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Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

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, 2019 and 2018 and by level within the fair value hierarchy:

Fair value measurement as of December 31, 2019:


			Quoted prices in		Significant other		Significant
Financial assets			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 funds and checking accounts	$	18,305	$	18,305	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		16,081		—		16,081		—
U.S. government agency obligations		25,816		—		25,816		—
Corporate bonds		115,890		—		115,890		—
Commercial paper		38,573		—		38,573		—
Municipal bonds		3,500		—		3,500		—
Restricted cash:
Commercial money market account		408		408		—		—
Total financial assets	$	218,573	$	18,713	$	199,860	$	—

Fair value measurement as of December 31, 2018:


			Quoted prices in		Significant other		Significant
Financial assets			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 funds and checking accounts	$	15,081	$	15,081	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		19,539		—		19,539		—
U.S. government agency obligations		17,859		—		17,859		—
Corporate bonds		75,910		—		75,910		—
Commercial paper		50,390		—		50,390		—
Municipal bonds		4,000		—		4,000		—
Restricted cash:
Commercial money market account		769		769		—		—
Total financial assets	$	183,548	$	15,850	$	167,698	$	—

Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 18,305	$ 15,081
Marketable securities	136,701	146,302
Income tax receivable	816	664
Other receivables	971	926
Prepaid expenses	8,863	4,805
Restricted cash, current		361
Total current assets	165,656	168,139
Operating lease right-of-use asset	3,036
Marketable securities, non-current	63,159	21,396
Property and equipment, net	700	880
Restricted cash	408	408
Total assets	232,959	190,823
Current liabilities:
Accounts payable and accrued expenses	19,665	13,622
Operating lease liability, current	967
Current portion of deferred revenue	22,262	26,825
Total current liabilities	42,894	40,447
Operating lease liability, non-current	3,352
Deferred revenue, non-current		15,184
Deferred lease obligation		1,562
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at December 31, 2019 and December 31, 2018, zero shares issued and outstanding at December 31, 2019 and December 31, 2018
Common stock; $0.001 par value; 100,000,000 shares authorized at December 31, 2019 and December 31, 2018, 46,720,225 shares and 39,547,558 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	47	39
Additional paid-in capital	587,223	428,059
Accumulated deficit	(400,727)	(294,354)
Accumulated other comprehensive income (loss)	170	(114)
Total stockholders’ equity	186,713	133,630
Total liabilities and stockholders’ equity	$ 232,959	$ 190,823

Condensed Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Other comprehensive income, tax	$ 0	$ 0	$ 0

Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 8,863	$ 4,805
Prepaid R&D clinical costs	8,498	4,377
Prepaid insurance	181	245
Other prepaid costs	$ 184	$ 183

Net Loss per Share - Additional Information (Detail) - shares		1 Months Ended					12 Months Ended
	Jun. 04, 2019	Dec. 31, 2019	May 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units vested shares					83,791
Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units vested shares		36,666	74,166				110,832	83,791
Restricted Stock Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, vested		36,666	74,166
Restricted Stock Units [Member] \| 2014 Equity Incentive Plan [Member] \| Executive Officers [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, vested		36,666	74,166
Restricted stock units, approved and granted				215,000		83,791
Restricted Stock Units [Member] \| 2014 Equity Incentive Plan [Member] \| Director [Member] \| Share-based Payment Arrangement, Nonemployee [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, vested							0
Restricted stock units, approved and granted	24,000						24,000
Employee Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents							4,450,517	4,004,422	3,492,141
Restricted Stock Units [Member] \| Executive Officers [Member] \| Share-based Payment Arrangement, Employee [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents							104,168
Restricted Stock Units [Member] \| 2014 Equity Incentive Plan [Member] \| Director [Member] \| Share-based Payment Arrangement, Nonemployee [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents	24,000

Condensed Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Condensed Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (106,373)	$ (74,013)	$ (58,125)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	12,568	9,478	5,793
Modification of equity awards		616	537
Depreciation and amortization	198	370	495
Amortization expense component of lease expense	601
Noncash expense related to oral formulation license agreement	4,000
Accretion of available-for-sale marketable securities	(1,381)	(1,820)	(582)
Realized loss (gain) on sale of available-for-sale marketable securities		5	(5)
Realized gain on sale of property and equipment			(41)
Deferred rent costs		(156)	148
Deferred revenue	(19,747)	42,009
Changes in operating assets and liabilities:
Income tax receivable	(152)	67	121
Other receivables	(45)	(803)	(36)
Prepaid expenses	(4,058)	(3,170)	(105)
Accounts payable and accrued expenses	6,043	5,116	(3,027)
Operating lease liability	(879)
Net cash used in operating activities	(109,225)	(22,301)	(54,827)
Investing activities
Proceeds from maturities of available-for-sale marketable securities	253,584	175,300	82,156
Proceeds from sale of available-for-sale marketable securities		79,808	8,755
Proceeds from the redemptions of available-for-sale marketable securities, at par	2,000
Purchases of available-for-sale marketable securities	(286,082)	(337,854)	(127,394)
Purchases of property and equipment	(18)	(73)	(58)
Proceeds from sale of property and equipment			41
Net cash used in investing activities	(30,516)	(82,819)	(36,500)
Financing activities
Proceeds from the sale of common stock in a follow-on public offering, net of issuance costs	136,498	92,063	86,224
Proceeds from the sale of common stock under license agreement		14,556
Proceeds from the exercise of stock options	6,106	4,194	1,699
Net cash provided by financing activities	142,604	110,813	87,923
Net increase (decrease) in cash, cash equivalents and restricted cash	2,863	5,693	(3,404)
Cash, cash equivalents and restricted cash at beginning of period	15,850	10,157	13,561
Cash, cash equivalents and restricted cash at end of period	18,713	$ 15,850	$ 10,157
Noncash investing and financing activities
Shares of common stock issued in connection with oral formulation license agreement	4,000
Shares of common stock issued in exchange for consulting services	$ 197

Income Taxes - Components of Income Taxes (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
State	$ (816)	$ (389)	$ (204)
Total Current	(816)	(389)	(204)
Deferred:
Income Tax Expense (Benefit), Total	$ (816)	$ (389)	$ (204)

Quarterly Results of Operations (Unaudited) - Schedule of Selected Financial Data for Each Quarter (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 4,511	$ 5,785	$ 5,208	$ 4,382	$ 5,533	$ 5,062	$ 2,874		$ 19,886	$ 13,469	$ 911
Net loss - Basic and Diluted	$ (28,611)	$ (32,842)	$ (22,960)	$ (21,960)	$ (20,652)	$ (19,400)	$ (17,194)	$ (16,767)	$ (106,373)	$ (74,013)	$ (58,125)
Net loss per share, Basic and Diluted	$ (0.61)	$ (0.74)	$ (0.58)	$ (0.56)	$ (0.52)	$ (0.51)	$ (0.52)	$ (0.51)	$ (2.49)	$ (2.06)	$ (1.86)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Available-for-Sale Marketable Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) position	Dec. 31, 2018 USD ($) position	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities		$ 79,808,000	$ 8,755,000
Realized (losses) gains		$ (5,000)	$ 5,000
Number of available-for-sale marketable securities in unrealized loss positions \| position	16	69
Total number of positions \| position	81	84
Other-than-temporary impairments on securities	$ 0	$ 0
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sale of available-for-sale marketable securities	$ 0	79,808,000
Realized (losses) gains		$ (5,000)

Restricted Cash

12 Months Ended

Dec. 31, 2019

Receivables [Abstract]

Restricted Cash

7. Restricted Cash

The Company is required to maintain a stand-by letter of credit as a security deposit under its lease for its office space in Stamford, Connecticut (refer to Note 17, Commitments and Contingencies: Leases). The fair value of the letter of credit approximates its contract value. The Company’s bank requires the Company to maintain a restricted cash balance to serve as collateral for the letter of credit issued to the landlord by the bank. As of December 31, 2019, the restricted cash balance for the Stamford lease was invested in a commercial money market account.

The letter of credit balance for the Stamford lease was required to remain at $769 through May 2019 and thereafter, upon request from the Company, was eligible to 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 was contingent upon the Company not being in default of any provisions of that lease prior to request for the reduction. In July 2019, the Company was granted the reduction in the balance of the letter of credit. As of December 31, 2019, the Company had $408 of restricted cash related to the Stamford lease in long-term assets. As of December 31, 2018, the Company had $361 of restricted cash related to the Stamford lease in current assets and $408 in long-term assets, respectively.

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the Balance Sheets that sum to the total of the same such amounts shown in the Statements of Cash Flows.


	December 31, 2019		December 31, 2018
Cash and cash equivalents	$	18,305	$	15,081
Restricted cash, current assets		—		361
Restricted cash, long-term assets		408		408
Total cash, cash equivalents, and restricted cash shown in the Statements of Cash Flows	$	18,713	$	15,850

Stock-Based Compensation - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Detail)		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum		1.55%	2.51%	1.85%
Risk-free interest rate, maximum		2.62%	3.09%	2.57%
Expected volatility, minimum		71.10%	82.60%	75.30%
Expected volatility, maximum		75.20%	92.80%	84.50%
Expected dividend yield		0.00%	0.00%	0.00%
Re-Measurement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield		0.00%	0.00%	0.00%
Share-based Payment Arrangement, Nonemployee [Member] \| Consultants [Member] \| Re-Measurement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	2.59%		1.82%	1.28%
Risk-free interest rate, maximum	2.62%		3.02%	2.39%
Expected volatility, minimum	58.90%		58.20%	74.60%
Expected volatility, maximum	84.60%		101.00%	87.30%
Share-based Payment Arrangement, Nonemployee [Member] \| Consultants [Member] \| Re-Measurement [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	9 months 22 days		3 months	7 months 13 days
Share-based Payment Arrangement, Nonemployee [Member] \| Consultants [Member] \| Re-Measurement [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	8 years 2 months 9 days		8 years 11 months 9 days	9 years 11 months 9 days
Employee Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility			75.00%	79.00%
Expected volatility, minimum		71.00%	83.00%	75.00%
Expected volatility, maximum		75.00%	93.00%	85.00%
Expected dividend yield		0.00%
Expected life of options (in years)		6 years 3 months
Employee Options [Member] \| Share-based Payment Arrangement, Nonemployee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)				10 years
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

Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,032	$ 2,014
Less accumulated depreciation and amortization	1,332	1,134
Property, Plant and Equipment, Net, Total	700	880
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	211	211
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	628	628
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	61	47
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,132	$ 1,128

Income Taxes - Schedule of Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Valuation allowance	$ (114,136)	$ (89,815)
Deferred tax assets:
Net operating loss carryforwards	84,608	73,578
Federal and state tax credits	16,624	11,108
Deferred revenue	5,994	1,111
Stock-based compensation expense	4,481	3,605
Other	3,409	420
Deferred tax asset	115,116	89,822
Deferred tax liabilities:
Other	(980)	(7)
Deferred tax liabilities	$ (980)	$ (7)

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2019
Postemployment Benefits [Abstract]
Employee Benefit Plan	16. 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 at the beginning of the calendar quarter 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. 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, 2019, 2018 and 2017, employer contributions to the plan were $279, $198 and $174, respectively.

Summary of Significant Accounting Policies - Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) lease
Basis Of Presentation [Line Items]
Lease, Practical Expedient, Use of Hindsight [true false]	true
Lease, Practical Expedients, Package [true false]	true
Stamford Operating Lease [Member]
Basis Of Presentation [Line Items]
Annual incremental borrowing rate	7.00%
Operating lease, renewable term	5 years
Stamford Operating Lease [Member] \| ASC 842 [Member]
Basis Of Presentation [Line Items]
Number of operating lease \| lease	1
Annual incremental borrowing rate	7.00%
Operating lease, renewable term	5 years
Cumulative effect adjustment \| $	$ 0

Stock-Based Compensation - Summary of Compensation Expense Relating to Stock Options (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Oct. 31, 2018	Aug. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			$ 10,300,000	$ 8,401,000	$ 6,330,000
Compensation expense not yet recognized			$ 22,216,000
Weighted average period of compensation expense not yet recognized			2 years 8 months 27 days
Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from operations			$ 0	0	0
Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from financing activities			0	0	0
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			5,094,000	4,482,000	3,897,000
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			5,206,000	3,919,000	2,433,000
Shareholder Consulting Agreement [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			197,000
Restricted Stock Units [Member] \| Director [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			287,000
Restricted Stock Units [Member] \| Executive Officers [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			1,180,000	1,217,000
Restricted Stock Units [Member] \| Executive Officers [Member] \| Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense			$ 604,000	476,000
Modified Awards [Member] \| Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Accelerate vesting percentage	50.00%	50.00%
Modification period during which stock options may be exercised		6 months
Modified Awards [Member] \| Non Employee Stock Option [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense				96,000	$ 537,000
Modified Awards [Member] \| Non Employee Stock Option [Member] \| Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock option expense				$ 520,000
Modified Awards [Member] \| Non Employee Stock Option [Member] \| Chief Medical Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Consulting agreement maturity date	May 31, 2019
Modified Awards [Member] \| Non Employee Stock Option [Member] \| Chief Financial Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Consulting agreement maturity date		Feb. 15, 2018

Net Loss Per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

15. Net Loss per Share

The Company computes net loss per share in accordance with ASC 260‑10, Earnings per Share (see Note 2, Significant Accounting Policies – Income (Loss) per Share).

The denominators used in the net loss per share computations are as follows:


	Year Ended December 31,
	2019	2018	2017
Basic:
Weighted average common shares outstanding	42,669,333	35,892,786	31,202,842
Diluted:
Weighted average common shares outstanding - Basic	42,669,333	35,892,786	31,202,842
Common stock options*	—	—	—
Denominator for diluted net loss per share	42,669,333	35,892,786	31,202,842

*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,
	2019		2018		2017
Net loss	$	(106,373)	$	(74,013)	$	(58,125)
Weighted-average common shares outstanding:
Basic and Diluted		42,669,333		35,892,786		31,202,842
Net loss per share, Basic and Diluted	$	(2.49)	$	(2.06)	$	(1.86)

As of December 31, 2019, 2018 and 2017, 4,450,517, 4,004,422 and 3,492,141 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. In addition, 104,168 unvested restricted stock units issued to executive officers that were outstanding at December 31, 2019 were also not included in the computation of diluted net loss per share because to do so would have been anti-dilutive. The 36,666 and 74,166 restricted stock units that vested and were settled in shares of common stock in December 2019 and May 2019, respectively, were included in the computation of basic and diluted net loss per share for the year ended December 31, 2019. The 24,000 restricted stock units granted in June 2019 to the non-employee members of the Board of Directors were also not included in the computation of diluted net loss per share because to do so would have been anti-dilutive (see Note 13, Stock-Based Compensation).

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	$ 133,630	$ 86,780	$ 50,725
Other comprehensive income before reclassifications	284	(49)	(68)
Amount reclassified from accumulated other comprehensive loss (income)		5	(5)
Net current period other comprehensive income	284	(44)	(73)
Balance, Value	186,713	133,630	86,780
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, Value	(114)	(70)	3
Net current period other comprehensive income	284	(44)	(73)
Balance, Value	$ 170	$ (114)	$ (70)

Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	May 31, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash in current assets			$ 361
Restricted cash balance	$ 408		408
Stamford Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Letter of credit, remaining amount	$ 408	$ 769
Letter of credit, remaining amount date	2019-05
Operating lease, expiration date	Nov. 30, 2023
Restricted cash in current assets			361
Restricted cash balance	$ 408		$ 408

Restricted Cash - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 18,305	$ 15,081
Restricted cash in current assets		361
Restricted cash balance	408	408
Total cash, cash equivalents, and restricted cash shown in the Condensed Statements of Cash Flows	$ 18,713	$ 15,850	$ 10,157	$ 13,561

Available-for-Sale Marketable Securities - Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Amortized Cost of marketable debt securities, contractual maturity, Less than one year	$ 136,565	$ 146,363
Amortized Cost of marketable debt securities, contractual maturity, One year to two years	63,125	21,449
Amortized Cost	199,690	167,812
Fair value of marketable debt securities, contractual maturity, Less than one year	136,701	146,302
Fair value of marketable debt securities, contractual maturity, One year to two years	63,159	21,396
Total fair Value of marketable debt securities, contractual maturity	$ 199,860	$ 167,698

Revenue Recognition - Additional Information (Detail) ¥ in Billions		1 Months Ended			3 Months Ended							12 Months Ended
	May 17, 2018 USD ($) item	Mar. 31, 2017 USD ($)	Apr. 30, 2013 USD ($) item	Apr. 30, 2012 USD ($) item	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) Milestone item	Dec. 31, 2018 USD ($) Milestone	Dec. 31, 2017 USD ($) Milestone	Apr. 30, 2013 JPY (¥)	Apr. 30, 2013 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, current					$ 22,262,000				$ 26,825,000			$ 22,262,000	$ 26,825,000
Deferred revenue, non current									15,184,000				15,184,000
Total revenue					4,511,000	$ 5,785,000	$ 5,208,000	$ 4,382,000	5,533,000	$ 5,062,000	$ 2,874,000	$ 19,886,000	$ 13,469,000	$ 911,000
Number of milestone event probable of occurrence or achieved \| Milestone												0	0	0
License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue												$ 19,746,000	$ 13,436,000	$ 530,000
Royalty [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer												0
VFMCRP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, current					22,262,000				26,825,000			22,262,000	26,825,000
Deferred revenue, non current									15,184,000				15,184,000
Receivables					0				0			0	0
Other assets					0				0			0	0
Deferred revenue	$ 55,444,000				0							0
Number of combined performance obligations for revenue recognized \| item	1
Number of performance obligations for revenue recognized \| item	2
upfront payment	$ 50,000,000
Premium from sale of stock	$ 5,444,000
Remaining performance obligations					$ 22,262,000							$ 22,262,000
Remaining performance obligation, expected timing of satisfaction, year					2020							2020
VFMCRP Agreement [Member] \| License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue												$ 33,182,000
Maruishi and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Receivables					$ 0				0			0	0
Other assets					0				0			0	0
Deferred revenue					0				$ 0			$ 0	$ 0
Number of license agreements \| item												2
Remaining performance obligations					$ 0							$ 0
Maruishi Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized \| item			2
Premium from sale of stock			$ 337,000
Upfront non-refundable, non-creditable license fee and premium from sale of stock			15,337,000
Maruishi Agreement [Member] \| Clinical Development and Regulatory Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration																$ 10,500,000
Maruishi Agreement [Member] \| One-time Sales Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration \| ¥															¥ 1
Maruishi Agreement [Member] \| License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price			10,200,000
Upfront payments on obligations			9,637,000
Maruishi Agreement [Member] \| R&D Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price			6,200,000
Upfront payments on obligations			$ 5,700,000
CKDP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of combined performance obligations for revenue recognized \| item				1
Premium from sale of stock				$ 83,000
CKDP Agreement [Member] \| Clinical Development and Regulatory Milestones [Member] \| Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration				3,750,000
CKDP Agreement [Member] \| License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer				$ 646,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized \| item												2
Maruishi Pharmaceutical Co., Ltd. [Member] \| License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue														530,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue		$ 843,000												$ 843,000

