Cara Therapeutics (CARA) 10-Q 2 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 27, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	CARA
Entity Registrant Name	Cara Therapeutics, Inc.
Entity Central Index Key	1,346,830
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		32,608,485

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 11,792	$ 12,092
Marketable securities	91,190	46,184
Income tax receivable	705	852
Other receivables	97	87
Prepaid expenses	1,492	1,530
Restricted cash, current	700	700
Total current assets	105,976	61,445
Property and equipment, net	1,302	1,614
Restricted cash	769	769
Total assets	108,047	63,828
Current liabilities:
Accounts payable and accrued expenses	7,272	11,533
Total current liabilities	7,272	11,533
Deferred lease obligation	1,701	1,570
Commitments and contingencies (Note 14)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at September 30, 2017 and December 31, 2016, zero shares issued and outstanding at September 30, 2017 and December 31, 2016
Common stock; $0.001 par value; 100,000,000 shares authorized at September 30, 2017 and December 31, 2016, 32,608,485 shares and 27,296,863 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	33	27
Additional paid-in capital	305,165	212,866
Accumulated deficit	(206,164)	(162,171)
Accumulated other comprehensive income	40	3
Total stockholders' equity	99,074	50,725
Total liabilities and stockholders' equity	$ 108,047	$ 63,828

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
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	32,608,485	27,296,863
Common stock, shares outstanding	32,608,485	27,296,863

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue:
License and milestone fees			$ 530
Collaborative revenue			313
Clinical compound revenue			68	$ 86
Total revenue			911	86
Operating expenses:
Research and development	$ 9,151	$ 9,671	36,948	28,976
General and administrative	3,805	2,102	8,877	7,195
Total operating expenses	12,956	11,773	45,825	36,171
Operating loss	(12,956)	(11,773)	(44,914)	(36,085)
Other income	367	176	788	498
Loss before benefit from income taxes	(12,589)	(11,597)	(44,126)	(35,587)
Benefit from income taxes	145	55	178	279
Net loss	$ (12,444)	$ (11,542)	$ (43,948)	$ (35,308)
Net loss per share - Basic and Diluted	$ (0.38)	$ (0.42)	$ (1.43)	$ (1.29)
Weighted average shares:
Basic and Diluted	32,591,550	27,282,863	30,729,752	27,275,133
Other comprehensive income, net of tax of $0:
Unrealized gains (losses) on available-for-sale marketable securities	$ 53	$ (21)	$ 37	$ 55
Total comprehensive loss	$ (12,391)	$ (11,563)	$ (43,911)	$ (35,253)

Condensed Statements of Compre5

Condensed Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Other comprehensive income, tax	$ 0	$ 0	$ 0	$ 0

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Follow-on Public Offering [Member]	Common Stock [Member]	Common Stock [Member]Follow-on Public Offering [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]Follow-on Public Offering [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, Value at Dec. 31, 2015	$ 105,044		$ 27		$ 209,943		$ (104,891)	$ (35)
Balance, Shares at Dec. 31, 2015			27,254,863
Stock-based compensation expense	1,971				1,971
Shares issued upon exercise of stock options, Value	40				40
Shares issued upon exercise of stock options, Shares			28,000
Net loss	(35,308)						(35,308)
Other comprehensive income	55							55
Balance, Value at Sep. 30, 2016	71,802		$ 27		211,954		(140,199)	20
Balance, Shares at Sep. 30, 2016			27,282,863
Balance, Value at Dec. 31, 2016	50,725		$ 27		212,866		(162,171)	3
Balance, Shares at Dec. 31, 2016			27,296,863
Sale of common stock, net of underwriting discounts and commissions and offering expenses, Value		$ 86,224		$ 5		$ 86,219
Sale of common stock, net of underwriting discounts and commissions and offering expenses, Shares				5,117,500
Stock-based compensation expense	4,046				4,046
Modification of equity awards	474				474
Shares issued upon exercise of stock options, Value	1,516		$ 1		1,515
Shares issued upon exercise of stock options, Shares			194,122
Net loss	(43,948)						(43,948)
Other comprehensive income	37							37
Balance, Value at Sep. 30, 2017	$ 99,074		$ 33		305,165		(206,164)	$ 40
Balance, Shares at Sep. 30, 2017			32,608,485
Cumulative effect adjustment upon adoption of ASU 2016-09					$ 45		$ (45)

Condensed Statements of Stockh7

Condensed Statements of Stockholders' Equity (Parenthetical) - Follow-on Public Offering [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)$ / shares
Sale of common stock, per share | $ / shares	$ 18
Underwriting discounts and commissions and offering expenses | $	$ 5,891

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (43,948)	$ (35,308)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,046	1,971
Modification of equity awards	474
Depreciation and amortization	370	1,346
Accretion/amortization on available-for-sale marketable securities	(356)	(183)
Realized gain on sale of available-for-sale marketable securities	(4)	(12)
Realized gain on sale of property and equipment	(41)
Deferred rent costs	131	(158)
Changes in operating assets and liabilities:
Income tax receivable	147	(279)
Other receivables	(10)	(35)
Prepaid expenses	38	(3,091)
Accounts payable and accrued expenses	(4,261)	1,556
Net cash used in operating activities	(43,414)	(34,193)
Investing activities
Proceeds from maturities of available-for-sale marketable securities	65,406	59,650
Proceeds from sale of available-for-sale marketable securities	5,730	23,368
Purchases of available-for-sale marketable securities	(115,745)	(57,123)
Change in restricted cash		(769)
Purchases of property and equipment	(58)	(648)
Proceeds from sale of property and equipment	41
Net cash (used in) provided by investing activities	(44,626)	24,478
Financing activities
Proceeds from sale of common stock in a follow-on public offering, net of issuance costs	86,224
Proceeds from the exercise of stock options	1,516	40
Net cash provided by financing activities	87,740	40
Net cash decrease for the period	(300)	(9,675)
Cash and cash equivalents at beginning of period	12,092	15,101
Cash and cash equivalents at end of period	$ 11,792	5,426
Noncash investing and financing activities
Tenant improvements paid by landlord		$ 1,094

