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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 02, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	CARA
Entity Registrant Name	Cara Therapeutics, Inc.
Entity Central Index Key	0001346830
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		46,417,700
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-36279
Entity Tax Identification Number	753175693
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	Connecticut
Entity Address, Postal Zip Code	06902
City Area Code	203
Local Phone Number	406-3700

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 18,494	$ 15,081
Marketable securities	96,815	146,302
Income tax receivable	984	664
Other receivables	605	926
Prepaid expenses	7,512	4,805
Restricted cash, current	361	361
Total current assets	124,771	168,139
Operating lease right-of-use asset	3,344
Marketable securities, non-current	20,320	21,396
Property and equipment, net	798	880
Restricted cash	408	408
Total assets	149,641	190,823
Current liabilities:
Accounts payable and accrued expenses	12,766	13,622
Operating lease liability, current	923
Current portion of deferred revenue	26,473	26,825
Total current liabilities	40,162	40,447
Operating lease liability, non-current	3,849
Deferred revenue, non-current	6,085	15,184
Deferred lease obligation		1,562
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at June 30, 2019 and December 31, 2018, zero shares issued and outstanding at June 30, 2019 and December 31, 2018
Common stock; $0.001 par value; 100,000,000 shares authorized at June 30, 2019 and December 31, 2018, 40,027,916 shares and 39,547,558 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	40	39
Additional paid-in capital	438,614	428,059
Accumulated deficit	(339,274)	(294,354)
Accumulated other comprehensive income (loss)	165	(114)
Total stockholders’ equity	99,545	133,630
Total liabilities and stockholders’ equity	$ 149,641	$ 190,823

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Total revenue	$ 5,208	$ 2,874	$ 9,590	$ 2,874
Operating expenses:
Research and development	24,356	17,002	47,964	30,429
General and administrative	4,994	3,685	8,902	7,382
Total operating expenses	29,350	20,687	56,866	37,811
Operating loss	(24,142)	(17,813)	(47,276)	(34,937)
Other income	947	467	2,036	778
Loss before benefit from income taxes	(23,195)	(17,346)	(45,240)	(34,159)
Benefit from income taxes	235	152	320	198
Net loss	$ (22,960)	$ (17,194)	$ (44,920)	$ (33,961)
Net loss per share:
Basic and Diluted	$ (0.58)	$ (0.52)	$ (1.13)	$ (1.03)
Weighted average shares:
Basic and Diluted	39,818,162	33,315,809	39,685,954	33,000,487
Other comprehensive income, net of tax of $0:
Change in unrealized gains (losses) on available-for- sale marketable securities	$ 92	$ 57	$ 279	$ 13
Total comprehensive loss	(22,868)	(17,137)	(44,641)	(33,948)
License and Milestone Fees [Member]
Revenue:
Total revenue	$ 5,208	$ 2,874	9,450	$ 2,874
Clinical Compound Revenue [Member]
Revenue:
Total revenue			$ 140

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, Value at Dec. 31, 2017	$ 86,780	$ 33	$ 307,158	$ (220,341)	$ (70)
Balance, Shares at Dec. 31, 2017		32,662,255
Stock-based compensation expense	1,871		1,871
Shares issued upon exercise of stock options, Value	263		263
Shares issued upon exercise of stock options, Shares		37,688
Net loss	(16,767)			(16,767)
Other comprehensive income (loss)	(44)				(44)
Balance, Value at Mar. 31, 2018	72,103	$ 33	309,292	(237,108)	(114)
Balance, Shares at Mar. 31, 2018		32,699,943
Balance, Value at Dec. 31, 2017	86,780	$ 33	307,158	(220,341)	(70)
Balance, Shares at Dec. 31, 2017		32,662,255
Net loss	(33,961)
Other comprehensive income (loss)	13
Balance, Value at Jun. 30, 2018	73,076	$ 34	327,401	(254,302)	(57)
Balance, Shares at Jun. 30, 2018		34,059,214
Balance, Value at Mar. 31, 2018	72,103	$ 33	309,292	(237,108)	(114)
Balance, Shares at Mar. 31, 2018		32,699,943
Sale of common stock under license agreement, Value	14,556	$ 1	14,555
Sale of common stock under license agreement, Shares		1,174,827
Stock-based compensation expense	2,069		2,069
Shares issued upon exercise of stock options, Value	1,485		1,485
Shares issued upon exercise of stock options, Shares		184,444
Net loss	(17,194)			(17,194)
Other comprehensive income (loss)	57				57
Balance, Value at Jun. 30, 2018	73,076	$ 34	327,401	(254,302)	(57)
Balance, Shares at Jun. 30, 2018		34,059,214
Balance, Value at Dec. 31, 2018	133,630	$ 39	428,059	(294,354)	(114)
Balance, Shares at Dec. 31, 2018		39,547,558
Stock-based compensation expense	2,234		2,234
Shares issued upon exercise of stock options, Value	234		234
Shares issued upon exercise of stock options, Shares		17,291
Shares issued for consulting services	197		197
Shares issued for consulting services, Shares		10,195
Net loss	(21,960)			(21,960)
Other comprehensive income (loss)	187				187
Balance, Value at Mar. 31, 2019	114,522	$ 39	430,724	(316,314)	73
Balance, Shares at Mar. 31, 2019		39,575,044
Balance, Value at Dec. 31, 2018	133,630	$ 39	428,059	(294,354)	(114)
Balance, Shares at Dec. 31, 2018		39,547,558
Net loss	(44,920)
Other comprehensive income (loss)	279
Balance, Value at Jun. 30, 2019	99,545	$ 40	438,614	(339,274)	165
Balance, Shares at Jun. 30, 2019		40,027,916
Balance, Value at Mar. 31, 2019	114,522	$ 39	430,724	(316,314)	73
Balance, Shares at Mar. 31, 2019		39,575,044
Stock-based compensation expense	2,681		2,681
Shares issued upon exercise of stock options, Value	3,975	$ 1	3,974
Shares issued upon exercise of stock options, Shares		378,706
Shares issued upon vesting of restricted stock units	1,235		1,235
Shares issued upon vesting of restricted stock units, Shares		74,166
Net loss	(22,960)			(22,960)
Other comprehensive income (loss)	92				92
Balance, Value at Jun. 30, 2019	$ 99,545	$ 40	$ 438,614	$ (339,274)	$ 165
Balance, Shares at Jun. 30, 2019		40,027,916

