Cara Therapeutics (CARA) 10-K 10 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Mar. 03, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
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		27,303,321
Entity Public Float			$ 102,480,638

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 12,092	$ 15,101
Marketable securities	46,184	91,640
Income tax receivable	852	384
Other receivables	87	80
Prepaid expenses	1,530	1,729
Restricted cash, current	700
Total current assets	61,445	108,934
Property and equipment, net	1,614	1,263
Restricted cash	769	700
Total assets	63,828	110,897
Current liabilities:
Accounts payable and accrued expenses	11,533	5,268
Total current liabilities	11,533	5,268
Deferred lease obligation	1,570	585
Commitments and contingencies (Note 19)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at December 31, 2016 and December 31, 2015; zero shares issued and outstanding at December 31, 2016 and December 31, 2015
Common stock; $0.001 par value; 100,000,000 shares authorized at December 31, 2016 and December 31, 2015; 27,296,863 shares and 27,254,863 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively	27	27
Additional paid-in capital	212,866	209,943
Accumulated deficit	(162,171)	(104,891)
Accumulated other comprehensive income (loss)	3	(35)
Total stockholders' equity	50,725	105,044
Total liabilities and stockholders' equity	$ 63,828	$ 110,897

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	27,296,863	27,254,863
Common stock, shares outstanding	27,296,863	27,254,863

Statements of Comprehensive Los

Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
License and milestone fees		$ 1,710	$ 302
Collaborative revenue		2,093	2,201
Clinical compound revenue	$ 86	0	674
Total revenue	86	3,803	3,177
Operating expenses:
Research and development	49,253	21,221	15,068
General and administrative	9,233	7,770	6,181
Total operating expenses	58,486	28,991	21,249
Operating loss	(58,400)	(25,188)	(18,072)
Other income	652	101	126
Loss before benefit from income taxes	(57,748)	(25,087)	(17,946)
Benefit from income taxes	468	397	201
Net loss	$ (57,280)	$ (24,690)	$ (17,745)
Net loss per share:
Basic and Diluted	$ (2.10)	$ (1)	$ (0.85)
Weighted average shares:
Basic and Diluted	27,279,008	24,620,372	20,965,935
Other comprehensive income (loss), net of tax of $0:
Change in unrealized gains (losses) on available for sale marketable securities	$ 38	$ (35)
Total comprehensive loss	$ (57,242)	$ (24,725)	$ (17,745)

Statements of Comprehensive Lo5

Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Other comprehensive income (loss), tax	$ 0	$ 0	$ 0

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	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 Income (Loss) [Member]	Convertible Preferred Stock [Member]
Balance, Value at Dec. 31, 2013															$ 65,586
Balance, Value at Dec. 31, 2013	$ (54,075)				$ 4				$ 8,377				$ (62,456)
Sale of common stock, net of underwriting discounts and commissions and offering expenses, Value		$ 56,297	$ 100			$ 6				$ 56,291	$ 100
Balance, Shares at Dec. 31, 2013															29,186,929
Balance, Shares at Dec. 31, 2013					4,288,243
Sale of common stock, net of underwriting discounts and commissions and offering expenses, 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
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
Sale of common stock, net of underwriting discounts and commissions and offering expenses, Value				$ 75,231				$ 4				$ 75,227
Sale of common stock, net of underwriting discounts and commissions and offering expenses, 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
Stock-based compensation expense	$ 2,800								2,800
Shares issued upon exercise of stock options, Value	123								123
Shares issued upon exercise of stock options, Shares					42,000
Net loss	(57,280)												(57,280)
Other comprehensive income (loss)	38													38
Balance, Value at Dec. 31, 2016	$ 50,725				$ 27				$ 212,866				$ (162,171)	$ 3
Balance, Shares at Dec. 31, 2016	0
Balance, Shares at Dec. 31, 2016					27,296,863

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, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (57,280)	$ (24,690)	$ (17,745)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,800	2,514	1,371
Depreciation & amortization	1,465	839	783
Amortization/accretion of available-for-sale marketable securities	(218)	(18)
Realized gain on sale of available-for-sale marketable securities	(23)
Deferred rent costs	(114)	(289)	(265)
Loss on write-off of fixed assets		2
Changes in operating assets and liabilities:
Income tax receivable	(468)	(184)	(139)
Other receivables	(7)	(80)
Prepaid expenses	199	(1,442)	388
Accounts payable and accrued expenses	6,265	3,322	(12)
Deferred revenue		(1,452)	(2,023)
Net cash used in operating activities	(47,381)	(21,478)	(17,642)
Investing activities
Proceeds from maturities of available-for-sale marketable securities	80,380
Proceeds from sale of available-for-sale marketable securities	34,003
Purchase of available-for-sale marketable securities	(68,648)	(91,657)
Change in restricted cash	(769)
Purchases of property and equipment	(717)	(20)	(42)
Net cash provided by (used in) investing activities	44,249	(91,677)	(42)
Financing activities
Proceeds from sale of common stock			100
Proceeds from the exercise of stock options	123	362	128
Proceeds from initial public offering, net of issuance costs			57,762
Net cash provided by financing activities	123	75,593	57,990
Net cash (decrease) increase for the period	(3,009)	(37,562)	40,306
Cash and cash equivalents at beginning of period	15,101	52,663	12,357
Cash and cash equivalents at end of period	12,092	15,101	52,663
Noncash financing activities
Conversion of convertible preferred stock to common stock			65,586
Reclassification of prepaid IPO costs paid in 2013			$ 1,465
Tenant improvements paid by landlord	$ 1,094
Follow On Offering [Member]
Financing activities
Proceeds from follow-on offering, net of issuance costs		$ 75,231

Business

Business	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	1. Business Cara Therapeutics, Inc., or 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, 2016, 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 Stockholders’ Equity Collaborations As of December 31, 2016, the Company had unrestricted cash and cash equivalents and marketable securities of $58,276 and an accumulated deficit of $162,171. 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 $57,280 and had net cash used in operating activities of $47,381 for the year ended December 31, 2016. 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, or 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, 2016
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 or 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 non-cash non-employees 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 are 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 and cash equivalents and marketable securities are held by three 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 and other investments with original maturities of three months or less. 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 available-for-sale The Company reviews its available-for-sale If a decline in the fair value of an available-for-sale 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 Current accounting guidance defines fair value, establishes a framework for measuring fair value in accordance with Accounting Standards Codification, or 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 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, U.S. government agency obligations, corporate bonds, commercial paper and money market funds with similar underlying investments 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 third-party pricing services. 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, or December 31, 2016. 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 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 R&D 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 identification of individual elements in a multiple-element arrangement and the estimation of the selling price of each element involves significant judgment, including evaluation as to whether each delivered element has standalone value. 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. The Company has determined that its R&D services deliverables, as applicable, represent separate units of accounting because similar services are sold separately by other vendors. The Company determines the estimated selling price for deliverables within each agreement using vendor specific objective evidence, or VSOE, of selling price, if available, or third party evidence, or 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. Arrangement consideration allocated to R&D 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’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, or 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. R&D expenses include, among other costs, salaries and other personnel-related costs, including consultant costs, and costs to conduct clinical trials using CRO’s, which include upfront, milestone and monthly expenses as well as reimbursement for pass through costs. The amount of clinical trial expense recognized in any period varies depending on the duration and progress of each clinical trial, including the required level of patient enrollment, the rate at which patients actually enroll in and drop-out Non-refundable 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 non-employee non-employee Compensation Stock Compensation . non-employee 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 term), (iv) expected dividend yield on the Company’s common stock, and (v) risk-free interest rates. The Company’s common stock has been traded on a public exchange only since January 31, 2014. Since that time, exercises of stock options have been limited due to various factors, including fluctuations in the Company’s stock price to below the exercise prices of awards, blackout periods during which exercises are not allowed, among others. Therefore, the Company believes that as of December 31, 2016, it does not have sufficient company-specific information available to determine the expected term based on its historical data. As a result, the expected term 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 (6.25 years), an accepted method for the Company’s option grants under the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment. Similarly, since January 31, 2014, 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. As of January 1, 2017, the Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting Accounting Pronouncements Recently Adopted The Company accounts for options granted to non-employee 505-50, Equity-Based Payments to Non-Employees. non-employees non-employee 505-50, re-measurement 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 exercised during the period, when the effect is dilutive. Common stock equivalents may include outstanding stock options, which are included under the treasury stock method when dilutive. For each of the years ended December 31, 2016, 2015 and 2014, the Company excluded the effects of potentially dilutive shares that were outstanding during those respective periods from the denominator as their inclusion would be anti-dilutive due to the Company’s net losses during those periods. 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 as 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. Lease incentives made by landlords to or on behalf of the Company for leasehold improvements 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. Accounting Pronouncements Recently Adopted As of December 31, 2016, the Company adopted Accounting Standards Update, or ASU, 2014-15 Presentation of Financial Statements – Going Concern (Subtopic 205-40), 2014-15, 2014-15 2014-15 10-K As of January 1, 2017, the Company adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting 2016-09, Topic 718 Compensation – Stock Compensation 2016-09 2016-09 Recent Accounting Pronouncements Not Yet Adopted In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805), Clarifying the Definition of a Business, 2017-01 , 2017-01 2017-01 2017-01 2017-01 In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, 2016-20, 2016-20 2014-09. 2014-09. 2016-20 In November, 2016, the Financial Accounting Standards Board, or FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash 2016-18, beginning-of-period end-of-period 2016-18 2016-18 2016-18, In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments 2016-13, 2016-13 available-for-sale 2016-13 2016-13 In May 2016, the FASB issued ASU No. 2016-12 , Revenue from Contracts with Customers (Topic 606), Narrow-Scope Improvements and Practical Expedients 2016-12, No. 2014-09 Revenue from Contracts with Customers (Topic 606) 2014-09, 2016-12 2014-09, No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date 2015-14 . 2014-09, 2016-12 In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606), Identifying Performance Obligations and Licensing 2016-10 , 2016-10 2016-10 2016-10 2014-09, 2015-14. 2014-09, 2016-10 In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606), Principal versus Agent Considerations (Reporting Revenue Gross versus Net) 2016-08, 2014-09 2016-08 2014-09, 2015-14. 2014-09, 2016-08 In May 2014, the FASB issued ASU 2014-09 2014-09, 2014-09. The Company is currently accounting for those two contracts under ASC 605-25 605-28. 2016-08, 2016-10, 2016-12 2016-20, 605-25 605-28 In particular, regarding the CKD Agreement and the Maruishi Agreement, the following aspects of ASC 606, as amended, are the same as those under ASC 605-25 605-28. 605-28 ASU 2014-09, 2015-14, 2014-09 2014-09 2014-09