Business

Business	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	1. Business Cara Therapeutics, Inc. (the “Company”, “we”, “our” or “us”) 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 peripheral 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 September 30, 2017, the Company has raised aggregate net proceeds of approximately $291,100 from several rounds of equity financing, including its initial public offering, or IPO, which closed in February 2014 and two follow-on Collaborations On April 5, 2017, the Company completed its second follow-on S-3, Stockholders’ Equity As of September 30, 2017, the Company had unrestricted cash and cash equivalents and marketable securities of $102,982 and an accumulated deficit of $206,164. 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 net losses of $43,948 and $35,308 and had net cash used in operating activities of $43,414 and $34,193 for the nine months ended September 30, 2017 and 2016, respectively. 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.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	2. Basis of Presentation The unaudited interim condensed financial statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, they do not include all information and disclosures necessary for a presentation of the Company’s financial position, results of operations and cash flows in conformity with generally accepted accounting principles in the United States of America, or GAAP. In the opinion of management, these unaudited interim financial statements reflect all adjustments, consisting primarily of normal recurring accruals, necessary for a fair presentation of results for the periods presented. The results of operations for interim periods are not necessarily indicative of the results for the full year. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by SEC rules and regulations; however, the Company believes that the disclosures are adequate to make the information presented not misleading. The condensed balance sheet data for the year ended December 31, 2016 were derived from audited financial statements, but do not include all disclosures required by GAAP. These unaudited interim condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes thereto included in the Company’s Annual Report on Form 10-K Use of Estimates The preparation of financial statements in conformity with 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 Significant Accounting Policies There have been no material changes to the significant accounting policies previously disclosed in Note 2 to the Financial Statements in the Company’s Annual Report on Form 10-K Accounting Pronouncements Recently Adopted As of January 1, 2017, the Company adopted Accounting Standards Update, or 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 May 2017, the Financial Accounting Standards Board, or FASB, issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) – Scope of Modification Accounting 2017-09, 2017-09 2017-09, Stock-based Compensation 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 February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02, 2016-02 right-of-use right-of-use 2016-02 2016-02 2016-02 2016-02 In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09, The Company currently recognizes revenue only from a license agreement with Maruishi, or the Maruishi Agreement, and a license agreement with CKDP, or the CKDP Agreement. Under each of these agreements, the Company has recognized revenue from upfront and milestone payments and may earn additional future milestone payments upon the achievement of defined clinical and regulatory events. The Company has also recognized revenue from a sub-license 2014-09, 2014-09. The Company is currently accounting for the Maruishi Agreement and the CKDP Agreement under ASC 605-25, Multiple-Element Arrangements 605-25, 605-28, Milestone Method 605-28. 2016-08, 2016-10, 2016-12 2016-20, 605-25 605-28 605-25 605-28. In particular, the following aspects of ASC 606, as amended, are the same as those under ASC 605-25 605-28 605-25. Although the milestone method guidance under ASC 605-28 ASU 2014-09, 2015-14, 2014-09 2014-09 2014-09

Available-for-Sale Marketable S

Available-for-Sale Marketable Securities	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Marketable Securities	3. Available-for-Sale As of September 30, 2017 and December 31, 2016, the Company’s available-for-sale available-for-sale The following tables summarize the Company’s available-for-sale As of September 30, 2017 Gross Unrealized Estimated Type of Security Amortized Cost Gains Losses Money market funds $ 42,826 $ 49 $ — $ 42,875 U.S. government agency obligations 7,800 1 (1 ) 7,800 Corporate bonds 19,368 — (5 ) 19,363 Commercial paper 21,156 — (4 ) 21,152 Total available-for-sale $ 91,150 $ 50 $ (10 ) $ 91,190 As of December 31, 2016 Gross Unrealized Estimated Type of Security Amortized Cost Gains Losses 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 All available-for-sale The Company classifies its marketable debt securities based on their contractual maturity dates. As of September 30, 2017, the Company’s marketable debt securities mature at various dates through June 2018. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows. The table does not include money market funds that are classified as available-for-sale As of September 30, 2017 As of December 31, 2016 Contractual maturity Amortized Cost Fair Value Amortized Cost Fair Value Less than one year $ 48,324 $ 48,315 $ 37,913 $ 37,908 During the nine months ended September 30, 2017, the Company sold shares of two investments in commercial paper before their respective maturity dates and shares in a money market fund with a total fair value of $5,730 that were all classified as available-for-sale The following tables show the fair value of the Company’s available-for-sale As of September 30, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross U.S. government agency obligations $ 3,498 $ (1 ) $ — $ — $ 3,498 $ (1 ) Corporate bonds 18,016 (5 ) — — 18,016 (5 ) Commercial paper 8,193 (4 ) — — 8,193 (4 ) Total $ 29,707 $ (10 ) $ — $ — $ 29,707 $ (10 ) As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value 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 ) As of September 30, 2017 and December 31, 2016, the Company held a total of 17 out of 28 positions and 18 out of 34 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)	9 Months Ended
	Sep. 30, 2017
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 Balance, December 31, 2016 $ 3 Other comprehensive income before reclassifications 41 Amount reclassified from accumulated other comprehensive income (4 ) Net current period other comprehensive income 37 Balance, September 30, 2017 $ 40 Balance, December 31, 2015 $ (35 ) Other comprehensive income before reclassifications 67 Amount reclassified from accumulated other comprehensive income (12 ) Net current period other comprehensive income 55 Balance, September 30, 2016 $ 20 The reclassifications out of AOCI and into net loss were as follows: Three Months Ended Nine Months Ended Affected Line Item in the Component of AOCI 2017 2016 2017 2016 Statements of Operations Unrealized gains on available-for-sale $ — $ 12 $ 4 $ 12 Other income — — — — Benefit from income taxes $ — $ 12 $ 4 $ 12 The amount reclassified out of AOCI into net loss was determined by specific identification.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. Fair Value Measurements As of September 30, 2017 and December 31, 2016, the Company’s financial instruments consisted of cash and cash equivalents, available-for-sale Available-for-sale Current accounting guidance defines fair value, establishes a framework for measuring fair value in accordance with 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. 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 third-party pricing services as of September 30, 2017 or December 31, 2016. The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016. Fair value measurement as of September 30, 2017 Financial assets Quoted prices in Significant other Significant active markets for observable unobservable identical assets inputs inputs Type of Instrument Total (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Money market fund and checking accounts $ 11,792 $ 11,792 $ — $ — Available-for-sale Money market fund 42,875 — 42,875 — U.S. government agency obligations 7,800 — 7,800 — Corporate bonds 19,363 — 19,363 — Commercial paper 21,152 — 21,152 — Restricted cash: Commercial money market account 1,469 1,469 — — Total financial assets $ 104,451 $ 13,261 $ 91,190 $ — Fair value measurement as of December 31, 2016: Financial assets Quoted prices in Significant other Significant active markets for observable unobservable identical assets inputs inputs Type of Instrument Total (Level 1) (Level 2) (Level 3) 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: Commercial money market account 1,469 1,469 — — Total financial assets $ 59,745 $ 13,561 $ 46,184 $ — 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

