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Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	$ 78,066	$ 118,902
Level 1
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	15,478	22,275
Level 2
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	62,588	96,627
Commercial Paper
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	17,645	47,686
Commercial Paper \| Level 2
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	17,645	47,686
Certificates of Deposit
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	5,982	5,408
Certificates of Deposit \| Level 2
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	5,982	5,408
Corporate Debt Securities
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	11,071	23,544
Corporate Debt Securities \| Level 2
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	11,071	23,544
U.S. Government and Agency Obligations
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	43,368	42,264
U.S. Government and Agency Obligations \| Level 1
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	15,478	22,275
U.S. Government and Agency Obligations \| Level 2
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value	$ 27,890	$ 19,989

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 40,326	$ 44,973
Investment securities	78,066	118,902
Prepaid expenses and other current assets	4,947	2,808
Total current assets	123,339	166,683
Property and equipment, net	3,946	4,232
Operating lease right-of-use asset	2,510
Restricted cash	500	500
Other assets	82
Total assets	130,377	171,415
Current liabilities:
Accounts payable and accrued expenses	5,498	5,265
Accrued compensation and related expenses	2,118	2,279
Other current liabilities	724	381
Total current liabilities	8,340	7,925
Operating lease liability, non-current	4,849
Unvested stock liability	49	202
Deferred rent		3,063
Total liabilities	13,238	11,190
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par; 10,000 shares authorized, no shares issued or outstanding at December 31, 2019 or 2018
Common stock and paid-in capital, $0.001 par; 200,000 shares authorized, 24,296 and 24,263 shares issued and outstanding at December 31, 2019; 24,188 and 24,061 shares issued and outstanding at December 31, 2018	210,793	203,544
Accumulated other comprehensive income	148	61
Accumulated deficit	(93,802)	(43,380)
Total stockholders’ equity	117,139	160,225
Total liabilities and stockholders’ equity	$ 130,377	$ 171,415

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering	Convertible Preferred Stock	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Common Stock Initial Public Offering	Common stock and Paid-In Capital	Common stock and Paid-In Capital Initial Public Offering	Accumulated Other Comprehensive Income	Accumulated Deficit
Temporary equity, Beginning Balance at Dec. 31, 2016			$ 17,740
Temporary equity, Beginning Balance, Shares at Dec. 31, 2016			17,258,000
Beginning Balance, Shares at Dec. 31, 2016						1,165,000
Beginning Balance at Dec. 31, 2016	$ (6,204)							$ 904			$ (7,108)
Temporary equity, Issuance of convertible preferred stock, net of issuance costs				$ 11,960
Temporary equity, Issuance of convertible preferred stock, net of issuance costs, shares				11,505,000
Vesting of shares subject to repurchase	2							2
Vesting of shares subject to repurchase, shares						287,000
Exercise of stock options	66							66
Exercise of stock options, shares						98,000
Stock-based compensation	271							271
Net loss	(9,157)										(9,157)
Ending Balance at Dec. 31, 2017	(15,022)							1,243			(16,265)
Ending Balance, Shares at Dec. 31, 2017						1,550,000
Temporary equity, Ending Balance at Dec. 31, 2017			$ 29,700
Temporary equity, Ending Balance, Shares at Dec. 31, 2017			28,763,000
Temporary equity, Issuance of convertible preferred stock, net of issuance costs					$ 63,275
Temporary equity, Issuance of convertible preferred stock, net of issuance costs, shares					19,641,000
Issuance of common stock		$ 106,472							$ 106,472
Issuance of common stock, shares							6,900,000
Conversion of preferred stock into common stock	92,975		$ (92,975)					92,975
Conversion of preferred stock into common stock, shares			(48,404,000)			14,713,000
Vesting of shares subject to repurchase	21							21
Vesting of shares subject to repurchase, shares						541,000
Exercise of stock options	231							231
Exercise of stock options, shares						337,000
Issuance of stock pursuant to Stock Purchase Plan	282							282
Issuance of stock under Stock Purchase Plan, shares						20,000
Stock-based compensation	2,320							2,320
Comprehensive Income (loss)	61									$ 61
Net loss	(27,115)										(27,115)
Ending Balance at Dec. 31, 2018	160,225							203,544		61	(43,380)
Ending Balance, Shares at Dec. 31, 2018						24,061,000
Vesting of shares subject to repurchase	94							94
Vesting of shares subject to repurchase, shares						63,000
Exercise of stock options	$ 126							126
Exercise of stock options, shares	90,322					90,000
Issuance of stock pursuant to Stock Purchase Plan	$ 735							735
Issuance of stock under Stock Purchase Plan, shares						49,000
Stock-based compensation	6,294							6,294
Comprehensive Income (loss)	87									87
Net loss	(50,422)										(50,422)
Ending Balance at Dec. 31, 2019	$ 117,139							$ 210,793		$ 148	$ (93,802)
Ending Balance, Shares at Dec. 31, 2019						24,263,000

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Beginning balance	$ 344	$ 159	$ 68
Increase (decrease) for prior year tax positions	70	0	0
Increase (decrease) for current year tax positions	472	185	91
Ending balance	$ 886	$ 344	$ 159

Organization and Basis of Presentation

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Basis of Presentation

1. ORGANIZATION AND BASIS OF PRESENTATION

Description of Business

Crinetics Pharmaceuticals, Inc. (the “Company”) is a clinical stage pharmaceutical company incorporated in Delaware on November 18, 2008 and based in San Diego, California. The Company is focused on the discovery, development and commercialization of novel therapeutics for rare endocrine diseases and endocrine-related tumors. In January 2017, the Company established a wholly-owned Australian subsidiary, Crinetics Australia Pty Ltd (“CAPL”), in order to conduct various preclinical and clinical activities for its development candidates.

On July 6, 2018, the Company effected a 1-for-3.29 reverse stock split of its common stock. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse stock split. The reverse stock split resulted in an adjustment to the conversion prices of the Company’s Series A and B preferred stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying consolidated financial statements and notes to the consolidated financial statements give retroactive effect to the reverse stock split for all periods presented.

Principles of Consolidation and Foreign Currency Transactions

The consolidated financial statements include the accounts of the Company and CAPL. All intercompany accounts and transactions have been eliminated in consolidation. The functional currency of both the Company and CAPL is the U.S. dollar. Assets and liabilities that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the consolidated statements of operations and were not material for all periods presented.

Segment Reporting

Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.

Liquidity and Going Concern

From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure.

As of December 31, 2019, the Company had $118.4 million in unrestricted cash, cash equivalents and investment securities. The Company believes it has sufficient cash to meet its funding requirements for at least the next 12 months. However, the Company has experienced net losses and negative cash flows from operating activities since its inception and has an accumulated deficit of $93.8 million as of December 31, 2019. The Company expects to continue to incur net losses for the foreseeable future and believes it will need to raise substantial additional capital to accomplish its business plan over the next several years. The Company plans to continue to fund its losses from operations and capital funding needs through a combination of equity offerings, debt financings or other sources, including potential collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations and future prospects. There can be no assurance as to the availability or terms upon which such financing and capital might be available in the future.

On August 13, 2019 the Company entered into a Sales Agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (collectively, the “Sales Agents”), under which the Company may, from time to time, sell shares of its common stock having an aggregate offering price of up to $75.0 million through the Sales Agents (the “ATM Offering”).