Available-for-Sale Marketable S

Available-for-Sale Marketable Securities	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Marketable Securities	3. Available-for-Sale As of December 31, 2016, and 2015, the Company’s available-for-sale The following tables summarize the Company’s available-for-sale As of December 31, 2016 Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Value Money market funds $ 8,268 $ 8 $ — $ 8,276 U.S. Treasury securities 2,523 — (1 ) 2,522 U.S. government agency obligations 3,501 1 — 3,502 Corporate bonds 16,683 — (6 ) 16,677 Commercial paper 15,206 3 (2 ) 15,207 Total available-for-sale $ 46,181 $ 12 $ (9 ) $ 46,184 As of December 31, 2015 Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Value Money market funds $ 42,017 $ — $ (31 ) $ 41,986 U.S. Treasury securities 2,528 — — 2,528 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 $ 91,675 $ 5 $ (40 ) $ 91,640 All available-for-sale The Company classifies its marketable debt securities based on their contractual maturity dates. As of December 31, 2016, the Company’s marketable debt securities mature at various dates through August 2017. 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 As of December 31, 2016 2015 Contractual maturity Amortized Cost Fair Value Amortized Cost Fair Value Less than one year $ 37,913 $ 37,908 $ 49,657 $ 49,653 During the year ended December 31, 2016, the Company sold shares of money market funds with a total fair value of $34,003 that were classified as available-for-sale available-for-sale The following tables show the fair value of the Company’s available-for-sale Less than 12 Months 12 Months or Greater Total As of December 31, 2016 Fair Value Gross Fair Gross Fair Gross U.S. Treasury securities $ 2,522 $ (1 ) $ — $ — $ 2,522 $ (1 ) Corporate bonds 9,919 (6 ) — — 9,919 (6 ) Commercial paper 5,227 (2 ) — — 5,227 (2 ) Total $ 17,668 $ (9 ) $ — $ — $ 17,668 $ (9 ) Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Gross Fair Gross Fair Gross Money market 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, 2016, and 2015, the Company held a total of 18 out of 34 positions and 14 out of 23 positions, respectively, 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

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	4. Accumulated Other Comprehensive Income (Loss) The following table summarizes the changes in accumulated other comprehensive income (loss), or AOCI, net of tax, from unrealized gains (losses) on available-for-sale Total Accumulated Other Comprehensive Income (Loss) 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 ) Other comprehensive loss before reclassifications 61 Amount reclassified from accumulated other comprehensive income (23 ) Net current period other comprehensive income 38 Balance, December 31, 2016 $ 3 The reclassifications out of AOCI and into net loss were as follows: Component of AOCI Year Ended December 31, 2016 2015 Affected Line Item in the Comprehensive Loss Unrealized gains (losses) on available-for-sale Realized gains on sale of securities $ 23 $ — Other income — — Income tax benefit $ 23 $ — Net of tax The amount reclassified out of AOCI into net loss was determined by specific identification.

Prepaid Expenses

Prepaid Expenses	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Prepaid Expenses	5. Prepaid Expenses As of December 31, 2016, the amount of prepaid expenses was $1,530, consisting of $1,256 of prepaid R&D clinical costs, $112 of prepaid insurance, and $162 of other costs. As of December 31, 2015, the amount of 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.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net Property and equipment, net consists of the following: December 31, 2016 2015 Computer and office equipment $ 149 $ 314 Laboratory equipment 795 232 Furniture and fixtures 173 155 Software — 126 Leasehold improvements 8,582 7,453 $ 9,699 $ 8,280 Less accumulated depreciation and amortization 8,085 7,017 Property and equipment, net $ 1,614 $ 1,263 Depreciation and amortization expense included in R&D expense and General and administrative expense was $1,465, $839 and $783 for the years ended December 31, 2016, 2015 and 2014, respectively. In connection with the Company’s relocation of its operating facility from Shelton, Connecticut to Stamford, Connecticut, the Company accelerated the amortization of the Shelton leasehold improvements during the period from December 2015 (signing of the Stamford lease) to May 2016 (the date that the Shelton facility was vacated) (see Note 19, Commitments and Contingencies wrote-off re-located

Restricted Cash

Restricted Cash	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Restricted Cash	7. Restricted Cash The Company is required to maintain stand-by Commitments and Contingencies The restricted cash balance for the Shelton lease remains at $700 through the end of the lease term in October 2017. 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 subsequently deposited 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 December 31, 2016, the Company had $700 of restricted cash related to the Shelton lease in current assets and $769 of restricted cash related to the Stamford lease in long-term assets. As of December 31, 2015, the Company had $700 of restricted cash related to the Shelton lease in long-term assets.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2016
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, 2016 2015 Accounts payable $ 4,738 $ 1,965 Accrued research projects 4,352 1,542 Accrued professional fees 163 371 Accrued compensation and benefits 1,514 1,204 Accrued other 766 186 $ 11,533 $ 5,268

Connecticut Innovations, Inc. S

Connecticut Innovations, Inc. Stock Warrant	12 Months Ended
	Dec. 31, 2016
Text Block [Abstract]
Connecticut Innovations, Inc. Stock Warrant	9. Connecticut Innovations, Inc. Stock Warrant In September 2007, the Company entered into a $4,000 term loan, or Loan, with Connecticut Innovations Inc., or CII, which was repaid 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. 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, 2016
Text Block [Abstract]
Convertible Preferred Stock	10. Convertible Preferred Stock Upon the closing of the Company’s IPO on February 5, 2014, all 29,186,929 shares of the Company’s convertible 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, 2016, 2015 and 2014, there were no shares of convertible preferred stock issued or outstanding. The former holders of shares of convertible 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, 2016
Equity [Abstract]
Stockholders' Equity	11. 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, 2016, there were 27,296,863 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 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, and were sold pursuant to an exemption from registration under such 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, or 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, or the Offering. The Offering was made pursuant to the Company’s Registration Statement on Form S-3 No. 333-203072), 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, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	12. Fair Value Measurements The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2016, and 2015 and by level within the fair value hierarchy: Fair value measurement as of December 31, 2016: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash and cash equivalents: Money market fund and checking accounts $ 12,092 $ 12,092 $ — $ — Available-for-sale Money market fund 8,276 — 8,276 — U.S. Treasury securities 2,522 — 2,522 — U.S. government agency obligations 3,502 — 3,502 — Corporate bonds 16,677 — 16,677 — Commercial paper 15,207 — 15,207 — Restricted cash: Money market fund 1,469 1,469 — — Total financial assets $ 59,745 $ 13,561 $ 46,184 $ — 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 fund, savings account and checking account $ 15,101 $ 15,101 $ — $ — Available-for-sale Money market funds 41,986 — 41,986 — U.S. Treasury securities 2,528 — 2,528 — 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 $ — 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