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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (28,611)	$ (32,842)	$ (22,960)	$ (21,960)	$ (20,652)	$ (19,400)	$ (17,194)	$ (16,767)	$ (106,373)	$ (74,013)	$ (58,125)
Weighted-average common shares outstanding:
Basic and Diluted									42,669,333	35,892,786	31,202,842
Net loss per share, Basic and Diluted	$ (0.61)	$ (0.74)	$ (0.58)	$ (0.56)	$ (0.52)	$ (0.51)	$ (0.52)	$ (0.51)	$ (2.49)	$ (2.06)	$ (1.86)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

10. Fair Value Measurements

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2019 and 2018 and by level within the fair value hierarchy:

Fair value measurement as of December 31, 2019:


			Quoted prices in		Significant other		Significant
Financial assets			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 funds and checking accounts	$	18,305	$	18,305	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		16,081		—		16,081		—
U.S. government agency obligations		25,816		—		25,816		—
Corporate bonds		115,890		—		115,890		—
Commercial paper		38,573		—		38,573		—
Municipal bonds		3,500		—		3,500		—
Restricted cash:
Commercial money market account		408		408		—		—
Total financial assets	$	218,573	$	18,713	$	199,860	$	—

Fair value measurement as of December 31, 2018:


			Quoted prices in		Significant other		Significant
Financial assets			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 funds and checking accounts	$	15,081	$	15,081	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		19,539		—		19,539		—
U.S. government agency obligations		17,859		—		17,859		—
Corporate bonds		75,910		—		75,910		—
Commercial paper		50,390		—		50,390		—
Municipal bonds		4,000		—		4,000		—
Restricted cash:
Commercial money market account		769		769		—		—
Total financial assets	$	183,548	$	15,850	$	167,698	$	—

There were no purchases, sales or maturities of Level 3 financial assets and no unrealized gains or losses related to Level 3 available-for-sale marketable securities for the years ended December 31, 2019, 2018 and 2017. There were no transfers of financial assets between Levels 1, 2, or 3 classifications during the years ended December 31, 2019 and 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

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, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	$ 38,744	$ 132,755
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(27)	(119)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	38,744	132,755
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(27)	(119)
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	3,185	16,392
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(2)	(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	3,185	16,392
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(2)	(1)
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Fair Value	2,400	5,596
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(1)	(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	2,400	5,596
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(1)	(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	28,895	71,322
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(23)	(94)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	28,895	71,322
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(23)	(94)
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	4,264	39,445
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(1)	(23)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	4,264	39,445
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (1)	$ (23)

Prepaid Expenses	12 Months Ended
Prepaid Expenses	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses	5. Prepaid Expenses As of December 31, 2019, the amount of prepaid expenses was $8,863, consisting of $8,498 of prepaid R&D clinical costs, $181 of prepaid insurance and $184 of other costs. As of December 31, 2018, the amount of prepaid expenses was $4,805, consisting of $4,377 of prepaid R&D clinical costs, $245 of prepaid insurance and $183 of other costs.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

13. Stock-Based Compensation

2019 Inducement Plan

On October 30, 2019, the Company’s Board of Directors adopted the 2019 Inducement Plan, or the 2019 Plan, which is a non-stockholder approved stock plan adopted pursuant to the “inducement exception” provided under Nasdaq Listing Rule 5635(c)(4), or Rule 5635, for the purpose of awarding (i) non-statutory stock options, (ii) restricted stock awards, (iii) restricted stock unit awards, (iv) other stock awards (collectively, the Inducement Awards) to new employees of the Company, as inducement material to such new employees entering into employment with the Company. On November 20, 2019, the Company filed a Registration Statement on Form S-8 with the SEC covering the offering of up to 300,000 shares of its common stock, par value $0.001, pursuant to the Company’s 2019 Plan. During the year ended December 31, 2019, the Company granted 47,500 stock options under the 2019 Plan to new employees. Initial grants of Inducement Awards made to employees vest as to 25% on the first anniversary of the date of grant and the balance ratably over the next 36 months and subsequent grants vest monthly over a period of four years from the grant date.

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 stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, performance stock awards and other forms of equity compensation, collectively referred to as Stock Awards. Additionally, the 2014 Plan provides for the grant of performance cash awards. Incentive stock options may be granted only to employees. All other awards may be granted to employees, including officers, non-employee directors, and consultants. No incentive stock options may be granted under the 2014 Plan after the tenth anniversary of the effective date of the 2014 Plan. Stock Awards granted under the 2014 Plan vest at the rate specified by the Plan administrator. Initial grants of Stock Awards made to employees and non-employee consultants generally vest as to 25% on the first anniversary of the date of grant and the balance ratably over the next 36 months and subsequent grants vest monthly over a period of four years from the grant date. Beginning in 2018, stock options initially granted to members of the Company’s Board of Directors vest over a period of three years in equal installments from the date of the grant, subject to the option holder’s continued service as a Director through such date. Subsequent grants to Directors that are made automatically at Annual Meetings of Stockholders vest fully on the first anniversary of the date of grant. The Plan administrator determines the term of Stock Awards granted under the 2014 Plan up to a maximum of ten years.

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, 2020, the aggregate number of shares of common stock that may be issued pursuant to Stock Awards under the 2014 Plan automatically increased from 6,086,907 to 7,488,513. 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.

Restricted Stock Units

In June 2019, the Board of Directors, upon the recommendation of the Compensation Committee, amended the Company’s non-employee director compensation policy. Pursuant to the terms of the amended policy, each non-employee director was entitled to receive, at the time of the Company’s 2019 Annual Meeting of Stockholders, 6,000 restricted stock units. As a result, on June 4, 2019, the date of the Company’s 2019 Annual Meeting of Stockholders, an aggregate of 24,000 restricted stock units were granted to Directors under the 2014 Plan with a grant date fair value of $20.47 per share. The restricted stock units vest on the earlier of (i) June 4, 2020 and (ii) immediately prior to the Company’s next Annual Meeting of Stockholders following the grant date, subject to the recipient’s continued service through such date. As a result, the Company will recognize compensation expense associated with these restricted stock units ratably over the one-year vesting period following the grant date. For the year ended December 31, 2019, $287 of stock compensation expense relating to the Board of Directors’ restricted stock units was recognized in the Statements of Comprehensive Loss, all of which related to G&A expense. None of the 24,000 restricted stock units vested or were settled in shares of the Company’s common stock as of December 31, 2019.

In March 2019, the Compensation Committee of the Company’s Board of Directors approved and granted a total of 215,000 restricted stock units to executive officers under the 2014 Plan with a grant date fair value of $16.10 per share. Vesting of the restricted stock units was contingent on the achievement of certain performance targets, subject to the recipient’s continuous service through the vesting events. At the date of grant, the Company concluded that the probability of achievement of the performance targets could not be determined until they were achieved, and accordingly, the Company would recognize compensation expense associated with these awards when, and to the extent, the restricted stock units vested in accordance with achievement of the performance targets. In December 2019 and May 2019, performance targets relating to 36,666 and 74,166 restricted stock units, respectively, had been achieved and thus such restricted stock units vested and the awards were settled in shares of common stock. As a result, $1,784 of stock compensation expense relating to the vesting of these restricted stock units was recognized in the Statements of Comprehensive Loss for the year ended December 31, 2019, consisting of $1,180 relating to G&A expense and $604 relating to R&D expense.

In September 2018, the Company granted a total of 83,791 restricted stock units to executive officers under the 2014 Plan with a grant date fair value of $20.21 per share. Vesting of the restricted stock units was contingent on the achievement of certain performance targets through the first quarter of 2019, subject to the recipient’s continuous service through the vesting events. At the date of grant, the Company concluded that the probability of achievement of the performance targets could not be determined until they were achieved, and accordingly, the Company would recognize compensation expense associated with these awards when, and to the extent, the restricted stock units vested in accordance with achievement of the performance targets. As of December 31, 2018, all of the performance targets had been achieved and, consequently, all of the restricted stock units had vested. As a result, $1,693 of stock compensation expense relating to the vesting of restricted stock units was recognized in the Statement of Comprehensive Loss for the year ended December 31, 2018, consisting of $1,217 relating to G&A stock compensation expense and $476 relating to R&D stock compensation expense. In addition, all of the 83,791 restricted stock units were converted to outstanding shares of the Company’s common stock as of December 31, 2018.

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 expired and no further grants of stock options or restricted stock are allowed.

The Company accounts for stock options granted to employees and non-employee members of the Board of Directors in accordance with ASC 718, Compensation – Stock Compensation. The Company also occasionally grants stock options to non-employee consultants. Prior to January 1, 2019, the Company used the Black-Scholes option valuation model to re-measure the fair value of all outstanding options that had been granted to non-employee consultants during the vesting period of each tranche in accordance with ASC 505‑50. Under ASC 505‑50, upon re-measurement of each award, income or expense was recognized during its vesting term. On January 1, 2019, the Company used the Black-Scholes option valuation model to re-measure the fair value of all outstanding unvested options that had been granted to non-employee consultants in accordance with ASU 2018‑07 (see Note 2, Accounting Pronouncements Recently Adopted).

A summary of the Company’s stock option activity related to employees, non-employee members of the Board of Directors and non-employee consultants for the 2019 Plan, the 2014 Plan and the 2004 Plan as of and for the year ended December 31, 2019 is as follows:


		Weighted		Aggregate
	Number of	Average Exercise		Intrinsic
	Shares	Price		Value
Outstanding, December 31, 2018	4,004,422	$	13.34
Granted	1,324,000		17.44
Exercised	(555,847)		10.98
Expired	—		—
Forfeited	(322,058)		15.12
Outstanding, December 31, 2019	4,450,517	$	14.73	$	10,350
Weighted average remaining contractual life as of December 31, 2019 (in years)	7.35
Options exercisable, December 31, 2019	2,407,027	$	12.97	$	8,733
Weighted average remaining contractual life as of December 31, 2019 (in years)	6.18
Options vested and expected to vest as of December 31, 2019	4,450,517	$	14.73	$	10,350
Weighted average remaining contractual life as of December 31, 2019 (in years)	7.35

The total fair value of options vested during the years ended December 31, 2019, 2018 and 2017 was $10,074, $9,023 and $5,303, respectively. The intrinsic value of options exercised during the years ended December 31, 2019, 2018 and 2017 was $5,741, $3,893 and $2,285, respectively.

During the years ended December 31, 2019, 2018 and 2017, the Company granted 1,324,000, 1,197,500 and 1,328,500 stock options, respectively, to employees, non-employee members of the Board of Directors or non-employee consultants under the 2019, 2014 and 2004 plans. 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,
	2019		2018		2017
Risk-free interest rate	1.55% - 2.62	%	2.51% - 3.09	%	1.85% - 2.57	%
Expected volatility	71.1% - 75.2	%	82.6% - 92.8	%	75.3% - 84.5	%
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 options (in years)	—		—		10

The weighted average grant date fair value of options granted to employees, non-employee members of the Board of Directors for their Board service and non-employee consultants during the years ended December 31, 2019, 2018 and 2017 was $11.67, $11.99 and $11.46, respectively.

On January 1, 2019, the Company used the Black Scholes option valuation model to remeasure the fair value of all outstanding unvested options that had been granted to non-employee consultants in accordance with ASU 2018-07. At the end of each fiscal quarter during the years ended December 31, 2018 and 2017, the Company used the Black-Scholes option valuation model to re-measure the fair value of all outstanding options that had been granted to non-employee consultants during the vesting period of each tranche in accordance with ASC 505‑50. The range of assumptions used by the Company on January 1, 2019 and during the years ended December 31, 2018 and 2017 are as follows:


	January 1,	December 31,
	2019	2018	2017
Risk-free interest rate	2.59% - 2.62%	1.82% - 3.02%	1.28% - 2.39%
Expected volatility	58.9% - 84.6%	58.2% - 101.0%	74.6% - 87.3%
Expected dividend yield	0%	0%	0%
Expected life of non-employee options (in years)	0.81 - 8.19	0.25 - 8.94	0.62 - 9.94

The weighted average fair value of outstanding options that had been granted to nonemployee consultants during the years ended December 31, 2018 and 2017 was $8.74 and $10.16, respectively. There were no options granted to nonemployee consultants during the year ended December 31, 2019.

During the years ended December 31, 2019, 2018 and 2017, the Company recognized compensation expense relating to stock options as follows:



	Year Ended December 31,
	2019		2018		2017
Research and development	$	5,206	$	3,919	$	2,433
General and administrative		5,094		4,482		3,897
Total stock option expense	$	10,300	$	8,401	$	6,330

The following were excluded from the table above as they are not related to stock options: compensation expense for i) the issuance of common stock relating to the consulting agreement for $197 in G&A expense for the year ended December 31, 2019; ii) the vesting of executives’ restricted stock units for $604 and $476 in R&D expense for the years ended December 31, 2019 and 2018, respectively, and $1,180 and $1,217 in G&A expense for the years ended December 31, 2019 and 2018, respectively; and iii) compensation expense relating to the Board of Directors’ restricted stock units for $287 in G&A expense for the year ended December 31, 2019.

In October 2018, the Company modified the terms of its former Chief Medical Officer’s outstanding Stock Awards to accelerate 50% of the unvested shares underlying his outstanding stock options immediately as of the modification date, and specify that the remainder of the unvested shares would vest monthly through the date of termination of his continuous service to the Company as a Consultant. As of the modification date, the Company entered into a consulting agreement with the former Chief Medical Officer under which he provided continuous service to the Company as a Consultant by providing transition services and other services upon request by the Company. Pursuant to the terms of the separation and consulting agreement, such Stock Awards continued to vest under their original vesting conditions as long as he provided continuous service to the Company (including as a consultant). The term of his consulting agreement ended on May 31, 2019.

In August 2017, the Company modified the terms of its former Chief Financial Officer’s outstanding Stock Awards to (1) accelerate 50% of the 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 may be exercised through the six-month anniversary of the date of termination of his continuous service to the Company. As of the modification date, the Company entered into a consulting agreement with the former Chief Financial Officer under which he provided continuous service to the Company by assisting with the transition of his role to the Company’s Chief Financial Officer. Pursuant to the terms of the 2014 Plan and his outstanding Stock Awards, such Stock Awards continued to vest under their original vesting conditions as long as he provided continuous service to the Company (including as a consultant). The term of his consulting agreement ended on February 15, 2018.

The Company determined that the acceleration of vesting for Stock Awards in 2018 and 2017 that would have vested based on their original vesting terms through the term of the consulting services were Type 1 modifications pursuant to ASC 718, Compensation – Stock Compensation, because those Stock Awards would have vested whether or not the vesting of those Stock Awards had been accelerated. However, acceleration of vesting for the remaining Stock Awards was a Type 3 modification pursuant to ASC 718 because absent the modification terms, those Stock Awards would have been forfeited as of the last day that the former Chief Medical Officer and Chief Financial Officer provided continuous service as a consultant.

During the year ended December 31, 2018, with respect to these modifications for the former Chief Medical Officer, the Company recognized $520 of compensation expense, including expense based on marking to market the fair value of the modified Stock Awards in accordance with ASC 505‑50, which is included in Research and development expense in the total compensation expense table above.

During the years ended December 31, 2018 and 2017, with respect to these modifications for the former Chief Financial Officer, the Company recognized $96 and $537 of compensation expense, respectively, including expense based on marking to market the fair value of the modified Stock Awards in accordance with ASC 505‑50, which is included in General and administrative expense in the total compensation expense table above.

As of December 31, 2019, the total compensation expense relating to unvested options granted to employees, non-employee members of the Board of Directors and non-employee consultants that had not yet been recognized was $22,216, which is expected to be realized over a weighted average period of 2.74 years. The Company will issue shares upon exercise of options from common stock reserved.

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, 2019, 2018 and 2017.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Property and Equipment, Net

6. Property and Equipment, Net

Property and equipment, net consists of the following:


	December 31,
	2019		2018
Computer and office equipment	$	211	$	211
Laboratory equipment		628		628
Furniture and fixtures		61		47
Leasehold improvements		1,132		1,128
	$	2,032	$	2,014
Less accumulated depreciation and amortization		1,332		1,134
Property and equipment, net	$	700	$	880

Depreciation and amortization expense included in R&D expense and General and administrative expense was $198, $370 and $495 for the years ended December 31, 2019, 2018 and 2017, respectively.

During the year ended December 31, 2017, the Company wrote-off $7,816 of fully-depreciated Shelton property and equipment, including leasehold improvements, that was not re-located to the Stamford headquarters (see Note 17, Commitments and Contingencies). During the year ended December 31, 2017, the Company sold fully-depreciated Shelton property and equipment for net proceeds of $41.