On August 13, 2019, the Company also filed a registration statement on Form S-3 (the “Shelf Registration Statement”), covering the offering of up to $300.0 million of common stock, preferred stock, debt securities, warrants and units. The Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to $75.0 million of Company common stock from time to time through the ATM Offering. The Registration Statement became effective on August 29, 2019. The shares to be sold under the Sales Agreement may be issued and sold pursuant to the Shelf Registration Statement.

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 15,990	$ 2,664
Capitalized research expenses	4,864	6,355
R&D and other tax credits	4,676	1,788
Lease liability	1,560	0
Accrued expenses and other, net	2,229	2,636
Total deferred tax assets	29,319	13,443
Deferred tax liabilities:
Right-of use asset	(702)	0
Other deferred tax liabilities	(22)	(866)
Net of deferred tax assets and liabilities	28,595	12,577
Less: valuation allowance	(28,595)	(12,577)
Net deferred tax assets	$ 0	$ 0

Convertible Preferred Stock

12 Months Ended

Dec. 31, 2019

Temporary Equity Disclosure [Abstract]

Convertible Preferred Stock

8. CONVERTIBLE PREFERRED STOCK

In April and December 2017, pursuant to a Series A preferred stock purchase agreement entered into in October 2015 which called for an initial closing and, upon the achievement of certain specified milestones, subsequent closings, the Company issued an aggregate of 11,505,268 shares of Series A convertible preferred stock for gross proceeds of $12.0 million, net of offering costs of $40,000. In February and March 2018, the Company issued an aggregate of 19,641,200 shares of its Series B convertible preferred stock for gross proceeds of $63.5 million, net of issuance costs incurred in connection with this offering of $0.2 million.

The holders of the convertible preferred stock were entitled to certain customary preferences, such as dividend and liquidation priority in relationship to the common shareholders, and certain anti-dilution protection. The convertible preferred stock was classified outside of stockholders’ equity (deficit) because the shares contained certain redemption features that were not solely within the control of the Company. In connection with the Company’s initial public offering (“IPO”), the outstanding shares of the Company’s Series A and Series B convertible preferred stock automatically converted into 14,712,571 shares of common stock (see Note 9).

Net Loss Per Share - Schedule of Potentially Dilutive Securities (in Common Stock Equivalent Shares) not Included in Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities (in common stock equivalent shares) excluded from calculation of diluted net loss per share	3,160	2,466	10,108
Convertible Preferred Stock Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities (in common stock equivalent shares) excluded from calculation of diluted net loss per share			8,743
Common Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities (in common stock equivalent shares) excluded from calculation of diluted net loss per share	3,127	2,339	838
Unvested Common Stock Subject to Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities (in common stock equivalent shares) excluded from calculation of diluted net loss per share	33	127	527

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Financial Assets Measured at Fair Value on Recurring Basis

Financial assets measured at fair value on a recurring basis as of December 31, 2019 and 2018 were as follows (in thousands):

	As of December 31, 2019
	Level 1		Level 2		Level 3		Total
Investment securities:
U.S. government and agency obligations	$	15,478	$	27,890	$	—	$	43,368
Certificates of deposit		—		5,982		—		5,982
Commercial paper		—		17,645		—		17,645
Corporate debt securities		—		11,071		—		11,071
Total assets measured at fair value	$	15,478	$	62,588	$	—	$	78,066

	As of December 31, 2018
	Level 1		Level 2		Level 3		Total
Investment securities:
U.S. government and agency obligations	$	22,275	$	19,989	$	—	$	42,264
Certificates of deposit		—		5,408		—		5,408
Commercial paper		—		47,686		—		47,686
Corporate debt securities		—		23,544		—		23,544
Total assets measured at fair value	$	22,275	$	96,627	$	—	$	118,902

Equity Incentive Plans - Summary of Activity Under Stock Option Plans (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding, Beginning balance \| shares	2,339,157
Options Outstanding, Granted \| shares	900,175
Options Outstanding, Exercised \| shares	(90,322)
Options Outstanding, Forfeited and expired \| shares	(21,619)
Options Outstanding, Ending balance \| shares	3,127,391
Options Exercisable, Ending balance \| shares	1,236,908
Weighted-Average Exercise Price, Beginning balance \| $ / shares	$ 6.40
Weighted-Average Exercise Price, Granted \| $ / shares	23.96
Weighted Average Exercise Price, Exercised \| $ / shares	1.40
Weighted Average Exercise Price, Forfeited and expired \| $ / shares	17.35
Weighted-Average Exercise Price, Ending balance \| $ / shares	11.52
Weighted-Average Exercise Price, Exercisable \| $ / shares	$ 6.96
Weighted-Average Remaining Term, Ending balance	8 years 4 months 24 days
Weighted-Average Remaining Term, Exercisable	7 years 10 months 24 days
Aggregate Intrinsic Value, Ending balance \| $	$ 42,777
Aggregate Intrinsic Value, Exercisable \| $	$ 22,510

Investment Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Available-For-Sale Investment Securities Held by the Company

Available-for-sale investment securities consisted of the following as of December 31, 2019 and 2018 (in thousands):

	As of December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Available-for-sale investment securities:
U.S. government and agency obligations	$	43,275	$	94	$	(1	)	$	43,368
Certificates of deposit		5,931		51		—			5,982
Commercial paper		17,645		—		—			17,645
Corporate debt securities		11,067		7		(3	)		11,071
Total	$	77,918	$	152	$	(4	)	$	78,066

	As of December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Available-for-sale investment securities:
U.S. government and agency obligations	$	42,193	$	72	$	(1	)	$	42,264
Certificates of deposit		5,408		—		—			5,408
Commercial paper		47,686		—		—			47,686
Corporate debt securities		23,554		2		(12	)		23,544
Total	$	118,841	$	74	$	(13	)	$	118,902

Income Taxes - Schedule of Domestic and Foreign Pre-Tax Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Loss before income taxes - Domestic	$ (48,643)	$ (25,876)	$ (8,141)
Loss before income taxes - Foreign	(1,779)	(1,239)	(1,016)
Loss before income taxes - Consolidated	$ (50,422)	$ (27,115)	$ (9,157)

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands		2 Months Ended	12 Months Ended
	Aug. 13, 2019	Mar. 06, 2020	Dec. 31, 2018	Dec. 31, 2019
Subsequent Event [Line Items]
Number of common stock shares issued			24,188	24,296
Proceeds from issuance of common stock, net	$ 75,000		$ 106,472
Subsequent Event \| ATM Offering
Subsequent Event [Line Items]
Number of common stock shares issued		275,764
Proceeds from issuance of common stock, net		$ 6,400

Equity Incentive Plans - Stock-based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 6,294	$ 2,320	$ 271
Included in Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	3,190	1,100	122
Included in General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,104	$ 1,220	$ 149

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

11. INCOME TAXES

The Company is subject to taxation in the United States, California and Australia; however, as it has operated at a loss since inception, it has not paid income taxes in any of the jurisdictions in which it has operated. At December 31, 2019, the Company had federal, state, and foreign net operating loss (“NOL”) carryforwards of approximately $54.5 million, $61.6 million and $0.4 million, respectively. The federal loss carryforwards generated after 2017 will carryforward indefinitely and can be used to offset up to 80% of future annual taxable income, while those loss carryforwards generated prior to 2018 begin expiring in 2035, unless previously utilized. State loss carryforwards also begin expiring in 2035, unless previously utilized, while the Company’s foreign loss carryforwards do not expire. The Company also has federal and California R&D credit carryforwards totaling $4.0 million and $1.9 million, respectively. The federal credits begin to expire in 2030 unless previously utilized, while the state credits do not expire.