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
Condensed Statements of Cash Flows - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (44,920)	$ (33,961)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	6,249	3,940
Depreciation and amortization	100	239
Amortization expense component of lease expense	293
Accretion of available-for-sale marketable securities	(803)	(559)
Realized loss on sale of available-for-sale marketable securities		15
Deferred rent costs		(23)
Deferred revenue	(9,450)	52,569
Changes in operating assets and liabilities:
Income tax receivable	(320)	258
Other receivables	321	7
Prepaid expenses	(2,609)	(3,980)
Accounts payable and accrued expenses	(856)	4,047
Operating lease liability	(427)
Net cash (used in) provided by operating activities	(52,422)	22,552
Investing activities
Proceeds from maturities of available-for-sale marketable securities	122,881	56,700
Proceeds from sale of available-for-sale marketable securities		11,150
Purchases of available-for-sale marketable securities	(71,236)	(98,271)
Purchases of property and equipment	(18)	(21)
Net cash provided by (used in) investing activities	51,627	(30,442)
Financing activities
Proceeds from the sale of common stock under license agreement		14,556
Proceeds from the exercise of stock options	4,208	1,748
Net cash provided by financing activities	4,208	16,304
Net increase in cash, cash equivalents and restricted cash	3,413	8,414
Cash, cash equivalents and restricted cash at beginning of period	15,850	10,157
Cash, cash equivalents and restricted cash at end of period	19,263	$ 18,571
Noncash investing and financing activities
Shares of common stock issued in exchange for consulting services (recorded as a prepaid expense)	$ 197

Basis of Presentation

6 Months Ended

Jun. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Basis of Presentation

2. Basis of Presentation

The unaudited interim condensed financial statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC. Accordingly, they do not include all information and disclosures necessary for a presentation of the Company’s financial position, results of operations and cash flows in conformity with generally accepted accounting principles in the United States of America, or GAAP. In the opinion of management, these unaudited interim financial statements reflect all adjustments, consisting primarily of normal recurring accruals, necessary for a fair presentation of results for the periods presented. The results of operations for interim periods are not necessarily indicative of the results for the full year. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by SEC rules and regulations; however, the Company believes that the disclosures are adequate to make the information presented not misleading. The condensed balance sheet data as of December 31, 2018 were derived from audited financial statements, but do not include all disclosures required by GAAP. These unaudited interim condensed financial statements should be read in conjunction with the audited financial statements and accompanying notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, as of the date of the financial statements as well as the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from the Company’s estimates and assumptions. Significant estimates include the fair value of marketable securities that are classified as level 2 of the fair value hierarchy, useful lives of fixed assets, the periods over which certain revenues will be recognized, including licensing and collaborative revenue recognized from non-refundable up-front 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.

Significant Accounting Policies

There have been no material changes to the significant accounting policies previously disclosed in Note 2 to the Financial Statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, except for the recent adoption of new accounting pronouncements as disclosed below.

Accounting Pronouncements Recently Adopted

Leases

On January 1, 2019, the Company adopted ASC 842, Leases, 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 15, 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 Condensed Balance Sheets.

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 Condensed Statements 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.

Other Accounting Pronouncements Recently Adopted

In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting, or ASU 2018-07, which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. Accordingly, under ASU 2018-07, the fair value of stock options granted to nonemployees will be measured only on the grant date, the amount of which will be recognized as compensation expense over the nonemployee’s service (vesting) period in the same period(s) and in the same manner as if the Company had paid cash for the goods or services instead of paying with or using share-based payment awards. On an award-by-award basis, the Company may elect to use the contractual term as the expected term when estimating the fair value of a nonemployee award to satisfy the measurement objective. Prior guidance under Subtopic 505-50 required the fair value of nonemployee stock options to be marked to market at each reporting period during the service period, which resulted in volatility of compensation expense during that period. The Company adopted ASU 2018-07 on January 1, 2019 on a modified retrospective basis and remeasured, on that date, the fair value of all outstanding unvested stock options that had been granted to nonemployees. The adoption of ASU 2018-07 did not have a material effect on its results of operations, financial position or cash flows because grants of stock options to nonemployees have been insignificant.

Accounting Pronouncements Not Yet Adopted

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 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 10, Collaboration and Licensing Agreements and Note 11, 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 does not expect that the adoption of ASU 2018-13 will 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 2019, 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. As such, the Company expects to adopt ASU 2016-13 on January 1, 2020 and is currently evaluating the effect it will have on its results of operations, financial position and cash flows.

Available-for-Sale Marketable Securities

6 Months Ended

Jun. 30, 2019

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Marketable Securities

3. Available-for-Sale Marketable Securities

As of June 30, 2019 and December 31, 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 June 30, 2019 and December 31, 2018:

As of June 30, 2019

			Gross Unrealized
Type of Security	Amortized Cost		Gains		Losses			Estimated Fair Value
U.S. Treasury securities	$	12,992	$	32	$	—		$	13,024
U.S. government agency obligations		12,447		16		—			12,463
Corporate bonds		62,529		109		(6	)		62,632
Commercial paper		23,502		14		—			23,516
Municipal bonds		5,500		—		—			5,500
Total available-for-sale marketable securities	$	116,970	$	171	$	(6	)	$	117,135

As of December 31, 2018

			Gross Unrealized
Type of Security	Amortized Cost		Gains		Losses			Estimated Fair 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 June 30, 2019, the Company’s marketable debt securities mature at various dates through March 2021. The amortized cost and fair values of marketable debt securities by contractual maturity were as follows.

	As of June 30, 2019				As of December 31, 2018
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	96,712	$	96,815	$	146,363		146,302
One year to two years		20,258		20,320		21,449		21,396
Total	$	116,970	$	117,135	$	167,812	$	167,698

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.

As of June 30, 2019

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Corporate bonds	$	4,756	$	(6	)	$	—	$	—	$	4,756	$	(6	)
Total	$	4,756	$	(6	)	$	—	$	—	$	4,756	$	(6	)

As of December 31, 2018

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized 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 June 30, 2019 and December 31, 2018, the Company held a total of 6 out of 58 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 June 30, 2019 and December 31, 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.

Accumulated Other Comprehensive Income (Loss)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Accumulated Other Comprehensive Income (Loss)

4. Accumulated Other Comprehensive Income (Loss)

The following table summarizes the changes in accumulated other comprehensive income (loss), or AOCI, net of tax, from unrealized gains (losses) on available-for-sale marketable securities, the Company's only component of AOCI, for the six months ended June 30, 2019 and June 30, 2018.