Commitments and Contingencies - Schedule of Other Information related to Stamford Lease (Detail) - Stamford Operating Lease [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Other Commitments [Line Items]
Operating cash outflows relating to operating lease	$ 1,215
ROU assets obtained in exchange for new operating lease liabilities	$ 3,636
Remaining lease term-operating lease (years)	3 years 10 months 24 days
Discount rate - operating lease	7.00%

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 198	$ 370	$ 495
Proceeds from sale of property and equipment			41
Shelton Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Write-off of fully-depreciated Shelton property and equipment			7,816
Proceeds from sale of property and equipment			$ 41

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Schedule of Other Information related to Stamford Lease

Other information related to the Stamford Lease was as follows:


	Year Ended
	December 31, 2019
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows relating to operating lease	$	1,215
ROU assets obtained in exchange for new operating lease liabilities	$	3,636
Remaining lease term-operating lease (years)		3.9
Discount rate - operating lease		7.0	%

Schedule of Future Minimum Lease Payments under Non-cancellable Operating Leases, Reconciliation of Undiscounted Cash Flows to the Operating Lease Liability

Future minimum lease payments under non-cancellable operating leases, as well as a reconciliation of these undiscounted cash flows to the operating lease liability as of December 31, 2019, were as follows:


Year Ending December 31,
2020	$	1,239
2021		1,264
2022		1,288
2023		1,164
2024		—
Total future minimum lease payments, undiscounted		4,955
Less imputed interest		(636)
Total	$	4,319

Operating lease liability reported as of December 31, 2019:
Operating lease liability - current	$	967
Operating lease liability - non-current		3,352
Total	$	4,319

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2019

Payables And Accruals [Abstract]

Schedule of Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following:


	December 31, 2019		December 31, 2018
Accounts payable	$	9,100	$	4,371
Accrued research projects		6,637		6,079
Accrued professional fees		635		802
Accrued compensation and benefits		3,293		2,370
Total	$	19,665	$	13,622

Business - Additional Information (Detail) - USD ($) $ in Thousands						1 Months Ended		3 Months Ended								12 Months Ended
	Jul. 29, 2019	Jul. 23, 2018	Jul. 18, 2018	Apr. 05, 2017	Mar. 30, 2017	Jul. 31, 2019	May 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nature Of Business [Line Items]
Date of formation																Jul. 02, 2004
Proceeds from equity and debt financing								$ 519,600								$ 519,600
Upfront and milestone payments received in connection with license agreements								89,000								89,000
Proceeds from sale of common stock in connection with license agreement																	$ 14,556
Unrestricted cash and cash equivalents and marketable securities								218,165								218,165
Accumulated deficit								400,727				$ 294,354				400,727	294,354
Net loss								$ 28,611	$ 32,842	$ 22,960	$ 21,960	$ 20,652	$ 19,400	$ 17,194	$ 16,767	106,373	74,013	$ 58,125
Net cash (used in) provided by operating activities																$ (109,225)	$ (22,301)	$ (54,827)
Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued																6,325,000	5,175,000	5,117,500
Common Stock [Member] \| Follow-on Public Offering [Member]
Nature Of Business [Line Items]
Common stock, shares issued			5,175,000		5,117,500
Proceeds from issuance of common stock net	$ 136,498
Common Stock [Member] \| Underwriter's Over-Allotment [Member]
Nature Of Business [Line Items]
Common stock, shares issued	825,000	675,000	675,000	667,500	667,500	825,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Nature Of Business [Line Items]
Proceeds from sale of common stock in connection with license agreement							$ 14,556
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Common Stock [Member]
Nature Of Business [Line Items]
Common stock, shares issued							1,174,827

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Feb. 24, 2020	Jun. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	CARA
Security Exchange Name	NASDAQ
Entity Registrant Name	CARA THERAPEUTICS, INC.
Entity Central Index Key	0001346830
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		46,725,225
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-36279
Entity Address, Address Line One	4 Stamford Plaza
Entity Address, Address Line Two	107 Elm Street
Entity Address, Address Line Three	9th Floor
Entity Address, City or Town	Stamford
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06902
City Area Code	203
Local Phone Number	406-3700
Entity Public Float			$ 783,719,032

Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2019

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 marketable securities, the Company’s only component of AOCI, for the years ended December 31, 2019, 2018 and 2017.


	Total Accumulated
	Other Comprehensive
	Income (Loss)
Balance, December 31, 2016	$	3
Other comprehensive loss before reclassifications		(68)
Amount reclassified from accumulated other comprehensive income		(5)
Net current period other comprehensive loss		(73)
Balance, December 31, 2017		(70)
Other comprehensive loss before reclassifications		(49)
Amount reclassified from accumulated other comprehensive loss		5
Net current period other comprehensive loss		(44)
Balance, December 31, 2018		(114)
Other comprehensive income before reclassifications		284
Amount reclassified from accumulated other comprehensive loss		—
Net current period other comprehensive income		284
Balance, December 31, 2019	$	170

Schedule of Reclassification Out of Accumulated Other Comprehensive Income

The reclassifications out of AOCI and into net loss were as follows:


							Affected Line Item in the
	Year Ended December 31,						Statements of
Component of AOCI	2019		2018		2017		Operations
Unrealized gains (losses) on available-for-sale marketable securities
Realized (losses) gains on sale of securities	$	—	$	(5)	$	5	Other income
		—		—		—	Benefit from income taxes
	$	—	$	(5)	$	5

Revenue Recognition

12 Months Ended

Dec. 31, 2019

Revenue Recognition [Abstract]

Revenue Recognition

12. Revenue Recognition

The Company currently recognizes revenue in accordance with ASC 606, as amended, for the VFMCRP, Maruishi and CKDP agreements (see Note 11, Collaboration and Licensing Agreements). Under each of these agreements, the Company has recognized revenue from upfront payments and, under the Maruishi Agreement and the CKDP Agreement, from clinical development milestone payments. The Company has also recognized revenue from a sub-license payment earned under the Maruishi Agreement. Under the Maruishi Agreement and the CKDP Agreement, the Company may earn additional future milestone payments upon the achievement of defined clinical events, and under the VFMCRP Agreement, the Maruishi Agreement and the CKDP Agreement upon the achievement of defined regulatory events and, under the VFMCRP Agreement and the Maruishi Agreement, from sales milestones. The Company may also recognize revenue in the future from royalties on net sales under all three agreements. In addition, the Company has recognized revenue upon the delivery of clinical compound to Maruishi in accordance with separate supply agreements.

Contract balances

As of December 31, 2019, the Company had deferred revenue, current of $22,262 related to the performance obligations from the VFMCRP Agreement and had no balances of receivables, other assets or deferred revenue, non-current related to the VFMCRP Agreement. There were no balances of receivables, other assets or deferred revenue relating to the Maruishi and CKDP agreements as of December 31, 2019. As of December 31, 2018, the Company had deferred revenue, current of $26,825 and deferred revenue, non-current of $15,184 related to the performance obligations from the VFMCRP Agreement and had no balances of receivables or other assets related to the VFMCRP Agreement. There were no balances of receivables, other assets or deferred revenue relating to the Maruishi and CKDP agreements as of December 31, 2018.

Performance obligations

Under the VFMCRP Agreement, the Company’s performance obligations of granting a license to allow VFMCRP to commercialize CR845/difelikefalin injection worldwide, except in the United States, Japan and South Korea, which occurred at inception of the contract in May 2018, and performing R&D services by the Company to obtain sufficient clinical data which will be shared with VFMCRP to allow them to receive regulatory approval to sell CR845/difelikefalin in the licensed territory, are not distinct, and are accounted for as a single performance obligation during the period that the R&D services are rendered (see Note 11, Collaboration and Licensing Agreements).

The Company’s distinct performance obligations under the Maruishi Agreement include transfer of the license to the Company’s IP, which allowed Maruishi to develop and commercialize CR845/difelikefalin, for acute pain and uremic pruritus indications in Japan, which occurred at inception of the contract in 2013, and performance of R&D services, which occurred from 2013 to 2015, as those services were rendered. The Company agreed to conduct limited work on an oral tablet formulation of CR845/difelikefalin and to conduct Phase 1 and proof-of-concept Phase 2 clinical trials of an intravenous formulation of CR845/difelikefalin to be used to treat patients with uremic pruritus. The Company agreed to transfer the data and information from such development to Maruishi for its efforts to obtain regulatory approval in Japan. These activities are referred to as R&D services.

The Company’s only performance obligation under the supply agreement with Maruishi is to deliver clinical compound to Maruishi in accordance with the receipt of purchase orders. If and when the Company enters into a supply agreement with VFMCRP, the Company’s only performance obligation under this supply agreement would be to deliver CR845/difelikefalin injection to VFMCRP in accordance with the receipt of purchase orders.

Under the CKDP Agreement, the Company’s only performance obligation is to transfer the license to the Company’s IP related to CR845/difelikefalin, which occurred at inception of the contract in 2012.

Upon execution of the VFMCRP Agreement, the Maruishi Agreement and the CKDP Agreement, the Company received a single fixed payment from each counterparty in exchange for granting the respective licenses and performing its other obligations. In addition, each of the counterparties made an equity investment in the Company’s common stock.

Transaction price allocated to the remaining performance obligations

At inception of the VFMCRP Agreement, the entire transaction price of $55,444 was allocated to the one combined performance obligation, as described above. As of December 31, 2019, $33,182 of that amount was recognized as license and milestone fees revenue based on the percentage of R&D services that had been completed. As of December 31, 2019, there were no remaining performance obligations under either the Maruishi Agreement or the CKDP Agreement, although the Company is eligible to receive milestone payments and sales royalties in the future.

Significant judgments

In applying ASC 606, as amended, to its three contracts, the Company made the following judgments that significantly affect the timing and amount of revenue recognition:

1.Determination of the number of distinct performance obligations in a contract

The VFMCRP Agreement contains one combined performance obligation, which includes the Company’s two performance obligations to grant a license to VFMCRP and conduct R&D services. Both of those performance obligations are inputs to the promise, within the context of the contract, to transfer a combined output for which VFMCRP has contracted (the ability of VFMCRP to commercialize the Licensed Product) (see Note 11, Collaboration and Licensing Agreements, for further discussion).

The Maruishi Agreement contains two distinct performance obligations: the granting of the license and the promise to deliver defined R&D services. Under the Maruishi Agreement, the license and the R&D services represent distinct goods or services from each other because Maruishi is able to benefit from the license on its own or together with other resources that are readily available to it (i.e., capable of being distinct). Maruishi’s ability to benefit from the license without the R&D services is indicated by its ability to conduct clinical trials of CR845/difelikefalin on its own and by the provision in the Maruishi Agreement whereby if the Company suspends or discontinues its development activity, the Company will provide information regarding its development efforts up to that point so that Maruishi may continue development and commercialization of the product in Japan. Therefore, the R&D services do not significantly affect Maruishi’s ability to use and benefit from the license.

In addition, the Company’s promise in the Maruishi contract to transfer the license is separately identifiable from the promise to provide defined R&D services (i.e., distinct within the context of the contract) because the Company is not using the goods or services as inputs to produce or deliver the combined output or outputs specified by the customer. The combined output specified by Maruishi is its right to conduct development activities related to CR845/difelikefalin in Japan, which could result in regulatory approval in Japan. That right is derived from the Company’s grant of the license. Maruishi is conducting clinical trials on its own and does not require the R&D services provided by the Company. Furthermore, the R&D services do not significantly modify or customize the license and vice versa. Finally, the license and R&D services are not highly interdependent or highly interrelated because the Company is able to fulfill its promise to transfer the initial license independently from its promise to subsequently provide the R&D services, which Maruishi can obtain on its own.

The only performance obligation in the CKDP Agreement is the granting of the license.

2.Determination of the transaction price, including whether any variable consideration is included at inception of the contract

The transaction price is the amount of consideration that the Company expects to be entitled to in exchange for transferring promised goods or services to the customer. The transaction price must be determined at inception of a contract and may include amounts of variable consideration. However, there is a constraint on inclusion of variable consideration, such as milestone payments or sales-based royalty payments, in the transaction price related to licenses of IP, if there is uncertainty at inception of the contract as to whether such consideration will be recognized in the future (see Note 2, Significant Accounting Policies: Revenue Recognition).

The decision as to whether or not it is probable that a significant reversal of revenue will occur in the future, depends on the likelihood and magnitude of the reversal and is highly susceptible to factors outside the entity’s influence (for example, the Company cannot determine the outcome of clinical trials; the Company cannot determine if or when they or the counterparty will initiate or complete clinical trials; and the Company’s ability to obtain regulatory approval is difficult). In addition, the uncertainty is not expected to be resolved for a long period of time (in the order of years) and finally, the Company has limited experience in the field.

Therefore, at inception of the VFMCRP Agreement, the Maruishi Agreement and the CKDP Agreement, milestones and sales-based royalty payments were not included in the transaction price based on the factors noted above.

Under the VFMCRP Agreement, the single combined performance obligation will be satisfied as the R&D services are rendered and the transaction price, including the upfront payment of $50,000 and the premium on the common stock purchased by VFMCRP of $5,444, will be recognized as revenue as the R&D services are performed based on the costs incurred as a percentage of the estimated total costs to be incurred to complete the performance obligation. The remaining potential consideration was considered to be variable consideration and was constrained at inception of the contract, including regulatory and sales milestones and sales royalties (see Note 11, Collaboration and Licensing Agreements).

All performance obligations under the Maruishi Agreement and the CKDP Agreement were satisfied by the end of 2015. In the future, any milestone event will be recognized in accordance with Note 2, Significant Accounting Polices: Revenue Recognition, as milestone and license fee revenue and collaboration revenue based upon the relative standalone selling prices of the two performance obligations at inception of the Maruishi Agreement, and as milestone and license fee revenue under the CKDP Agreement.

Under the Maruishi Agreement, the transaction price includes only the non-refundable and non-creditable upfront license fee of $15,337, including the premium of $337 from the sale of Company stock to Maruishi, that was paid to the Company at inception of the contract. The remaining potential consideration was considered to be variable consideration and was constrained at inception of the contract, including an aggregate of up to $10,500, which the Company is eligible to receive upon achievement of clinical development and regulatory milestones, a one-time sales milestone of one billion Yen when a certain sales level is attained; a mid-double-digit percentage of all non-royalty payments received by Maruishi from its sub-licensees, if any; and tiered royalties based on net sales of products containing CR845/difelikefalin in Japan, if any, with minimum royalty rates in the low double digits and maximum royalty rates in the low twenties.

Under the CKDP Agreement, the transaction price includes only the non-refundable and non-creditable upfront license fee of $646, including the premium of $83 from the sale of Company stock to CKDP, that was paid to the Company at inception of the contract. The remaining consideration was considered to be variable consideration and was constrained at inception of the contract, including an aggregate of up to $3,750, which the Company is eligible to earn upon achievement of clinical development and regulatory milestones. The Company is also eligible to receive a mid-double-digit percentage of all non-royalty payments received by CKDP from its sub-licensees, if any, and tiered royalties ranging from the high single digits to the high teens based on net sales of products containing CR845/difelikefalin in South Korea, if any.

3.Determination of the estimate of the standalone selling price of performance obligations

In order to recognize revenue under ASC 606, as amended, for contracts for which more than one distinct performance obligation has been identified, the Company must allocate the transaction price to the performance obligations based upon their standalone selling prices. The best evidence of standalone selling price is an observable price of a good or service when sold separately by an entity in similar circumstances to similar customers. If such evidence is not available, standalone selling price should be estimated so that the amount that is allocated to each performance obligation equals the amount that the entity expects to receive for transferring goods or services. The Company has identified more than one performance obligation only in the Maruishi Agreement. Since evidence based on observable prices is not available for the performance obligations under the Maruishi Agreement, the Company considered market conditions and entity-specific factors, including those contemplated in negotiating the agreements, as well as certain internally developed estimates.

At inception of the Maruishi Agreement, the Company determined the estimate of standalone selling price for the license performance obligation by using the adjusted market assessment approach. Under this method, the Company forecasted and analyzed CR845/difelikefalin in the Japanese market, the phase of clinical development as well as considered recent similar license arrangements within the same phase of clinical development, therapeutic area, type of agreement, etc. To estimate the standalone selling price of the R&D services, the Company forecasted its expected costs of satisfying that performance obligation and added a margin for that service.

4.Determination of the method of allocation of the transaction price to the distinct performance obligations

At inception of the Maruishi Agreement, the Company allocated the transaction price of $15,337 between the two performance obligations based on their relative standalone selling prices, determined as described above. The Company determined that the license and the R&D services had estimated standalone selling prices of $10,200 and $6,200, respectively. The resulting percentage allocations were applied to the $15,337 of total transaction price, which resulted in $9,637 being allocated to the license performance obligation, which was recognized immediately as license revenue, while $5,700 was allocated to the R&D services performance obligation. The amount allocated to the R&D services performance obligation was initially recorded as deferred revenue and was recognized as collaborative revenue as the R&D services were provided through July 2015.

Since both the VFMCRP Agreement and the CKDP Agreement each contain only one distinct performance obligation, at the inception of each of those agreements, the entire transaction price was allocated to the respective performance obligation.

5.Determination of the timing of revenue recognition for contracts

Revenue should be recognized when, or as, an entity satisfies a performance obligation by transferring a promised good or service to a customer; i.e., when the customer obtains control of the good or service. The licenses granted to both Maruishi and CKDP are being accounted for as distinct performance obligations. As discussed below, both licenses relate to functional IP for which revenue is recognized at a point in time – in the case of these two license agreements, the point in time is at inception of the contract because the customer obtained control of the license at that point.

The licenses grant Maruishi and CKDP the right to use the Company’s IP relating to CR845/difelikefalin as it existed at the point in time that the licenses were granted. That IP has significant standalone functionality as it provides the customer with the ability to perform a function or task, such as to manufacture CR845/difelikefalin and conduct clinical trials, and is considered to be functional IP.

During the license periods, the Company is continuing to develop and advance CR845/difelikefalin by conducting clinical trials. Those development efforts are for its own benefit and do not substantively change the significant standalone functionality of the licensed IP granted to Maruishi or CKDP. Therefore, the Company’s ongoing development efforts do not significantly affect the IP’s utility to which Maruishi or CKDP have rights. Furthermore, if the Company abandons its development efforts, Maruishi or CKDP may still continue to develop CR845/difelikefalin in their respective countries.

The R&D services performance obligation under the Maruishi Agreement represents a separate performance obligation. The R&D services were provided to Maruishi by the Company from inception of the agreement in 2013 through the third quarter of 2015, at which time the Company had fulfilled its promise related to the R&D services. Revenue related to the R&D services performance obligation was recognized as services were performed based on the costs incurred as a percentage of the estimated total costs to be incurred to complete the performance obligation.

Similarly, under the VFMCRP Agreement, revenue related to the single distinct performance obligation, which includes both granting of the license and performance of the R&D services, will be recognized as the R&D services are performed, based on the costs incurred as a percentage of the estimated total costs to be incurred to complete the performance obligation. The Company expects that the remaining amount of the transaction price that was allocated to the combined performance obligation of $22,262 at December 31, 2019 will be recognized by 2020, as the R&D services are performed, subject to certain development and regulatory uncertainties.

6.Determination of consideration as variable consideration, including factors related to inclusion in the transaction price at inception of the contract and timing of recognition as revenue.

The VFMCRP Agreement, the Maruishi Agreement and the CKDP Agreement contain potential payments related to achievement of defined milestone events and royalties upon net sales of future products, which are considered to be variable consideration because of the uncertainty of occurrence of any of those events specified in those agreements at inception of the agreements. Therefore, those potential payments were not included in the transaction price at the inception of the agreements.

Revenue related to achievement of milestone events is recognized when the Company has determined that it is probable that a milestone event will be achieved and there will not be a significant reversal of revenue in future periods. Upon probability of achievement of a milestone event, the most likely amount of variable consideration is included in the transaction price. Subsequent changes to the transaction price, after contract initiation, are allocated to the performance obligations in the contract on the same basis as at contract inception. Revenue for variable consideration is recognized in the same manner (point in time or over time) as for the performance obligations to which the payment amounts were allocated.