Collaborations

Collaborations	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	13. Collaborations Chong Kun Dang Pharmaceutical Corporation In April, 2012, the Company entered into a license agreement with CKD, or 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 non-creditable pre-defined 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 convertible preferred stock, which shares were automatically converted into 69,444 shares of common stock upon the closing of the Company’s initial public offering. 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 During the year ended December 31, 2015, the Company met the milestone criteria, as set forth in the CKD Agreement, for the completion of both a Phase 1b trial of Oral CR845 in the United States and a Phase 2 trial of CR845 in uremic pruritus patients in the United States. Both milestones were considered to be substantive and, therefore, the total amount of the milestone payments earned, $626 (net of South Korean withholding tax of $124), was recognized as milestone revenue upon achievement of the milestones, of which $417 (net of South Korean withholding tax of $83) was due to the Company as of December 31, 2015. The next potential milestone that the Company could be entitled to receive under the CKD Agreement will be a clinical development milestone for the listing in the South Korean National Health Insurance Program of I.V. CR845 for pain. If achieved, this milestone will result in a payment of $500, 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, or 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 Summary of Significant Accounting Policies – Revenue Recognition 605-25, 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 605-25. 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 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, 2016, 2015 and 2014, the Company recognized clinical compound revenue of $86, $0 and $674, 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 convertible 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 were 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). In connection with the Company’s IPO in 2014, all shares of Junior A convertible preferred stock were automatically converted into 842,105 shares of the Company’s common stock (see Note 11, Stockholders’ Equity, above). The Company incurred R&D expense related to the Maruishi Agreement of $0, $1,583 (consisting of clinical trial costs related to the R&D services deliverable) and $3,558 (consisting of $3,000 of clinical trial costs related to the R&D services deliverable and $558 related to the cost of clinical compound sold to Maruishi) during years ended December 31, 2016, 2015 and 2014, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	14. Stock-Based Compensation 2014 Equity Incentive Plan The Company’s 2014 Equity Incentive Plan, or the 2014 Plan, is administered by the Company’s Board of Directors or a duly authorized committee thereof, referred to as the Plan administrator. The 2014 Plan provides for the grant of incentive stock options, non-statutory non-employee non-employee non-employee 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 automatically increases 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. On January 1, 2016 and January 1, 2017, 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 3,101,707 and 3,920,613, respectively. 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. 2004 Stock Incentive Plan The Company’s 2004 Stock Incentive Plan, or 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 Compensation – Stock Compensation non-employee 505-50, 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 non-employee Weighted- Aggregate Number of Average Intrinsic Options Exercise Price Value Outstanding at December 31, 2015 1,658,408 $ 10.27 Granted 1,078,000 6.55 Exercised (42,000 ) 2.93 Expired (32,499 ) 11.03 Forfeited (113,501 ) 11.52 Outstanding at December 31, 2016 2,548,408 $ 8.75 $ 4,144 Weighted average remaining contractual life as of December 31, 2016 (yrs) 8.18 Options exercisable at December 31, 2016 1,007,334 $ 9.26 $ 1,461 Weighted average remaining contractual life as of December 31, 2016 (yrs) 6.96 Options vested and expected to vest at December 31, 2016 2,417,327 $ 8.76 $ 3,929 Weighted average remaining contractual life as of December 31, 2016 (yrs) 8.11 The total fair value of options vested during the years ended December 31, 2016, 2015 and 2014 was $3,589, $2,489 and $393, respectively. The intrinsic value of options exercised during the years ended December 31, 2016, 2015 and 2014 was $126, $1,748 and $2,055, respectively. During the years ended December 31, 2016, 2015 and 2014, the Company granted 1,078,000, 774,000 and 884,000 stock options, respectively, to employees, non-employee non-employee Summary of Significant Accounting Policies - Stock-Based Compensation Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.19% - 1.93% 1.43% - 1.89% 1.64% - 2.72% Expected volatility 67.8% - 77.8% 64.0% - 67.4% 64.9% - 71.3% Expected dividend yield 0% 0% 0% Expected life of employee and Board of Directors’ options (in years) 6.25 6.25 6.25 Expected life of non-employee 10 10 10 The weighted average grant date fair value of options granted to employees, non-employee non-employee At the end of each fiscal quarter during the years ended December 31, 2016, 2015 and 2014, the Company used the Black-Scholes option valuation model with the following ranges of assumptions to re-measure non-employee 505-50: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.35% - 2.38% 1.81% - 2.15% 1.96% - 2.72% Expected volatility 70.8% - 75.5% 70.6% - 72.2% 69% - 71% Expected dividend yield 0% 0% 0% Expected life of non-employee 7.08 - 9.60 8.1 - 8.8 6 - 10 Under ASC 505-50, re-measurement The weighted average fair value of outstanding options that had been granted to nonemployee consultants, as re-measured During the years ended December 31, 2016, 2015 and 2014, the Company recognized compensation expense in the accompanying Statements of Comprehensive Loss relating to stock options, as follows: Year Ended December 31, 2016 2015 2014 Research and development $ 1,301 $ 1,073 $ 349 General and administrative 1,499 1,441 1,022 Total stock option expense $ 2,800 $ 2,514 $ 1,371 As of December 31, 2016, the total compensation expense relating to unvested options granted to employees, non-employee non-employee The Company does not expect to realize any tax benefits from its stock option activity or the recognition of stock-based compensation expense because the Company currently has net operating losses and has a full valuation allowance against its deferred tax assets. Accordingly, no amounts related to excess tax benefits have been reported in cash flows from operations or cash flows from financing activities for the years ended December 31, 2016, 2015 and 2014.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes The Company’s benefit from income taxes is as follows: December 31, 2016 2015 2014 Current: Federal $ — $ — $ — State (468 ) (397 ) (201 ) (468 ) (397 ) (201 ) Deferred: Federal — — — State — — — — — — Benefit from income taxes $ (468 ) $ (397 ) $ (201 ) The Company’s tax benefits relate to state R&D tax credits exchanged for cash. The State of Connecticut provides companies with the opportunity to exchange certain R&D credit carryforwards for cash in exchange for foregoing the carryforward of the R&D credit. The program provides for such exchange of the R&D credits at a rate of 65% of the annual R&D 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, 2016 2015 2014 Income taxes using U.S. federal statutory rate 34.00 % 34.00 % 34.00 % State income taxes, net of federal benefit 5.44 % 5.95 % 5.23 % Impact of R&D tax credit on effective tax rate 3.24 % 3.14 % 3.03 % Stock option shortfalls and cancellations -0.07 % -0.03 % -0.69 % Permanent items and other -0.64 % -0.41 % -0.57 % Change in valuation allowance -41.17 % -41.07 % -39.88 % 0.81 % 1.58 % 1.12 % Significant components of the Company’s deferred tax assets are as follows: December 31, 2016 2015 Net operating loss carryforwards $ 57,887 $ 36,217 Federal and state tax credits 6,221 4,315 Accelerated depreciation 259 1,206 Stock-based compensation expense 1,783 1,106 Other 641 189 66,791 43,033 Valuation allowance (66,791 ) (43,033 ) Net deferred tax asset $ — $ — A 100% valuation allowance has been recorded on the deferred tax asset as of December 31, 2016 and 2015 because management believes it is more likely than not that the asset will not be realized. The change in the valuation allowance during 2016 and 2015 was $23,758 and $10,317, respectively. The Company has a tax benefit of approximately $840 related to the exercise of non-qualified paid-in-capital 2016-09 The Company applies the provisions of ASC 740, Income Taxe During 2016, the Internal Revenue Service’s examination of the Company’s 2014 U.S. federal tax return completed with no adjustments proposed. At December 31, 2016, the Company had federal and state net operating loss carryforwards of approximately $151,583 and $145,222, 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 section 382. The Company also had federal and state R&D tax credit carryforwards of approximately $5,480 and $810, 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 2006 through 2016 remain open to U.S. federal and state tax examinations.