	Total Accumulated Other Comprehensive Income (Loss)
Balance, December 31, 2018	$	(114	)
Other comprehensive income before reclassifications		279
Amount reclassified from accumulated other comprehensive income		—
Net current period other comprehensive income		279
Balance, June 30, 2019	$	165

Balance, December 31, 2017	$	(70	)
Other comprehensive loss before reclassifications		(2	)
Amount reclassified from accumulated other comprehensive loss		15
Net current period other comprehensive income		13
Balance, June 30, 2018	$	(57	)

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

	Three Months Ended June 30,				Six Months Ended June 30,					Affected Line Item in the Statements of
Component of AOCI	2019		2018		2019		2018			Operations
Unrealized gains (losses) on available- for-sale marketable securities
Realized gains (losses) on sale of securities	$	—	$	—	$	—	$	(15	)	Other income
		—		—		—		—		Benefit from income taxes
	$	—	$	—	$	—	$	(15	)

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

Fair Value Measurements

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. Fair Value Measurements

As of June 30, 2019 and December 31, 2018, the Company’s financial instruments consisted 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 Condensed 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.

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 third-party pricing services as of June 30, 2019 or December 31, 2018.

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of June 30, 2019 and December 31, 2018.

Fair value measurement as of June 30, 2019:

Financial assets			Quoted prices in		Significant other		Significant
			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market funds and checking accounts	$	18,494	$	18,494	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		13,024		—		13,024		—
U.S. government agency obligations		12,463		—		12,463		—
Corporate bonds		62,632		—		62,632		—
Commercial paper		23,516		—		23,516		—
Municipal bonds		5,500		—		5,500		—
Restricted cash:
Commercial money market account		769		769		—		—
Total financial assets	$	136,398	$	19,263	$	117,135	$	—

Fair value measurement as of December 31, 2018:

Financial assets			Quoted prices in		Significant other		Significant
			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market 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 six months ended June 30, 2019. There were no transfers of financial assets between Levels 1, 2, or 3 classifications during the six months ended June 30, 2019.

- 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

Collaboration and Licensing Agreements

6 Months Ended

Jun. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration and Licensing Agreements

10. 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.

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, 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 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 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 six months ended June 30, 2019, the Company recognized clinical compound revenue of $140 from the sale of clinical compound to Maruishi and as a result, the Company incurred R&D expense of $126 during the respective period. There were no clinical compound sales to Maruishi during the six months ended June 30, 2018.

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.

Revenue Recognition

6 Months Ended

Jun. 30, 2019

Revenue Recognition [Abstract]

Revenue Recognition

11. Revenue Recognition

The Company currently recognizes revenue in accordance with ASC 606, as amended, for the VFMCRP, Maruishi and CKDP agreements (see Note 10, 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 June 30, 2019, the Company had deferred revenue, current of $26,473 and deferred revenue, non-current of $6,085 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 June 30, 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 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 10, 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. For the three and six months ended June 30, 2019, $5,208 and $9,450, respectively, were recognized as license and milestone fees revenue based on the percentage of R&D services that were completed during the period. As of June 30, 2019, $22,886 of the $55,444 has been recognized as license and milestone fees revenue based on the percentage of R&D services that has been completed since the inception of the VFMCRP Agreement. As of June 30, 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:

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 10, 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.

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.

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 10, 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 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.

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.

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.

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 $32,558 at June 30, 2019 will be recognized by 2020, as the R&D services are performed, subject to certain development and regulatory uncertainties.

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 six months ended June 30, 2019 and 2018, 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.

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.

Net Loss Per Share

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

12. Net Loss Per Share

The Company computes basic net income (loss) per share by dividing net income (loss) by the weighted-average number of shares of common stock outstanding. Diluted net income per share includes the potential dilutive effect of common stock equivalents as if such securities were exercised during the period, when the effect is dilutive. Common stock equivalents may include outstanding stock options or restricted stock units, which are included using the treasury stock method when dilutive. For the three and six months ended June 30, 2019 and 2018, the Company excluded the effects of potentially dilutive shares that were outstanding during those respective periods from the denominator as their inclusion would be anti-dilutive due to the Company’s net losses during those periods.

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Basic:
Weighted average common shares outstanding		39,818,162		33,315,809		39,685,954		33,000,487

Diluted:
Weighted average common shares outstanding - Basic		39,818,162		33,315,809		39,685,954		33,000,487
Common stock options*		—		—		—		—
Denominator for diluted net loss per share		39,818,162		33,315,809		39,685,954		33,000,487

*	No amounts were considered as their effects would be anti-dilutive.

Basic and diluted net loss per share are computed as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2019			2018			2019			2018
Net loss	$	(22,960	)	$	(17,194	)	$	(44,920	)	$	(33,961	)

Weighted-average common shares outstanding:
Basic and Diluted		39,818,162			33,315,809			39,685,954			33,000,487

Net loss per share, Basic and Diluted	$	(0.58	)	$	(0.52	)	$	(1.13	)	$	(1.03	)

As of June 30, 2019 and 2018, 4,705,722 and 3,871,194 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, 140,834 unvested restricted stock units issued to executive officers that were outstanding at June 30, 2019 were also not included in the computation of diluted net loss per share because to do so would have been anti-dilutive. The 74,166 restricted stock units that vested and were settled in shares of common stock in May 2019 were included in the computation of basic and diluted net loss per share for the three and six months ended June 30, 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).

On July 29, 2019, the Company issued and sold 6,325,000 shares of its common stock in a follow-on public offering, which includes the exercise of the underwriters’ option to purchase 825,000 additional shares of its common stock (see Note 16, Subsequent Events).

Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

13. Stock-Based Compensation

2014 Equity Incentive Plan

The Company’s 2014 Equity Incentive Plan, or the 2014 Plan, is administered by the Company’s Board of Directors or a duly authorized committee thereof, referred to as the Plan administrator. The 2014 Plan provides for the grant of incentive stock options, non-statutory 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. 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, 2019, the aggregate number of shares of common stock that may be issued pursuant to Stock Awards under the 2014 Plan automatically increased from 4,900,481 to 6,086,907. 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 three and six months ended June 30, 2019, $41 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 June 30, 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 May 2019, performance targets relating to 74,166 restricted stock units had been achieved and thus such restricted stock units vested and the awards were settled in shares of common stock. As a result, $1,194 of stock compensation expense relating to the vesting of these restricted stock units was recognized in the Statements of Comprehensive Loss for the three and six months ended June 30, 2019, consisting of $590 relating to G&A expense and $604 relating to R&D expense.