The Maruishi Agreement and the CKDP Agreement specify that certain development milestones will be achieved at pre-specified defined phases of a clinical trial (such as initiation or completion or other pre-specified time during a clinical trial as specified in the agreements).

During the years ended December 31, 2019, 2018 and 2017, no milestone events were probable of occurrence or achieved.

Sublicense payments

VFMCRP’s, Maruishi’s and CKDP’s right to grant sub-licenses is explicitly stated in their respective license agreements. The amount of any potential sub-license fees to be received by the Company, which is based on a formula, is considered to be variable consideration and is constrained from inclusion in the transaction price at inception of the contract since at that time it was probable that there would be a reversal of such revenue in the future because the Company did not know if a sublicense would be granted in the future.

In March 2017, Maruishi entered into a sub-license agreement to the Maruishi Agreement with Kissei in Japan for development and sales/marketing of CR845/difelikefalin for the treatment of uremic pruritus in dialysis patients in Japan. The Company first learned that the terms of the sub-license agreement had been finalized less than a month before the sub-licensee publicly announced the agreement. At that time, the Company determined that the sub-license fee would not be constrained from inclusion in the transaction price. Consequently, the Company included the amount of the sub-license fee in the transaction price and recognized revenue of $843 in the same manner as described above for milestone payments.

Sales-based Royalty Payments

The VFMCRP Agreement, CKDP Agreement and Maruishi Agreement each allow the Company to earn sales-based royalty payments in exchange for a license of intellectual property. In that case, the Company will recognize revenue for a sales-based royalty only when (or as) the later of the following events occurs:

The subsequent sale or usage occurs.

The performance obligation to which some or all of the sales-based royalty has been allocated has been satisfied (or partially satisfied).

Since the sale (item a, above) occurs after the license was delivered (item b, above), the sales-based royalty exception, to exclude such royalty payments from the transaction price, applies to the overall revenue stream. Therefore, sales-based royalty payments are recognized as revenue when the customer’s sales occur. To date, no royalties have been earned or were otherwise due to the Company.

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-cancellable Operating Leases, Reconciliation of Undiscounted Cash Flows to the Operating Lease Liability (Detail) $ in Thousands	Dec. 31, 2019 USD ($)
Operating Lease Liabilities, Payments Due [Abstract]
2020	$ 1,239
2021	1,264
2022	1,288
2023	1,164
Total future minimum lease payments, undiscounted	4,955
Less imputed interest	(636)
Operating lease liability	4,319
Operating lease liability reported as of December 31, 2019:
Operating lease liability - current	967
Operating lease liability - non-current	3,352
Total	$ 4,319

Condensed Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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	46,720,225	39,547,558
Common stock, shares outstanding	46,720,225	39,547,558

Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Follow-on Public Offering [Member]
Price per share	$ 23.00	$ 19.00	$ 18.00
Underwriting discounts and commissions and offering expenses	$ 8,977	$ 6,262	$ 5,891
License Agreements [Member]
Price per share	$ 23.42

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019	2018	2017
Basic:
Weighted average common shares outstanding	42,669,333	35,892,786	31,202,842
Diluted:
Weighted average common shares outstanding - Basic	42,669,333	35,892,786	31,202,842
Common stock options*	—	—	—
Denominator for diluted net loss per share	42,669,333	35,892,786	31,202,842

*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,
	2019		2018		2017
Net loss	$	(106,373)	$	(74,013)	$	(58,125)
Weighted-average common shares outstanding:
Basic and Diluted		42,669,333		35,892,786		31,202,842
Net loss per share, Basic and Diluted	$	(2.49)	$	(2.06)	$	(1.86)

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

17. Commitments and Contingencies

License Agreement with Enteris Biopharma, Inc.

On August 20, 2019, the Company entered into the Enteris License Agreement, pursuant to which Enteris granted to the Company a non-exclusive, royalty-bearing license, including the right to grant sublicenses, under certain proprietary technology and patent rights related to or covering formulations for oral delivery of peptide active pharmaceutical ingredients with functional excipients to enhance permeability and/or solubility, known as Enteris’s Peptelligence® technology, to develop, manufacture and commercialize products using such technology worldwide, excluding Japan and South Korea.

As consideration for the licensed rights under the Enteris License Agreement, the Company paid an upfront fee equal to $8,000, consisting of $4,000 in cash and $4,000 in shares of the Company’s common stock pursuant to the Purchase Agreement (see Note 9, Stockholders’ Equity). As a result, the Company recognized R&D expense of $8,000 related to the Enteris License Agreement during the year ended December 31, 2019.

The Company is also obligated, pursuant to the Enteris License Agreement, to pay Enteris (1) milestone payments upon the achievement of certain development, regulatory and commercial milestones and (2) low-single digit royalty percentages on net sales of licensed products, subject to reductions in specified circumstances. Until the second anniversary of the entry into the Enteris License Agreement, the Company has the right, but not the obligation, to terminate its obligation to pay any royalties under the Enteris License Agreement in exchange for a lump sum payment in cash, or the Royalty Buyout. Subject to certain conditions, the Company may elect to pay 50% of the lump sum due under the Royalty Buyout in shares of the Company’s common stock pursuant to the Purchase Agreement. During the year ended December 31, 2019, no milestone payments or royalties were paid to Enteris by the Company.

The Enteris License Agreement will expire on a country-by-country, licensed product-by-licensed product basis upon the later of (1) the expiration (or invalidation) of all valid claims in licensed patent rights that cover such product in such country, (2) the end of the calendar quarter in which generic competition (as defined in the Enteris License Agreement) occurs for such product in such country and (3) ten years from the first commercial sale of such product.

Either party may terminate the Enteris License Agreement upon written notice if the other party has failed to remedy a material breach within 60 days (or 30 days in the case of a material breach of a payment obligation). Enteris may terminate the Enteris License Agreement upon 30 days’ written notice to the Company if the Company or any of its affiliates formally challenge the validity of any licensed patent rights or assists a third party in doing so. The Company may terminate the Enteris License Agreement for any reason or no reason (a) prior to receipt of first regulatory approval for a licensed product in the United States for any indication upon 30 days’ prior written notice to Enteris or (b) on or after receipt of first regulatory approval for a licensed product in the United States for any indication upon 60 days’ prior written notice to Enteris.

Manufacturing Agreement with Patheon UK Limited

On July 8, 2019, the Company entered into a Master Manufacturing Services Agreement, or MSA, with Patheon UK Limited, or Patheon. The MSA governs the general terms under which Patheon, or one of its affiliates, will provide non-exclusive manufacturing services to the Company for the drug products specified by the Company from time to time. Pursuant to the MSA, the Company has agreed to order from Patheon at least a certain percentage of its commercial requirements for a product under a related Product Agreement. Each Product Agreement that the Company may enter into from time to time will be governed by the terms of the MSA, unless expressly modified in such Product Agreement.

The MSA has an initial term ending December 31, 2023, and will automatically renew after the initial term for successive terms of two years each if there is a Product Agreement in effect, unless either party gives notice of its intention to terminate the MSA at least 18 months prior to the end of the then current term.

Either party may terminate the MSA or a Product Agreement upon written notice if the other party (1) has failed to remedy a material breach within a specified time or (2) is declared insolvent or bankrupt, voluntarily files a petition of bankruptcy or assigns such agreement for the benefit of creditors. The Company may terminate a Product Agreement (a) upon 90 days’ prior written notice if any governmental agency takes any action that prevents the Company from selling the relevant product in the relevant territory, (b) upon six months’ prior written notice if it does not intend to order manufacturing services due to a product’s discontinuance in the market, or (c) upon 90 days’ prior written notice if it determines that the manufacture or supply of a product likely infringes third-party rights. Patheon may terminate the MSA or a Product Agreement (i) upon six months’ prior written notice if the Company assigns such agreement to an assignee that is unacceptable to Patheon for certain reasons, or (ii) upon 30 days’ prior written notice if, after the first year of commercial sales, the Company forecasts zero volume for 12 months.

The MSA contains, among other provisions, customary representations and warranties by the parties, a grant to Patheon of certain limited license rights to the Company’s intellectual property in connection with Patheon’s performance of the services under the MSA, certain indemnification rights in favor of both parties, limitations of liability and customary confidentiality provisions.

On July 8, 2019, and July 9, 2019, the Company entered into two related Product Agreements under the MSA, one with each of Patheon and Patheon Manufacturing Services LLC, or Patheon Greenville, to govern the terms and conditions of the manufacture of commercial supplies of CR845/difelikefalin injection, the Company’s lead product candidate. Pursuant to the Product Agreements, Patheon and Patheon Greenville will manufacture commercial supplies of CR845/difelikefalin injection at the Monza, Italy and Greenville, North Carolina manufacturing sites, respectively, from active pharmaceutical ingredient supplied by the Company. Patheon and Patheon Greenville will be responsible for supplying the other required raw materials and packaging components, and will also provide supportive manufacturing services such as quality control testing for raw materials, packaging components and finished product.

Leases

In December 2015, the Company entered into a lease agreement, or the Stamford Lease, 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 and is renewable for one five-year term.

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. Prior to January 1, 2019, the Company recorded monthly rent expense on a straight-line basis from March 2016, upon taking possession of the Premises, through December 31, 2018. As of December 31, 2018, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $864.

As of the Commencement Date, the Stamford Lease landlord had made tenant improvements of $1,094 to the leased premises. Such amount was included in Property and equipment, net and in Deferred lease obligation as of December 31, 2018. The portion of Deferred lease obligation that is related to tenant improvements was being amortized as a reduction to rent expense over the same term as rent expense. As of December 31, 2018, the balance of Deferred lease obligation related to tenant improvements was $698.

Total rent expense under the Stamford Lease was $974 and $935 for the years ended December 31, 2018 and 2017, 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 7, Restricted Cash).

On January 1, 2019, the Company adopted ASC 842 (see Note 2 – Basis of Presentation: Accounting Pronouncements Recently Adopted). Under ASC 842, since the Company adopted the practical expedients not to re-evaluate whether a contract is or contains a lease and to maintain the lease classification under ASC 840, the Stamford Lease continues to be accounted for as an operating lease.

Upon adoption of ASC 842, the Company was required to establish an operating lease ROU asset and operating lease liability for the Stamford Lease. In establishing the ROU asset, the operating lease liability of $5,198 was reduced by lease incentives relating to tenant improvements of $698 and deferred lease obligation of $864, which were outstanding on December 31, 2018.

Under ASC 842, lease expense is recognized on a straight-line basis over the lease term. As a result, $937 of operating lease cost, or lease expense, was recognized for the year ended December 31, 2019, consisting of $656 relating to R&D lease expense and $281 relating to G&A lease expense.

Other information related to the Stamford Lease was as follows:


	Year Ended
	December 31, 2019
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows relating to operating lease	$	1,215
ROU assets obtained in exchange for new operating lease liabilities	$	3,636
Remaining lease term-operating lease (years)		3.9
Discount rate - operating lease		7.0	%


Year Ending December 31,
2020	$	1,239
2021		1,264
2022		1,288
2023		1,164
2024		—
Total future minimum lease payments, undiscounted		4,955
Less imputed interest		(636)
Total	$	4,319

Operating lease liability reported as of December 31, 2019:
Operating lease liability - current	$	967
Operating lease liability - non-current		3,352
Total	$	4,319

Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2019

Receivables [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash


	December 31, 2019		December 31, 2018
Cash and cash equivalents	$	18,305	$	15,081
Restricted cash, current assets		—		361
Restricted cash, long-term assets		408		408
Total cash, cash equivalents, and restricted cash shown in the Statements of Cash Flows	$	18,713	$	15,850

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	9. 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, 2019, there were 46,720,225 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. In December 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 36,666 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On August 20, 2019, the Company entered into a Non-Exclusive License Agreement, or the Enteris License Agreement, with Enteris Biopharma, Inc., or Enteris (see Note 17, Commitments and Contingencies for additional information regarding the Enteris License Agreement). As consideration for the licensed rights under the Enteris License Agreement, the Company paid an upfront fee equal to $8,000, consisting of $4,000 in cash and $4,000 in shares of the Company’s common stock. In connection with the Enteris License Agreement, on August 20, 2019, the Company entered into a Common Stock Purchase Agreement, or the Purchase Agreement, with Enteris and its affiliate, EBP Holdco LLC, collectively referred to as Purchaser, pursuant to which the Company issued and sold to Purchaser 170,793 shares of its common stock in a private placement in satisfaction of the $4,000 portion of the upfront fee payable in shares of the Company’s common stock pursuant to the Enteris License Agreement, and for no additional consideration, based on a purchase price of $23.42 per share, which was equal to the 30-day volume weighted average price of the Company’s common stock on August 20, 2019. In addition, if the Company exercises its right, but not obligation, to terminate its obligation to pay any royalties under the Enteris License Agreement in exchange for a lump sum payment in cash, it may elect to make 50% of the payment in stock by issuing additional shares of the Company’s common stock valued at the 30-day volume weighted average price of the Company’s common stock as of such exercise. Pursuant to its obligations under the Purchase Agreement, the Company effected the registration and sale of the shares issued and sold to Purchaser thereunder in accordance with the applicable requirements of the Securities Act of 1933, as amended, or the Securities Act, through the filing of an automatic shelf registration statement on Form S-3ASR (File No. 333-233666) with the SEC on September 9, 2019. In addition, the Purchase Agreement includes customary representations, warranties and covenants by the Company (see Note 17, Commitments and Contingencies). On July 24, 2019, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC and Jefferies LLC, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 6,325,000 shares of its common stock, which included the exercise of the underwriters’ option to purchase 825,000 additional shares of common stock, at a public offering price of $23.00 per share. The Company closed this offering on July 29, 2019, including the full exercise of the underwriters’ option to purchase 825,000 additional shares of common stock. The Company received net proceeds of $136,498, after deducting $8,977 of underwriting discounts and commissions and offering expenses. This offering was made pursuant to the Company’s Shelf Registration Statement on Form S-3 (File No. 333-230333), or the Shelf Registration Statement, filed with the SEC on March 15, 2019 and declared effective on April 4, 2019, and a related prospectus supplement dated July 24, 2019, which was filed with the SEC on July 25, 2019. The Shelf Registration Statement provides for aggregate offerings of up to $300,000 of common stock, preferred stock, debt securities, warrants or any combination thereof. The securities registered under the Shelf Registration Statement include unsold securities that had been registered under the Company’s previous shelf registration statement (File No. 333-216657) that was declared effective on March 24, 2017. In May 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 74,166 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On March 20, 2019, or the Effective Date, the Company entered into a consulting agreement with an existing stockholder. In accordance with the agreement, the stockholder provided various consulting services to the Company in exchange for 10,195 unregistered shares of the Company’s common stock. The closing price of the Company’s common stock on the Effective Date was $19.37 per share. The services provided by the consultant were performed during the six-month period following the Effective Date. During the year ended December 31, 2019, stock-based compensation expense of $197 was recognized in the Statements of Comprehensive Loss, all of which related to G&A expense. In December 2018, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 83,791 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On July 18, 2018, the Company entered into an underwriting agreement with Jefferies LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of up to 5,175,000 shares of its common stock, including 675,000 shares of common stock the underwriters had the option to purchase, at a public offering price of $19.00 per share. This offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus dated March 24, 2017 and prospectus supplement dated July 18, 2018, which was filed with the SEC on July 20, 2018. On July 23, 2018, the Company closed the offering, including the full exercise of the underwriters’ option to purchase 675,000 additional shares of common stock. The Company received net proceeds of $92,063, after deducting $6,262 relating to underwriting discounts and commissions and offering expenses. On May 17, 2018, the Company issued 1,174,827 shares of its common stock to Vifor in connection with the license agreement entered into with VFMCRP (refer to Note 11, Collaboration and Licensing Agreements). 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 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 2017 Offering. The 2017 Offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus supplement dated March 30, 2017, which was filed with the SEC on March 31, 2017. On April 5, 2017, the Company closed the 2017 Offering, including the full exercise of the underwriters’ option to purchase 667,500 additional shares of common stock. The Company received net proceeds of $86,224, after deducting $5,891 relating to underwriting discounts and commissions and offering expenses.

Legal Matters	12 Months Ended
Legal Matters	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Legal Matters	18. Legal Matters From time to time, the Company may become subject to arbitration, litigation or claims arising in the ordinary course of its business. The Company is not currently a party to any arbitration or legal proceeding that, if determined adversely to the Company, would have a material adverse effect on its business, operating results or financial condition. The results of any future claims or proceedings cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors.

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2019

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, 2019		December 31, 2018
Accounts payable	$	9,100	$	4,371
Accrued research projects		6,637		6,079
Accrued professional fees		635		802
Accrued compensation and benefits		3,293		2,370
Total	$	19,665	$	13,622

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

The Company’s benefit from income taxes is as follows:


	December 31,
	2019		2018		2017
Current:
Federal	$	—	$	—	$	—
State		(816)		(389)		(204)
		(816)		(389)		(204)
Deferred:
Federal		—		—		—
State		—		—		—
		—		—		—
Benefit from income taxes	$	(816)	$	(389)	$	(204)

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,
	2019		2018		2017
Income taxes using U.S. federal statutory rate	21.00	%	21.00	%	34.00	%
State income taxes, net of federal benefit	(1.99)	%	6.82	%	5.33	%
Tax Cuts and Jobs Act	0.00	%	0.00	%	(44.43)	%
Impact of R&D tax credit on effective tax rate	4.34	%	3.48	%	3.25	%
Stock option shortfalls and cancellations	(0.17)	%	(0.43)	%	0.21	%
Permanent items and other	0.36	%	(0.15)	%	(0.56)	%
Change in valuation allowance	(22.76)	%	(31.76)	%	2.55	%
Provision to return	(0.02)	%	0.03	%	0.00	%
Non-taxable revenue	0.00	%	1.54	%	0.00	%
	0.76	%	0.53	%	0.35	%

Significant components of the Company’s deferred tax assets and liabilities are as follows:


	December 31,
	2019		2018
Valuation allowance	$	(114,136)	$	(89,815)

Net operating loss carryforwards		84,608		73,578
Federal and state tax credits		16,624		11,108
Deferred revenue		5,994		1,111
Stock-based compensation expense		4,481		3,605
Other		3,409		420
Deferred tax assets		115,116		89,822

Other		(980)		(7)
Deferred tax liabilities:		(980)		(7)

Net deferred tax asset:	$	—	$	—

A 100% valuation allowance has been recorded on the deferred tax asset as of December 31, 2019 and 2018 because management believes it is more likely than not that the asset will not be realized. The change in the valuation allowance during 2019 and 2018 was an increase of $24,321 and $23,642, respectively.