Future utilization of the Company’s NOL and R&D credit carryforwards to offset future taxable income may be subject to a substantial annual limitation as a result of ownership changes that may have occurred or that could occur in the future pursuant to Internal Revenue Code Sections 382 and 383. These ownership changes may limit the amount of NOL and R&D credit carryforwards that can be utilized to offset future taxable income and tax, respectively. In general, an “ownership change” as defined by the tax code results from a transaction or series of transactions over a three-year period resulting in an ownership change of more than 50 percent of the outstanding stock of a company by certain stockholders or public groups. The Company has not completed an analysis regarding the limitation of NOL and R&D credit carryforwards.

The Company’s federal income tax returns from 2015 forward, state income tax returns from 2014 forward, and its Australian tax returns beginning in 2017 are subject to examination by tax authorities; however, the Company’s tax attribute carryforwards such as NOLs and R&D credits generated in closed years are also subject to examination and remeasurement. No such audits are underway

Deferred tax assets and liabilities

Net deferred tax assets are comprised of the following as of December 31, 2019 and 2018 (in thousands):

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	15,990		$	2,664
Capitalized research expenses		4,864			6,355
R&D and other tax credits		4,676			1,788
Lease liability		1,560			—
Accrued expenses and other, net		2,229			2,636
Total deferred tax assets		29,319			13,443
Deferred tax liabilities:
Right-of use asset		(702	)		—
Other deferred tax liabilities		(22	)		(866	)
Net of deferred tax assets and liabilities		28,595			12,577
Less: valuation allowance		(28,595	)		(12,577	)
Net deferred tax assets	$	—		$	—

Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Management assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use existing deferred tax assets. Based on the weight of available evidence, including the Company’s history of operating losses, management has determined that it is more likely than not that the Company’s net deferred tax assets will not be realized. Accordingly, a valuation allowance has been established by the Company to fully offset these net deferred tax assets.

Income tax benefit

For the three years in the period ended December 31, 2019, domestic and foreign pre-tax loss were (in thousands):

	Year ended December 31,
	2019			2018			2017
Loss before income taxes - Domestic	$	(48,643	)	$	(25,876	)	$	(8,141	)
Loss before income taxes - Foreign		(1,779	)		(1,239	)		(1,016	)
Loss before income taxes - Consolidated	$	(50,422	)	$	(27,115	)	$	(9,157	)

A reconciliation of income tax expense to the amount computed by applying the statutory federal income tax rate to the loss from operations for the three years in the period ended December 31, 2019 is as follows (in thousands):

	Year ended December 31,
	2019			2018			2017
Expected income tax benefit at federal statutory rate	$	(10,589	)	$	(5,694	)	$	(3,113	)
State income tax benefit, net of federal benefit		(3,431	)		(1,758	)		(474	)
Tax effect of
Change in valuation allowance		16,064			7,724			2,112
R&D credit		(2,485	)		(1,129	)		(525	)
Federal rate change		—			(52	)		1,602
Australian tax incentive		307			362			176
Other		134			547			222
Provision for income taxes	$	—		$	—		$	—

Changes to the Company’s unrecognized tax benefits are summarized in the following table (in thousands):

	Year ended December 31,
	2019		2018		2017
Beginning balance	$	344	$	159	$	68
Increase (decrease) for prior year tax positions		70		—		—
Increase (decrease) for current year tax positions		472		185		91
Ending balance	$	886	$	344	$	159

Due to the existence of the valuation allowance, future changes in unrecognized tax benefits would not have any effect on the Company’s effective tax rate. The Company does not foresee any material changes to its unrecognized tax benefits within the next twelve months.

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Federal operating loss carryforwards	$ 54,500
State operating loss carryforwards	61,600
Domestic operating loss carryforwards	400
Research and development credit carryforwards	$ 4,676	$ 1,788
Operating loss and research and development credit carryforwards, limitations on use	Future utilization of the Company’s NOL and R&D credit carryforwards to offset future taxable income may be subject to a substantial annual limitation as a result of ownership changes that may have occurred or that could occur in the future pursuant to Internal Revenue Code Sections 382 and 383. These ownership changes may limit the amount of NOL and R&D credit carryforwards that can be utilized to offset future taxable income and tax, respectively. In general, an “ownership change” as defined by the tax code results from a transaction or series of transactions over a three-year period resulting in an ownership change of more than 50 percent of the outstanding stock of a company by certain stockholders or public groups.
Minimum
Operating Loss Carryforwards [Line Items]
Cumulative change in ownership percentage	50.00%
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Period for cumulative change in ownership	3 years
California
Operating Loss Carryforwards [Line Items]
Research and development credit carryforwards	$ 1,900
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, future taxable income, offset percentage	80.00%
Research and development credit carryforwards	$ 4,000
Research and development credit carryforwards, begin to expire	2030
Federal \| Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2035
State \| Earliest Tax Year
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration year	2035

Operating Lease

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Operating Lease

6. OPERATING LEASE

2018 Operating Lease. In February 2018, as amended in March 2018, the Company entered into a non-cancelable operating lease for a new facility in San Diego, California. The lease has an initial term of seven years which expires in August 2025, and the Company has an option to extend the term of the lease for an additional five years and has a termination option subject to early termination fees. The lease is subject to base lease payments and additional charges for common area maintenance and other costs and includes certain lease incentives and tenant improvement allowances. Rent expense is being recognized on a straight-line basis over the term of the lease. The Company’s estimated incremental fully collateralized borrowing rate of 8.0% was used in its present value calculation as the facility lease does not have a stated rate and the implicit rate was not readily determinable.

Under the terms of the lease, the Company provided the lessor with an irrevocable letter of credit in the amount of $0.5 million. The lessor is entitled to draw on the letter of credit in the event of any default by the Company under the terms of the lease.

Future Minimum Payments. As of December 31, 2019, future minimum payments under non-cancellable operating leases were as follows (in thousands):

Year ending December 31,	Minimum Payments
2020	$	1,123
2021		1,173
2022		1,208
2023		1,244
2024		1,280
Thereafter		871
Total future minimum lease payments		6,899
Less imputed interest		1,326
Total operating lease liability		5,573
Less operating lease liability, current		724
Operating lease liability, non-current	$	4,849

Rent expense is recorded on a straight-line basis over the term of the Company’s facility lease. Rent expense was $1.0 million, $0.6 million and $0.2 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Cash paid for amounts included in the measurement of lease liabilities for operating cash flow from operating leases was $1.1 million during the year ended December 31, 2019.

Subsequent Events

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Events

14. SUBSEQUENT EVENTS

Between January 1, 2020 and March 6, 2020, the Company sold a total of 275,764 shares of common stock pursuant to its ATM Offering for net proceeds of $6.4 million, after deducting commissions.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. COMMITMENTS AND CONTINGENCIES

Litigation

From time to time, the Company may be subject to various claims and suits arising in the ordinary course of business. The Company does not expect that the resolution of these matters will have a material adverse effect on its financial position or results of operations.