Stock Options

Under the 2014 Plan, the Company granted 241,000 and 136,500 stock options during the three months ended June 30, 2019 and 2018, respectively, and 1,198,000 and 732,500 stock options during the six months ended June 30, 2019 and 2018, respectively. The fair values of stock options granted during the three and six months ended June 31, 2019 and 2018 were estimated as of the dates of grant using the Black-Scholes option pricing model with the following assumptions:

	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Risk-free interest rate	1.95% - 2.36%	2.85% - 2.94%	1.95% - 2.62%	2.51% - 2.94%
Expected volatility	73.06% - 73.78%	85.7% - 92.8%	73.06%-75.19%	85.7% - 92.8%
Expected dividend yield	0%	0%	0%	0%
Expected life of employee options (in years)	6.25	6.25	6.25	6.25
Expected life of non-employee options (in years)	—	—	—	—

The weighted-average grant date fair value per share of options granted to employees, non-employee members of the Company’s Board of Directors for their Board service and non-employee consultants during the three months ended June 30, 2019 and 2018 was $13.07 and $10.49, respectively, and during the six months ended June 30, 2019 and 2018 was $11.28 and $10.51, respectively.

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. 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, Other Accounting Pronouncements Recently Adopted). The range of assumptions used by the Company on January 1, 2019 and June 30, 2018 are as follows:

	January 1,	June 30,
	2019	2018
Risk-free interest rate	2.59% - 2.62%	1.92% - 2.82%
Expected volatility	58.9% - 84.6%	60.4% - 96.2%
Expected dividend yield	0%	0%
Expected life of non-employee options (in years)	0.81 - 8.19	0.25 - 8.69

During the three and six months ended June 30, 2019 and 2018, the Company recognized compensation expense relating to stock options (excluding compensation expense related to i) the issuance of common stock relating to the consulting agreement for $99 in G&A expense for the three and six months ended June 30, 2019; ii) the vesting of executives’ restricted stock units for $604 in R&D expense and $590 in G&A expense for the three and six months ended June 30, 2019; and iii) compensation expense relating to the Board of Directors’ restricted stock units for $41 in G&A expense for the three and six months ended June 30, 2019), as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	1,326	$	852	$	2,408		1,500
General and administrative		1,355		1,217		2,507		2,440
Total stock option expense	$	2,681	$	2,069	$	4,915	$	3,940

A summary of stock option award activity related to employees, non-employee members of the Company’s Board of Directors and non-employee consultants as of and for the six months ended June 30, 2019 is presented below:

	Number of Shares			Weighted Average Exercise Price
Outstanding, December 31, 2018		4,004,422		$	13.34
Granted		1,198,000			16.77
Exercised		(395,997	)		10.63
Forfeited		(100,703	)		16.22
Outstanding, June 30, 2019		4,705,722		$	14.39
Options exercisable, June 30, 2019		2,034,916

The Company does not expect to realize any tax benefits from its stock option activity or the recognition of stock-based compensation expense because the Company currently has net operating losses and has a full valuation allowance against its deferred tax assets. Accordingly, no amounts related to excess tax benefits have been reported in cash flows from operations for the six months ended June 30, 2019 and 2018.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

15. Commitments and Contingencies

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 purposes 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 $246 and $491 for the three and six months ended June 30, 2018, respectively.

In connection with the signing of the Stamford Lease, the Company entered into a standby letter of credit agreement for $769, which serves as a security deposit for the Premises. The standby letter of credit is automatically renewed annually through November 2023. This standby letter of credit is secured with restricted cash in a money market account (refer to Note 6, Restricted Cash).

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, $234 of operating lease cost, or lease expense, was recognized for the three months ended June 30, 2019, consisting of $164 relating to R&D lease expense and $70 relating to G&A lease expense. For the six months ended June 30, 2019, $469 of operating lease cost was recognized, consisting of $328 relating to R&D lease expense and $141 relating to G&A lease expense.

Other information related to the Stamford Lease was as follows:

	Three Months Ended			Six Months Ended
	June 30, 2019			June 30, 2019
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows relating to operating lease	$	(302	)	$	(603	)
ROU assets obtained in exchange for new operating lease liabilities	$	—		$	3,636
Remaining lease term-operating lease (years)	4.4			4.4
Discount rate - operating lease		7.0	%		7.0	%

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 June 30, 2019, were as follows:

Year Ending December 31,
2019 (Excluding the six months ended June 30, 2019)	$	613
2020		1,239
2021		1,264
2022		1,288
2023		1,164
Total future minimum lease payments, undiscounted		5,568
Less imputed interest		(796	)
Total	$	4,772

Operating lease liability reported as of June 30, 2019:
Operating lease liability - current	$	923
Operating lease liability - non-current		3,849
Total	$	4,772

Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Use of Estimates

Significant Accounting Policies

Recent Accounting Pronouncements

Accounting Pronouncements Recently Adopted

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

Other Accounting Pronouncements Recently Adopted

Accounting Pronouncements Not Yet Adopted

Available-for-Sale Marketable Securities (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2019 and December 31, 2018:

As of June 30, 2019

			Gross Unrealized
Type of Security	Amortized Cost		Gains		Losses			Estimated Fair Value
U.S. Treasury securities	$	12,992	$	32	$	—		$	13,024
U.S. government agency obligations		12,447		16		—			12,463
Corporate bonds		62,529		109		(6	)		62,632
Commercial paper		23,502		14		—			23,516
Municipal bonds		5,500		—		—			5,500
Total available-for-sale marketable securities	$	116,970	$	171	$	(6	)	$	117,135

As of December 31, 2018

			Gross Unrealized
Type of Security	Amortized Cost		Gains		Losses			Estimated Fair 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 June 30, 2019				As of December 31, 2018
Contractual maturity	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Less than one year	$	96,712	$	96,815	$	146,363		146,302
One year to two years		20,258		20,320		21,449		21,396
Total	$	116,970	$	117,135	$	167,812	$	167,698

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

As of June 30, 2019

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Corporate bonds	$	4,756	$	(6	)	$	—	$	—	$	4,756	$	(6	)
Total	$	4,756	$	(6	)	$	—	$	—	$	4,756	$	(6	)