The Company applies the provisions of ASC 740, Income Taxes, which prescribes a comprehensive model for how a company should recognize, measure, present, and disclose in its financial statements uncertain tax positions that the Company has taken or expects to take on a tax return. The financial statements reflect expected future tax consequences of such positions presuming the taxing authorities possess full knowledge of the position and all relevant facts. As of December 31, 2019 and 2018, the Company had no unrecognized tax benefits or related interest and penalties accrued. In the event the Company determines that accrual of interest or penalties are necessary in the future, the amount will be presented as a component of income tax expense.

At December 31, 2019, the Company had federal and state net operating loss carryforwards of $349,525 and $189,157, respectively. The federal and state tax loss carryforwards will begin to expire in 2026 and 2027, respectively, unless previously utilized. The federal net operating losses arising in 2018 and forward have an unlimited carryforward period, however will only offset 80% of taxable income in a carryforward year. The federal 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 $15,274 and $1,448, 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 2019 remain open to U.S. federal and state tax examinations.

On December 22, 2017, the United States enacted the Tax Cuts and Jobs Act, or the TCJA. The TCJA, which is also commonly referred to as “U.S. tax reform”, significantly changes U.S. corporate income tax laws by, among other provisions, reducing the maximum U.S. corporate income tax rate from 35% to 21% starting in 2018. As of December 31, 2019 and 2018, the Company did not have any foreign subsidiaries and the international aspects of the TCJA were not applicable.

On December, 22, 2017, SAB 118 was issued by the SEC due to the complexities involved in accounting for the TCJA. SAB 118 requires the Company to include in its financial statements a reasonable estimate of the impact of the TCJA on earnings to the extent such estimate has been determined. The Company finalized its accounting for the TCJA as of December 31, 2018, which resulted in insignificant adjustments.

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 19,886	$ 13,469	$ 911
Operating expenses:
Research and development	113,820	75,531	48,524
General and administrative	17,745	15,320	11,872
Total operating expenses	131,565	90,851	60,396
Operating loss	(111,679)	(77,382)	(59,485)
Other income	4,490	2,980	1,156
Loss before benefit from income taxes	(107,189)	(74,402)	(58,329)
Benefit from income taxes	816	389	204
Net loss	$ (106,373)	$ (74,013)	$ (58,125)
Net loss per share:
Basic and Diluted	$ (2.49)	$ (2.06)	$ (1.86)
Weighted average shares:
Basic and Diluted	42,669,333	35,892,786	31,202,842
Other comprehensive income (loss), net of tax of $0:
Change in unrealized gains (losses) on available-for-sale marketable securities	$ 284	$ (44)	$ (73)
Total comprehensive loss	(106,089)	(74,057)	(58,198)
License and Milestone Fees [Member]
Revenue:
Total revenue	19,746	13,436	530
Collaborative Revenue [Member]
Revenue:
Total revenue			313
Clinical Compound Revenue [Member]
Revenue:
Total revenue	$ 140	$ 33	$ 68

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended				12 Months Ended
	Aug. 20, 2019	Jul. 29, 2019	Mar. 20, 2019	Jul. 23, 2018	Jul. 18, 2018	Apr. 05, 2017	Mar. 30, 2017	Dec. 31, 2019	Jul. 31, 2019	May 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 04, 2019
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized								100,000,000			100,000,000	100,000,000	100,000,000
Common stock, par value								$ 0.001			$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares authorized								5,000,000			5,000,000	5,000,000	5,000,000
Preferred stock, par value								$ 0.001			$ 0.001	$ 0.001	$ 0.001
Common stock, shares outstanding								46,720,225			39,547,558	46,720,225	39,547,558
Common stock, shares issued								46,720,225			39,547,558	46,720,225	39,547,558
Preferred stock, shares issued								0			0	0	0
Preferred Stock Shares Outstanding								0			0	0	0
Restricted stock units vested shares											83,791
Unregistered common stock exchanged for consulting services												$ 197
Compensation expense												10,300	$ 8,401	$ 6,330
Shareholder Consulting Agreement [Member]
Subsidiary Sale Of Stock [Line Items]
Price per share			$ 19.37
Number of shares of unregistered common stock exchanged for consulting services			10,195
Consulting services performance period			6 months
General and Administrative [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense												5,094	$ 4,482	$ 3,897
General and Administrative [Member] \| Shareholder Consulting Agreement [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense												$ 197
Non-Exclusive License Agreement
Subsidiary Sale Of Stock [Line Items]
Upfront fee	$ 8,000
Upfront fee payable, cash	4,000
Upfront fee payable, stock	$ 4,000
Price per share	$ 23.42
Share price average, Determination period	30 days
Percentage of payment, stock	50.00%
Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Aggregate offering price of securities															$ 300,000
Follow-on Public Offering [Member]
Subsidiary Sale Of Stock [Line Items]
Price per share								$ 23.00			$ 19.00	$ 23.00	$ 19.00	$ 18.00
Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Restricted stock units vested shares								36,666		74,166		110,832	83,791
Common stock, shares issued												6,325,000	5,175,000	5,117,500
Number of shares of unregistered common stock exchanged for consulting services												10,195
Common Stock [Member] \| Non-Exclusive License Agreement
Subsidiary Sale Of Stock [Line Items]
Upfront fee payable, stock	$ 4,000
Common stock, shares issued	170,793
Common Stock [Member] \| Follow-on Public Offering [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued									6,325,000
Common stock, shares issued					5,175,000		5,117,500
Price per share					$ 19.00		$ 18.00		$ 23.00
Proceeds from issuance of common stock net of underwriting discounts, commissions and estimated offering expenses		$ 136,498
Proceeds from issuance of common stock net of underwriting discounts and offering costs				$ 92,063		$ 86,224
Common Stock [Member] \| Underwriter's Over-Allotment [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued		825,000		675,000	675,000	667,500	667,500		825,000
Underwriting discounts, commission and offering expenses		$ 8,977		$ 6,262		$ 5,891

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Aug. 20, 2019	Jul. 08, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	May 31, 2016
Other Commitments [Line Items]
Research and development			$ 113,820	$ 75,531	$ 48,524
Deferred lease obligation				1,562
Operating lease liability			4,319
Operating lease cost			937
Research and Development [Member]
Other Commitments [Line Items]
Operating lease cost			656
General and Administrative [Member]
Other Commitments [Line Items]
Operating lease cost			$ 281
Stamford Operating Lease [Member]
Other Commitments [Line Items]
Operating Lease, renewable term			5 years
Operating lease, expiration date			Nov. 01, 2023
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. Prior to January 1, 2019, the Company recorded monthly rent expense on a straight-line basis from March 2016, upon taking possession of the Premises, through December 31, 2018. As of December 31, 2018, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $864.
Tenant improvement expenses							$ 1,094
Deferred lease obligation				864
Lease, rent expense				974	$ 935
Tenant improvement incentives				698
Stamford Operating Lease [Member] \| ASC 842 [Member]
Other Commitments [Line Items]
Operating Lease, renewable term			5 years
Operating lease liability						$ 5,198
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] \| Standby Letter of Credit [Member] \| Maximum [Member]
Other Commitments [Line Items]
Letter of credit, renewal date			Nov. 30, 2023
Stamford Operating Lease [Member] \| Leasehold Improvements [Member]
Other Commitments [Line Items]
Deferred lease obligation				$ 698
Non-Exclusive License Agreement
Other Commitments [Line Items]
Upfront fee	$ 8,000
Upfront fee payable, cash	4,000
Upfront fee payable, stock	$ 4,000
Research and development			$ 8,000
Percentage of payment, stock	50.00%
Payment of milestone payment			0
Payments for Royalties			$ 0
License agreement expiration period, first commercial sale	10 years
Agreement Termination Notice Description	Either party may terminate the Enteris License Agreement upon written notice if the other party has failed to remedy a material breach within 60 days (or 30 days in the case of a material breach of a payment obligation). Enteris may terminate the Enteris License Agreement upon 30 days' written notice to the Company if the Company or any of its affiliates formally challenge the validity of any licensed patent rights or assists a third party in doing so. The Company may terminate the Enteris License Agreement for any reason or no reason (a) prior to receipt of first regulatory approval for a licensed product in the United States for any indication upon 30 days' prior written notice to Enteris or (b) on or after receipt of first regulatory approval for a licensed product in the United States for any indication upon 60 days' prior written notice to Enteris.
Agreement termination period for material breach	60 days
Agreement termination period for material breach of a payment obligation	30 days
Agreement termination period for challenged patent rights	30 days
Agreement termination period prior to first regulatory approval	30 days
Agreement termination period after first regulatory approval	60 days
MSA
Other Commitments [Line Items]
Agreement initial term, expiration date		Dec. 31, 2023
Agreement renewal term		2 years
MSA \| Minimum [Member]
Other Commitments [Line Items]
Termination notice effective period		18 months
MSA or Product Agreement
Other Commitments [Line Items]
Agreement Termination Notice Description		Either party may terminate the MSA or a Product Agreement upon written notice if the other party (1) has failed to remedy a material breach within a specified time or (2) is declared insolvent or bankrupt, voluntarily files a petition of bankruptcy or assigns such agreement for the benefit of creditors. The Company may terminate a Product Agreement (a) upon 90 days' prior written notice if any governmental agency takes any action that prevents the Company from selling the relevant product in the relevant territory, (b) upon six months' prior written notice if it does not intend to order manufacturing services due to a product's discontinuance in the market, or (c) upon 90 days' prior written notice if it determines that the manufacture or supply of a product likely infringes third-party rights. Patheon may terminate the MSA or a Product Agreement (i) upon six months' prior written notice if the Company assigns such agreement to an assignee that is unacceptable to Patheon for certain reasons, or (ii) upon 30 days' prior written notice if, after the first year of commercial sales, the Company forecasts zero volume for 12 months.
Termination notice effective period upon government agency restrictions		90 days
Termination notice effective period upon discontinuance in the market		6 months
Termination notice period if likely infringes on third-party rights		90 days
Termination notice period if assignee is unacceptable		6 months
Termination notice period if zero volume is forecasted after first year of commercial sales		30 days

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Percentage of annual research and development credit for cash	65.00%
Valuation allowance on the deferred tax asset	100.00%	100.00%
Change in valuation allowance	$ 24,321,000	$ 23,642,000
Unrecognized tax benefits, related interest and penalties	$ 0	$ 0
Tax examinations, description	tax years 2006 through 2019 remain open to U.S. federal and state tax examinations.
Income taxes using U.S. federal statutory rate	21.00%	21.00%	34.00%
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Income taxes using U.S. federal statutory rate			35.00%
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 349,525,000
Operating Loss Carryforwards, Limitations on Use	80%
Federal [Member] \| R&D Tax Credit Carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 15,274,000
Federal [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards expiration year	2026
Federal [Member] \| Earliest Tax Year [Member] \| R&D Tax Credit Carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit expiration year	2025
State and Local [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 189,157,000
State and Local [Member] \| R&D Tax Credit Carryforwards [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 1,448,000
State and Local [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards expiration year	2027

Collaboration and Licensing Agreements	12 Months Ended
Collaboration and Licensing Agreements	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and Licensing Agreements	11. Collaboration and Licensing Agreements Vifor Fresenius Medical Care Renal Pharma Ltd. On May 17, 2018, the Company entered into a license agreement, or the VFMCRP Agreement, with VFMCRP under which the Company granted VFMCRP an exclusive, royalty-bearing license, or the VFMCRP License, to seek regulatory approval to commercialize, import, export, use, distribute, offer for sale, promote, sell and otherwise commercialize CR845/difelikefalin injection, or the Licensed Product, for all therapeutic uses to prevent, inhibit or treat itch associated with pruritus in hemodialysis and peritoneal-dialysis patients, or the Field, worldwide (excluding the United States, Japan and South Korea), or the Territory. VFMCRP cannot perform development activities on their own unless specifically allocated to VFMCRP by the Joint Development Committee, or JDC, and Joint Steering Committee, or JSC. The Company’s membership on the JSC or JDC is at its sole discretion and is not its obligation. The Company is responsible, at its own cost, to undertake clinical and non-clinical development, or the R&D services. The Company is also responsible to provide all content and subject matter expertise required for registration with the European Medicines Agency, or EMA, in the European Union, or the EU, that will be needed by VFMCRP for such registration, including participation in regulatory meetings, as needed. If third-party costs incurred by the Company with respect to its clinical development for the EMA registration exceed $20,000, such excess costs will be shared equally by the Company and VFMCRP. VFMCRP will contribute, at its own cost, its clinical development expertise as reasonably useful for such development activities, such as preparing the clinical results that the Company presents to it in a format acceptable to the EMA to obtain marketing approval in the EU. The Company has identified two performance obligations under ASC 606: (1) granting of the VFMCRP License and (2) the R&D services. The Company has determined that these two performance obligations are not capable of being distinct (i.e., do not have standalone value for VFMCRP) because VFMCRP cannot benefit (derive potential cash flows) from either one on its own or together with other resources that are readily available to it since VFMCRP is relying on the Company’s expertise in investigating chronic kidney disease-associated pruritus, or CKD-aP, and its know-how obtained from multiple years of pre-clinical and clinical development, and years of interactions with the FDA which other companies or CROs would not have. The VFMCRP License does not provide benefit to VFMCRP until and unless the Company conducts the pivotal clinical trials and other supportive trials in CKD-aP to gather sufficient clinical data for VFMCRP to obtain marketing approval in the Territory. Furthermore, VFMCRP does not have the right to perform development activities on its own unless specifically allocated by the JDC or JSC. The two identified performance obligations are also not distinct within the context of the contract, (i.e., are not separately identifiable from each other) because of the nature of the promise within the context of the contract. The nature of the promise is to transfer a combined deliverable to VFMCRP based on the agreement (to support the ability of VFMCRP to commercialize the Licensed Product) and the Company determined that the VFMCRP License and the R&D services are inputs rather than a transfer of each of these goods and services individually. In addition, the two identified performance obligations are highly interrelated and interdependent because satisfaction of both performance obligations is required for VFMCRP to derive benefit from the VFMCRP Agreement for commercialization of the Licensed Product in the Territory. Therefore, the two performance obligations are not distinct from each other and are accounted for as a single performance obligation. Upon entry into the VFMCRP Agreement, VFMCRP made a non-refundable, non-creditable $50,000 upfront payment to the Company and Vifor purchased 1,174,827 shares of the Company’s common stock, or the Vifor Shares, for $20,000 at a price of $17.024 per share, which represents a premium over a pre-determined average closing price of the Company’s common stock. The purchase of the Company’s common stock was governed by a separate stock purchase agreement. The excess of the stock purchase price over the cost of the Vifor Shares at the closing price of the Company’s common stock on the purchase date of $5,444 was added to the upfront payment for accounting purposes. The Company is eligible to receive from VFMCRP regulatory and commercial milestone payments in the aggregate of up to $470,000, consisting of up to $30,000 in regulatory milestones and up to $440,000 in tiered commercial milestones, all of which are sales-related. The Company is also eligible to receive tiered double-digit royalty payments based on annual net sales, as defined in the VFMCRP Agreement, of CR845/difelikefalin injection in the Licensed Territories. The Company retains full commercialization rights for CR845/difelikefalin injection for the treatment of CKD-aP in the United States except in the dialysis clinics of Fresenius Medical Care North America, or FMCNA, where VFMCRP and the Company will promote CR845/difelikefalin injection under a profit-sharing arrangement (subject to the terms and conditions of the VFMCRP Agreement) based on net FMCNA clinic sales recorded by the Company. At inception of the VFMCRP Agreement, there was significant uncertainty as to whether marketing approval would be obtained in the Territory for the Licensed Product. Therefore, at that time, there was a significant probability that any potential revenue from sales of the Licensed Product that would be included in the transaction price would be reversed when the uncertainty is resolved. Consequently, any sales royalties and sales milestones are constrained from the transaction price at inception of the VFMCRP Agreement and will be recognized as revenue if, and when, such sales transactions occur in the future. At inception of the VFMCRP Agreement, the transaction price of $55,444 was allocated entirely to the one combined performance obligation, as described above, and was initially recorded as deferred revenue. License and milestone revenue will be recognized proportionately as the R&D services are conducted (i.e., prior to submission of an NDA). The license also requires VFMCRP to promote and take orders in the U.S. for sale by the Company to FMC U.S. Dialysis Clinics and allows VFMCRP to grant sub-licenses, which, in certain cases, requires the Company’s prior written consent. The Company retains the rights to import, distribute, promote, sell and otherwise commercialize the Licensed Product outside of the Field and outside of the Territory. The Company retains the rights to make and have made the Licensed Product in the Territory for commercial sale by VFMCRP in the Field in or outside the Territory and for supply of Licensed Product to VFMCRP under the terms of a supply agreement, or the Supply Agreement. The supply price will be the Company’s cost of goods sold, as calculated under U.S. GAAP, plus an agreed upon margin. The Supply Agreement will co-terminate with the VFMCRP Agreement. In regards to a supply agreement, the VFMCRP Agreement only includes a requirement for the Company to negotiate in good faith with VFMCRP. After the execution of the VFMCRP Agreement, a separate agreement to supply them with the Licensed Product would be entered into, although the Company has no obligation to execute a supply agreement. In the event that the parties fail to enter into a Supply Agreement or if the Company fails to provide Licensed Product on a timely basis, VFMCRP has the right to manufacture or have manufactured the Licensed Product in and outside the Territory. The Supply Agreement will be accounted for as a customer option that is not a material right because the selling price of the Licensed Product under the Supply Agreement is the Company’s cost of goods sold plus an agreed upon margin, which is commensurate with the “cost of goods sold plus” model that the Company would charge other parties under similar agreements (the standalone selling price) and not at a discount. Therefore, the sale of clinical compound to VFMCRP is not a performance obligation under the VFMCRP Agreement but rather the Supply Agreement is a separate agreement from the VFMCRP Agreement. The only performance obligation under the Supply Agreement is the delivery of the Licensed Product to VFMCRP for commercialization. Revenue from the sale of the Licensed Product to VFMCRP will be recognized as Clinical Supply revenue in the Company’s Statements of Comprehensive Loss as sales of the Licensed Product occur. As of December 31, 2019, no supply agreement has been entered into between the Company and VFMCRP. The VFMCRP Agreement terminates upon the expiration of all royalty terms with respect to the Licensed Products, which expire on a Product-by-Product and country-by-country basis, at the latest of (a) the expiration of all patent rights licensed to VFMCRP covering such Licensed Product; (b) the expiration of all regulatory and data exclusivity applicable to such Licensed Product in such country and (c) the tenth anniversary of the first commercial sale of such Product in such country. The VFMCRP Agreement may be terminated earlier by either party for material breach that is not cured within 60 days, bankruptcy by either party and by both parties upon mutual written consent. The Company may terminate the VFMCRP Agreement if VFMCRP challenges the validity of any licensed patent rights, except if such patent challenge results from the Company’s action against VFMCRP for infringement of any licensed patent in the Territory. In addition, upon the earlier of (1) the acceptance for filing of an NDA covering Licensed Product filed with the FDA (after completion of the Phase 3 program) or (2) the third anniversary of the Effective Date, the VFMCRP Agreement may be terminated by VFMCRP in its entirety or with respect to any countries within the Territory upon written notice to the Company. Such termination will be effective twelve months following the date of such notice. If the VFMCRP Agreement terminates early for any reason stated above, VFMCRP’s licenses will terminate, VFMCRP’s rights to use the Company’s confidential information and the Company’s know-how will revert to the Company and VFMCRP will assign and transfer to the Company all right, title and interest in all regulatory applications (IND’s and NDA’s), regulatory approval applications and regulatory approvals in the Territory covering Licensed Product. 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/difelikefalin for acute pain and/or uremic pruritus in Japan. Maruishi has the right to grant sub-licenses in Japan, which entitles the Company to receive sub-license fees, net of prior payments made by Maruishi to the Company. 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/difelikefalin in the United States and Japan, respectively. In addition, the Company provided Maruishi specific clinical development services for CR845/difelikefalin used in Maruishi’s field of use. Under the Maruishi Agreement, the Company identified two performance obligations in accordance with ASC 606: (1) the license; and (2) the R&D services specific to the uremic pruritus field of use (specified as Phase 1 and proof-of-concept clinical trials), both of which were determined to have standalone value. The Company determined that these performance obligations had standalone value due to the fact that Maruishi obtained the right to develop the compound on its own and the Company was specifically contracted to perform specific R&D services as noted above. The Company believes that these early stage R&D services performed by the Company did not require any specific expertise or know-how, but rather could have been completed by outside third parties, therefore providing standalone value to Maruishi. In March 2017, Maruishi entered into a sub-license agreement with Kissei Pharmaceutical Co. Ltd., or Kissei, for the development and sales/marketing of CR845/difelikefalin (called MR13A9 by Maruishi) for the treatment of uremic pruritus in dialysis patients in Japan. Consequently, for the year ended December 31, 2017, the Company recognized revenue of $843 related to the sub-license fee. The Company allocated the amount of the sub-license fee to each of the two identified performance obligations in the same proportion as the upfront license fee that the Company received at inception of the Maruishi Agreement. Accordingly, $530 was recognized as license and milestone fees revenue and $313 was recognized as collaborative revenue. Under the terms of the Maruishi Agreement, the Company is eligible to receive milestone payments upon the achievement of defined clinical and regulatory events as well as tiered, low double-digit royalties with respect to any sales of the licensed product sold in Japan by Maruishi, if any, and share in any sub-license fees. During the years ended December 31, 2019, 2018 and 2017, the Company recognized clinical compound revenue of $140, $33 and $68, respectively, from the sale of clinical compound to Maruishi. The Company incurred R&D expense related to the Maruishi Agreement of $126, $30 and $61 (all related to the cost of clinical compound sold to Maruishi) during the years ended December 31, 2019, 2018 and 2017, respectively. Chong Kun Dang Pharmaceutical Corporation In April 2012, the Company entered into a license agreement, or the CKDP Agreement, with Chong Kun Dang Pharmaceutical Corporation, or CKDP, in South Korea, under which the Company granted CKDP an exclusive license to develop, manufacture and commercialize drug products containing CR845/difelikefalin in South Korea. The Company and CKDP are each required to use commercially reasonable efforts, at their respective expense, to develop, obtain regulatory approval for and commercialize CR845/difelikefalin in the United States and South Korea, respectively. The Company identified the granting of the license as its only performance obligation under the CKDP Agreement. Under the terms of the CKDP Agreement, the Company is eligible to receive milestone payments upon the achievement of defined clinical and regulatory events as well as tiered royalties, with percentages ranging from the high single digits to the high teens, based on net sales of products containing CR845/difelikefalin in South Korea, if any, and share in any sub-license fees.