Quarterly Data (unaudited) - Summary of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Grant revenues	$ 321	$ 505		$ 367	$ 781	$ 548	$ 657	$ 442	$ 1,193	$ 2,428	$ 2,045
Type of Revenue Extensible List	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Research and development expenses	$ 12,143	$ 11,823	$ 10,285	$ 7,255	$ 7,651	$ 6,886	$ 5,222	$ 4,720	$ 41,506	$ 24,479	$ 9,233
General and administrative expenses	3,392	3,911	3,060	3,156	2,561	1,732	1,118	1,248	13,519	6,659	1,939
Total operating expenses	15,535	15,734	13,345	10,411	10,212	8,618	6,340	5,968	55,025	31,138	11,172
Net loss	$ (14,549)	$ (14,430)	$ (12,427)	$ (9,016)	$ (8,495)	$ (7,588)	$ (5,568)	$ (5,464)	$ (50,422)	$ (27,115)	$ (9,157)
Net loss per share - basic and diluted	$ (0.60)	$ (0.60)	$ (0.51)	$ (0.37)	$ (0.35)	$ (0.38)	$ (2.41)	$ (2.92)	$ (2.09)	$ (2.23)	$ (6.68)

- Definition

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

+ References + Details

Operating Lease - Additional Information (Details) - 2018 Operating Lease - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Leased Assets [Line Items]
Operating lease, initial term	7 years
Operating lease expiration period	2025-08
Operating lease, option to extend term	five years
Lessee,operating lease, discount rate	8.00%
Irrevocable letter of credit	$ 0.5
Rent expense	1.0	$ 0.6	$ 0.2
Cash paid for operating lease liabilities	$ 1.1

Investment Securities - Additional Information (Details) - Security	Dec. 31, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Available-for-sale investment securities maturity period, maximum	24 months	24 months
Available-for-sale, unrealized loss position, twelve month or more	0

Convertible Preferred Stock - Additional Information (Details) - USD ($)		2 Months Ended	9 Months Ended	12 Months Ended
	Jul. 20, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
Net proceeds from issuance of convertible preferred stock				$ 63,275,000	$ 11,969,000
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued			11,505,268		11,505,268
Net proceeds from issuance of convertible preferred stock			$ 12,000,000
Convertible preferred stock, issuance costs			$ 40,000
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued		19,641,200
Net proceeds from issuance of convertible preferred stock		$ 63,500,000
Convertible preferred stock, issuance costs		$ 200,000
Series A and B Convertible Preferred Stock \| Initial Public Offering
Temporary Equity [Line Items]
Stock issued upon conversion of convertible securities	14,712,571

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Feb. 28, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	CRNX
Entity Registrant Name	Crinetics Pharmaceuticals, Inc.
Entity Central Index Key	0001658247
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		24,566,896
Entity Public Float			$ 422.8
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-38583
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3744114
Entity Address, Address Line One	10222 Barnes Canyon Road
Entity Address, Address Line Two	Bldg. #2
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	450-6464
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Certain sections of the registrant’s definitive proxy statement for the 2020 annual meeting of stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after end of the fiscal year covered by this Form 10-K are incorporated by reference into Part III of this Form 10-K.

Organization and Basis of Presentation - Additional Information (Details) $ in Thousands			12 Months Ended
	Aug. 13, 2019 USD ($)	Jul. 06, 2018	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)
Organization And Basis Of Presentation [Line Items]
Number of operating segments \| Segment			1
Unrestricted cash, cash equivalents and investments securities			$ 118,400
Accumulated deficit			$ 93,802	$ 43,380
Maximum amount of common stock preferred stock debt securities warrants and units to be issued	$ 300,000
Issuance and sale of Common Stock	75,000			$ 106,472
Registration Statement effective date			Aug. 29, 2019
Minimum
Organization And Basis Of Presentation [Line Items]
Period of sufficient cash to meet its funding requirements			12 months
Maximum \| SVB Leerink LLC and Cantor Fitzgerald & Co.
Organization And Basis Of Presentation [Line Items]
Sale of common stock at offering price	$ 75,000
Common Stock
Organization And Basis Of Presentation [Line Items]
Stock reverse stock split		1-for-3.29
Stock split conversion ratio		0.3040

Quarterly Data (unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Quarterly Data (unaudited)

13. QUARTERLY DATA (unaudited)

The following quarterly financial data, in the opinion of management, reflects all adjustments, consisting of normal recurring adjustments, necessary for a fair presentation of results for the periods presented (in thousands, except per share amounts):

	Year Ended December 31, 2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Grant revenues	$	367		$	—		$	505		$	321
Research and development expenses	$	7,255		$	10,285		$	11,823		$	12,143
General and administrative expenses	$	3,156		$	3,060		$	3,911		$	3,392
Total operating expenses	$	10,411		$	13,345		$	15,734		$	15,535
Net loss	$	(9,016	)	$	(12,427	)	$	(14,430	)	$	(14,549	)
Net loss per share – basic and diluted	$	(0.37	)	$	(0.51	)	$	(0.60	)	$	(0.60	)

	Year Ended December 31, 2018
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Grant revenues	$	442		$	657		$	548		$	781
Research and development expenses	$	4,720		$	5,222		$	6,886		$	7,651
General and administrative expenses	$	1,248		$	1,118		$	1,732		$	2,561
Total operating expenses	$	5,968		$	6,340		$	8,618		$	10,212
Net loss	$	(5,464	)	$	(5,568	)	$	(7,588	)	$	(8,495	)
Net loss per share – basic and diluted	$	(2.92	)	$	(2.41	)	$	(0.38	)	$	(0.35	)

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock and paid-in capital, par value	$ 0.001	$ 0.001
Common stock and paid-in capital, shares authorized	200,000	200,000
Common stock and paid-in capital, shares issued	24,296	24,188
Common stock and paid-in capital, shares outstanding	24,263	24,061

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (50,422)	$ (27,115)	$ (9,157)
Reconciliation of net loss to net cash used in operating activities:
Stock-based compensation	6,294	2,320	271
Depreciation and amortization	887	471	128
Noncash lease expense	226
Accretion of purchase discounts and amortization of premiums on investment securities, net	(1,229)	(433)
Other	(4)
Increase (decrease) in cash resulting from changes in:
Prepaid expenses and other current assets	(2,221)	(1,802)	(783)
Accounts payable and accrued expenses	696	7,361	47
Operating lease liability	(608)
Deferred rent		(261)	15
Net cash used in operating activities	(46,381)	(19,459)	(9,479)
Investing activities:
Purchases of investment securities	(108,136)	(118,399)
Maturities of investment securities	150,295
Purchases of property and equipment	(492)	(1,059)	(304)
Net cash provided by (used in) investing activities	41,667	(119,458)	(304)
Financing activities:
Proceeds from issuance of convertible preferred stock, net		63,275	11,969
Proceeds from issuance of common stock, net		106,472
Proceeds from exercise of stock options	126	451	66
Repurchase of unvested shares	(59)
Repayments of borrowings under long-term debt			(212)
Net cash provided by financing activities	67	170,198	11,823
Net change in cash, cash equivalents and restricted cash	(4,647)	31,281	2,040
Cash, cash equivalents and restricted cash - beginning of period	45,473	14,192	12,152
Cash, cash equivalents and restricted cash - end of period	40,826	45,473	14,192
Supplemental disclosure of cash flow information:
Cash paid for interest			8
Non-cash financing activity:
Purchase of shares pursuant to Stock Purchase Plan	735	282
Change in unvested stock liability	94	21	$ 2
Amounts accrued for purchases of property and equipment	$ 112	42
Tenant improvement allowance		$ 3,304