Restricted Cash

Restricted Cash	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Restricted Cash	6. 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. For the Stamford lease, the letter of credit balance remains at $769 through May 2019 and may, upon request from the Company, thereafter be reduced to $408 through the end of the lease term in November 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 September 30, 2017 and 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.

Prepaid Expenses

Prepaid Expenses	9 Months Ended
	Sep. 30, 2017
Text Block [Abstract]
Prepaid Expenses	7. Prepaid expenses As of September 30, 2017, prepaid expenses were $1,492, consisting of $984 of prepaid R&D clinical costs, $346 of prepaid insurance and $162 of other prepaid costs. As of December 31, 2016, prepaid expenses were $1,530 consisting of $1,256 of prepaid R&D clinical costs, $112 of prepaid insurance and $162 of other prepaid costs.

Accounts Payable and Accrued Ex

Accounts Payable and Accrued Expenses	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Accounts Payable and Accrued Expenses	8. Accounts Payable and Accrued Expenses Accounts payable and accrued expenses consist of the following: September 30, 2017 December 31, 2016 Accounts payable $ 1,187 $ 4,738 Accrued research projects 3,758 4,352 Accrued professional fees 473 163 Accrued compensation and benefits 1,496 1,514 Accrued other 358 766 Total $ 7,272 $ 11,533

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity On March 30, 2017, the Company entered into an underwriting agreement with Piper Jaffray & Co. and Stifel, Nicolaus & Company, Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of up to 5,117,500 shares of its common stock, including 667,500 shares of common stock the underwriters had the option to purchase, at a public offering price of $18.00 per share, or the Offering. The Offering was made pursuant to the Company’s Registration Statement on Form S-3 No. 333-216657), On April 5, 2017, the Company closed the Offering, including the full exercise of the underwriters’ option to purchase 667,500 additional shares of common stock. The Company received net proceeds of approximately $86,224, after deducting the underwriting discounts and commissions and offering expenses paid by the Company of $294.