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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
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	0
Unrealized losses	$ 0	$ 0	$ 0

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

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. Estimates include the fair value of marketable securities that are classified as level 2 of the fair value hierarchy, useful lives of fixed assets, the periods over which certain revenues will be recognized, including licensing and collaborative revenue recognized from non-refundable up-front and milestone payments, the determination of prepaid research and development, or R&D, clinical costs and accrued research projects, the amount of non-cash compensation costs related to share-based payments to employees and non-employees and the periods over which those costs are expensed, the incremental borrowing rate used in lease calculations and the likelihood of realization of deferred tax assets.

Concentrations of Credit Risk

Financial instruments, which potentially subject the Company to significant concentrations of credit risk consist primarily of cash equivalents and marketable securities. The Company invests its cash reserves in money market funds or high-quality marketable securities in accordance with its investment policy. The stated objectives of its investment policy 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 four 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, or ASC, section 320‑10‑20. The Company considers its marketable securities to be available-for-sale and, accordingly, these investments are recorded at fair value with unrealized gains and losses recorded in Accumulated other comprehensive income (loss), or AOCI, as a separate component of stockholders’ equity. Available-for-sale marketable securities are reported as Marketable securities, current and Marketable Securities, noncurrent in the Balance Sheets. Other income includes interest and dividends, accretion/amortization of discounts/premiums and realized gains and losses on sales of securities and other-than-temporary impairment, or OTTI, declines in the fair value of securities, if any. The cost of securities sold is based on the specific identification method.

The Company reviews its available-for-sale marketable securities for OTTI declines in fair value below its cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below its cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell, the security before recovery of its amortized cost basis. The Company’s assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security.

If a decline in the fair value of an available-for-sale marketable debt security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value. If the Company intends to sell the security or it is more likely than not that the Company will be forced to sell the security before recovery of the amortized cost of the security, the loss is recognized in net income. Otherwise, the loss is separated into a portion representing a credit loss, which is recorded in net income, and the remainder is recorded in Other comprehensive income, or OCI, net of taxes. See Note 2, Recent Accounting Pronouncements Not Yet Adopted, Note 3, Available-for-Sale Marketable Securities, and Note 10, Fair Value Measurements.

Fair Value of Financial Instruments

The Company applies fair value accounting for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities which are required to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions and credit risks.

The Company’s financial instruments consist of cash, cash equivalents, available-for-sale marketable securities, prepaid expenses, restricted cash, accounts payable and accrued liabilities. The fair values of cash, cash equivalents, prepaid expenses, restricted cash, accounts payable and accrued liabilities approximate their carrying values due to the short-term nature of these financial instruments. Available-for-sale marketable securities are reported on the Company’s Balance Sheets as Marketable Securities at their fair values, based upon pricing of securities with the same or similar investment characteristics as provided by third-party pricing services, as described below.

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.

The Company records transfers between levels in the hierarchy by assuming that the transfer occurred at the end of the quarter or year-to-date period.

Valuation Techniques - Level 2 Inputs

The Company estimates the fair values of its financial instruments categorized as level 2 in the fair value hierarchy, including U.S. Treasury securities, U.S. government agency obligations, corporate bonds, commercial paper and municipal bonds, 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, 2019 or December 31, 2018.

Property and Equipment

Property and equipment (consisting of computer, office and laboratory equipment, furniture and fixtures 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
Short-term laboratory equipment		2 years
Furniture and fixtures		7 years
Leasehold improvements		lesser of useful life of asset or life of lease (Stamford - 7 years)

ASC 360, Property, Plant and Equipment, addresses the financial accounting and reporting for impairment or disposal of long-lived assets. The Company reviews the recorded values of property and equipment for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset or group of assets may not be fully recoverable.

Revenue Recognition

On January 1, 2018, the Company adopted Accounting Standards Update, or ASU, 2014‑09, Revenue from Contracts with Customers (Topic 606), or ASC 606, as amended by ASU 2016‑08, 2016‑10, 2016‑12 and 2016‑20 using the full retrospective method. Under ASC 606, the Company recognizes revenue in an amount that reflects the consideration to which it expects to be entitled in exchange for the transfer of promised goods or services to customers. To determine revenue recognition for contracts with customers that are within the scope of ASC 606, the Company performs the following steps: (1) identifies the contract with the customer, (2) identifies the performance obligations in the contract, (3) determines the transaction price, (4) allocates the transaction price to the performance obligations in the contract, and (5) recognizes revenue when (or as) the entity satisfies a performance obligation. The Company has concluded that upon adoption of ASC 606, as amended, there was no impact on its results of operations, financial position or cash flows for any period presented from its only two revenue-related contracts, which were in effect at that time: the CKDP Agreement or the Maruishi Agreement (see Note 11, Collaboration and Licensing Agreements and Note 12, Revenue Recognition).

The Company has entered into agreements to license its intellectual property, or IP, related to CR845/difelikefalin to develop, manufacture and/or commercialize drug products. These agreements typically contain multiple performance obligations, including licenses of IP 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.

The Company identifies agreements as contracts that create enforceable rights and obligations when the agreement is approved by the parties, identifies the rights of the parties and the payment terms, has commercial substance and it is probable that the Company will collect the consideration to which it will be entitled in exchange for the goods and services that will be transferred to the customer. The counterparty is considered to be a customer when it has contracted with the Company to obtain goods and services that are the output of the Company’s ordinary activities (i.e., development of pharmaceutical products) in exchange for consideration.

A performance obligation is a promise to transfer distinct goods or services to a customer. Performance obligations that are both capable of being distinct and distinct within the context of the contract are considered to be separate performance obligations. Performance obligations are capable of being distinct if the counterparty is able to benefit from the good or service on its own or together with other resources that are readily available to it. Performance obligations are distinct within the context of the contract when each performance obligation is separately identifiable from each other; i.e., the Company is not using the goods or services as inputs to produce or deliver the combined output or outputs specified by the customer; one or more of the goods or services does not significantly modify or customize one of the other goods or services in the contract; and goods or services are not highly interdependent or not highly interrelated. Performance obligations that are not distinct are accounted for as a single performance obligation over the period that goods or services are transferred to the customer. The determination of whether performance obligations in a contract are distinct may require significant judgment.

The transaction price is the amount of consideration that the Company expects to be entitled to in exchange for transferring promised goods or services to the customer based on the contract terms at inception of a contract. There is a constraint on inclusion of variable consideration related to licenses of IP, such as milestone payments or sales-based royalty payments, in the transaction price if there is uncertainty at inception of the contract as to whether such consideration will be recognized in the future because it is probable that there will be a significant reversal of revenue in the future when the uncertainty is resolved. The determination of whether or not it is probable that a significant reversal of revenue will occur in the future depends on the likelihood and magnitude of the reversal. Factors that could increase the likelihood or magnitude of a reversal of revenue include (a) the susceptibility of the amount of consideration to factors outside the entity’s influence, such as the outcome of clinical trials, the timing of initiation of clinical trials by the counterparty and the approval of drug product candidates by regulatory agencies, (b) situations in which the uncertainty is not expected to be resolved for a long period of time, and (c) level of the Company’s experience in the field. When it becomes probable that events will occur, for which variable consideration was constrained at inception of the contract, the Company allocates the related consideration to the separate performance obligations in the same manner as described below.

At inception of a contract, the Company allocates the transaction price to the distinct performance obligations based upon their relative standalone selling prices. Standalone selling price is the price at which an entity would sell a promised good or service separately to a customer. The best evidence of standalone selling price is an observable price of a good or service when sold separately by an entity in similar circumstances to similar customers. Since the Company typically does not have such evidence, it estimates standalone selling price so that the amount that is allocated to each performance obligation equals the amount that the Company expects to receive for transferring goods or services. The methods that the Company uses to make such estimates include (1) the adjusted market assessment approach, under which the Company forecasts and analyzes CR845/difelikefalin in the appropriate market, the phase of clinical development as well as considering recent similar license arrangements within the same phase of clinical development, therapeutic area, type of agreement, etc. and (2) the expected cost of satisfying the performance obligations plus a margin, or the expected cost plus a margin approach.

The Company recognizes revenue when, or as, it satisfies a performance obligation by transferring a promised good or service to a customer and the customer obtains control of the good or service. Revenue related to the grant of a license that is a distinct performance obligation and that is deemed to be functional IP is recognized at the point in time that the Company has the right to payment for the license, the customer has legal title to the license and can direct the use of the license (for example, to grant sublicenses), the customer has the significant risks and rewards of ownership of the license and the customer has accepted the asset (license) by signing the license agreement.

Recognition of revenue related to R&D services that are a distinct performance obligation or that are combined with granting of a license as a single performance obligation is deferred at inception of a contract and is recognized as those services are performed based on the costs incurred as a percentage of the estimated total costs to be incurred to complete the performance obligation.

Milestone payments are considered to be variable consideration and are not included in the transaction price at inception of the contract if it is uncertain that the milestone will be achieved. Rather, when it becomes probable that the milestone will be achieved and, therefore, there will not be a significant reversal of revenue in future periods, the respective amount to be earned is included in the transaction price, allocated to the distinct performance obligations based on their relative standalone selling price and recognized as revenue, as described above. Sales milestones and sales-based royalty payments related to a license of IP are recognized as revenue when the respective sales occur.

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, compensation and other personnel-related costs, including consultant costs, and costs to conduct clinical trials using clinical research organizations, or 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 of the clinical trial, and the number of sites involved in the trial as well as the activities to be performed by the sites each period. R&D costs also include costs to manufacture product candidates and clinical supplies, laboratory supplies costs, facility-related costs and stock-based compensation for R&D personnel. Non-refundable R&D advance payments are deferred and capitalized as prepaid R&D expense. The capitalized amounts are expensed as the related goods are delivered or services are performed. As of December 31, 2019 and 2018, the Company recorded $8,498 and $4,377 as prepaid R&D expense, respectively.

Income Taxes

The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized.

The Company applies the provisions of ASC 740, Income Taxes, which prescribes a comprehensive model for how a company should recognize, measure, present and disclose in its financial statements uncertain tax positions that it has taken or expects to take on a tax return. There were no material uncertain tax positions taken as of December 31, 2019 and December 31, 2018. The Company does not have any interest or penalties accrued related to tax positions as it does not have any unrecognized tax benefits. In the event the Company determines that accrual of interest or penalties are necessary in the future, the amount will be presented as a component of interest expense.

Stock-Based Compensation

The Company grants stock options to employees, non-employee members of the Company’s Board of Directors and non-employee consultants as compensation for services performed. Employee and non-employee members of the Board of Directors’ awards of stock-based compensation are accounted for in accordance with ASC 718, Compensation - Stock Compensation, or ASC 718. ASC 718 requires all share-based payments to employees and non-employee directors, including grants of stock options, to be recognized in the Statements of Comprehensive Loss based on their grant date fair values. The grant date fair value of stock options is estimated using the Black-Scholes option valuation model.

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 and blackout periods during which exercises are not allowed, among others. Therefore, the Company believes that as of December 31, 2019, 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. 110, Share-Based Payment.

During the period from January 31, 2014 to December 31, 2018, the Company’s stock had not traded on a public exchange for a sufficient period of time to approximate its expected term (as noted above). Therefore, the Company calculated the volatility for stock options granted using an analysis of guideline companies in accordance with ASC 718. Volatility calculated in this manner had been in the range of 83% - 93% and 75% - 85% for stock options granted during the years ended December 31, 2018 and 2017, respectively.

Beginning on January 1, 2019, the Company determined that it had sufficient company-specific trading activity of its common stock available to use that activity exclusively to calculate the volatility of the Company’s common stock. Volatility calculated in this manner was in the range of 71% - 75% for the period of January 31, 2014 to each respective grant date within the year ended December 31, 2019. Volatility of the Company’s common stock from January 31, 2014 to December 31, 2018 and 2017 was 75% and 79%, respectively.

The expected dividend yield is zero as the Company has never paid dividends and does not currently anticipate paying any in the foreseeable future. Risk-free interest rates are based on quoted U.S. Treasury rates for securities with maturities approximating the option’s expected term.

As of January 1, 2017, the Company adopted ASU 2016‑09, Improvements to Employee Share-Based Payment Accounting, or ASU 2016-09. On the date of adoption of ASU 2016‑09, the Company began to account for forfeitures of unvested stock options as they occur rather than estimate forfeiture rates that were applied to unvested stock option awards, as under the previous accounting guidance. Accordingly, on the date of adoption, the Company recorded a cumulative effect adjustment to stockholders’ equity of $45 thousand for all stock option awards that were unvested as of that date.

Prior to January 1, 2019, the Company accounted for stock options granted to non-employee consultants under ASC 505‑50, Equity-Based Payments to Non-Employees. As such, the Company estimated the fair value of each option to non-employees using the Black-Scholes model, with the expected term of stock options granted to non-employees initially equal to the options’ maximum contractual life of ten years, at issuance. On each subsequent reporting date until performance was complete, the Company revalued all outstanding options granted to non-employee consultants during the vesting period of each tranche. Under ASC 505‑50, upon re-measurement of each award, income or expense was recognized during its vesting term.

On January 1, 2019, the Company adopted ASU 2018‑07, Compensation – Stock Compensation (Topic 718), Improvements to Non-employee Share-Based Payment Accounting, or ASU 2018-07, which expanded the scope of ASC 718 to include share-based payment transactions for acquiring goods and services from non-employees. As a result, the fair value of all outstanding unvested stock options that had been granted to non-employees as of January 1, 2019 was remeasured on that date. The adoption of ASU 2018‑07 did not have a material effect on the Company’s results of operations, financial position or cash flows because grants of stock options to nonemployees have been insignificant.

For all share-based payments granted to employees and non-employees, compensation cost relating to awards with service-based graded vesting schedules is recognized using the straight-line method over the requisite service period.

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, 2019, 2018 and 2017, 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 pruritus and pain.

Leases

Prior to January 1, 2019, the Company recognized rent expense for operating leases on a straight-line basis over the term of the lease, beginning on the date the Company took possession of the property. Rent expense included 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 determined 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 was one of the factors used to determine whether a lease was classified as operating or capital and was 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 was included in deferred rent and classified within long-term liabilities for the year ended December 31, 2018. Lease incentives made by landlords to or on behalf of the Company for leasehold improvements were recorded as deferred rent and classified as long-term liabilities for the year ended December 31, 2018. Deferred rent related to landlord incentives was amortized using the straight-line method over the lease term as an offset to rent expense for the years ended December 31, 2018 and 2017, respectively.