Balance Sheet Details - Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment at cost	$ 5,570	$ 4,973
Less accumulated depreciation and amortization	1,624	741
Total	3,946	4,232
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment at cost	3,494	3,494
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment at cost	1,468	915
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment at cost	567	523
Computers and Software
Property Plant And Equipment [Line Items]
Property and equipment at cost	$ 41	$ 41

Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Components of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):

	December 31, 2019		December 31, 2018
Prepaid research and development costs	$	2,478	$	8
Australian tax incentive receivable		929		1,016
SBIR grant receivable		225		568
Interest receivable		224		340
Prepaid expenses and other assets		1,091		876
Total	$	4,947	$	2,808

Components of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):

	December 31, 2019		December 31, 2018
Leasehold improvements	$	3,494	$	3,494
Lab equipment		1,468		915
Office equipment		567		523
Computers and software		41		41
Property and equipment at cost		5,570		4,973
Less accumulated depreciation and amortization		1,624		741
Total	$	3,946	$	4,232

Investment Securities - Summary of Available-For-Sale Investment Securities Held by the Company (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	$ 77,918	$ 118,841
Available-for-sale investment securities, Gross Unrealized Gains	152	74
Available-for-sale investment securities, Gross Unrealized Losses	(4)	(13)
Available-for-sale investment securities, Fair Market Value	78,066	118,902
U.S. Government and Agency Obligations
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	43,275	42,193
Available-for-sale investment securities, Gross Unrealized Gains	94	72
Available-for-sale investment securities, Gross Unrealized Losses	(1)	(1)
Available-for-sale investment securities, Fair Market Value	43,368	42,264
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	5,931	5,408
Available-for-sale investment securities, Gross Unrealized Gains	51
Available-for-sale investment securities, Fair Market Value	5,982	5,408
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	17,645	47,686
Available-for-sale investment securities, Fair Market Value	17,645	47,686
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investment securities, Amortized Cost	11,067	23,554
Available-for-sale investment securities, Gross Unrealized Gains	7	2
Available-for-sale investment securities, Gross Unrealized Losses	(3)	(12)
Available-for-sale investment securities, Fair Market Value	$ 11,071	$ 23,544

Equity Incentive Plans

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity Incentive Plans

10. EQUITY INCENTIVE PLANS

2018 Incentive Award Plan

The Company adopted the 2018 Incentive Award Plan (the “2018 Plan”) in July 2018. Under the 2018 Plan, which expires in July 2028, the Company may grant equity-based awards to individuals who are employees, officers, directors or consultants of the Company. Options issued under the 2018 Plan will generally expire ten years from the date of grant and vest over a four-year period. As of December 31, 2019, an aggregate of 2,217,222 shares of common stock were available for issuance under the 2018 Plan.

The 2018 Plan contains a provision that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2028 in an amount equal to the lesser of: (i) 5% of the aggregate number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding calendar year, or (ii) such lesser amount determined by the Company. Under this evergreen provision, on January 1, 2020, an additional 1,214,804 shares became available for future issuance under the 2018 Plan.

2015 Stock Incentive Plan

In February 2015, the Company adopted the Crinetics Pharmaceuticals, Inc. 2015 Stock Incentive Plan (the “2015 Plan”), which provided for the issuance of equity awards to the Company’s employees, members of its board of directors and consultants. In general, options issued under this plan vest over four years and expire after 10 years. Subsequent to the adoption of the 2018 Plan, no additional equity awards can be made under the 2015 Plan.

Certain awards issued under the 2015 Plan allowed for exercise prior to vesting. Shares issued under such early-exercise provisions are subject to repurchase by the Company until they become fully vested. As of December 31, 2019, 33,048 unvested shares issued under early-exercise provisions were subject to repurchase by the Company. The consolidated balance sheet reflects an unvested stock liability of $49,000 and $202,000 as of December 31, 2019 and 2018, respectively.

2018 Employee Stock Purchase Plan

In July 2018, the Company adopted the 2018 Employee Stock Purchase Plan (the “ESPP”). The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. As of December 31, 2019, an aggregate of 423,137 shares of common stock were available for issuance under the ESPP.

The ESPP contains a provision that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2028 in an amount equal to the lesser of: (i) 1% of the aggregate number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding calendar year, or (ii) such lesser amount determined by the Company. Under this evergreen provision, on January 1, 2020, an additional 242,961 shares became available for future issuance under the ESPP.

Stock Option Activity

Activity under the Company’s stock option plans during the year ended December 31, 2019 was as follows:

				Weighted-		Weighted-		Aggregate
				Average		Average		Intrinsic
	Options			Exercise		Remaining		Value
	Outstanding			Price		Term		(000’s)
Balance at December 31, 2018		2,339,157		$	6.40
Granted		900,175		$	23.96
Exercised		(90,322	)	$	1.40
Forfeited and expired		(21,619	)	$	17.35
Balance at December 31, 2019		3,127,391		$	11.52		8.4	$	42,777
Exercisable at December 31, 2019		1,236,908		$	6.96		7.9	$	22,510

Aggregate intrinsic value is calculated as the difference between the closing price of the Company’s common stock at December 31, 2019 and the exercise price of stock options that had strike prices below the closing price.

The total intrinsic value of options exercised during 2019 and 2018 was $2.0 million and $2.4 million, respectively.

Fair Value of Stock Option Awards

The following table summarizes the weighted average assumptions used to estimate the fair value of stock options granted under the Company’s stock option plans and the shares purchasable under the ESPP during the periods presented:

	Year ended December 31,
Stock Option Awards	2019			2018			2017
Expected option term	5.9 years			6.0 years			6.0 years
Expected volatility		78	%		70	%		71	%
Risk free interest rate		2.3	%		2.8	%		2.1	%
Expected dividend yield		—	%		—	%		—	%

	Year ended December 31,
ESPP	2019			2018			2017
Expected option term	1.8 years			1.1 years			N/A
Expected volatility		65	%		66	%	N/A
Risk free interest rate		2.2	%		2.4	%	N/A
Expected dividend yield		—	%		—	%	N/A

The key assumptions used in determining the fair value of equity awards, and the Company’s rationale, were as follows: (i) Expected option term - the expected term represents the period that options are expected to be outstanding and has been estimated using the simplified method, which is an average of the contractual option term and its vesting period; (ii) Expected volatility - the expected volatility assumption is based on volatilities of a peer group of similar companies in the biotechnology industry whose share prices are publicly available; (iii) Risk-free interest rate - the risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero coupon U.S. Treasury notes with maturities that approximate the expected terms of awards; and (iv) Expected dividend yield - the expected dividend yield assumption is zero as the Company has never paid dividends and has no present intention to do so in the future.

The weighted-average fair value of stock options granted to employees during the years ended December 31, 2019, 2018 and 2017 was $16.35, $4.66 and $0.85 per share, respectively. The weighted-average fair value of awards under the ESPP during the years ended December 31, 2019 and 2018 was $10.59 and $8.15 per share, respectively.