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Net Loss per Share	16. Net Loss per Share The Company computes net loss per share 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 computations are as follows: Year Ended December 31, 2016 2015 2014 Basic: Weighted average shares outstanding 27,279,008 24,620,372 20,965,935 Diluted: Weighted average shares outstanding - Basic 27,279,008 24,620,372 20,965,935 Common stock options * — — — Demoninator for diluted net loss per share 27,279,008 24,620,372 20,965,935 * No amounts were considered as their effects would be anti-dilutive. Basic and diluted net loss per share are computed as follows: Year Ended December 31, 2016 2015 2014 Net loss $ (57,280 ) $ (24,690 ) $ (17,745 ) Weighted-average common shares outstanding: Basic and Diluted 27,279,008 24,620,372 20,965,935 Net loss per share: Basic and Diluted $ (2.10 ) $ (1.00 ) $ (0.85 ) As of December 31, 2016, and 2015, 2,548,408 and 1,658,408 stock options, respectively, were outstanding, which could potentially dilute basic earnings per share in the future, but were not included in the computation of diluted net loss per share because to do so would have been anti-dilutive.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	17. 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 $154, $164 and $169 for the years ended December 31, 2016, 2015 and 2014, respectively. Included in accounts payable and accrued expenses as of December 31, 2015 was $21 for amounts due to this stockholder.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2016
Postemployment Benefits [Abstract]
Employee Benefit Plan	18. 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 years ended December 31, 2016 and 2015, employer contributions to the plan were $118 and $80, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	19. Commitments and Contingencies Contractual obligations and commitments as of December 31, 2016, comprising future minimum lease payments under the Company’s Stamford and Shelton leases, were as follows: Payment Due for the Year Ending December 31, 2017 2018 2019 2020 2021 Thereafter Total Stamford operating lease $ 875 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,383 $ 8,075 Shelton operating lease 740 — — — — — 740 $ 1,615 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,383 $ 8,815 Stamford Operating Lease In December 2015, the Company entered into a lease agreement, or the Stamford Lease, with Four Stamford Plaza Owner LLC, or the Landlord, for office space in Stamford, Connecticut, or the Premises, for the purpose of relocating its headquarters. The initial term of the Stamford Lease commenced in May 2016, or the Commencement Date, and ends in November 2023. The Stamford Lease requires monthly lease payments, including rent escalations and rent holidays, during the initial lease term. The Company began to make rental payments from the Commencement Date. The Company records monthly rent expense on a straight-line basis from March 2016, upon taking possession of the Premises, through October 2023. As of December 31, 2016, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $583. The Stamford Lease is renewable for one five-year term. As of December 31, 2016, the Stamford landlord had made tenant improvements of approximately $1,094 to the leased premises. Such amount was included in Property and equipment, net and in Deferred lease obligation on the Company’s Balance Sheet on the Commencement Date. The portion of Deferred lease obligation that is related to tenant improvements is being amortized as a reduction to rent expense over the same term as rent expense. During the year ended December 31, 2016, the Company amortized $107 of Deferred lease obligation related to tenant improvements. Total rent expense under the Stamford operating lease was $797 for the year ended December 31, 2016. 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 2023. This standby letter of credit is secured with restricted cash in a money market account (refer to Note 7, Restricted Cash Shelton Operating Lease In May 2016, the Company relocated its headquarters to Stamford, Connecticut and vacated its former operating facility in Shelton, Connecticut, although the Company continues to lease its former Shelton operating facility under an operating lease which commenced in 2007 and terminates on October 13, 2017. The Shelton lease agreement, as amended, requires monthly lease payments through its term. The Company recorded monthly rent expense associated with the Shelton lease on a straight-line basis from inception of the lease through May 2016. In accordance with the accounting guidance in ASC 420-10-25-13 A reconciliation of the balances of the accrued Shelton lease cease-use Balance, January 1, 2016 $ — Additional accruals 1,312 Rental payments (556 ) Balance, December 31, 2016 $ 756 At inception of the Shelton lease, the Company received an incentive allowance from the landlord of $2,127, which was included in Property and equipment, net and Deferred lease obligation on the Company’s Balance Sheets. From inception of the Shelton lease through May 2016, the Company amortized the portion of Deferred lease obligation that is related to the incentive allowance over the same time period as rent expense as a reduction to rent expense. As of December 31, 2015, Deferred lease obligation included $374 of unamortized incentive allowance plus $211 of accrued rent. As of May 2016, when the Company vacated the Shelton facility, the Company wrote off the remaining balance of Deferred lease obligation and related rent expense of $429 related to the Shelton lease. Total rent expense under the Shelton operating lease was $1,127, $665 and $643 for the years ended December 31, 2016, 2015 and 2014, respectively. 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 The Company accelerated the amortization of the Shelton leasehold improvements from the date of signing of the Stamford lease in December 2015 through the date that the Company vacated the Shelton facility in May 2016. Additional amortization expense as a result of such acceleration amounted to $899 (additional net loss per share of $0.03) for the year ended December 31, 2016 and $67 for the year ended December 31, 2015.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Legal Matters	20. 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, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations	21. Quarterly Results of Operations (Unaudited) The following tables contain selected financial data for each quarter of the years ended December 31, 2016 and 2015. 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, 2016 and 2015. The operating results for any period are not necessarily indicative of results for any future periods. Year Ended December 31, 2016 First Second Third Fourth Revenues $ 7 $ 79 $ — $ — Net loss - Basic and Diluted (10,692 ) (13,075 ) (11,542 ) (21,971 ) Loss per share - Basic and Diluted $ (0.39 ) $ (0.48 ) $ (0.42 ) $ (0.81 ) 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 )