Collaborations

Collaborations	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	10. Collaborations Maruishi Pharmaceutical Co., Ltd. In April 2013, the Company entered into 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. Maruishi has the right to grant sub-licenses sub-license At inception of the Maruishi Agreement, the Company identified two deliverables under ASC 605-25: In March 2017, Maruishi entered into a sub-license sub-license sub-license The Company recognized $68 and $86 of clinical compound revenue during the nine months ended September 30, 2017 and 2016, respectively, from the sale of clinical compound to Maruishi but did not recognize any clinical compound revenue during the three months ended September 30, 2017 or 2016. The Company incurred $61 and $78 of R&D expense during the nine months ended September 30, 2017 and 2016, respectively, consisting of cost of clinical compound but did not recognize any R&D expense related to the Maruishi Agreement during the three months ended September 30, 2017 and 2016.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net 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 using the treasury stock method when dilutive. For the three and nine months ended September 30, 2017 and 2016, 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. The denominators for the three and nine months ended September 30, 2017 reflect the issuance of 5,117,500 common shares in the Offering on April 5, 2017, on a weighted-average basis (see Note 9, Stockholders’ Equity The denominators used in the net loss per share computations are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Basic: Weighted average common shares outstanding 32,591,550 27,282,863 30,729,752 27,275,133 Diluted: Weighted average common shares outstanding -Basic 32,591,550 27,282,863 30,729,752 27,275,133 Common stock options* — — — — Denominator for diluted net loss per share 32,591,550 27,282,863 30,729,752 27,275,133 * No amounts were considered as their effects would be anti-dilutive. Basic and diluted net loss per share are computed as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net loss $ (12,444 ) $ (11,542 ) $ (43,948 ) $ (35,308 ) Weighted-average common shares outstanding: Basic and Diluted 32,591,550 27,282,863 30,729,752 27,275,133 Net loss per share, Basic and Diluted $ (0.38 ) $ (0.42 ) $ (1.43 ) $ (1.29 ) As of September 30, 2017 and 2016, 3,492,786 and 2,299,117 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.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	12. 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 The aggregate number of shares of the Company’s common stock reserved for issuance under the 2014 Plan has automatically increased on January 1 of each year, beginning on January 1, 2015 and will continue to increase on January 1 of each year 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, 2017, the aggregate number of shares of common stock that may be issued pursuant to Stock Awards under the 2014 Plan automatically increased from 3,101,707 to 3,920,613. 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. Under the 2014 Plan, the Company granted 415,000 and 1,253,500 stock options during the three and nine months ended September 30, 2017, respectively, and 75,000 and 797,000 stock options during the three and nine months ended September 30, 2016, respectively. The fair values of stock options granted during the three and nine months ended September 30, 2017 and 2016 were estimated as of the dates of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Risk-free interest rate 1.87% - 1.97% 1.19% 1.85% - 2.57% 1.19% - 1.79% Expected volatility 81.4% - 81.7% 71.9% 75.3% - 83.3% 67.8% - 72.6% Expected dividend yield 0% 0% 0% 0% Expected life of employee options (in years) 6.25 6.25 6.25 6.25 Expected life of nonemployee options (in years) — — 10 10 The weighted-average grant date fair value of options granted to employees, non-employee non-employee As of September 30, 2017 and 2016, the Company used the Black-Scholes option valuation model with the following assumptions to re-measure non-employee 505-50: As of September 30, 2017 2016 Risk-free interest rate 1.28% -2.28% 1.35% - 1.56% Expected volatility 75.2% - 84.0% 73.9% - 74.6% Expected dividend yield 0% 0% Expected life of non-employee 0.88 - 9.44 7.33 - 9.60 The weighted-average fair value of outstanding options that had been granted to nonemployee consultants, as re-measured 505-50, On January 1, 2017, the Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting Basis of Presentation Recently Adopted Accounting Pronouncements 2016-09, During the three and nine months ended September 30, 2017 and 2016, the Company recognized compensation expense relating to stock options, as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 619 $ 375 $ 1,784 $ 867 General and administrative 1,475 402 2,736 1,104 Total stock option expense $ 2,094 $ 777 $ 4,520 $ 1,971 In connection with the retirement of the Company’s former Chief Financial Officer, effective August 15, 2017, or the Modification Date, the Company modified the terms of the former Chief Financial Officer’s outstanding Stock Awards to: (1) accelerate 50% of the 98,771 unvested shares underlying his outstanding Stock Awards immediately as of the Modification Date, and specify that the remainder will vest monthly through the date of termination of his continuous service to the Company and (2) extend the period during which his outstanding Stock Awards for an aggregate of 183,000 shares may be exercised through the six-month month-to-month The Company determined that the acceleration of vesting for Stock Awards that would have vested based on their original vesting terms through the term of the consulting services was a Type 1 modification pursuant to ASC 718, Compensation-Stock Compensation On the Modification Date, the Company recognized $474 of compensation expense, which is included in General and administrative expense in the table above, for the three and nine months ended September 30, 2017, with respect to these modifications. In addition, the Company expects to recognize compensation expense totaling $92 on a straight-line basis during the term of his continuous service to the Company and will mark to market the fair value of those Stock Awards in accordance with ASC 505-50 A summary of stock option award activity related to employees, non-employee non-employee Number of Weighted Outstanding, December 31, 2016 2,548,408 $ 8.75 Granted 1,253,500 16.40 Exercised (194,122 ) 7.81 Forfeited (115,000 ) 7.74 Outstanding, September 30, 2017 3,492,786 11.58 Options exercisable, September 30, 2017 1,366,118 $ 9.86 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 for the nine months ended September 30, 2017 and 2016.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes For the three months ended September 30, 2017 and 2016, pre-tax pre-tax 2016-09 The benefit from income taxes of $145 and $55 for the three months ended September 30, 2017 and 2016, respectively, and $178 and $279 for the nine months ended September 30, 2017 and 2016, respectively, relates to state R&D tax credits exchanged for cash pursuant to the Connecticut R&D Tax Credit Exchange Program, which permits qualified small businesses engaged in R&D activities within Connecticut to exchange their unused R&D tax credits for a cash amount equal to 65% of the value of the exchanged credits.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. Commitments and Contingencies Contractual obligations and commitments as of September 30, 2017, consisting of 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 $ 294 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,348 $ 7,459 Shelton operating lease 129 — — — — — 129 $ 423 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,348 $ 7,588 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 September 30, 2017 and December 31, 2016, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $823 and $583, respectively. The Stamford Lease is renewable for one five-year term. As of the Commencement Date, 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 that 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. As of September 30, 2017 and December 31, 2016, the balance of Deferred lease obligation related to tenant improvements was $878 and $987, respectively. In connection with the signing of the Stamford Lease, the Company entered into a standby letter of credit agreement, which serves as a security deposit for the Premises. The standby letter of credit 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 6, 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, or the Shelton Lease, which commenced in 2007 and has a termination date of October 13, 2017, with month-to-month The Shelton Lease, 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 Shelton 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 Three Months Ended September 30, 2017 2016 Balance July 1, 2017 $ 276 Balance, July 1, 2016 $ 1,232 Charges 90 Charges — Rental payments (247 ) Rental payments (234 ) Interest accretion 10 Interest accretion — Balance September 30, 2017 $ 129 Balance September 30, 2016 $ 998 Nine Months Ended September 30, 2017 2016 Balance, January 1, 2017 $ 756 Balance January 1, 2016 $ — Charges 90 Charges 1,312 Rental payments (741 ) Rental payments (314 ) Interest accretion 24 Interest accretion — Balance September 30, 2017 $ 129 Balance September 30, 2016 $ 998 In conjunction with the signing of the Shelton Lease, the Company entered into a standby letter of credit agreement, which expires 60 days after lease termination, as a security deposit for the premises. As of September 30, 2017 and December 31, 2016, the balance of the letter of credit was $700, which is secured with restricted cash (refer to Note 6, 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 nine months ended September 30, 2016.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with 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
Significant Accounting Policies	Significant Accounting Policies There have been no material changes to the significant accounting policies previously disclosed in Note 2 to the Financial Statements in the Company’s Annual Report on Form 10-K
Recent Accounting Pronouncements	Accounting Pronouncements Recently Adopted As of January 1, 2017, the Company adopted Accounting Standards Update, or 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 May 2017, the Financial Accounting Standards Board, or FASB, issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) – Scope of Modification Accounting 2017-09, 2017-09 2017-09, Stock-based Compensation 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 February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02, 2016-02 right-of-use right-of-use 2016-02 2016-02 2016-02 2016-02 In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09, The Company currently recognizes revenue only from a license agreement with Maruishi, or the Maruishi Agreement, and a license agreement with CKDP, or the CKDP Agreement. Under each of these agreements, the Company has recognized revenue from upfront and milestone payments and may earn additional future milestone payments upon the achievement of defined clinical and regulatory events. The Company has also recognized revenue from a sub-license 2014-09, 2014-09. The Company is currently accounting for the Maruishi Agreement and the CKDP Agreement under ASC 605-25, Multiple-Element Arrangements 605-25, 605-28, Milestone Method 605-28. 2016-08, 2016-10, 2016-12 2016-20, 605-25 605-28 605-25 605-28. In particular, the following aspects of ASC 606, as amended, are the same as those under ASC 605-25 605-28 605-25. Although the milestone method guidance under ASC 605-28 ASU 2014-09, 2015-14, 2014-09 2014-09 2014-09