On January 1, 2019, the Company adopted ASC 842, Leases, or ASC 842, under which it elected not to adjust prior comparative periods, which are reported under ASC 840. In addition, the Company elected to adopt both the practical expedient to use hindsight when determining the lease term and the package of practical expedients available under ASC 842, including:

No re-evaluation of whether a contract is or contains a lease (embedded lease);

Lease classification is grandfathered

No reassessment of initial direct costs

Upon adoption of ASC 842, the Company had only one lease, the Stamford Lease (see Note 17, Commitments and Contingencies: Leases), which is included in operating lease right-of-use asset, or ROU asset, operating lease liability – current and operating lease liability – non-current in the Company’s Balance Sheet.

In general, the Company determines if a contract, at its inception, is a lease or contains a lease based on whether the contract conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration. To determine whether a contract conveys the right to control the use of an identified asset for a period of time, the Company assesses whether, throughout the period of use, it has both the right to obtain substantially all of the economic benefits from use of the identified asset, and the right to direct the use of the identified asset. Both of these criteria are met by the Stamford Lease.

Under ASC 842, the Company determines the amount of the operating lease liability based on the present value of the future minimum lease payments over the remaining lease term. The amount of the operating lease ROU asset is equal to the amount of the lease liability, less accrued rent and lease incentives received from the landlord. Initial direct costs were deemed to be immaterial.

Since the Stamford Lease does not provide an implicit interest rate, the Company used an annual incremental borrowing rate of 7% based on the information available at the date of adoption for the purpose of determining the lease liability during the term of the lease.

As noted above, upon adoption of ASC 842, the Company used hindsight in determining the term of the Stamford Lease. Although the Stamford Lease is renewable for one five-year term, upon inception of the lease the renewal term was not included in the lease term since it was not reasonably certain that the Company will exercise that option. Accordingly, the lease term of the Stamford Lease was not adjusted upon adoption of ASC 842 to determine the operating lease ROU asset and operating lease liability.

The Stamford Lease contains both a lease and non-lease component which are accounted for separately. The Company allocates the consideration to the lease and the non-lease component on a relative standalone price basis. Lease expense under ASC 842 is recognized on a straight-line basis over the lease term in the Statement of Comprehensive Loss.

There was no cumulative effect adjustment as a result of the adoption of ASC 842 on January 1, 2019, which reflects the difference between the amount of lease expense under ASC 842 that would have been recognized from inception of the Stamford Lease through December 31, 2018 and the amount of rent expense actually recognized under ASC 840 during that same period.

Litigation Reserves

From time to time, the Company may become subject to arbitration, litigation or claims arising in the ordinary course of its 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

The Company adopted ASC 842 and ASU 2018-07 on January 1, 2019. See Note 2, Summary of Significant Accounting Policies: Leases and Stock-Based Compensation.

Recent Accounting Pronouncements Not Yet Adopted

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740), or ASU 2019-12, which removes specific exceptions to the general principles in Topic 740. ASU 2019-12 eliminates the need for an organization to analyze whether the following apply in a given period: i) exception to the incremental approach for intra-period tax allocation; ii) exceptions to accounting for basis differences when there are ownership changes in foreign investments; and iii) exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss. ASU 2019-12 also simplifies the accounting for income taxes for: i) franchise taxes that are partially based on income; ii) transactions with a government that result in a step up in the tax basis of goodwill; (iii) separate financial statements of legal entities that are not subject to tax; and iv) enacted changes in tax laws in interim periods. The amendments in ASU 2019-12 are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption of the amendments is permitted. An entity that elects to early adopt the amendments in an interim period should reflect any adjustments as of the beginning of the annual period that includes that interim period and must adopt all the amendments in the same period. The amendments in ASU 2019-12 related to separate financial statements of legal entities that are not subject to tax should be applied on a retrospective basis for all periods presented. The amendments related to changes in ownership of foreign equity method investments or foreign subsidiaries should be applied on a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. The amendments related to franchise taxes that are partially based on income should be applied on either a retrospective basis for all periods presented or a modified retrospective basis through a cumulative-effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. All other amendments should be applied on a prospective basis. As such, the Company expects to adopt ASU 2019-12 on January 1, 2021 and is currently evaluating the effect it will have on its results of operations, financial position and cash flows.

In November 2019, the FASB issued ASU 2019-08, Compensation – Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606), or ASU 2019-08, which requires companies to measure and classify share-based payment awards granted to a customer by applying the guidance in Topic 718. The amount recorded as a reduction to the transaction price is required to be measured on the basis of the grant-date fair value of the share-based payment award in accordance with Topic 718. The grant date is the date at which a grantor (supplier) and a grantee (customer) reach a mutual understanding of the key terms and conditions of a share-based payment award. The classification and subsequent measurement of the award are subject to the guidance in Topic 718 unless the share-based payment award is subsequently modified and the grantee is no longer a customer. For entities that have adopted ASU 2018-07, the amendments in ASU 2019-08 are effective in fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. An entity may also early adopt the amendments in ASU 2019-08, but not before it adopts the amendments in ASU 2018-07. The Company will adopt ASU 2019-08 on January 1, 2020 and determined that the adoption will not have a material effect on its results of operations, financial position or cash flows since the Company has not historically granted share-based payment awards to customers.

In November 2018, the FASB issued ASU No. 2018‑18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, or ASU 2018‑18, which clarifies the interaction between Topic 808 and Topic 606 by (1) clarifying that certain transactions between collaborative arrangement participants should be accounted for under Topic 606; (2) adding unit-of-account guidance in Topic 808 to align with the guidance in Topic 606; and (3) clarifying presentation guidance for transactions with a collaborative arrangement participant that are not accounted for under Topic 606. ASU 2018‑18 is effective for public business entities for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. The Company will adopt ASU 2018-18 on January 1, 2020 and has determined that ASU 2018‑18 will not have any effect on its financial position, results of operations or cash flows since all three of its collaboration and licensing agreements are accounted for under Topic 606 (see Note 11, Collaboration and Licensing Agreements and Note 12, Revenue Recognition).

In August 2018, the FASB issued ASU No. 2018‑13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, or ASU 2018‑13, which modifies the disclosure requirements on fair value measurements in Topic 820 to remove the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, the policy for timing of transfers between levels, and the valuation processes for Level 3 fair value measurements. ASU 2018‑13 also amends Topic 820 to clarify that the measurement uncertainty disclosure is to communicate information about the uncertainty in measurement as of the reporting date. ASU 2018‑13 also requires additional disclosure for changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period as well as the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU 2018‑13 is effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted upon issuance of ASU 2018‑13. The Company will adopt ASU 2018‑13, as applicable, on January 1, 2020. The Company determined that the adoption will not have a material effect on its results of operations, financial position or cash flows.

In June 2016, the FASB issued ASU No. 2016‑13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments, or ASU 2016‑13, which replaces the incurred loss impairment methodology in current GAAP, that delays recognition of a credit loss until it is probable that such loss has been incurred, with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU 2016‑13 modifies the other-than-temporary impairment model for available-for-sale debt securities by requiring (1) estimating expected credit losses only when the fair value is below the amortized cost of the asset; (2) recording a credit loss without regard to the length of time a security has been in an unrealized loss position; (3) limiting the measurement of the credit loss to the difference between the security’s amortized cost basis and its fair value and (4) presenting credit losses as an allowance rather than as a write-down, which will allow the Company to record reversals of credit losses in current period net income, a practice that is currently prohibited. In April and November 2019, respectively, codification improvements were issued to help clarify and correct certain portions of ASU 2016‑13. ASU 2016‑13 will be effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company will adopt ASU 2016-13 on January 1, 2020 and believes ASU 2016-13 will primarily impact the Company’s assessment of any potential impairment of its investments in debt securities, specifically its assessment of whether any portion of an unrealized loss in a given period relates to a credit loss. As a result, the Company will revise its internal controls and procedures as of January 1, 2020 to periodically assess whether any portion of an unrealized loss in a given period relates to a credit loss. As of December 31, 2019, the adoption of ASU 2016-13 is not expected to have a material impact on the Company's results of operations, financial position or cash flows.

Business	12 Months Ended
Business	Dec. 31, 2019
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 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 and raising capital. As of December 31, 2019, the Company has raised aggregate net proceeds of approximately $519,600 from several rounds of equity financing, including its initial public offering, or IPO, which closed in February 2014 and four follow-on public offerings of common stock, which closed in July 2019, July 2018, April 2017 and August 2015, respectively, and the issuance of convertible preferred stock and debt prior to the IPO. The Company had also received approximately $89,000 under its license agreements for CR845/difelikefalin, primarily with Vifor Fresenius Medical Care Renal Pharma Ltd., or VFMCRP, Maruishi Pharmaceutical Co. Ltd., or Maruishi, and Chong Kun Dang Pharmaceutical Corp., or CKDP, and an earlier product candidate for which development efforts ceased in 2007. Additionally, in May 2018, the Company received net proceeds of $14,556 from the issuance and sale of 1,174,827 shares of the Company’s common stock to Vifor (International) Ltd., or Vifor, in connection with the Company’s license agreement with VFMCRP (see Note 11, Collaboration and Licensing Agreements). As of December 31, 2019, the Company had unrestricted cash and cash equivalents and marketable securities of $218,165 and an accumulated deficit of $400,727. 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 $106,373 and had net cash used in operating activities of $109,225 for the year ended December 31, 2019. 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.

Available-for-Sale Marketable Securities

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Marketable Securities

3. Available-for-Sale Marketable Securities

As of December 31, 2019, and 2018, the Company’s available-for-sale marketable securities consisted of debt securities issued by the U.S. Treasury, U.S. government-sponsored entities and investment grade institutions as well as municipal bonds.

The following tables summarize the Company’s available-for-sale marketable securities by major type of security as of December 31, 2019, and 2018:

As of December 31, 2019


			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	16,052	$	31	$	(2)	$	16,081
U.S. government agency obligations		25,803		14		(1)		25,816
Corporate bonds		115,788		125		(23)		115,890
Commercial paper		38,547		27		(1)		38,573
Municipal bonds		3,500		—		—		3,500
Total available-for-sale marketable securities	$	199,690	$	197	$	(27)	$	199,860

As of December 31, 2018


			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	19,540	$	—	$	(1)	$	19,539
U.S. government agency obligations		17,860		—		(1)		17,859
Corporate bonds		75,999		5		(94)		75,910
Commercial paper		50,413		—		(23)		50,390
Municipal bonds		4,000		—		—		4,000
Total available-for-sale marketable securities	$	167,812	$	5	$	(119)	$	167,698

All available-for-sale marketable securities are classified as Marketable securities, current or Marketable Securities, non-current depending on the contractual maturity date of the individual available-for-sale security.

The Company classifies its marketable debt securities based on their contractual maturity dates. As of December 31, 2019, the Company’s marketable debt securities mature at various dates through December 2021. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows.


	As of December 31, 2019				As of December 31, 2018
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	136,565	$	136,701	$	146,363		146,302
One year to two years		63,125		63,159		21,449		21,396
Total	$	199,690	$	199,860	$	167,812	$	167,698

There were no sales of available-for-sale marketable securities during the year ended December 31, 2019. During the year ended December 31, 2018, the Company sold shares of its investments in available-for-sale marketable securities with a total fair value of $79,808. The cost of the available-for-sale marketable securities that were sold was determined by specific identification. The sales of the investments in available-for-sale marketable securities during the year ended December 31, 2018 resulted in realized losses of $(5).

The following tables show the fair value of the Company’s available-for-sale marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual investments have been in a continuous unrealized loss position.


	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury securities	$	3,185	$	(2)	$	—	$	—	$	3,185	$	(2)
U.S. government agency obligations		2,400		(1)		—		—		2,400		(1)
Corporate bonds		28,895		(23)		—		—		28,895		(23)
Commercial paper		4,264		(1)		—		—		4,264		(1)
Total	$	38,744	$	(27)	$	—	$	—	$	38,744	$	(27)


	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury securities	$	16,392	$	(1)	$	—	$	—	$	16,392	$	(1)
U.S. government agency obligations		5,596		(1)		—		—		5,596		(1)
Corporate bonds		71,322		(94)		—		—		71,322		(94)
Commercial paper		39,445		(23)		—		—		39,445		(23)
Total	$	132,755	$	(119)	$	—	$	—	$	132,755	$	(119)

As of December 31, 2019 and 2018, the Company held a total of 16 out of 81 positions and 69 out of 84 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 marketable securities is recoverable and that, therefore, it had no other-than-temporary impairments on these securities as of December 31, 2019, or 2018. The Company does not intend to sell these debt securities before maturity and the Company believes it is not more likely than not that it will be required to sell these securities before the recovery of their amortized cost basis, which may be maturity.

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets
Available-for-sale marketable securities	$ 199,860	$ 167,698
Recurring [Member]
Financial assets
Total financial assets	218,573	183,548
U.S. Government Agency Obligations [Member]
Financial assets
Available-for-sale marketable securities	25,816	17,859
U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	25,816	17,859
Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	115,890	75,910
Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	115,890	75,910
Municipal Bonds [Member]
Financial assets
Available-for-sale marketable securities	3,500	4,000
Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	3,500	4,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Total financial assets	18,713	15,850
Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Total financial assets	199,860	167,698
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	25,816	17,859
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	115,890	75,910
Significant Other Observable Inputs (Level 2) [Member] \| Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	3,500	4,000
Money Market Funds [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	18,305	15,081
Restricted cash	408	769
Money Market Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	18,305	15,081
Restricted cash	408	769
U.S. Treasury Securities [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	16,081	19,539
U.S. Treasury Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	16,081	19,539
Commercial Paper [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	38,573	50,390
Commercial Paper [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	$ 38,573	$ 50,390

Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 199,690	$ 167,812
Gross Unrealized Gains	197	5
Gross Unrealized Losses	(27)	(119)
Estimated Fair Value	199,860	167,698
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,052	19,540
Gross Unrealized Gains	31
Gross Unrealized Losses	(2)	(1)
Estimated Fair Value	16,081	19,539
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,803	17,860
Gross Unrealized Gains	14
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	25,816	17,859
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	115,788	75,999
Gross Unrealized Gains	125	5
Gross Unrealized Losses	(23)	(94)
Estimated Fair Value	115,890	75,910
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	38,547	50,413
Gross Unrealized Gains	27
Gross Unrealized Losses	(1)	(23)
Estimated Fair Value	38,573	50,390
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,500	4,000
Estimated Fair Value	$ 3,500	$ 4,000

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Useful Lives of Property and Equipment


Asset Category		Useful Lives
Computer and office equipment		5 years
Short-term laboratory equipment		2 years
Furniture and fixtures		7 years
Leasehold improvements		lesser of useful life of asset or life of lease (Stamford - 7 years)

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 9,100	$ 4,371
Accrued research projects	6,637	6,079
Accrued professional fees	635	802
Accrued compensation and benefits	3,293	2,370
Total	$ 19,665	$ 13,622

Quarterly Results of Operations (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Quarterly Results of Operations (Unaudited)

19. Quarterly Results of Operations (Unaudited)

The following tables contain selected financial data for each quarter of the years ended December 31, 2019 and 2018. 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, 2019 and 2018. The operating results for any period are not necessarily indicative of results for any future periods.


	Year Ended December 31, 2019
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
Revenues	$	4,382	$	5,208	$	5,785	$	4,511
Net loss - Basic and Diluted		(21,960)		(22,960)		(32,842)		(28,611)
Loss per share - Basic and Diluted	$	(0.56)	$	(0.58)	$	(0.74)	$	(0.61)


	Year Ended December 31, 2018
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
Revenues	$	—	$	2,874	$	5,062	$	5,533
Net loss - Basic and Diluted		(16,767)		(17,194)		(19,400)		(20,652)
Loss per share - Basic and Diluted	$	(0.51)	$	(0.52)	$	(0.51)	$	(0.52)

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance, Value at Dec. 31, 2016	$ 27	$ 212,866	$ (162,171)	$ 3	$ 50,725
Balance, Shares at Dec. 31, 2016	27,296,863
Sale of common stock, net of underwriting discounts and commissions and offering expenses, value	$ 5	86,219			86,224
Sale of common, net of underwriting discounts and commissions and offering expenses, shares	5,117,500
Stock-based compensation expense		5,793			5,793
Shares issued upon exercise of stock options, Value	$ 1	1,698			1,699
Shares issued upon exercise of stock options, Shares	247,892
Modification of equity awards		537			537
Cumulative effect adjustment upon adoption of ASU 2016-09		45	(45)
Net loss			(58,125)		(58,125)
Other comprehensive income (loss)				(73)	(73)
Balance, Value at Dec. 31, 2017	$ 33	307,158	(220,341)	(70)	86,780
Balance, Shares at Dec. 31, 2017	32,662,255
Sale of common stock under license agreement, Value	$ 1	14,555			14,556
Sale of common stock under license agreement, Shares	1,174,827
Sale of common stock, net of underwriting discounts and commissions and offering expenses, value	$ 5	92,058			92,063
Sale of common, net of underwriting discounts and commissions and offering expenses, shares	5,175,000
Stock-based compensation expense		7,785			7,785
Shares issued upon exercise of stock options, Value		4,194			4,194
Shares issued upon exercise of stock options, Shares	451,685
Shares issued upon vesting of executive restricted stock units		1,693			1,693
Shares issued upon vesting of executive restricted stock units, Shares	83,791
Modification of equity awards		616			616
Net loss			(74,013)		(74,013)
Other comprehensive income (loss)				(44)	(44)
Balance, Value at Dec. 31, 2018	$ 39	428,059	(294,354)	(114)	133,630
Balance, Shares at Dec. 31, 2018	39,547,558
Sale of common stock under license agreement, Value		4,000			4,000
Sale of common stock under license agreement, Shares	170,793
Sale of common stock, net of underwriting discounts and commissions and offering expenses, value	$ 7	136,491			136,498
Sale of common, net of underwriting discounts and commissions and offering expenses, shares	6,325,000
Stock-based compensation expense		10,587			10,587
Shares issued upon exercise of stock options, Value	$ 1	6,105			$ 6,106
Shares issued upon exercise of stock options, Shares	555,847				555,847
Shares issued for consulting services		197			$ 197
Shares issued for consulting services, Shares	10,195
Shares issued upon vesting of executive restricted stock units		1,784			1,784
Shares issued upon vesting of executive restricted stock units, Shares	110,832
Net loss			(106,373)		(106,373)
Other comprehensive income (loss)				284	284
Balance, Value at Dec. 31, 2019	$ 47	$ 587,223	$ (400,727)	$ 170	$ 186,713
Balance, Shares at Dec. 31, 2019	46,720,225