Summary of Significant Accoun30

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
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 or 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 non-cash non-employees
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 are 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 and cash equivalents and marketable securities are held by three 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 and other investments with original maturities of three months or less.
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 available-for-sale The Company reviews its available-for-sale If a decline in the fair value of an available-for-sale 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 Current accounting guidance defines fair value, establishes a framework for measuring fair value in accordance with Accounting Standards Codification, or 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 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, U.S. government agency obligations, corporate bonds, commercial paper and money market funds with similar underlying investments 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 third-party pricing services. 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, or December 31, 2016.
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 lesser of 10 years
Long-Lived Assets	Long-Lived Assets ASC 360, Property, Plant and Equipment
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 R&D 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 identification of individual elements in a multiple-element arrangement and the estimation of the selling price of each element involves significant judgment, including evaluation as to whether each delivered element has standalone value. 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. The Company has determined that its R&D services deliverables, as applicable, represent separate units of accounting because similar services are sold separately by other vendors. The Company determines the estimated selling price for deliverables within each agreement using vendor specific objective evidence, or VSOE, of selling price, if available, or third party evidence, or 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. Arrangement consideration allocated to R&D 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’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, or 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. R&D expenses include, among other costs, salaries and other personnel-related costs, including consultant costs, and costs to conduct clinical trials using CRO’s, which include upfront, milestone and monthly expenses as well as reimbursement for pass through costs. The amount of clinical trial expense recognized in any period varies depending on the duration and progress of each clinical trial, including the required level of patient enrollment, the rate at which patients actually enroll in and drop-out Non-refundable
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 non-employee non-employee Compensation Stock Compensation . non-employee 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 term), (iv) expected dividend yield on the Company’s common stock, and (v) risk-free interest rates. The Company’s common stock has been traded on a public exchange only since January 31, 2014. Since that time, exercises of stock options have been limited due to various factors, including fluctuations in the Company’s stock price to below the exercise prices of awards, blackout periods during which exercises are not allowed, among others. Therefore, the Company believes that as of December 31, 2016, it does not have sufficient company-specific information available to determine the expected term based on its historical data. As a result, the expected term 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 (6.25 years), an accepted method for the Company’s option grants under the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment. Similarly, since January 31, 2014, 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. As of January 1, 2017, the Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting Accounting Pronouncements Recently Adopted The Company accounts for options granted to non-employee 505-50, Equity-Based Payments to Non-Employees. non-employees non-employee 505-50, re-measurement
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 exercised during the period, when the effect is dilutive. Common stock equivalents may include outstanding stock options, which are included under the treasury stock method when dilutive. For each of the years ended December 31, 2016, 2015 and 2014, the Company excluded the effects of potentially dilutive shares that were outstanding during those respective periods from the denominator as their inclusion would be anti-dilutive due to the Company’s net losses during those periods.
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 as 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. Lease incentives made by landlords to or on behalf of the Company for leasehold improvements 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	Accounting Pronouncements Recently Adopted As of December 31, 2016, the Company adopted Accounting Standards Update, or ASU, 2014-15 Presentation of Financial Statements – Going Concern (Subtopic 205-40), 2014-15, 2014-15 2014-15 10-K As of January 1, 2017, the Company adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting 2016-09, Topic 718 Compensation – Stock Compensation 2016-09 2016-09 Recent Accounting Pronouncements Not Yet Adopted In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805), Clarifying the Definition of a Business, 2017-01 , 2017-01 2017-01 2017-01 2017-01 In December 2016, the FASB issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers, 2016-20, 2016-20 2014-09. 2014-09. 2016-20 In November, 2016, the Financial Accounting Standards Board, or FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash 2016-18, beginning-of-period end-of-period 2016-18 2016-18 2016-18, In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments 2016-13, 2016-13 available-for-sale 2016-13 2016-13 In May 2016, the FASB issued ASU No. 2016-12 , Revenue from Contracts with Customers (Topic 606), Narrow-Scope Improvements and Practical Expedients 2016-12, No. 2014-09 Revenue from Contracts with Customers (Topic 606) 2014-09, 2016-12 2014-09, No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date 2015-14 . 2014-09, 2016-12 In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606), Identifying Performance Obligations and Licensing 2016-10 , 2016-10 2016-10 2016-10 2014-09, 2015-14. 2014-09, 2016-10 In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606), Principal versus Agent Considerations (Reporting Revenue Gross versus Net) 2016-08, 2014-09 2016-08 2014-09, 2015-14. 2014-09, 2016-08 In May 2014, the FASB issued ASU 2014-09 2014-09, 2014-09. The Company is currently accounting for those two contracts under ASC 605-25 605-28. 2016-08, 2016-10, 2016-12 2016-20, 605-25 605-28 In particular, regarding the CKD Agreement and the Maruishi Agreement, the following aspects of ASC 606, as amended, are the same as those under ASC 605-25 605-28. 605-28 ASU 2014-09, 2015-14, 2014-09 2014-09 2014-09

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
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 Marketable32

Available-for-Sale Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Marketable Securities by Major Type of Security	The following tables summarize the Company’s available-for-sale As of December 31, 2016 Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Value Money market funds $ 8,268 $ 8 $ — $ 8,276 U.S. Treasury securities 2,523 — (1 ) 2,522 U.S. government agency obligations 3,501 1 — 3,502 Corporate bonds 16,683 — (6 ) 16,677 Commercial paper 15,206 3 (2 ) 15,207 Total available-for-sale $ 46,181 $ 12 $ (9 ) $ 46,184 As of December 31, 2015 Amortized Gross Unrealized Estimated Fair Type of Security Gains Losses Value Money market funds $ 42,017 $ — $ (31 ) $ 41,986 U.S. Treasury securities 2,528 — — 2,528 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 $ 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. As of December 31, 2016, the Company’s marketable debt securities mature at various dates through August 2017. 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 As of December 31, 2016 2015 Contractual maturity Amortized Cost Fair Value Amortized Cost Fair Value Less than one year $ 37,913 $ 37,908 $ 49,657 $ 49,653
Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities	The following tables show the fair value of the Company’s available-for-sale Less than 12 Months 12 Months or Greater Total As of December 31, 2016 Fair Value Gross Fair Gross Fair Gross U.S. Treasury securities $ 2,522 $ (1 ) $ — $ — $ 2,522 $ (1 ) Corporate bonds 9,919 (6 ) — — 9,919 (6 ) Commercial paper 5,227 (2 ) — — 5,227 (2 ) Total $ 17,668 $ (9 ) $ — $ — $ 17,668 $ (9 ) Less than 12 Months 12 Months or Greater Total As of December 31, 2015 Fair Value Gross Fair Gross Fair Gross Money market 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 Comprehensi33

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities	The following table summarizes the changes in accumulated other comprehensive income (loss), or AOCI, net of tax, from unrealized gains (losses) on available-for-sale Total Accumulated Other Comprehensive Income (Loss) 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 ) Other comprehensive loss before reclassifications 61 Amount reclassified from accumulated other comprehensive income (23 ) Net current period other comprehensive income 38 Balance, December 31, 2016 $ 3
Schedule of Reclassification Out of Accumulated Other Comprehensive Income	The reclassifications out of AOCI and into net loss were as follows: Component of AOCI Year Ended December 31, 2016 2015 Affected Line Item in the Comprehensive Loss Unrealized gains (losses) on available-for-sale Realized gains on sale of securities $ 23 $ — Other income — — Income tax benefit $ 23 $ — Net of tax

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and equipment, net consists of the following: December 31, 2016 2015 Computer and office equipment $ 149 $ 314 Laboratory equipment 795 232 Furniture and fixtures 173 155 Software — 126 Leasehold improvements 8,582 7,453 $ 9,699 $ 8,280 Less accumulated depreciation and amortization 8,085 7,017 Property and equipment, net $ 1,614 $ 1,263

Accounts Payable and Accrued 35

Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2016
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following: December 31, 2016 2015 Accounts payable $ 4,738 $ 1,965 Accrued research projects 4,352 1,542 Accrued professional fees 163 371 Accrued compensation and benefits 1,514 1,204 Accrued other 766 186 $ 11,533 $ 5,268

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2016, and 2015 and by level within the fair value hierarchy: Fair value measurement as of December 31, 2016: Financial assets Total Quoted prices in Significant other (Level 2) Significant (Level 3) Type of Instrument Cash and cash equivalents: Money market fund and checking accounts $ 12,092 $ 12,092 $ — $ — Available-for-sale Money market fund 8,276 — 8,276 — U.S. Treasury securities 2,522 — 2,522 — U.S. government agency obligations 3,502 — 3,502 — Corporate bonds 16,677 — 16,677 — Commercial paper 15,207 — 15,207 — Restricted cash: Money market fund 1,469 1,469 — — Total financial assets $ 59,745 $ 13,561 $ 46,184 $ — 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 fund, savings account and checking account $ 15,101 $ 15,101 $ — $ — Available-for-sale Money market funds 41,986 — 41,986 — U.S. Treasury securities 2,528 — 2,528 — 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 $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Stock Option Activity	A summary of the Company’s stock option activity related to employees, non-employee non-employee Weighted- Aggregate Number of Average Intrinsic Options Exercise Price Value Outstanding at December 31, 2015 1,658,408 $ 10.27 Granted 1,078,000 6.55 Exercised (42,000 ) 2.93 Expired (32,499 ) 11.03 Forfeited (113,501 ) 11.52 Outstanding at December 31, 2016 2,548,408 $ 8.75 $ 4,144 Weighted average remaining contractual life as of December 31, 2016 (yrs) 8.18 Options exercisable at December 31, 2016 1,007,334 $ 9.26 $ 1,461 Weighted average remaining contractual life as of December 31, 2016 (yrs) 6.96 Options vested and expected to vest at December 31, 2016 2,417,327 $ 8.76 $ 3,929 Weighted average remaining contractual life as of December 31, 2016 (yrs) 8.11
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, 2016 2015 2014 Risk-free interest rate 1.19% - 1.93% 1.43% - 1.89% 1.64% - 2.72% Expected volatility 67.8% - 77.8% 64.0% - 67.4% 64.9% - 71.3% Expected dividend yield 0% 0% 0% Expected life of employee and Board of Directors’ options (in years) 6.25 6.25 6.25 Expected life of non-employee 10 10 10
Summary of Compensation Expense Relating to Stock Options	During the years ended December 31, 2016, 2015 and 2014, the Company recognized compensation expense in the accompanying Statements of Comprehensive Loss relating to stock options, as follows: Year Ended December 31, 2016 2015 2014 Research and development $ 1,301 $ 1,073 $ 349 General and administrative 1,499 1,441 1,022 Total stock option expense $ 2,800 $ 2,514 $ 1,371
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, 2016, 2015 and 2014, the Company used the Black-Scholes option valuation model with the following ranges of assumptions to re-measure non-employee 505-50: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.35% - 2.38% 1.81% - 2.15% 1.96% - 2.72% Expected volatility 70.8% - 75.5% 70.6% - 72.2% 69% - 71% Expected dividend yield 0% 0% 0% Expected life of non-employee 7.08 - 9.60 8.1 - 8.8 6 - 10