Stock-Based Compensation Expense

Stock-based compensation expense for the equity awards issued by the Company to employees and non-employees for the periods presented below was as follows (in thousands):

	Year ended December 31,
	2019		2018		2017
Included in research and development	$	3,190	$	1,100	$	122
Included in general and administrative		3,104		1,220		149
Total stock-based compensation expense	$	6,294	$	2,320	$	271

Unrecognized stock-based compensation cost related to option awards was $17.7 million as of December 31, 2019, which is expected to be recognized over a remaining weighted-average period of approximately 2.8 years. Unrecognized stock-based compensation cost related to stock purchase rights under the Company’s ESPP was $0.4 million as of December 31, 2019, which is expected to be recognized over a remaining weighted-average period of approximately 1.2 years.

Operating Lease (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Schedule of Future Minimum Payments Under Non-cancellable Operating Leases

As of December 31, 2019, future minimum payments under non-cancellable operating leases were as follows (in thousands):

Year ending December 31,	Minimum Payments
2020	$	1,123
2021		1,173
2022		1,208
2023		1,244
2024		1,280
Thereafter		871
Total future minimum lease payments		6,899
Less imputed interest		1,326
Total operating lease liability		5,573
Less operating lease liability, current		724
Operating lease liability, non-current	$	4,849

Stockholder's Equity

12 Months Ended

Dec. 31, 2019

Stockholders Equity Note [Abstract]

Stockholders' Equity

9. STOCKHOLDERS’ EQUITY

Authorized Shares

In connection with the completion of the Company’s IPO on July 20, 2018, the Company amended and restated its certificate of incorporation to authorize 200,000,000 shares of common stock, par value $0.001 per share, and 10,000,000 shares of preferred stock, par value $0.001 per share.

Initial Public Offering

The Company completed its IPO in July 2018 whereby it sold 6,900,000 shares of common stock at a price to the public of $17.00 per share. Proceeds from the IPO were approximately $106.5 million, net of underwriting discounts and commissions and offering costs.

