal [Member] | Research and Development Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	3,642,000		$ 3,642,000
Federal [Member] | Research and Development Tax Credit Carryforward [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax credit expiration year			2,025
State and Local [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	89,899,000		$ 89,899,000
State and Local [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2,027
State and Local [Member] | Research and Development Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 707,000		$ 707,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Income Taxes Computed Using U.S. Federal Statutory Rate to that Reflected in Operations (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income taxes using U.S. federal statutory rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit	5.95%	5.23%	6.03%
Impact of R&D tax credit on effective tax rate	3.14%	3.03%	12.04%
Stock option shortfalls and cancellations	(0.03%)	(0.69%)	0.00%
Permanent items and other	(0.41%)	(0.57%)	(1.42%)
Change in valuation allowance	(41.07%)	(39.88%)	(49.90%)
Total	1.58%	1.12%	0.75%

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 36,217	$ 27,094
Federal and state tax credits	4,315	3,508
Accelerated depreciation	1,206	1,018
Deferred revenue		566
Stock-based compensation expense	1,106	333
Other	189	197
Gross deferred tax asset	43,033	32,716
Valuation allowance	(43,033)	(32,716)
Net deferred tax asset	$ 0	$ 0

License and Research Agreement

License and Research Agreement - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands

Apr. 01, 2005

Dec. 31, 2015

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2009

Dec. 31, 2008

Dec. 31, 2007

Dec. 31, 2006

Dec. 31, 2005

Feb. 05, 2014

Research and Development Assets Acquired Other than Through Business Combination [Line Items]

IPO closing date

Feb. 5, 2014

Glasgow License Agreement [Member]

Research and Development Assets Acquired Other than Through Business Combination [Line Items]

Issuance of common stock as compensation

200,000

Guarantee return on common stock issued as compensation

$ 1,000

Fair value of liability

$ 0

Probability factor percentage

10.00%

10.00%

10.00%

10.00%

10.00%

10.00%

10.00%

10.00%

10.00%

Decrease in fair value of liability

$ (35)

Public offering price in the IPO

$ 11

IPO closing date

Feb. 5, 2014

Net Loss per Share - Computatio

Net Loss per Share - Computation of Denominators Used in Net Loss per Share Available to Common Stockholders (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic:
Weighted average shares outstanding	24,620,372	20,965,935	4,133,138
Diluted:
Weighted average shares outstanding - Basic	24,620,372	20,965,935	4,133,138
Convertible preferred stock	0	0	0
Common stock options	0	0	0
Common stock warrants	0	0	0
Convertible promissory notes (as converted)	0	0	0
Denominator for diluted net loss per share available to common stockholders	24,620,372	20,965,935	4,133,138

Net Loss per Share - Computat77

Net Loss per Share - Computation of Basic and Diluted Net Loss per Share Available to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	$ (4,172)	$ (6,545)	$ (3,645)	$ (3,383)	$ (24,690)	$ (17,745)	$ (3,963)
Add back: extinguishment of preferred shares											891
Net loss available to common stockholders - Basic and Diluted									$ (24,690)	$ (17,745)	$ (3,072)
Weighted-average common shares outstanding available to common stockholders
Basic and Diluted									24,620,372	20,965,935	4,133,138
Net loss per share available to common stockholders:
Basic and Diluted									$ (1)	$ (0.85)	$ (0.74)

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Anti-Dilutive Common Stock Equivalents Excluded from Calculations of Diluted Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	1,658,408	1,022,360	490,160
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents			19,851
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents			12,554,171

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Warrant exercise date	Jul. 31, 2014

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - Consulting Agreement [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Related party transaction, total expenses	$ 164	$ 169	$ 134
Related party transaction, due to stockholder	$ 21	$ 35

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2015	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Defined contribution retirement plan, description		All employees over the age of 21 are eligible to participate in the plan after three consecutive months of service.
Employer contributions to the plan		$ 80
Defined contribution retirement plan, employer contribution percentage	3.00%
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution retirement plan, employee eligible age to participate		21 years
Defined contribution retirement plan, employee eligible service period		3 months

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	5 Months Ended	12 Months Ended
	May. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Shelton Operating Lease [Member]
Other Commitments [Line Items]
Operating lease, expiration date		Oct. 13, 2017
Incentive allowance received		$ 2,127,000
Unamortized incentive allowance		374,000	$ 582,000
Accrued rent		211,000	292,000
Operating lease, rent expense		665,000	$ 643,000	$ 616,000
Shelton Operating Lease [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, amount		$ 2,170,000
Letter of credit, expiration date		May 31, 2017
Amounts of drawings against letter of credit		$ 0
Letter of credit, annual reduction from 2008 to 2012					$ 294,000
Letter of credit, remaining amount					$ 700,000
Shelton Operating Lease [Member] | Minimum [Member]
Other Commitments [Line Items]
Term of lease		10 years
Stamford Operating Lease [Member]
Other Commitments [Line Items]
Incentive allowance received		$ 1,021,000
Term of lease		7 years 6 months
Additional amortization expense		$ 67,000
Operating Lease, description		The Stamford Lease commences upon completion of renovations to the Premises, which is expected to be in May 2016 (the "Commencement Date"), and ends 90 months thereafter. The Stamford Lease requires monthly lease payments, including rent escalations and rent holidays, during the initial lease term. The Company will begin to make rental payments from the Commencement Date. The Stamford Lease is renewable for one five-year term.
Operating Lease, renewable term		5 years
Stamford Operating Lease [Member] | From January through May 2016 [Member]
Other Commitments [Line Items]
Additional amortization expense	$ 899,000
Stamford Operating Lease [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, amount		$ 769,000
Letter of credit, expiration date		Dec. 16, 2016
Operating lease, renewable term description		Automatically renewed annually through November 1, 2023
Stamford Operating Lease [Member] | Maximum [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, renewal date		Nov. 1, 2023

Commitments and Contingencies83

Commitments and Contingencies - Schedule of Future Minimum Rental Payments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Stamford Operating Lease [Member]
Operating Leased Assets [Line Items]
2,016	$ 288
2,017	875
2,018	1,093
2,019	1,217
2,020	1,241
Thereafter	3,650
Total	8,364
Shelton Operating Lease [Member]
Operating Leased Assets [Line Items]
2,016	913
2,017	740
Total	$ 1,653

Quarterly Results of Operatio84

Quarterly Results of Operations - Schedule of Selected Financial Data for Each Quarter (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues		$ 2,440	$ 874	$ 489	$ 914	$ 1,125	$ 960	$ 178	$ 3,803	$ 3,177	$ 11,964
Net loss - Basic and Diluted	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	$ (4,172)	$ (6,545)	$ (3,645)	$ (3,383)	$ (24,690)	$ (17,745)	$ (3,963)
Loss per share - Basic and Diluted	$ (0.35)	$ (0.19)	$ (0.25)	$ (0.21)	$ (0.18)	$ (0.29)	$ (0.16)	$ (0.22)	$ (1)	$ (0.85)	$ (0.74)