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Components of Income Taxes (Benefit)	The Company’s benefit from income taxes is as follows: December 31, 2016 2015 2014 Current: Federal $ — $ — $ — State (468 ) (397 ) (201 ) (468 ) (397 ) (201 ) Deferred: Federal — — — State — — — — — — Benefit from income taxes $ (468 ) $ (397 ) $ (201 )
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, 2016 2015 2014 Income taxes using U.S. federal statutory rate 34.00 % 34.00 % 34.00 % State income taxes, net of federal benefit 5.44 % 5.95 % 5.23 % Impact of R&D tax credit on effective tax rate 3.24 % 3.14 % 3.03 % Stock option shortfalls and cancellations -0.07 % -0.03 % -0.69 % Permanent items and other -0.64 % -0.41 % -0.57 % Change in valuation allowance -41.17 % -41.07 % -39.88 % 0.81 % 1.58 % 1.12 %
Schedule of Significant Components of Company's Deferred Tax Assets	Significant components of the Company’s deferred tax assets are as follows: December 31, 2016 2015 Net operating loss carryforwards $ 57,887 $ 36,217 Federal and state tax credits 6,221 4,315 Accelerated depreciation 259 1,206 Stock-based compensation expense 1,783 1,106 Other 641 189 66,791 43,033 Valuation allowance (66,791 ) (43,033 ) Net deferred tax asset $ — $ —

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Computation of Denominators Used in Net Loss per Share	The denominators used in the net loss per share computations are as follows: Year Ended December 31, 2016 2015 2014 Basic: Weighted average shares outstanding 27,279,008 24,620,372 20,965,935 Diluted: Weighted average shares outstanding - Basic 27,279,008 24,620,372 20,965,935 Common stock options * — — — Demoninator for diluted net loss per share 27,279,008 24,620,372 20,965,935 * No amounts were considered as their effects would be anti-dilutive.
Computation of Basic and Diluted Net Loss per Share	Basic and diluted net loss per share are computed as follows: Year Ended December 31, 2016 2015 2014 Net loss $ (57,280 ) $ (24,690 ) $ (17,745 ) Weighted-average common shares outstanding: Basic and Diluted 27,279,008 24,620,372 20,965,935 Net loss per share: Basic and Diluted $ (2.10 ) $ (1.00 ) $ (0.85 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of Contractual Obligations and Commitments Comprising Future Minimum Lease Payments	Contractual obligations and commitments as of December 31, 2016, comprising future minimum lease payments under the Company’s Stamford and Shelton leases, were as follows: Payment Due for the Year Ending December 31, 2017 2018 2019 2020 2021 Thereafter Total Stamford operating lease $ 875 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,383 $ 8,075 Shelton operating lease 740 — — — — — 740 $ 1,615 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,383 $ 8,815
Schedule of Reconciliation of Balances of Accrued Shelton Lease Cease-Use Liability	A reconciliation of the balances of the accrued Shelton lease cease-use Balance, January 1, 2016 $ — Additional accruals 1,312 Rental payments (556 ) Balance, December 31, 2016 $ 756

Quarterly Results of Operatio41

Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016 and 2015. 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, 2016 and 2015. The operating results for any period are not necessarily indicative of results for any future periods. Year Ended December 31, 2016 First Second Third Fourth Revenues $ 7 $ 79 $ — $ — Net loss - Basic and Diluted (10,692 ) (13,075 ) (11,542 ) (21,971 ) Loss per share - Basic and Diluted $ (0.39 ) $ (0.48 ) $ (0.42 ) $ (0.81 ) 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 )

Business - Additional Informati

Business - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Date of formation									Jul. 2, 2004
Proceeds from equity and debt financing	$ 204,800								$ 204,800
Upfront and milestone payments earned in connection with license agreements	32,600								32,600
Unrestricted cash and cash equivalents and marketable securities	58,276								58,276
Accumulated deficit	(162,171)				$ (104,891)				(162,171)	$ (104,891)
Net loss	$ (21,971)	$ (11,542)	$ (13,075)	$ (10,692)	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	(57,280)	(24,690)	$ (17,745)
Net cash used in operating activities									$ (47,381)	$ (21,478)	$ (17,642)

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)Financial_InstitutionSegments	Dec. 31, 2015USD ($)	Dec. 31, 2014	Jan. 01, 2017USD ($)
Summary Of Significant Accounting Policies [Line Items]
Royalty revenue	$ 0
Prepaid R&D expense	$ 1,256,000	$ 1,500,000
Expected dividend yield	0.00%	0.00%	0.00%
Number of operating segments | Segments	1
ASU 2016-09 [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment in equity				$ 45,000
Cash And Cash Equivalents And Marketable Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of financial institutions | Financial_Institution	3
Nonemployee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	10 years	10 years	10 years
Nonemployee Options [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	10 years
Employee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	6 years 3 months

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2016
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

Available-for-Sale Marketable45

Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 46,181	$ 91,675
Gross Unrealized Gains	12	5
Gross Unrealized Losses	(9)	(40)
Estimated Fair Value	46,184	91,640
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,268	42,017
Gross Unrealized Gains	8
Gross Unrealized Losses		(31)
Estimated Fair Value	8,276	41,986
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,523	2,528
Gross Unrealized Losses	(1)
Estimated Fair Value	2,522	2,528
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,501	13,492
Gross Unrealized Gains	1	4
Estimated Fair Value	3,502	13,496
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,683	14,194
Gross Unrealized Losses	(6)	(6)
Estimated Fair Value	16,677	14,188
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,206	19,444
Gross Unrealized Gains	3	1
Gross Unrealized Losses	(2)	(3)
Estimated Fair Value	$ 15,207	$ 19,442

Available-for-Sale Marketable46

Available-for-Sale Marketable Securities - Schedule of Fair Values and Amortized Cost of Marketable Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Fair value of marketable debt securities, contractual maturity, Less than one year	$ 37,908	$ 49,653
Amortized Cost of marketable debt securities, contractual maturity, Less than one year	$ 37,913	$ 49,657

Available-for-Sale Marketable47

Available-for-Sale Marketable Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)Position	Dec. 31, 2015Position
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 34,003
Realized gains or losses	$ 23
Number of available-for-sale marketable securities in unrealized loss positions | Position	18	14
Total number of positions | Position	34	23
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 34,003
Realized gains or losses	$ 23

Available-for-Sale Marketable48

Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	$ 17,668	$ 57,132
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(9)	(40)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	17,668	57,132
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(9)	(40)
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	2,522
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(1)
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	2,522
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(1)
Money Market 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	9,919	14,187
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(6)	(6)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	9,919	14,187
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(6)	(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	5,227	11,960
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(2)	(3)
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Fair Value	0	0
Available-for-sale marketable securities, continuous unrealized loss position, 12 Months or Greater, Gross Unrealized Losses	0	0
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	5,227	11,960
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (2)	$ (3)

Accumulated Other Comprehensi49

Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, from Unrealized Gains (Losses) on Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (35)
Other comprehensive loss before reclassifications	61	$ (35)
Amount reclassified from accumulated other comprehensive income	(23)
Net current period other comprehensive income (loss)	38	(35)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ 3	$ (35)

Accumulated Other Comprehensi50

Accumulated Other Comprehensive Income (Loss) - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on sale of securities,Other income	$ 652	$ 101	$ 126
Income tax benefit	(468)	(397)	$ (201)
Net of tax	23
Accumulated Net Unrealized Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on sale of securities,Other income	23
Income tax benefit	$ 0	$ 0

Prepaid Expenses - Additional I

Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 1,530	$ 1,729
Prepaid R&D clinical costs	1,256	1,500
Prepaid insurance	112	98
Other prepaid costs	$ 162	35
Prepaid rent		$ 96