As of December 31, 2018

	Less than 12 Months					12 Months or Greater				Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized 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) (Tables)

6 Months Ended

Jun. 30, 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

	Total Accumulated Other Comprehensive Income (Loss)
Balance, December 31, 2018	$	(114	)
Other comprehensive income before reclassifications		279
Amount reclassified from accumulated other comprehensive income		—
Net current period other comprehensive income		279
Balance, June 30, 2019	$	165

Balance, December 31, 2017	$	(70	)
Other comprehensive loss before reclassifications		(2	)
Amount reclassified from accumulated other comprehensive loss		15
Net current period other comprehensive income		13
Balance, June 30, 2018	$	(57	)

Schedule of Reclassification Out of Accumulated Other Comprehensive Income

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

	Three Months Ended June 30,				Six Months Ended June 30,					Affected Line Item in the Statements of
Component of AOCI	2019		2018		2019		2018			Operations
Unrealized gains (losses) on available- for-sale marketable securities
Realized gains (losses) on sale of securities	$	—	$	—	$	—	$	(15	)	Other income
		—		—		—		—		Benefit from income taxes
	$	—	$	—	$	—	$	(15	)

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of June 30, 2019 and December 31, 2018.

Fair value measurement as of June 30, 2019:

Financial assets			Quoted prices in		Significant other		Significant
			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market funds and checking accounts	$	18,494	$	18,494	$	—	$	—
Available-for-sale marketable securities:
U.S. Treasury securities		13,024		—		13,024		—
U.S. government agency obligations		12,463		—		12,463		—
Corporate bonds		62,632		—		62,632		—
Commercial paper		23,516		—		23,516		—
Municipal bonds		5,500		—		5,500		—
Restricted cash:
Commercial money market account		769		769		—		—
Total financial assets	$	136,398	$	19,263	$	117,135	$	—

Fair value measurement as of December 31, 2018:

Financial assets			Quoted prices in		Significant other		Significant
			active markets for		observable		unobservable
			identical assets		inputs		inputs
Type of Instrument	Total		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents:
Money market 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	$	—

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 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:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Basic:
Weighted average common shares outstanding		39,818,162		33,315,809		39,685,954		33,000,487

Diluted:
Weighted average common shares outstanding - Basic		39,818,162		33,315,809		39,685,954		33,000,487
Common stock options*		—		—		—		—
Denominator for diluted net loss per share		39,818,162		33,315,809		39,685,954		33,000,487

*	No amounts were considered as their effects would be anti-dilutive.

Computation of Basic and Diluted Net Loss per Share

Basic and diluted net loss per share are computed as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2019			2018			2019			2018
Net loss	$	(22,960	)	$	(17,194	)	$	(44,920	)	$	(33,961	)

Weighted-average common shares outstanding:
Basic and Diluted		39,818,162			33,315,809			39,685,954			33,000,487

Net loss per share, Basic and Diluted	$	(0.58	)	$	(0.52	)	$	(1.13	)	$	(1.03	)

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Summary of Assumptions Used in Black-Scholes Option Pricing Model

The fair values of stock options granted during the three and six months ended June 31, 2019 and 2018 were estimated as of the dates of grant using the Black-Scholes option pricing model with the following assumptions:

	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Risk-free interest rate	1.95% - 2.36%	2.85% - 2.94%	1.95% - 2.62%	2.51% - 2.94%
Expected volatility	73.06% - 73.78%	85.7% - 92.8%	73.06%-75.19%	85.7% - 92.8%
Expected dividend yield	0%	0%	0%	0%
Expected life of employee options (in years)	6.25	6.25	6.25	6.25
Expected life of non-employee options (in years)	—	—	—	—

Summary of Compensation Expense Relating to Stock Options

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	1,326	$	852	$	2,408		1,500
General and administrative		1,355		1,217		2,507		2,440
Total stock option expense	$	2,681	$	2,069	$	4,915	$	3,940

Summary of Stock Option Activity

	Number of Shares			Weighted Average Exercise Price
Outstanding, December 31, 2018		4,004,422		$	13.34
Granted		1,198,000			16.77
Exercised		(395,997	)		10.63
Forfeited		(100,703	)		16.22
Outstanding, June 30, 2019		4,705,722		$	14.39
Options exercisable, June 30, 2019		2,034,916

Re-Measurement [Member]

Summary of Assumptions Used in Black-Scholes Option Pricing Model

	January 1,	June 30,
	2019	2018
Risk-free interest rate	2.59% - 2.62%	1.92% - 2.82%
Expected volatility	58.9% - 84.6%	60.4% - 96.2%
Expected dividend yield	0%	0%
Expected life of non-employee options (in years)	0.81 - 8.19	0.25 - 8.69

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Schedule of Other Information related to Stamford Lease

Other information related to the Stamford Lease was as follows:

	Three Months Ended			Six Months Ended
	June 30, 2019			June 30, 2019
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows relating to operating lease	$	(302	)	$	(603	)
ROU assets obtained in exchange for new operating lease liabilities	$	—		$	3,636
Remaining lease term-operating lease (years)	4.4			4.4
Discount rate - operating lease		7.0	%		7.0	%

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

Year Ending December 31,
2019 (Excluding the six months ended June 30, 2019)	$	613
2020		1,239
2021		1,264
2022		1,288
2023		1,164
Total future minimum lease payments, undiscounted		5,568
Less imputed interest		(796	)
Total	$	4,772

Operating lease liability reported as of June 30, 2019:
Operating lease liability - current	$	923
Operating lease liability - non-current		3,849
Total	$	4,772

Business - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended				6 Months Ended
	Jul. 29, 2019	Jul. 31, 2019	May 31, 2018	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Nature Of Business [Line Items]
Date of formation								Jul. 02, 2004
Proceeds from equity and debt financing				$ 383,200				$ 383,200
Upfront and milestone payments received in connection with license agreements				88,900				88,900
Proceeds from sale of common stock in connection with license agreement									$ 14,556
Unrestricted cash and cash equivalents and marketable securities				135,629				135,629
Accumulated deficit				339,274				339,274		$ 294,354
Net loss				$ 22,960	$ 21,960	$ 17,194	$ 16,767	44,920	33,961
Net cash (used in) provided by operating activities								$ (52,422)	$ 22,552
Common Stock [Member] \| Follow-on Public Offering [Member] \| Subsequent Event [Member]
Nature Of Business [Line Items]
Common stock, shares issued	6,325,000	6,325,000
Proceeds from issuance of common stock net	$ 136,446	$ 136,446
Common Stock [Member] \| Underwriter's Over-Allotment [Member] \| Subsequent Event [Member]
Nature Of Business [Line Items]
Common stock, shares issued	825,000	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