Shares of Common Stock Subject to Repurchase

In October 2015, in connection with the issuance of the Company’s Series A convertible preferred stock, certain of the Company’s founders entered into stock restriction agreements, whereby 1,914,893 of previously unrestricted shares of common stock became subject to repurchase by the Company upon the stockholder’s termination of employment or service to the Company. The Company’s repurchase rights lapsed as to 765,957 shares of common stock in October 2015, with the remainder scheduled to lapse at the rate of 23,936 shares monthly thereafter such that the shares of common stock would have been fully vested in October 2019. Under the terms of the stock restriction agreements, the shares of common stock were also subject to accelerated vesting upon certain events, such that all of these restricted shares became fully vested upon the closing of the Company’s Series B preferred stock financing in February 2018. The stock restriction agreements resulted in the deemed cancellation and reissuance of shares of common stock and therefore, for accounting purposes, the shares subject to repurchase were not considered to be outstanding until vested. The fair value of these shares as of October 2015 was recognized as compensation expense over the vesting period. For the years ended December 31, 2018 and 2017, the Company recognized stock-based compensation for these awards of $0.4 million and $0.2 million, respectively.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2019
Accounting Policies [Abstract]
Description of Business	Description of Business Crinetics Pharmaceuticals, Inc. (the “Company”) is a clinical stage pharmaceutical company incorporated in Delaware on November 18, 2008 and based in San Diego, California. The Company is focused on the discovery, development and commercialization of novel therapeutics for rare endocrine diseases and endocrine-related tumors. In January 2017, the Company established a wholly-owned Australian subsidiary, Crinetics Australia Pty Ltd (“CAPL”), in order to conduct various preclinical and clinical activities for its development candidates. On July 6, 2018, the Company effected a 1-for-3.29 reverse stock split of its common stock. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse stock split. The reverse stock split resulted in an adjustment to the conversion prices of the Company’s Series A and B preferred stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying consolidated financial statements and notes to the consolidated financial statements give retroactive effect to the reverse stock split for all periods presented.
Principles of Consolidation and Foreign Currency Transactions	Principles of Consolidation and Foreign Currency Transactions The consolidated financial statements include the accounts of the Company and CAPL. All intercompany accounts and transactions have been eliminated in consolidation. The functional currency of both the Company and CAPL is the U.S. dollar. Assets and liabilities that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the consolidated statements of operations and were not material for all periods presented.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Liquidity and Going Concern	Liquidity and Going Concern From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. As of December 31, 2019, the Company had $118.4 million in unrestricted cash, cash equivalents and investment securities. The Company believes it has sufficient cash to meet its funding requirements for at least the next 12 months. However, the Company has experienced net losses and negative cash flows from operating activities since its inception and has an accumulated deficit of $93.8 million as of December 31, 2019. The Company expects to continue to incur net losses for the foreseeable future and believes it will need to raise substantial additional capital to accomplish its business plan over the next several years. The Company plans to continue to fund its losses from operations and capital funding needs through a combination of equity offerings, debt financings or other sources, including potential collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations and future prospects. There can be no assurance as to the availability or terms upon which such financing and capital might be available in the future. On August 13, 2019 the Company entered into a Sales Agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (collectively, the “Sales Agents”), under which the Company may, from time to time, sell shares of its common stock having an aggregate offering price of up to $75.0 million through the Sales Agents (the “ATM Offering”). On August 13, 2019, the Company also filed a registration statement on Form S-3 (the “Shelf Registration Statement”), covering the offering of up to $300.0 million of common stock, preferred stock, debt securities, warrants and units. The Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to $75.0 million of Company common stock from time to time through the ATM Offering. The Registration Statement became effective on August 29, 2019. The shares to be sold under the Sales Agreement may be issued and sold pursuant to the Shelf Registration Statement.
Use of Estimates	Use of Estimates The Company’s consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes. The most significant estimates in the Company’s consolidated financial statements relate to accrued amounts receivable under the Australian research and development tax incentive program, accrued expenses and associated research and development expense, the assumptions underlying the determination of the estimated incremental borrowing rate for the determination of the Company’s operating lease right-of-use asset, and the assumptions underlying the determination of the fair value of equity awards for purposes of determining stock-based compensation. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Fair Value Measurements	Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s current financial assets, restricted cash and current financial liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include cash held in readily available checking and money market accounts, as well as short-term debt securities with maturities of three months or less when purchased. Restricted cash represents cash held as collateral for the Company’s facility lease and is reported as a long-term asset in the accompanying consolidated balance sheets.
Investment Securities	Investment Securities All investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Investments with contractual maturities beyond one year are also classified as short-term due to the Company’s ability to liquidate the investment for use in operations within the next 12 months. Realized gains and losses on investment securities are included in earnings and are derived using the specific identification method for determining the cost of securities sold. The Company has not realized any significant gains or losses on sales of available-for-sale investment securities during any of the periods presented. As all the Company’s investment holdings are in the form of debt securities, unrealized gains and losses that are determined to be temporary in nature are reported as a component of accumulated other comprehensive income. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. Interest income is recognized when earned and is included in investment income, as are the amortization of purchase premiums and accretion of purchase discounts on investment securities.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and investment securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Leases	Leases The Company determines if an arrangement is a lease at the inception of the arrangement. Beginning January 1, 2019, leases with a term longer than 12 months that are determined to be operating leases are included in operating lease assets, accrued expenses and other current liabilities and noncurrent operating lease liabilities in the consolidated balance sheets based on the present value of the minimum lease payments called for under the arrangement. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term.
Property and Equipment, Net	Property and Equipment, Net Property and equipment, which consist of lab equipment, and computer, software and office equipment, are stated at cost and depreciated on a straight-line basis over the estimated useful life of the related assets (generally three to five years). Leasehold improvements are stated at cost and amortized on a straight-line basis over the lesser of the remaining lease term of the related lease or the estimated useful life of the leasehold improvements. Repairs and maintenance costs are charged to expense as incurred and expenditures that materially extend the useful lives of assets are capitalized.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. The Company has not recognized any impairment losses in any of the periods presented in these consolidated financial statements.
Deferred Rent	Deferred Rent The Company’s facility lease includes incentives in the form of rent abatements and leasehold improvement allowances, as well as fixed annual rent escalations. The Company recognizes the aggregate rental expense, after considering incentives and stipulated rent escalations, on a straight-line basis over the lease term. Prior to January 1, 2019, the difference between rent expense and amounts paid under the lease was recorded as deferred rent in the accompanying consolidated balance sheets.
Grant Revenue Recognition	Grant Revenue Recognition The Company’s grant revenues are derived from Small Business Innovation Research Grants (“SBIR Grants”) from the National Institutes of Health. The Company recognizes SBIR Grant revenue as reimbursable grant costs are incurred up to pre-approved award limits within the budget period. The costs associated with these reimbursements are reflected as a component of research and development expense in the accompanying consolidated statements of operations. Earnings in excess of billings are included as a component of prepaid expenses and other current assets.
Research and Development Expense	Research and Development Expenses Research and development (“R&D”) expenses consist primarily of salaries, payroll taxes, employee benefits and stock-based compensation for individuals involved in R&D efforts, as well as consulting expenses, third-party R&D expenses, laboratory supplies, clinical materials and overhead, including facilities and depreciation costs, offset by the Australian Tax Incentive discussed below. R&D expenses are charged to expense as incurred. Payments made prior to the receipt of goods or services to be used in R&D are capitalized until the goods or services are received. Costs incurred under contracts with contract research organizations (“CROs”) that conduct and manage the Company’s clinical trials are also included in research and development expenses. The financial terms and activities of these agreements vary from contract to contract and may result in uneven expense levels. Generally, these agreements set forth activities that drive the recording of expenses such as start-up and initiation activities, enrollment and treatment of patients, or the completion of other clinical trial activities. Expenses related to clinical trials are accrued based on estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts that the Company is obligated to pay under its clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), the Company adjusts its accruals accordingly on a prospective basis. Revisions to contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. Accrued research and development expenses totaled $2.8 million and $3.6 million as of December 31, 2019 and 2018, respectively, and are a component of accounts payable and accrued expenses in the Consolidated Balance Sheets.
Australian Tax Incentive	Australian Tax Incentive CAPL is eligible to obtain a cash refund from the Australian Taxation Office for eligible research and development expenditures under the Australian R&D Tax Incentive Program (the “Australian Tax Incentive”). The Australian Tax Incentive is recognized as a reduction to R&D expense when there is reasonable assurance that the relevant expenditure has been incurred, the amount can be reliably measured and that the Australian Tax Incentive will be received. The Company recognized reductions to R&D expense of $1.0 million, $1.2 million and $0.5 million for the years ended December 31, 2019, 2018 and 2017, respectively.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the estimated grant date fair value of the Company’s equity awards, consisting of stock options and shares issued under the Company’s Employee Stock Purchase Plan, recognized over the requisite service period of such awards (usually the vesting period) on a straight-line basis. The Company estimates the fair value of equity awards using the Black-Scholes option pricing model on the date of grant and recognizes forfeitures as they occur. For stock awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable, or the performance condition has been achieved.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense, and any accrued interest and penalties would be included within the related tax liability. No such costs were recorded during the three years ended December 31, 2019.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of the Company’s net loss and the unrealized gains on the Company’s investment securities for all periods presented.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Dilutive common stock equivalents are comprised of convertible preferred stock, common stock subject to repurchase, and options outstanding under the Company’s stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive securities would be antidilutive.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements ASU 2016-02 In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use (“ROU”) model that requires a lessee to recognize a ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. ASU 2016-02 also requires disclosures to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. On January 1, 2019, the Company adopted ASU 2016-02, and the related ASUs, using the modified retrospective transition method. Under this transition method, the Company recognized and measured leases that existed at the adoption date in the consolidated balance sheet as of January 1, 2019. ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term, discounted at the rate implicit in the lease. If the rate implicit in the lease cannot be determined, Topic 842 requires the use of the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term for a similar amount to the lease payments in a similar economic environment. The operating lease ROU asset is also adjusted for any prepaid or accrued lease payments and any lease incentives received. Operating lease terms may include options to extend or terminate the lease when it is reasonably certain that these options will be exercised. Further, the Company has elected to recognize short-term lease payments on a straight-line basis over the associated lease term and variable lease payments in the period in which the obligation for those payments is incurred. Short-term and variable lease payments were not material in the first half of 2019. In connection with the adoption of ASU 2016-02, the Company elected the package of practical expedients requiring no reassessment of whether any expired or existing contracts contain leases, the lease classification of any expired or existing leases, or initial direct costs for any existing leases. The Company also made accounting policy elections not to apply the recognition requirements under ASU 2016-02 to any short-term leases and to account for each separate lease and associated non-lease components as a single lease component for the Company’s leases. Adoption of ASU 2016-02 resulted in recognition of a ROU asset of $2.8 million and an operating lease liability of $6.2 million, related to the lease of office and laboratory space; and the derecognition of deferred rent of $3.4 million for certain lease incentives received previously. Adoption of ASU 2016-02 also resulted in recognition of a deferred tax asset and a corresponding deferred tax liability) of $0.7 million. The comparative prior period information continues to be reported under the accounting standards in effect during those periods. ASU 2018-07 In June 2018, the FASB issued ASU 2018-07, “Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting”, which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees and 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. This ASU was adopted by the Company on January 1, 2019 using the modified retrospective transition method with no impact on the consolidated financial statements. As a result of adopting this ASU, the estimated fair values of awards issued to non-employees are determined at issuance and are no longer subject to revaluation over their vesting terms. Recent Accounting Pronouncements ASU 2016-13 In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“Topic 326”). Topic 326 amends guidance on reporting credit losses for assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, Topic 326 eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current GAAP, however Topic 326 will require that credit losses be presented as an allowance rather than as a write-down. This ASU update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. This update is effective for the company for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements. ASU 2018-13 In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement,” which improves the effectiveness of the disclosures required under ASC 820, “Fair Value Measurements and Disclosures” and modifies the disclosure requirements on fair value measurements, including the consideration of costs and benefits. The new standard is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Grant revenues	$ 1,193	$ 2,428	$ 2,045
Type of Revenue Extensible List	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 41,506	$ 24,479	$ 9,233
General and administrative	13,519	6,659	1,939
Total operating expenses	55,025	31,138	11,172
Loss from operations	(53,832)	(28,710)	(9,127)
Other income (expense):
Interest income	3,460	1,748	26
Other income (expense), net	(50)	(153)	(56)
Total other income (expense), net	3,410	1,595	(30)
Net loss	(50,422)	(27,115)	(9,157)
Other comprehensive income:
Unrealized gain on investment securities	87	61
Comprehensive loss	$ (50,335)	$ (27,054)	$ (9,157)
Net loss per share:
Net loss per share - basic and diluted	$ (2.09)	$ (2.23)	$ (6.68)
Weighted average shares - basic and diluted	24,175	12,142	1,371