Property and Equipment, Net - P

Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,699	$ 8,280
Less accumulated depreciation and amortization	8,085	7,017
Property and equipment, net	1,614	1,263
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	149	314
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	795	232
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	173	155
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross		126
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,582	$ 7,453

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 1,465	$ 839	$ 783
Shelton Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Wrote-off of fully-depreciated Shelton property and equipment	$ 397

Restricted Cash - Additional In

Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash balance	$ 769	$ 700
Restricted cash in current assets	700
Shelton Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash balance	$ 700	$ 700
Lease term	2017-10
Restricted cash in current assets	$ 700
Stamford Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash balance	$ 769
Lease term	2023-10
Letter of credit, remaining amount	$ 769
Letter of credit, remaining amount after three years	$ 408

Accounts Payable and Accrued 55

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accounts payable	$ 4,738	$ 1,965
Accrued research projects	4,352	1,542
Accrued professional fees	163	371
Accrued compensation and benefits	1,514	1,204
Accrued other	766	186
Total	$ 11,533	$ 5,268

Connecticut Innovations, Inc.56

Connecticut Innovations, Inc. Stock Warrant - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jul. 31, 2014	Jan. 30, 2014	Apr. 30, 2013	Dec. 31, 2016	Sep. 30, 2007
Class of Warrant or Right [Line Items]
Common stock issued in result of warrants exercise		5,750,000
Connecticut Innovations Inc [Member] | Common Stock [Member]
Class of Warrant or Right [Line Items]
Common stock issued in result of warrants exercise	6,383
Connecticut Innovations Inc [Member]
Class of Warrant or Right [Line Items]
Debt, face amount					$ 4,000
Repayment of term loan			$ 4,000
Exercise price, per share					$ 10.08
Number of shares to be purchased under warrant					19,851
Warrant exercise date				Jul. 31, 2014

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - shares	1 Months Ended	12 Months Ended
	Feb. 05, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Convertible Preferred stock, shares issued	29,186,929	0	0	0
Convertible Preferred stock, shares outstanding	29,186,929	0	0	0
Conversion of stock, shares issued	12,554,171
IPO closing date		Feb. 5, 2014

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 04, 2015	Jul. 29, 2015	Dec. 01, 2014	Jan. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
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		27,296,863
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
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
Private Placement [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share						$ 8.74
Net proceeds from offering of common stock						$ 100
Private Placement [Member] | 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
Private Placement [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued						11,442
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
Underwriter's Over-Allotment [Member] | Common Stock [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	564,516

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financial assets
Restricted cash	$ 769	$ 700
Recurring [Member]
Financial assets
Total financial assets	59,745	107,441
Recurring [Member] | US Government Corporations and Agencies Securities [Member]
Financial assets
Available-for-sale marketable securities	3,502	13,496
Recurring [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	16,677	14,188
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Total financial assets	13,561	15,801
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Total financial assets	46,184	91,640
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | US Government Corporations and Agencies Securities [Member]
Financial assets
Available-for-sale marketable securities	3,502	13,496
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	16,677	14,188
Recurring [Member] | Money Market Funds [Member]
Financial assets
Cash and cash equivalents	12,092	15,101
Available-for-sale marketable securities	8,276	41,986
Restricted cash	1,469
Recurring [Member] | Money Market Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Cash and cash equivalents	12,092	15,101
Restricted cash	1,469
Recurring [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	8,276	41,986
Recurring [Member] | U.S. Treasury Securities [Member]
Financial assets
Available-for-sale marketable securities	2,522	2,528
Recurring [Member] | U.S. Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	2,522	2,528
Recurring [Member] | Commercial Paper [Member]
Financial assets
Available-for-sale marketable securities	15,207	19,442
Recurring [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	$ 15,207	19,442
Recurring [Member] | Bank Certificate of Deposit [Member]
Financial assets
Restricted cash		700
Recurring [Member] | Bank Certificate of Deposit [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Restricted cash		$ 700

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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
Transfer of financial asset into level 3 of fair value	0	0	0
Fair value assets level 2 to level 1 transfers	0	0	0
Fair value assets level 1 to level 2 transfers	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	Jan. 30, 2014shares	Apr. 30, 2012USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Apr. 30, 2013USD ($)$ / sharesshares	Apr. 30, 2012USD ($)shares	Dec. 31, 2016USD ($)Deliverablesshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2012USD ($)	Feb. 05, 2014shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and milestone fee revenue								$ 1,710	$ 302
Withholding tax							$ (468)	(397)	(201)
Collaborative revenue								2,093	2,201
Clinical compound revenue							$ 86	$ 0	$ 674
Issuance of convertible preferred stock | shares							0	0	0		29,186,929
Research and development expense							$ 49,253	$ 21,221	$ 15,068
Convertible Preferred Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock converted to common shares, Shares | shares									(29,186,929)
Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock converted to common shares, Shares | shares									12,554,171
Chong Kun Dang Pharmaceutical Corporation [Member] | KOREA, REPUBLIC OF
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Withholding tax								124		$ 124
Withholding tax due								83
Chong Kun Dang Pharmaceutical Corporation [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock converted to common shares, Shares | shares						69,444
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				$ 480				1,084
Number of deliverables for revenue recognized | Deliverables							2
Value of arrangement					15,337
Revenue recognized from non-substantive milestones							$ 8,000
Revenue recognized from substantive milestones							2,500
Contractual foreign currency exchange adjustments			$ 275	20
Collaborative revenue								641
Amount due from milestone payments net of contractual foreign currency exchange adjustments			$ 1,725
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 premium of preferred stock					$ 337
Clinical trial costs related to the R&D services deliverable							0	1,583	$ 3,000
Research and development expense									3,558
Cost of clinical compound sold to Maruishi									$ 558
Maruishi Pharmaceutical Co., Ltd. [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock converted to common shares, Shares | shares	842,105
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] | Junior A Convertible Preferred Stock [Member] | Convertible Preferred Stock [Member] | Fair Value [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Stock purchase agreement, purchase price of preferred stock per share | $ / shares					$ 3.64
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 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront non-refundable, non-creditable license fee		$ 1,000
Milestone payments receivable		3,750				$ 3,750
License and milestone fee revenue						$ 646		626		$ 626
Milestone payment receivable								417
Next potential milestone that could be received								$ 500
Chong Kun Dang Agreement [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 Agreement [Member] | Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable		2,250				2,250
Chong Kun Dang Agreement [Member] | Regulatory Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable		$ 1,500				$ 1,500

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2017	Sep. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options vested		$ 3,589	$ 2,489	$ 393
Intrinsic value of options exercised		$ 126	$ 1,748	$ 2,055
Options granted		1,078,000	774,000	884,000
Compensation expense not yet recognized		$ 7,815
Weighted average period of compensation expense not yet recognized		2 years 9 months 15 days
Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options granted		$ 4.28	$ 7.17	$ 7.09
Nonemployee Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair values of outstanding options		$ 4.81	$ 10.05	$ 10.77
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	3,101,707			1,600,000
Options granted		1,078,000
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					3,920,613
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] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted	4 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, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Granted	1,078,000	774,000	884,000
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding at December 31, 2015	1,658,408
Number of Options, Granted	1,078,000
Number of Options, Exercised	(42,000)
Number of Options, Expired	(32,499)
Number of Options, Forfeited	(113,501)
Number of Options, Outstanding at December 31, 2016	2,548,408	1,658,408
Number of Options, Outstanding, Weighted average remaining contractual life as of December 31, 2016	8 years 2 months 5 days
Number of Options, Options exercisable at December 31, 2016	1,007,334
Number of Options, Exercisable, Weighted average remaining contractual life as of December 31, 2016	6 years 11 months 16 days
Number of Options, Options vested and expected to vest at December 31, 2016	2,417,327
Number of Options, Vested and expected to vest, Weighted average remaining contractual life as of December 31, 2016	8 years 1 month 10 days
Weighted-Average Exercise Price, Outstanding at December 31, 2015	$ 10.27
Weighted-Average Exercise Price, Granted	6.55
Weighted-Average Exercise Price, Exercised	2.93
Weighted-Average Exercise Price, Expired	11.03
Weighted-Average Exercise Price, Forfeited	11.52
Weighted-Average Exercise Price, Outstanding at December 31, 2016	8.75	$ 10.27
Weighted-Average Exercise Price, Options exercisable at December 31, 2016	9.26
Weighted-Average Exercise Price, Options vested and expected to vest at December 31, 2016	$ 8.76
Aggregate Intrinsic Value, Outstanding at December 31, 2016	$ 4,144
Aggregate Intrinsic Value, Options exercisable at December 31, 2016	1,461
Aggregate Intrinsic Value, Options vested and expected to vest at December 31, 2016	$ 3,929