Available-for-Sale Marketable Securities - Schedule of Fair Values and Continuous Unrealized Loss Positions of Available-for-Sale Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 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	$ 4,756	$ 132,755
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(6)	(119)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	4,756	132,755
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	(6)	(119)
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	4,756	71,322
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses	(6)	(94)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value	4,756	71,322
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses	$ (6)	(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		39,445
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(23)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		39,445
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(23)
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		16,392
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		16,392
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		(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		5,596
Available-for-sale marketable securities, continuous unrealized loss position, Less than 12 Months, Gross Unrealized Losses		(1)
Available-for-sale marketable securities, continuous unrealized loss position, Fair Value		5,596
Available-for-sale marketable securities, continuous unrealized loss position, Gross Unrealized Losses		$ (1)

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial assets
Available-for-sale marketable securities	$ 117,135	$ 167,698
Recurring [Member]
Financial assets
Total financial assets	136,398	183,548
U.S. Government Agency Obligations [Member]
Financial assets
Available-for-sale marketable securities	12,463	17,859
U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	12,463	17,859
Corporate Bonds [Member]
Financial assets
Available-for-sale marketable securities	62,632	75,910
Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	62,632	75,910
Municipal Bonds [Member]
Financial assets
Available-for-sale marketable securities	5,500	4,000
Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	5,500	4,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Total financial assets	19,263	15,850
Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Total financial assets	117,135	167,698
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government Agency Obligations [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	12,463	17,859
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	62,632	75,910
Significant Other Observable Inputs (Level 2) [Member] \| Municipal Bonds [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	5,500	4,000
Money Market Funds [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	18,494	15,081
Restricted cash	769	769
Money Market Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Recurring [Member]
Financial assets
Cash and cash equivalents	18,494	15,081
Restricted cash	769	769
U.S. Treasury Securities [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	13,024	19,539
U.S. Treasury Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	13,024	19,539
Commercial Paper [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	23,516	50,390
Commercial Paper [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Recurring [Member]
Financial assets
Available-for-sale marketable securities	$ 23,516	$ 50,390

Fair Value Measurements - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2019 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Purchases of financial assets	$ 0
Sales of financial assets	0
Maturities of financial assets	0
Transfer of financial asset into level 3 of fair value	0
Fair value assets level 2 to level 1 transfers	0
Fair value assets level 1 to level 2 transfers	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains	0
Unrealized losses	$ 0

Stockholders' Equity - Additional Information (Detail) - USD ($)			1 Months Ended		3 Months Ended			6 Months Ended
	Jul. 29, 2019	Mar. 20, 2019	Jul. 31, 2019	May 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Apr. 04, 2019	Dec. 31, 2018
Subsidiary Sale Of Stock [Line Items]
Restricted stock units vested shares				74,166
Common stock, shares issued				74,166	40,027,916			40,027,916			39,547,558
Number of shares of unregistered common stock exchanged for consulting services		10,195
Closing price of common stock		$ 19.37
Consulting services performance period		6 months
Unregistered common stock exchanged for consulting services		$ 197,000				$ 197,000
Compensation expense					$ 2,681,000		$ 2,069,000	$ 4,915,000	$ 3,940,000
General and Administrative [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense					1,355,000		$ 1,217,000	2,507,000	$ 2,440,000
General and Administrative [Member] \| Consulting Agreement [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense					$ 99,000			$ 99,000
Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Aggregate offering price of securities										$ 300,000,000
Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Restricted stock units vested shares				74,166	74,166
Number of shares of unregistered common stock exchanged for consulting services						10,195
Common Stock [Member] \| Follow-on Public Offering [Member] \| Subsequent Event [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued	6,325,000		6,325,000
Proceeds from issuance of common stock net of underwriting discounts, commissions and estimated offering expenses	$ 136,446,000		$ 136,446,000
Underwriting discounts, commission and estimated offering expenses	$ 9,029,000
Closing price of common stock			$ 23.00
Common Stock [Member] \| Underwriter's Over-Allotment [Member] \| Subsequent Event [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued	825,000		825,000

Collaboration and Licensing Agreements - Additional Information (Detail)		3 Months Ended		6 Months Ended
	May 17, 2018 USD ($) PerformanceObligation $ / shares shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 20, 2019 $ / shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase common stock per share amount \| $ / shares						$ 19.37
Revenue from contract with customer		$ 5,208,000	$ 2,874,000	$ 9,590,000	$ 2,874,000
Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer				$ 140,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable, non-creditable upfront payment	$ 50,000,000
Common stock, shares issued \| shares	1,174,827
Purchase of common stock value	$ 20,000,000
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	$ 5,444,000
Contract liabilities	$ 55,444,000
Number of combined performance obligations for revenue recognized \| PerformanceObligation	1
Number of days to terminate agreement				60 days
Termination notice effective period				12 months
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	$ 470,000,000
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	30,000,000
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	$ 440,000,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of clinical compound related to R&D expense				$ 126,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer				$ 140,000	$ 0