Available-for-Sale Marketable24

Available-for-Sale Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 Gross Unrealized Estimated Type of Security Amortized Cost Gains Losses Money market funds $ 42,826 $ 49 $ — $ 42,875 U.S. government agency obligations 7,800 1 (1 ) 7,800 Corporate bonds 19,368 — (5 ) 19,363 Commercial paper 21,156 — (4 ) 21,152 Total available-for-sale $ 91,150 $ 50 $ (10 ) $ 91,190 As of December 31, 2016 Gross Unrealized Estimated Type of Security Amortized Cost Gains Losses 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
Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity	The Company classifies its marketable debt securities based on their contractual maturity dates. As of September 30, 2017, the Company’s marketable debt securities mature at various dates through June 2018. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows. The table does not include money market funds that are classified as available-for-sale As of September 30, 2017 As of December 31, 2016 Contractual maturity Amortized Cost Fair Value Amortized Cost Fair Value Less than one year $ 48,324 $ 48,315 $ 37,913 $ 37,908
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 As of September 30, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value Gross U.S. government agency obligations $ 3,498 $ (1 ) $ — $ — $ 3,498 $ (1 ) Corporate bonds 18,016 (5 ) — — 18,016 (5 ) Commercial paper 8,193 (4 ) — — 8,193 (4 ) Total $ 29,707 $ (10 ) $ — $ — $ 29,707 $ (10 ) As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Gross Fair Value Gross Fair Value 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 )

Accumulated Other Comprehensi25

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2017
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 Balance, December 31, 2016 $ 3 Other comprehensive income before reclassifications 41 Amount reclassified from accumulated other comprehensive income (4 ) Net current period other comprehensive income 37 Balance, September 30, 2017 $ 40 Balance, December 31, 2015 $ (35 ) Other comprehensive income before reclassifications 67 Amount reclassified from accumulated other comprehensive income (12 ) Net current period other comprehensive income 55 Balance, September 30, 2016 $ 20
Schedule of Reclassification Out of Accumulated Other Comprehensive Income	The reclassifications out of AOCI and into net loss were as follows: Three Months Ended Nine Months Ended Affected Line Item in the Component of AOCI 2017 2016 2017 2016 Statements of Operations Unrealized gains on available-for-sale $ — $ 12 $ 4 $ 12 Other income — — — — Benefit from income taxes $ — $ 12 $ 4 $ 12

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
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 September 30, 2017 and December 31, 2016. Fair value measurement as of September 30, 2017 Financial assets Quoted prices in Significant other Significant active markets for observable unobservable identical assets inputs inputs Type of Instrument Total (Level 1) (Level 2) (Level 3) Cash and cash equivalents: Money market fund and checking accounts $ 11,792 $ 11,792 $ — $ — Available-for-sale Money market fund 42,875 — 42,875 — U.S. government agency obligations 7,800 — 7,800 — Corporate bonds 19,363 — 19,363 — Commercial paper 21,152 — 21,152 — Restricted cash: Commercial money market account 1,469 1,469 — — Total financial assets $ 104,451 $ 13,261 $ 91,190 $ — Fair value measurement as of December 31, 2016: Financial assets Quoted prices in Significant other Significant active markets for observable unobservable identical assets inputs inputs Type of Instrument Total (Level 1) (Level 2) (Level 3) 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: Commercial money market account 1,469 1,469 — — Total financial assets $ 59,745 $ 13,561 $ 46,184 $ —

Accounts Payable and Accrued 27

Accounts Payable and Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following: September 30, 2017 December 31, 2016 Accounts payable $ 1,187 $ 4,738 Accrued research projects 3,758 4,352 Accrued professional fees 473 163 Accrued compensation and benefits 1,496 1,514 Accrued other 358 766 Total $ 7,272 $ 11,533