Quarterly Results of Operations (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Selected Financial Data for Each Quarter


	Year Ended December 31, 2019
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
Revenues	$	4,382	$	5,208	$	5,785	$	4,511
Net loss - Basic and Diluted		(21,960)		(22,960)		(32,842)		(28,611)
Loss per share - Basic and Diluted	$	(0.56)	$	(0.58)	$	(0.74)	$	(0.61)


	Year Ended December 31, 2018
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
Revenues	$	—	$	2,874	$	5,062	$	5,533
Net loss - Basic and Diluted		(16,767)		(17,194)		(19,400)		(20,652)
Loss per share - Basic and Diluted	$	(0.51)	$	(0.52)	$	(0.51)	$	(0.52)

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net consists of the following:


	December 31,
	2019		2018
Computer and office equipment	$	211	$	211
Laboratory equipment		628		628
Furniture and fixtures		61		47
Leasehold improvements		1,132		1,128
	$	2,032	$	2,014
Less accumulated depreciation and amortization		1,332		1,134
Property and equipment, net	$	700	$	880

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment Institution	Dec. 31, 2018 USD ($)	Dec. 31, 2017	Jan. 01, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Prepaid R&D expense	$ 8,498	$ 4,377
Expected volatility, minimum	71.10%	82.60%	75.30%
Expected volatility, maximum	75.20%	92.80%	84.50%
Expected dividend yield	0.00%	0.00%	0.00%
Number of operating segments \| segment	1
Operating lease liability	$ 4,319
ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment				$ 45
Employee Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	6 years 3 months
Expected volatility, minimum	71.00%	83.00%	75.00%
Expected volatility, maximum	75.00%	93.00%	85.00%
Expected volatility		75.00%	79.00%
Expected dividend yield	0.00%
Non Employee Stock Option [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected life of options (in years)	10 years
Cash And Cash Equivalents And Marketable Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of financial institutions \| Institution	4

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding	4,004,422
Number of Options, Granted	1,324,000	1,197,500	1,328,500
Number of Options, Exercised	(555,847)
Number of Options, Forfeited	(322,058)
Number of Options, Outstanding	4,450,517	4,004,422
Number of Options, Outstanding, Weighted average remaining contractual life as of December 31, 2019	7 years 4 months 6 days
Number of Options, Options exercisable	2,407,027
Number of Options, Exercisable, Weighted average remaining contractual life as of December 31, 2019	6 years 2 months 5 days
Number of Options, Options vested and expected to vest at December 31, 2019	4,450,517
Number of Options, Vested and expected to vest, Weighted average remaining contractual life as of December 31, 2019	7 years 4 months 6 days
Weighted-Average Exercise Price, Outstanding	$ 13.34
Weighted-Average Exercise Price, Granted	17.44
Weighted-Average Exercise Price, Exercised	10.98
Weighted-Average Exercise Price, Forfeited	15.12
Weighted-Average Exercise Price, Outstanding	14.73	$ 13.34
Weighted-Average Exercise Price, Options exercisable, December 31,2019	12.97
Weighted-Average Exercise Price, Options vested and expected to vest at December 31, 2019	$ 14.73
Aggregate Intrinsic Value, Outstanding at December 31, 2019	$ 10,350
Aggregate Intrinsic Value, Options exercisable at December 31, 2019	8,733
Aggregate Intrinsic Value, Options vested and expected to vest at December 31, 2019	10,350
Fair value of options vested	10,074	$ 9,023	$ 5,303
Intrinsic value of options exercised	$ 5,741	$ 3,893	$ 2,285

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019		2018		2017
Risk-free interest rate	1.55% - 2.62	%	2.51% - 3.09	%	1.85% - 2.57	%
Expected volatility	71.1% - 75.2	%	82.6% - 92.8	%	75.3% - 84.5	%
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 options (in years)	—		—		10

Summary of Compensation Expense Relating to Stock Options

During the years ended December 31, 2019, 2018 and 2017, the Company recognized compensation expense relating to stock options as follows:



	Year Ended December 31,
	2019		2018		2017
Research and development	$	5,206	$	3,919	$	2,433
General and administrative		5,094		4,482		3,897
Total stock option expense	$	10,300	$	8,401	$	6,330

Summary of Stock Option Activity


		Weighted		Aggregate
	Number of	Average Exercise		Intrinsic
	Shares	Price		Value
Outstanding, December 31, 2018	4,004,422	$	13.34
Granted	1,324,000		17.44
Exercised	(555,847)		10.98
Expired	—		—
Forfeited	(322,058)		15.12
Outstanding, December 31, 2019	4,450,517	$	14.73	$	10,350
Weighted average remaining contractual life as of December 31, 2019 (in years)	7.35
Options exercisable, December 31, 2019	2,407,027	$	12.97	$	8,733
Weighted average remaining contractual life as of December 31, 2019 (in years)	6.18
Options vested and expected to vest as of December 31, 2019	4,450,517	$	14.73	$	10,350
Weighted average remaining contractual life as of December 31, 2019 (in years)	7.35

Share-based Payment Arrangement, Nonemployee [Member] | Consultants [Member] | Re-Measurement [Member]

Summary of Assumptions Used in Black-Scholes Option Pricing Model


	January 1,	December 31,
	2019	2018	2017
Risk-free interest rate	2.59% - 2.62%	1.82% - 3.02%	1.28% - 2.39%
Expected volatility	58.9% - 84.6%	58.2% - 101.0%	74.6% - 87.3%
Expected dividend yield	0%	0%	0%
Expected life of non-employee options (in years)	0.81 - 8.19	0.25 - 8.94	0.62 - 9.94

Accumulated Other Comprehensive Income (Loss) - Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Other income	$ 4,490	$ 2,980	$ 1,156
Benefit from income taxes	(816)	(389)	(204)
Net of tax		(5)	5
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]
Other income		(5)	5
Benefit from income taxes	$ 0	$ 0	$ 0

Collaboration and Licensing Agreements - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended							12 Months Ended
	May 17, 2018 USD ($) item $ / shares shares	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase of common stock value										$ 136,498	$ 92,063	$ 86,224
Revenue from contract with customer			$ 4,511	$ 5,785	$ 5,208	$ 4,382	$ 5,533	$ 5,062	$ 2,874	19,886	13,469	911
Collaborative Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer												313
Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer										$ 140	33	68
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable, non-creditable upfront payment	$ 50,000
Common stock, shares issued \| shares	1,174,827
Purchase of common stock value	$ 20,000
Purchase common stock per share amount \| $ / shares	$ 17.024
Closing prices of company common stock description	over a pre-determined average closing price of the Company's common stock.
Premium from sale of stock	$ 5,444
Contract liabilities	$ 55,444
Number of combined performance obligations for revenue recognized \| item	1
Number of performance obligations for revenue recognized \| item										2
Number of days to terminate agreement										60 days
Termination notice effective period										12 months
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Third-party cost for clinical development	$ 20,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Regulatory and Commercial Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	470,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	30,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Tiered Commercial Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	$ 440,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of performance obligations for revenue recognized \| item										2
Cost of clinical compound related to R&D expense										$ 126	30	61
Maruishi Pharmaceutical Co., Ltd. [Member] \| License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer		$ 843										843
Maruishi Pharmaceutical Co., Ltd. [Member] \| Collaborative Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer												313
Maruishi Pharmaceutical Co., Ltd. [Member] \| Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer										$ 140	$ 33	$ 68

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

Certain amounts in the prior years’ financial statements have been reclassified to conform to the current-year presentation due to the adoption of Accounting Standards Update, or ASU, No. 2016-18, Statement of Cash Flows (Topic 230), Restricted Cash, or ASU 2016-18, on January 1, 2018.

Use of Estimates

Concentrations of Credit Risk

Cash and Cash Equivalents

Marketable Securities

Fair Value of Financial Instruments

Level 1 – Observable inputs – quoted prices in active markets for identical assets and liabilities.

Level 3 – Unobservable inputs – includes amounts derived from valuation models where one or more significant inputs are unobservable and require the Company to develop relevant assumptions.

The Company records transfers between levels in the hierarchy by assuming that the transfer occurred at the end of the quarter or year-to-date period.

Valuation Techniques - Level 2 Inputs

Property and Equipment


Asset Category		Useful Lives
Computer and office equipment		5 years
Short-term laboratory equipment		2 years
Furniture and fixtures		7 years
Leasehold improvements		lesser of useful life of asset or life of lease (Stamford - 7 years)

Revenue Recognition

Research and Development Expenses

Income Taxes

Stock-Based Compensation

Income (Loss) Per Share

Segment Reporting

Leases

No re-evaluation of whether a contract is or contains a lease (embedded lease);

Lease classification is grandfathered

No reassessment of initial direct costs

Litigation Reserves

Accounting Pronouncements Recently Adopted

The Company adopted ASC 842 and ASU 2018-07 on January 1, 2019. See Note 2, Summary of Significant Accounting Policies: Leases and Stock-Based Compensation.

Recent Accounting Pronouncements Not Yet Adopted

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Components of Income Taxes (Benefit)

The Company’s benefit from income taxes is as follows:


	December 31,
	2019		2018		2017
Current:
Federal	$	—	$	—	$	—
State		(816)		(389)		(204)
		(816)		(389)		(204)
Deferred:
Federal		—		—		—
State		—		—		—
		—		—		—
Benefit from income taxes	$	(816)	$	(389)	$	(204)

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,
	2019		2018		2017
Income taxes using U.S. federal statutory rate	21.00	%	21.00	%	34.00	%
State income taxes, net of federal benefit	(1.99)	%	6.82	%	5.33	%
Tax Cuts and Jobs Act	0.00	%	0.00	%	(44.43)	%
Impact of R&D tax credit on effective tax rate	4.34	%	3.48	%	3.25	%
Stock option shortfalls and cancellations	(0.17)	%	(0.43)	%	0.21	%
Permanent items and other	0.36	%	(0.15)	%	(0.56)	%
Change in valuation allowance	(22.76)	%	(31.76)	%	2.55	%
Provision to return	(0.02)	%	0.03	%	0.00	%
Non-taxable revenue	0.00	%	1.54	%	0.00	%
	0.76	%	0.53	%	0.35	%

Schedule of Significant Components of Company's Deferred Tax Assets and Liabilities

Significant components of the Company’s deferred tax assets and liabilities are as follows:


	December 31,
	2019		2018
Valuation allowance	$	(114,136)	$	(89,815)

Net operating loss carryforwards		84,608		73,578
Federal and state tax credits		16,624		11,108
Deferred revenue		5,994		1,111
Stock-based compensation expense		4,481		3,605
Other		3,409		420
Deferred tax assets		115,116		89,822

Other		(980)		(7)
Deferred tax liabilities:		(980)		(7)

Net deferred tax asset:	$	—	$	—

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income taxes using U.S. federal statutory rate	21.00%	21.00%	34.00%
State income taxes, net of federal benefit	(1.99%)	6.82%	5.33%
Tax Cuts and Jobs Act	0.0000	0.0000	(0.4443)
Impact of R&D tax credit on effective tax rate	4.34%	3.48%	3.25%
Stock option shortfalls and cancellations	(0.17%)	(0.43%)	0.21%
Permanent items and other	0.36%	(0.15%)	(0.56%)
Change in valuation allowance	(22.76%)	(31.76%)	2.55%
Provision to return	(0.02%)	0.03%	0.00%
Non-taxable revenue	0.00%	1.54%	0.00%
Total	0.76%	0.53%	0.35%

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended					9 Months Ended	12 Months Ended
	Jun. 04, 2019	Dec. 31, 2019	Jun. 30, 2019	May 31, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015	Jan. 01, 2020	Nov. 20, 2019	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value		$ 0.001						$ 0.001	$ 0.001
Compensation expense								$ 10,300	$ 8,401	$ 6,330
Common stock, shares outstanding		46,720,225						46,720,225	39,547,558
Common stock, shares issued		46,720,225						46,720,225	39,547,558
Options granted								1,324,000	1,197,500	1,328,500
Fair value of options granted								$ 11.67	$ 11.99	$ 11.46
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 5,094	$ 4,482	$ 3,897
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								5,206	3,919	$ 2,433
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, vested		36,666		74,166
Director [Member] \| Restricted Stock Units [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								287
Executive Officers [Member] \| Restricted Stock Units [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								1,180	1,217
Executive Officers [Member] \| Restricted Stock Units [Member] \| Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 604	$ 476
Consultants [Member] \| Share-based Payment Arrangement, Nonemployee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair values of outstanding options									$ 8.74	$ 10.16
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		6,086,907						6,086,907
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												7,488,513
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] \| Maximum [Member] \| Incentive Stock Options [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
2014 Equity Incentive Plan [Member] \| Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted									3 years
2014 Equity Incentive Plan [Member] \| Director [Member] \| Share-based Payment Arrangement, Nonemployee [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								1 year
Restricted stock units, approved and granted	24,000							24,000
Restricted stock units, grant date fair value	$ 20.47
Compensation expense								$ 287
Restricted stock units, vested								0
2014 Equity Incentive Plan [Member] \| Executive Officers [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, approved and granted					215,000	83,791
Restricted stock units, grant date fair value					$ 16.10	$ 20.21
Compensation expense								$ 1,784	$ 1,693
Restricted stock units, vested		36,666		74,166
Common stock, shares outstanding									83,791
Common stock, shares issued		36,666		74,166				36,666
2014 Equity Incentive Plan [Member] \| Executive Officers [Member] \| Restricted Stock Units [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 1,180	$ 1,217
2014 Equity Incentive Plan [Member] \| Executive Officers [Member] \| Restricted Stock Units [Member] \| Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 604	$ 476
2014 Equity Incentive Plan [Member] \| Employee And Nonemployee Consultants [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] \| Employee And Nonemployee Consultants [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] \| Employee And Nonemployee Consultants [Member] \| Share Based Compensation Subsequent Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								4 years
2019 Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value													$ 0.001
2019 Inducement Plan [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													300,000
2019 Inducement Plan [Member] \| Share-based Payment Arrangement, Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted								47,500
2019 Inducement Plan [Member] \| Share-based Payment Arrangement, Employee [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%
2019 Inducement Plan [Member] \| Share-based Payment Arrangement, Employee [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
2019 Inducement Plan [Member] \| Share-based Payment Arrangement, Employee [Member] \| Share Based Compensation Subsequent Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								4 years
Non-employee Director Compensation Policy [Member] \| Director [Member] \| Share-based Payment Arrangement, Nonemployee [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted per director			6,000
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

Available-for-Sale Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

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 marketable securities by major type of security as of December 31, 2019, and 2018:

As of December 31, 2019


			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	16,052	$	31	$	(2)	$	16,081
U.S. government agency obligations		25,803		14		(1)		25,816
Corporate bonds		115,788		125		(23)		115,890
Commercial paper		38,547		27		(1)		38,573
Municipal bonds		3,500		—		—		3,500
Total available-for-sale marketable securities	$	199,690	$	197	$	(27)	$	199,860

As of December 31, 2018


			Gross Unrealized				Estimated Fair
Type of Security	Amortized Cost		Gains		Losses		Value
U.S. Treasury securities	$	19,540	$	—	$	(1)	$	19,539
U.S. government agency obligations		17,860		—		(1)		17,859
Corporate bonds		75,999		5		(94)		75,910
Commercial paper		50,413		—		(23)		50,390
Municipal bonds		4,000		—		—		4,000
Total available-for-sale marketable securities	$	167,812	$	5	$	(119)	$	167,698

Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity


	As of December 31, 2019				As of December 31, 2018
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	136,565	$	136,701	$	146,363		146,302
One year to two years		63,125		63,159		21,449		21,396
Total	$	199,690	$	199,860	$	167,812	$	167,698

Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities


	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury securities	$	3,185	$	(2)	$	—	$	—	$	3,185	$	(2)
U.S. government agency obligations		2,400		(1)		—		—		2,400		(1)
Corporate bonds		28,895		(23)		—		—		28,895		(23)
Commercial paper		4,264		(1)		—		—		4,264		(1)
Total	$	38,744	$	(27)	$	—	$	—	$	38,744	$	(27)


	Less than 12 Months				12 Months or Greater				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury securities	$	16,392	$	(1)	$	—	$	—	$	16,392	$	(1)
U.S. government agency obligations		5,596		(1)		—		—		5,596		(1)
Corporate bonds		71,322		(94)		—		—		71,322		(94)
Commercial paper		39,445		(23)		—		—		39,445		(23)
Total	$	132,755	$	(119)	$	—	$	—	$	132,755	$	(119)

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Accumulated Other Comprehensive Income (Loss)

4. Accumulated Other Comprehensive Income (Loss)


	Total Accumulated
	Other Comprehensive
	Income (Loss)
Balance, December 31, 2016	$	3
Other comprehensive loss before reclassifications		(68)
Amount reclassified from accumulated other comprehensive income		(5)
Net current period other comprehensive loss		(73)
Balance, December 31, 2017		(70)
Other comprehensive loss before reclassifications		(49)
Amount reclassified from accumulated other comprehensive loss		5
Net current period other comprehensive loss		(44)
Balance, December 31, 2018		(114)
Other comprehensive income before reclassifications		284
Amount reclassified from accumulated other comprehensive loss		—
Net current period other comprehensive income		284
Balance, December 31, 2019	$	170

The reclassifications out of AOCI and into net loss were as follows:


							Affected Line Item in the
	Year Ended December 31,						Statements of
Component of AOCI	2019		2018		2017		Operations
Unrealized gains (losses) on available-for-sale marketable securities
Realized (losses) gains on sale of securities	$	—	$	(5)	$	5	Other income
		—		—		—	Benefit from income taxes
	$	—	$	(5)	$	5

The amounts reclassified out of AOCI into net loss were determined by specific identification.

Summary of Significant Accounting Policies - Summary of Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2019
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	5 years
Short-term Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	2 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	7 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, description	lesser of useful life of asset or life of lease (Stamford - 7 years)
Leasehold Improvements [Member] \| Stamford [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	7 years

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Defined contribution, plan name	401(k)
Defined contribution retirement plan, description	All employees over the age of 21 are eligible to participate in the plan at the beginning of the calendar quarter after three consecutive months of service
Employer contributions to the plan	$ 279	$ 198	$ 174
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

Net Loss per Share - Computation of Denominators Used in Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic:
Weighted average common shares outstanding	42,669,333	35,892,786	31,202,842
Diluted:
Weighted average common shares outstanding - Basic	42,669,333	35,892,786	31,202,842
Common stock options	0	0	0
Denominator for diluted net loss per share	42,669,333	35,892,786	31,202,842