Revenue Recognition - Additional Information (Detail) ¥ in Billions		1 Months Ended		3 Months Ended		6 Months Ended		13 Months Ended
	May 17, 2018 USD ($) PerformanceObligation	Apr. 30, 2013 USD ($) PerformanceObligation	Apr. 30, 2012 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) PerformanceObligation Milestone	Jun. 30, 2018 USD ($) Milestone	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Apr. 30, 2013 JPY (¥)
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Deferred revenue, current				$ 26,473,000		$ 26,473,000		$ 26,473,000	$ 26,825,000
Deferred revenue, non current				6,085,000		6,085,000		6,085,000	15,184,000
Total revenue				5,208,000	$ 2,874,000	$ 9,590,000	$ 2,874,000
Number of milestone event probable of occurrence or achieved \| Milestone						0	0
License and Milestone Fees [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue				5,208,000	$ 2,874,000	$ 9,450,000	$ 2,874,000
Royalty [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenue from contract with customer						0
VFMCRP Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Deferred revenue, current				26,473,000		26,473,000		26,473,000	26,825,000
Deferred revenue, non current				6,085,000		6,085,000		6,085,000	15,184,000
Receivables				0		0		0	0
Other assets				0		0		0	0
Deferred revenue	$ 55,444,000								0
Number of combined performance obligations for revenue recognized \| PerformanceObligation	1
Number of performance obligations for revenue recognized \| PerformanceObligation	2
upfront payment	$ 50,000,000
Premium from sale of stock	$ 5,444,000
Remaining performance obligations				$ 32,558,000		$ 32,558,000		$ 32,558,000
Remaining performance obligation, expected timing of satisfaction, year				2020		2020		2020
VFMCRP Agreement [Member] \| License and Milestone Fees [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue				$ 5,208,000		$ 9,450,000		$ 22,886,000
Maruishi and CKDP Agreements [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Receivables				0		0		0	0
Other assets				0		0		0	0
Deferred revenue				$ 0		$ 0		$ 0	$ 0
Number of remaining performance obligations \| PerformanceObligation						0
Maruishi Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Number of performance obligations for revenue recognized \| PerformanceObligation		2				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]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration		10,500,000
Maruishi Agreement [Member] \| One-time Sales Milestone [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration \| ¥										¥ 1
Maruishi Agreement [Member] \| License [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Estimated selling price		10,200,000
Upfront payments on obligations		9,637,000
Maruishi Agreement [Member] \| R&D Services [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Estimated selling price		6,200,000
Upfront payments on obligations		$ 5,700,000
CKDP Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Premium from sale of stock			$ 83,000
CKDP Agreement [Member] \| Clinical Development and Regulatory Milestones [Member] \| Maximum [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration			3,750,000
CKDP Agreement [Member] \| License [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenue from contract with customer			$ 646,000

Net Loss per Share - Additional Information (Detail) - shares		1 Months Ended				3 Months Ended	6 Months Ended
	Jul. 29, 2019	Jul. 31, 2019	Jun. 30, 2019	May 31, 2019	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units vested shares				74,166
Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units vested shares				74,166		74,166
Common Stock [Member] \| Follow-on Public Offering [Member] \| Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued	6,325,000	6,325,000
Common Stock [Member] \| Underwriter's Over-Allotment [Member] \| Subsequent Event [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued	825,000	825,000
Restricted Stock Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, vested			0	74,166
Restricted Stock Units [Member] \| Executive Officers [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive unvested restricted stock units outstanding			140,834			140,834	140,834
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, approved and granted					215,000
Restricted Stock Units [Member] \| 2014 Equity Incentive Plan [Member] \| Non-employee Members of Board of Directors [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Restricted stock units, approved and granted							24,000
Employee Options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive common stock equivalents							4,705,722	3,871,194

Stock-Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 04, 2019	Jun. 30, 2019	May 31, 2019	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2015	Jan. 01, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 2,681,000	$ 2,069,000	$ 4,915,000	$ 3,940,000
Common stock, shares outstanding		40,027,916			40,027,916		40,027,916				39,547,558
Common stock, shares issued		40,027,916	74,166		40,027,916		40,027,916				39,547,558
Fair value of options granted					$ 13.07	$ 10.49	$ 11.28	$ 10.51
Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from operations							$ 0	$ 0
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 1,355,000	$ 1,217,000	2,507,000	2,440,000
General and Administrative [Member] \| Consulting Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					99,000		99,000
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					1,326,000	$ 852,000	2,408,000	$ 1,500,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 1,194,000		$ 1,194,000
Restricted stock units, vested		0	74,166
Common stock, shares outstanding		0			0		0
Common stock, shares issued			74,166
Restricted Stock Units [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 590,000		$ 590,000
Restricted Stock Units [Member] \| Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					604,000		604,000
Board of Directors [Member] \| Restricted Stock Units [Member] \| General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 41,000		$ 41,000
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	4,900,481
Options granted					241,000	136,500	1,198,000	732,500
2014 Equity Incentive Plan [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense					$ 41,000		$ 41,000
2014 Equity Incentive Plan [Member] \| Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date							25.00%
2014 Equity Incentive Plan [Member] \| Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted							36 months
2014 Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards granted							10 years
2014 Equity Incentive Plan [Member] \| 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] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted							4 years
2014 Equity Incentive Plan [Member] \| Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted							3 years
2014 Equity Incentive Plan [Member] \| Board of Directors [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, approved and granted	24,000						24,000
Restricted stock units, grant date fair value	$ 20.47
Restricted stock units vesting date	Jun. 04, 2020
2014 Equity Incentive Plan [Member] \| Board of Directors [Member] \| Subsequent Grants of Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted							1 year
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
Restricted stock units, grant date fair value				$ 16.10
Non-employee Director Compensation Policy [Member] \| Non-employee Director [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, approved and granted		6,000

Stock-Based Compensation - Summary of Re-measurement of Assumptions Used in Black-Scholes Option Pricing Model (Detail)			3 Months Ended		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum			1.95%	2.85%	1.95%	2.51%
Risk-free interest rate, maximum			2.36%	2.94%	2.62%	2.94%
Expected volatility, minimum			73.06%	85.70%	73.06%	85.70%
Expected volatility, maximum			73.78%	92.80%	75.19%	92.80%
Expected dividend yield			0.00%	0.00%	0.00%	0.00%
Re-Measurement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	2.59%	1.92%
Risk-free interest rate, maximum	2.62%	2.82%
Expected volatility, minimum	58.90%	60.40%
Expected volatility, maximum	84.60%	96.20%
Expected dividend yield	0.00%	0.00%
Re-Measurement [Member] \| Nonemployee Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	9 months 21 days	3 months
Re-Measurement [Member] \| Nonemployee Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options (in years)	8 years 2 months 8 days	8 years 8 months 8 days

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - 2014 Equity Incentive Plan [Member] - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding, December 31, 2018			4,004,422
Number of Options, Granted	241,000	136,500	1,198,000	732,500
Number of Options, Exercised			(395,997)
Number of Options, Forfeited			(100,703)
Number of Options, Outstanding, June 30, 2019	4,705,722		4,705,722
Number of Options, Options exercisable, June 30, 2019	2,034,916		2,034,916
Weighted-Average Exercise Price, Outstanding, December 31, 2018			$ 13.34
Weighted-Average Exercise Price, Granted			16.77
Weighted-Average Exercise Price, Exercised			10.63
Weighted-Average Exercise Price, Forfeited			16.22
Weighted-Average Exercise Price, Outstanding, June 30, 2019	$ 14.39		$ 14.39