Stock-Based Compensation - Su64

Stock-Based Compensation - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.19%	1.43%	1.64%
Risk-free interest rate, maximum	1.93%	1.89%	2.72%
Expected volatility, minimum	67.80%	64.00%	64.90%
Expected volatility, maximum	77.80%	67.40%	71.30%
Expected dividend yield	0.00%	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	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	10 years

Stock-Based Compensation - Su65

Stock-Based Compensation - Summary of Re-measurement of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.19%	1.43%	1.64%
Risk-free interest rate, maximum	1.93%	1.89%	2.72%
Expected volatility, minimum	67.80%	64.00%	64.90%
Expected volatility, maximum	77.80%	67.40%	71.30%
Expected dividend yield	0.00%	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	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	1.35%	1.81%	1.96%
Risk-free interest rate, maximum	2.38%	2.15%	2.72%
Expected volatility, minimum	70.80%	70.60%	69.00%
Expected volatility, maximum	75.50%	72.20%	71.00%
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)	7 years 29 days	8 years 1 month 6 days	6 years
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)	9 years 7 months 6 days	8 years 9 months 18 days	10 years

Stock-Based Compensation - Su66

Stock-Based Compensation - Summary of Compensation Expense Relating to Stock Options (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 2,800	$ 2,514	$ 1,371
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	1,301	1,073	349
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 1,499	$ 1,441	$ 1,022

Income Taxes - Components of In

Income Taxes - Components of Income Taxes (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 0	$ 0	$ 0
State	(468)	(397)	(201)
Total Current	(468)	(397)	(201)
Deferred:
Federal	0	0	0
State	0	0	0
Total Deferred	0	0	0
Benefit from income taxes	$ (468)	$ (397)	$ (201)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Percentage of annual R&D credit for cash			65.00%
Valuation allowance on the deferred tax asset	100.00%	100.00%
Change in valuation allowance			$ 23,758,000	$ 10,317,000
Tax benefit on exercise of non-qualified stock options and disqualified disposition of incentive stock options			$ 840,000
Unrecognized tax benefits, related interest and penalties	$ 0	$ 0
Tax examinations, description			Tax years 2006 through 2016 remain open to U.S. federal and state tax examinations.
Earliest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2,006
Latest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2,016
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	151,583,000		$ 151,583,000
Federal [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2,026
Federal [Member] | R&D Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credit carryforwards	5,480,000		$ 5,480,000
Federal [Member] | R&D Tax Credit Carryforwards [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	145,222,000		$ 145,222,000
State and Local [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2,027
State and Local [Member] | R&D Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 810,000		$ 810,000

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, 2016	Dec. 31, 2015	Dec. 31, 2014
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	5.44%	5.95%	5.23%
Impact of R&D tax credit on effective tax rate	3.24%	3.14%	3.03%
Stock option shortfalls and cancellations	(0.07%)	(0.03%)	(0.69%)
Permanent items and other	(0.64%)	(0.41%)	(0.57%)
Change in valuation allowance	(41.17%)	(41.07%)	(39.88%)
Total	0.81%	1.58%	1.12%

Income Taxes - Schedule of Sign

Income Taxes - Schedule of Significant Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 57,887	$ 36,217
Federal and state tax credits	6,221	4,315
Accelerated depreciation	259	1,206
Stock-based compensation expense	1,783	1,106
Other	641	189
Gross deferred tax asset	66,791	43,033
Valuation allowance	(66,791)	(43,033)
Net deferred tax asset	$ 0	$ 0

Net Loss per Share - Computatio

Net Loss per Share - Computation of Denominators Used in Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic:
Weighted average shares outstanding	27,279,008	24,620,372	20,965,935
Diluted:
Weighted average shares outstanding - Basic	27,279,008	24,620,372	20,965,935
Common stock options	0	0	0
Denominator for diluted net loss per share	27,279,008	24,620,372	20,965,935

Net Loss per Share - Computat72

Net Loss per Share - Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (21,971)	$ (11,542)	$ (13,075)	$ (10,692)	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	$ (57,280)	$ (24,690)	$ (17,745)
Weighted-average common shares outstanding:
Basic and Diluted									27,279,008	24,620,372	20,965,935
Net loss per share:
Basic and Diluted	$ (0.81)	$ (0.42)	$ (0.48)	$ (0.39)	$ (0.35)	$ (0.19)	$ (0.25)	$ (0.21)	$ (2.10)	$ (1)	$ (0.85)

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Employee Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	2,548,408	1,658,408

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - Consulting Agreement [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Related party transaction, total expenses	$ 154	$ 164	$ 169
Related party transaction, due to stockholder		$ 21

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2015	Dec. 31, 2016	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		$ 118	$ 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 - Schedule of Contractual Obligations and Commitments Comprising Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Operating Leased Assets [Line Items]
2,017	$ 1,615
2,018	1,093
2,019	1,217
2,020	1,241
2,021	1,266
Thereafter	2,383
Total	8,815
Stamford Operating Lease [Member]
Operating Leased Assets [Line Items]
2,017	875
2,018	1,093
2,019	1,217
2,020	1,241
2,021	1,266
Thereafter	2,383
Total	8,075
Shelton Operating Lease [Member]
Operating Leased Assets [Line Items]
2,017	740
Total	$ 740

Commitments and Contingencies77

Commitments and Contingencies - Additional Information (Detail) - USD ($)	May 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2012
Other Commitments [Line Items]
Deferred lease obligation		$ 1,570,000	$ 585,000
Lease minimum rental payment		$ 8,815,000
Stamford Operating Lease [Member]
Other Commitments [Line Items]
Operating Lease, description		The Stamford Lease requires monthly lease payments, including rent escalations and rent holidays, during the initial lease term. The Company began to make rental payments from the Commencement Date. The Company records monthly rent expense on a straight-line basis from March 2016, upon taking possession of the Premises, through October 2023. As of December 31, 2016, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $583. The Stamford Lease is renewable for one five-year term.
Operating Lease, renewable term		5 years
Operating lease, expiration date		Oct. 31, 2023
Deferred lease obligation		$ 583,000
Tenant improvement expenses		1,094,000
Operating lease, rent expense		797,000
Lease minimum rental payment		8,075,000
Stamford Operating Lease [Member] | Leasehold Improvements [Member]
Other Commitments [Line Items]
Amortization of deferred lease obligation		107,000
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 2023.
Stamford Operating Lease [Member] | Maximum [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, renewal date		Nov. 30, 2023
Shelton Operating Lease [Member]
Other Commitments [Line Items]
Operating lease, expiration date		Oct. 13, 2017
Operating lease, rent expense		$ 1,127,000	665,000	$ 643,000
Accrued cease use date liability	$ 1,312,000	1,312,000
Lease minimum rental payment		740,000
Restructuring liability		756,000
Accumulated deferred lease obligation, written off	$ 429,000
Incentive allowance received		2,127,000
Unamortized incentive allowance			374,000
Accrued rent			211,000
Additional amortization expense		$ 899,000	$ 67,000
Additional loss per share		$ 0.03
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

Commitments and Contingencies78

Commitments and Contingencies - Schedule of Reconciliation of Balances of Accrued Shelton Lease Cease-Use Liability (Detail) - Shelton Operating Lease [Member] - USD ($) $ in Thousands	May 31, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Additional accruals	$ 1,312	$ 1,312
Rental payments		(556)
Balance, December 31, 2016		$ 756

Quarterly Results of Operatio79

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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues			$ 79	$ 7		$ 2,440	$ 874	$ 489	$ 86	$ 3,803	$ 3,177
Net loss - Basic and Diluted	$ (21,971)	$ (11,542)	$ (13,075)	$ (10,692)	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	$ (57,280)	$ (24,690)	$ (17,745)
Loss per share - Basic and Diluted	$ (0.81)	$ (0.42)	$ (0.48)	$ (0.39)	$ (0.35)	$ (0.19)	$ (0.25)	$ (0.21)	$ (2.10)	$ (1)	$ (0.85)