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
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: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Basic: Weighted average common shares outstanding 32,591,550 27,282,863 30,729,752 27,275,133 Diluted: Weighted average common shares outstanding -Basic 32,591,550 27,282,863 30,729,752 27,275,133 Common stock options* — — — — Denominator for diluted net loss per share 32,591,550 27,282,863 30,729,752 27,275,133 * 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: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net loss $ (12,444 ) $ (11,542 ) $ (43,948 ) $ (35,308 ) Weighted-average common shares outstanding: Basic and Diluted 32,591,550 27,282,863 30,729,752 27,275,133 Net loss per share, Basic and Diluted $ (0.38 ) $ (0.42 ) $ (1.43 ) $ (1.29 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2017
Summary of Assumptions Used in Black-Scholes Option Pricing Model	The fair values of stock options granted during the three and nine months ended September 30, 2017 and 2016 were estimated as of the dates of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Risk-free interest rate 1.87% - 1.97% 1.19% 1.85% - 2.57% 1.19% - 1.79% Expected volatility 81.4% - 81.7% 71.9% 75.3% - 83.3% 67.8% - 72.6% Expected dividend yield 0% 0% 0% 0% Expected life of employee options (in years) 6.25 6.25 6.25 6.25 Expected life of nonemployee options (in years) — — 10 10
Summary of Compensation Expense Relating to Stock Options	During the three and nine months ended September 30, 2017 and 2016, the Company recognized compensation expense relating to stock options, as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Research and development $ 619 $ 375 $ 1,784 $ 867 General and administrative 1,475 402 2,736 1,104 Total stock option expense $ 2,094 $ 777 $ 4,520 $ 1,971
Summary of Stock Option Activity	A summary of stock option award activity related to employees, non-employee non-employee Number of Weighted Outstanding, December 31, 2016 2,548,408 $ 8.75 Granted 1,253,500 16.40 Exercised (194,122 ) 7.81 Forfeited (115,000 ) 7.74 Outstanding, September 30, 2017 3,492,786 11.58 Options exercisable, September 30, 2017 1,366,118 $ 9.86
Re-Measurement [Member]
Summary of Assumptions Used in Black-Scholes Option Pricing Model	As of September 30, 2017 and 2016, the Company used the Black-Scholes option valuation model with the following assumptions to re-measure non-employee 505-50: As of September 30, 2017 2016 Risk-free interest rate 1.28% -2.28% 1.35% - 1.56% Expected volatility 75.2% - 84.0% 73.9% - 74.6% Expected dividend yield 0% 0% Expected life of non-employee 0.88 - 9.44 7.33 - 9.60

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Contractual Obligations and Commitments Consisting of Future Minimum Lease Payments	Contractual obligations and commitments as of September 30, 2017, consisting of 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 $ 294 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,348 $ 7,459 Shelton operating lease 129 — — — — — 129 $ 423 $ 1,093 $ 1,217 $ 1,241 $ 1,266 $ 2,348 $ 7,588
Schedule of Reconciliation of Balances of Accrued Shelton Lease Cease-Use Liability	A reconciliation of the balances of the accrued Shelton Lease cease-use Three Months Ended September 30, 2017 2016 Balance July 1, 2017 $ 276 Balance, July 1, 2016 $ 1,232 Charges 90 Charges — Rental payments (247 ) Rental payments (234 ) Interest accretion 10 Interest accretion — Balance September 30, 2017 $ 129 Balance September 30, 2016 $ 998 Nine Months Ended September 30, 2017 2016 Balance, January 1, 2017 $ 756 Balance January 1, 2016 $ — Charges 90 Charges 1,312 Rental payments (741 ) Rental payments (314 ) Interest accretion 24 Interest accretion — Balance September 30, 2017 $ 129 Balance September 30, 2016 $ 998

Business - Additional Informati

Business - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 05, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Nature Of Business [Line Items]
Date of formation				Jul. 2, 2004
Proceeds from equity and debt financing		$ 291,100		$ 291,100
Upfront and milestone payments received in connection with license agreements		33,500		33,500
Unrestricted cash and cash equivalents and marketable securities		102,982		102,982
Accumulated deficit		206,164		206,164		$ 162,171
Net loss		$ (12,444)	$ (11,542)	(43,948)	$ (35,308)
Net cash used in operating activities				43,414	$ 34,193
Follow-on Public Offering [Member]
Nature Of Business [Line Items]
Proceeds from offering of common stock				86,224
Follow-on Public Offering [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Proceeds from offering of common stock	$ 86,224			$ 5

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail) $ in Thousands	Jan. 01, 2017USD ($)
ASU 2016-09 [Member]
Basis Of Presentation [Line Items]
Cumulative-effect adjustment to stockholders' equity	$ 45

Available-for-Sale Marketable33

Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 91,150	$ 46,181
Gross Unrealized Gains	50	12
Gross Unrealized Losses	(10)	(9)
Estimated Fair Value	91,190	46,184
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,826	8,268
Gross Unrealized Gains	49	8
Estimated Fair Value	42,875	8,276
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,523
Gross Unrealized Losses		(1)
Estimated Fair Value		2,522
US Government Corporations and Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,800	3,501
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(1)
Estimated Fair Value	7,800	3,502
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,368	16,683
Gross Unrealized Losses	(5)	(6)
Estimated Fair Value	19,363	16,677
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,156	15,206
Gross Unrealized Gains		3
Gross Unrealized Losses	(4)	(2)
Estimated Fair Value	$ 21,152	$ 15,207

Available-for-Sale Marketable34

Available-for-Sale Marketable Securities - Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Amortized Cost of marketable debt securities, contractual maturity, Less than one year	$ 48,324	$ 37,913
Fair value of marketable debt securities, contractual maturity, Less than one year	$ 48,315	$ 37,908