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018	May 31, 2016
Other Commitments [Line Items]
Deferred lease obligation						$ 1,562,000
Operating lease liability	$ 4,772,000		$ 4,772,000
Stamford Operating Lease [Member]
Other Commitments [Line Items]
Operating Lease, renewable term	5 years		5 years
Operating lease, expiration date			Nov. 30, 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.
Deferred lease obligation						864,000
Tenant improvement expenses							$ 1,094,000
Lease, rent expense		$ 246,000		$ 491,000
Tenant improvement incentives						698,000
Operating lease cost	$ 234,000		$ 469,000
Stamford Operating Lease [Member] \| Research and Development [Member]
Other Commitments [Line Items]
Operating lease cost	164,000		328,000
Stamford Operating Lease [Member] \| General and Administrative [Member]
Other Commitments [Line Items]
Operating lease cost	$ 70,000		$ 141,000
Stamford Operating Lease [Member] \| ASC 842 [Member]
Other Commitments [Line Items]
Operating Lease, renewable term	5 years		5 years
Operating lease liability					$ 5,198,000
Stamford Operating Lease [Member] \| Standby Letter of Credit [Member]
Other Commitments [Line Items]
Letter of credit, amount	$ 769,000		$ 769,000
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						$ 698,000

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	Jun. 30, 2019 USD ($)
Operating Lease Liabilities, Payments Due [Abstract]
2019 (Excluding the six months ended June 30, 2019)	$ 613
2020	1,239
2021	1,264
2022	1,288
2023	1,164
Total future minimum lease payments, undiscounted	5,568
Less imputed interest	(796)
Operating lease liability	4,772
Operating lease liability reported as of June 30, 2019:
Operating lease liability - current	923
Operating lease liability - non-current	3,849
Total	$ 4,772

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	6 Months Ended
	Jul. 29, 2019	Jul. 08, 2019	Jul. 31, 2019	Jun. 30, 2019	Mar. 20, 2019
Subsequent Event [Line Items]
Purchase common stock per share amount					$ 19.37
MSA or Product Agreement [Member]
Subsequent Event [Line Items]
Agreement initial term, expiration date				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.
Subsequent Event [Member] \| MSA [Member]
Subsequent Event [Line Items]
Agreement initial term, expiration date		Dec. 31, 2023
Agreement renewal term		2 years
Subsequent Event [Member] \| MSA [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Termination notice effective period		18 months
Common Stock [Member] \| Follow-on Public Offering [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, shares issued	6,325,000		6,325,000
Purchase common stock per share amount			$ 23.00
Proceeds from issuance of common stock net of underwriting discounts, commissions and estimated offering expenses	$ 136,446		$ 136,446
Underwriting discounts, commission and estimated offering expenses	$ 9,029
Common Stock [Member] \| Underwriter's Over-Allotment [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, shares issued	825,000		825,000

Basis of Presentation - Additional Information (Detail) - Stamford Operating Lease [Member]	Jun. 30, 2019 Lease	Jan. 01, 2019 USD ($)
Basis Of Presentation [Line Items]
Annual incremental borrowing rate	7.00%
Operating lease, renewable term	5 years
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

Restricted Cash - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash in current assets	$ 361	$ 361
Restricted cash balance	408	408
Stamford Lease [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Letter of credit, remaining amount	769
Letter of credit, through the end of lease term	$ 408
Letter of credit, remaining amount date	2019-05
Operating lease, expiration date	Nov. 30, 2023
Restricted cash in current assets	$ 361	361
Restricted cash balance	$ 408	$ 408

Prepaid Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 7,512	$ 4,805
Prepaid R&D clinical costs	6,461	4,377
Prepaid insurance	671	245
Other prepaid costs	$ 380	$ 183

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 2,485	$ 4,371
Accrued research projects	7,795	6,079
Accrued professional fees	527	802
Accrued compensation and benefits	1,959	2,370
Total	$ 12,766	$ 13,622

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended	18 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Pre-tax losses	$ 23,195	$ 17,346	$ 45,240	$ 34,159
Benefit from income taxes	$ 235	$ 152	$ 320	$ 198
Percentage of annual research and development credit for cash			65.00%
Income tax rate					35.00%	21.00%

Condensed Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 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	40,027,916	39,547,558
Common stock, shares outstanding	40,027,916	39,547,558

Available-for-Sale Marketable Securities - Summary of Available-for-Sale Marketable Securities by Major Type of Security (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 116,970	$ 167,812
Gross Unrealized Gains	171	5
Gross Unrealized Losses	(6)	(119)
Estimated Fair Value	117,135	167,698
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,992	19,540
Gross Unrealized Gains	32
Gross Unrealized Losses		(1)
Estimated Fair Value	13,024	19,539
U.S. Government Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,447	17,860
Gross Unrealized Gains	16
Gross Unrealized Losses		(1)
Estimated Fair Value	12,463	17,859
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,529	75,999
Gross Unrealized Gains	109	5
Gross Unrealized Losses	(6)	(94)
Estimated Fair Value	62,632	75,910
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,502	50,413
Gross Unrealized Gains	14
Gross Unrealized Losses		(23)
Estimated Fair Value	23,516	50,390
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,500	4,000
Estimated Fair Value	$ 5,500	$ 4,000

Available-for-Sale Marketable Securities - Schedule of Amortized Cost and Fair Values of Marketable Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Amortized Cost of marketable debt securities, contractual maturity, Less than one year	$ 96,712	$ 146,363
Amortized Cost of marketable debt securities, contractual maturity, One year to two years	20,258	21,449
Amortized Cost	116,970	167,812
Fair value of marketable debt securities, contractual maturity, Less than one year	96,815	146,302
Fair value of marketable debt securities, contractual maturity,One year to two years	20,320	21,396
Total fair Value of marketable debt securities, contractual maturity	$ 117,135	$ 167,698

Available-for-Sale Marketable Securities - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($) Position	Dec. 31, 2018 USD ($) Position
Investments Debt And Equity Securities [Abstract]
Number of available-for-sale marketable securities in unrealized loss positions	6	69
Total number of positions	58	84
Other-than-temporary impairments on securities \| $	$ 0	$ 0

Restricted Cash - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 18,494	$ 15,081
Restricted cash in current assets	361	361
Restricted cash balance	408	408
Total cash, cash equivalents, and restricted cash shown in the Condensed Statements of Cash Flows	$ 19,263	$ 15,850	$ 18,571	$ 10,157