Available-for-Sale Marketable35

Available-for-Sale Marketable Securities - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)Position	Sep. 30, 2016USD ($)	Dec. 31, 2016Position
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 5,730	$ 23,368
Realized gains	$ 4	$ 12
Number of available-for-sale marketable securities in unrealized loss positions | Position	17		18
Total number of positions | Position	28		34
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 5,730
Realized gains	$ 4

Available-for-Sale Marketable36

Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	$ 29,707	$ 17,668
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(10)	(9)
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	29,707	17,668
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(10)	(9)
US Government Corporations and Agencies 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	3,498
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	3,498
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(1)
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)
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	18,016	9,919
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(5)	(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	18,016	9,919
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(5)	(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	8,193	5,227
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(4)	(2)
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	8,193	5,227
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (4)	$ (2)

Accumulated Other Comprehensi37

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	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance		$ 3	$ (35)
Other comprehensive income before reclassifications		41	67
Amount reclassified from accumulated other comprehensive income	$ (12)	(4)	(12)
Net current period other comprehensive income		37	55
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ 20	$ 40	$ 20

Accumulated Other Comprehensi38

Accumulated Other Comprehensive Income (Loss) - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income	$ 367	$ 176	$ 788	$ 498
Benefit from income taxes	(145)	(55)	(178)	(279)
Net of tax		12	4	12
Accumulated Net Unrealized Investment Gain Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income		12	4	12
Benefit from income taxes	$ 0	$ 0	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets
Restricted cash	$ 769	$ 769
Recurring [Member]
Financial assets
Total financial assets	104,451	59,745
Recurring [Member] | US Government Corporations and Agencies Securities [Member]
Financial assets
Available-for-sale marketable securities	7,800	3,502
Recurring [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	19,363	16,677
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets
Total financial assets	13,261	13,561
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Total financial assets	91,190	46,184
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | US Government Corporations and Agencies Securities [Member]
Financial assets
Available-for-sale marketable securities	7,800	3,502
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	19,363	16,677
Recurring [Member] | Money Market Funds [Member]
Financial assets
Cash and cash equivalents	11,792	12,092
Available-for-sale marketable securities	42,875	8,276
Restricted cash	1,469	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	11,792	12,092
Restricted cash	1,469	1,469
Recurring [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	42,875	8,276
Recurring [Member] | U.S. Treasury Securities [Member]
Financial assets
Available-for-sale marketable securities		2,522
Recurring [Member] | U.S. Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities		2,522
Recurring [Member] | Commercial Paper [Member]
Financial assets
Available-for-sale marketable securities	21,152	15,207
Recurring [Member] | Commercial Paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets
Available-for-sale marketable securities	$ 21,152	$ 15,207

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases of financial assets	$ 0	$ 0
Sales of financial assets	0	0
Maturities of financial assets	0	0
Transfer of financial asset into level 3 of fair value	0	0
Fair value assets level 2 to level 1 transfers	0	0
Fair value assets level 1 to level 2 transfers	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains	0	0
Unrealized losses	$ 0	$ 0

Restricted Cash - Additional In

Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash in current assets	$ 700	$ 700
Restricted cash balance	769	769
Shelton Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash in current assets	700	700
Stamford Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Letter of credit, remaining amount	769
Letter of credit, through the end of lease term	$ 408
Letter of credit, remaining amount date	2019-05
Operating lease, expiration date	Nov. 30, 2023
Restricted cash balance	$ 769	$ 769

Prepaid Expenses - Additional I

Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 1,492	$ 1,530
Prepaid R&D clinical costs	984	1,256
Prepaid insurance	346	112
Other prepaid costs	$ 162	$ 162

Accounts Payable and Accrued 43

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 1,187	$ 4,738
Accrued research projects	3,758	4,352
Accrued professional fees	473	163
Accrued compensation and benefits	1,496	1,514
Accrued other	358	766
Total	$ 7,272	$ 11,533

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Apr. 05, 2017	Sep. 30, 2017	Mar. 30, 2017
Follow-on Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share		$ 18
Common Stock [Member] | Follow-on Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share			$ 18
Proceeds from issuance of common stock net of underwriting discounts and offering costs	$ 86,224
Common stock, shares issued	5,117,500	5,117,500
Offering expenses paid	$ 294
Maximum [Member] | Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares subscribed			5,117,500
Maximum [Member] | Common Stock [Member] | Underwriter's Over-Allotment [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares subscribed			667,500
Common stock, shares issued	667,500

Collaborations - Additional Inf

Collaborations - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)Deliverables	Sep. 30, 2016USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and milestone fee revenue			$ 530,000
Collaborative revenue			313,000
Clinical compound revenue			68,000	$ 86,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and milestone fee revenue			$ 530,000
Number of deliverables for revenue recognized | Deliverables			2
Collaborative revenue			$ 313,000
Sub-license fee			843,000
Clinical compound revenue	$ 0	$ 0	68,000	86,000
Cost of clinical compound related to R&D expense	$ 0	$ 0	$ 61,000	$ 78,000

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Detail) - shares	Apr. 05, 2017	Sep. 30, 2017	Sep. 30, 2016
Common Stock [Member] | Follow-on Public Offering [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock issued	5,117,500	5,117,500
Employee Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents		3,492,786	2,299,117

Net Loss per Share - Computatio

Net Loss per Share - Computation of Denominators Used in Net Loss per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic:
Weighted average common shares outstanding	32,591,550	27,282,863	30,729,752	27,275,133
Diluted:
Weighted average common shares outstanding - Basic	32,591,550	27,282,863	30,729,752	27,275,133
Common stock options	0	0	0	0
Denominator for diluted net loss per share	32,591,550	27,282,863	30,729,752	27,275,133

Net Loss per Share - Computat48

Net Loss per Share - Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net loss	$ (12,444)	$ (11,542)	$ (43,948)	$ (35,308)
Weighted-average common shares outstanding:
Basic and Diluted	32,591,550	27,282,863	30,729,752	27,275,133
Net loss per share, Basic and Diluted	$ (0.38)	$ (0.42)	$ (1.43)	$ (1.29)

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 15, 2017	Jan. 01, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2015	Jan. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options granted			$ 10	$ 3.92	$ 11.61	$ 3.81
ASU 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cumulative-effect adjustment to stockholders' equity								$ 45
Nonemployee Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair values of outstanding options			$ 8.31	$ 5.75	$ 8.31	$ 5.75
Nonemployee Options [Member] | Modified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares outstanding as of modification date	98,771
Accelerate vesting percentage	50.00%
Number of stock options exercise period extended	183,000
Modification period during which stock options may be exercised					6 months
Compensation expense	$ 92
Nonemployee Options [Member] | General and Administrative [Member] | Modified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense			$ 474		$ 474
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						3,920,613
Options granted			415,000	75,000	1,253,500	797,000
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

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.87%		1.85%	1.19%
Risk-free interest rate, maximum	1.97%	1.19%	2.57%	1.79%
Expected volatility, minimum	81.40%		75.30%	67.80%
Expected volatility, maximum	81.70%	71.90%	83.30%	72.60%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Employee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	6 years 2 months 30 days	6 years 2 months 30 days	6 years 2 months 30 days	6 years 2 months 30 days
Nonemployee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)			10 years	10 years

Stock-Based Compensation - Su51

Stock-Based Compensation - Summary of Re-measurement of Assumptions Used in Black-Scholes Option Pricing Model (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	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
Re-Measurement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield			0.00%	0.00%
Re-Measurement [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			1.28%	1.35%
Expected volatility			75.20%	73.90%
Re-Measurement [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			2.28%	1.56%
Expected volatility			84.00%	74.60%
Re-Measurement [Member] | Nonemployee Options [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)			10 months 17 days	7 years 3 months 29 days
Re-Measurement [Member] | Nonemployee Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)			9 years 5 months 9 days	9 years 7 months 6 days

Stock-Based Compensation - Su52

Stock-Based Compensation - Summary of Compensation Expense Relating to Stock Options (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 2,094	$ 777	$ 4,520	$ 1,971
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	619	375	1,784	867
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense	$ 1,475	$ 402	$ 2,736	$ 1,104

Stock-Based Compensation - Su53

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - 2014 Equity Incentive Plan [Member] - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding at December 31, 2016			2,548,408
Number of Options, Granted	415,000	75,000	1,253,500	797,000
Number of Options, Exercised			(194,122)
Number of Options, Forfeited			(115,000)
Number of Options, Outstanding at September 30 2017	3,492,786		3,492,786
Number of Options, Options exercisable at September 30 2017	1,366,118		1,366,118
Weighted-Average Exercise Price, Outstanding at December 31, 2016			$ 8.75
Weighted-Average Exercise Price, Granted			16.40
Weighted-Average Exercise Price, Exercised			7.81
Weighted-Average Exercise Price, Forfeited			7.74
Weighted-Average Exercise Price, Outstanding at September 30 2017	$ 11.58		11.58
Weighted-Average Exercise Price, Options exercisable at September 30 2017	$ 9.86		$ 9.86

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Pre-tax losses	$ (12,589)	$ (11,597)	$ (44,126)	$ (35,587)
Benefit from income taxes	$ (145)	$ (55)	$ (178)	$ (279)
Percentage of annual research and development credit for cash	65.00%

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Contractual Obligations and Commitments Consisting of Future Minimum Lease Payments (Detail) $ in Thousands	Sep. 30, 2017USD ($)
Operating Leased Assets [Line Items]
2,017	$ 423
2,018	1,093
2,019	1,217
2,020	1,241
2,021	1,266
Thereafter	2,348
Total	7,588
Stamford Operating Lease [Member]
Operating Leased Assets [Line Items]
2,017	294
2,018	1,093
2,019	1,217
2,020	1,241
2,021	1,266
Thereafter	2,348
Total	7,459
Shelton Operating Lease [Member]
Operating Leased Assets [Line Items]
2,017	129
Total	$ 129

Commitments and Contingencies56

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Other Commitments [Line Items]
Deferred lease obligation		$ 1,701			$ 1,570
Lease minimum rental payment		$ 7,588
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 June 30, 2017 and December 31, 2016, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $648 and $583, respectively. The Stamford Lease is renewable for one five-year term.
Operating Lease, renewable term		5 years
Operating lease, expiration date		Nov. 30, 2023
Deferred lease obligation		$ 823			583
Tenant improvement expenses	$ 1,094
Lease minimum rental payment		7,459
Stamford Operating Lease [Member] | Leasehold Improvements [Member]
Other Commitments [Line Items]
Deferred lease obligation		$ 878			987
Stamford Operating Lease [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
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
Accrued cease use date liability	$ 1,312
Lease minimum rental payment		$ 129
Restructuring liability		129	$ 998	$ 276	756	$ 1,232
Additional amortization expense			$ 899
Additional loss per share			$ 0.03
Shelton Operating Lease [Member] | Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, remaining amount		$ 700			$ 700
Letter of credit, expiration period after lease termination		60 days

Commitments and Contingencies57

Commitments and Contingencies - Schedule of Reconciliation of Balances of Accrued Shelton Lease Cease-Use Liability (Detail) - Shelton Operating Lease [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, beginning balance	$ 276	$ 1,232	$ 756
Charges	90		90	$ 1,312
Rental payments	(247)	(234)	(741)	(314)
Interest accretion	10		24
Restructuring reserve, ending balance	$ 129	$ 998	$ 129	$ 998