Net Loss Per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

12. NET LOSS PER SHARE

Potentially dilutive securities (in common stock equivalent shares) not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in thousands):

	Year ended December 31,
	2019		2018		2017
Convertible preferred stock outstanding		—		—		8,743
Common stock options		3,127		2,339		838
Unvested common stock subject to repurchase		33		127		527
Total		3,160		2,466		10,108

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities

Net deferred tax assets are comprised of the following as of December 31, 2019 and 2018 (in thousands):

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	15,990		$	2,664
Capitalized research expenses		4,864			6,355
R&D and other tax credits		4,676			1,788
Lease liability		1,560			—
Accrued expenses and other, net		2,229			2,636
Total deferred tax assets		29,319			13,443
Deferred tax liabilities:
Right-of use asset		(702	)		—
Other deferred tax liabilities		(22	)		(866	)
Net of deferred tax assets and liabilities		28,595			12,577
Less: valuation allowance		(28,595	)		(12,577	)
Net deferred tax assets	$	—		$	—

Schedule of Domestic and Foreign Pre-Tax Loss

Income tax benefit

For the three years in the period ended December 31, 2019, domestic and foreign pre-tax loss were (in thousands):

	Year ended December 31,
	2019			2018			2017
Loss before income taxes - Domestic	$	(48,643	)	$	(25,876	)	$	(8,141	)
Loss before income taxes - Foreign		(1,779	)		(1,239	)		(1,016	)
Loss before income taxes - Consolidated	$	(50,422	)	$	(27,115	)	$	(9,157	)

Schedule of Reconciliation of Income Tax Expense

	Year ended December 31,
	2019			2018			2017
Expected income tax benefit at federal statutory rate	$	(10,589	)	$	(5,694	)	$	(3,113	)
State income tax benefit, net of federal benefit		(3,431	)		(1,758	)		(474	)
Tax effect of
Change in valuation allowance		16,064			7,724			2,112
R&D credit		(2,485	)		(1,129	)		(525	)
Federal rate change		—			(52	)		1,602
Australian tax incentive		307			362			176
Other		134			547			222
Provision for income taxes	$	—		$	—		$	—

Schedule of Unrecognized Tax Benefits

Changes to the Company’s unrecognized tax benefits are summarized in the following table (in thousands):

	Year ended December 31,
	2019		2018		2017
Beginning balance	$	344	$	159	$	68
Increase (decrease) for prior year tax positions		70		—		—
Increase (decrease) for current year tax positions		472		185		91
Ending balance	$	886	$	344	$	159

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Use of Estimates

The Company’s consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes. The most significant estimates in the Company’s consolidated financial statements relate to accrued amounts receivable under the Australian research and development tax incentive program, accrued expenses and associated research and development expense, the assumptions underlying the determination of the estimated incremental borrowing rate for the determination of the Company’s operating lease right-of-use asset, and the assumptions underlying the determination of the fair value of equity awards for purposes of determining stock-based compensation. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.

Fair Value Measurements

The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Observable inputs such as quoted prices in active markets.

Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly.

Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

The carrying amounts of the Company’s current financial assets, restricted cash and current financial liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments.

Cash, Cash Equivalents and Restricted Cash

Cash and cash equivalents include cash held in readily available checking and money market accounts, as well as short-term debt securities with maturities of three months or less when purchased. Restricted cash represents cash held as collateral for the Company’s facility lease and is reported as a long-term asset in the accompanying consolidated balance sheets.

Investment Securities

All investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Investments with contractual maturities beyond one year are also classified as short-term due to the Company’s ability to liquidate the investment for use in operations within the next 12 months.

Realized gains and losses on investment securities are included in earnings and are derived using the specific identification method for determining the cost of securities sold. The Company has not realized any significant gains or losses on sales of available-for-sale investment securities during any of the periods presented. As all the Company’s investment holdings are in the form of debt securities, unrealized gains and losses that are determined to be temporary in nature are reported as a component of accumulated other comprehensive income. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. Interest income is recognized when earned and is included in investment income, as are the amortization of purchase premiums and accretion of purchase discounts on investment securities.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and investment securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.

Leases

The Company determines if an arrangement is a lease at the inception of the arrangement. Beginning January 1, 2019, leases with a term longer than 12 months that are determined to be operating leases are included in operating lease assets, accrued expenses and other current liabilities and noncurrent operating lease liabilities in the consolidated balance sheets based on the present value of the minimum lease payments called for under the arrangement. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term.

Property and Equipment, Net

Property and equipment, which consist of lab equipment, and computer, software and office equipment, are stated at cost and depreciated on a straight-line basis over the estimated useful life of the related assets (generally three to five years). Leasehold improvements are stated at cost and amortized on a straight-line basis over the lesser of the remaining lease term of the related lease or the estimated useful life of the leasehold improvements.

Repairs and maintenance costs are charged to expense as incurred and expenditures that materially extend the useful lives of assets are capitalized.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. The Company has not recognized any impairment losses in any of the periods presented in these consolidated financial statements.

Deferred Rent

The Company’s facility lease includes incentives in the form of rent abatements and leasehold improvement allowances, as well as fixed annual rent escalations. The Company recognizes the aggregate rental expense, after considering incentives and stipulated rent escalations, on a straight-line basis over the lease term. Prior to January 1, 2019, the difference between rent expense and amounts paid under the lease was recorded as deferred rent in the accompanying consolidated balance sheets.

Grant Revenue Recognition

The Company’s grant revenues are derived from Small Business Innovation Research Grants (“SBIR Grants”) from the National Institutes of Health. The Company recognizes SBIR Grant revenue as reimbursable grant costs are incurred up to pre-approved award limits within the budget period. The costs associated with these reimbursements are reflected as a component of research and development expense in the accompanying consolidated statements of operations. Earnings in excess of billings are included as a component of prepaid expenses and other current assets.

Research and Development Expenses

Research and development (“R&D”) expenses consist primarily of salaries, payroll taxes, employee benefits and stock-based compensation for individuals involved in R&D efforts, as well as consulting expenses, third-party R&D expenses, laboratory supplies, clinical materials and overhead, including facilities and depreciation costs, offset by the Australian Tax Incentive discussed below. R&D expenses are charged to expense as incurred. Payments made prior to the receipt of goods or services to be used in R&D are capitalized until the goods or services are received. Costs incurred under contracts with contract research organizations (“CROs”) that conduct and manage the Company’s clinical trials are also included in research and development expenses. The financial terms and activities of these agreements vary from contract to contract and may result in uneven expense levels. Generally, these agreements set forth activities that drive the recording of expenses such as start-up and initiation activities, enrollment and treatment of patients, or the completion of other clinical trial activities. Expenses related to clinical trials are accrued based on estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts that the Company is obligated to pay under its clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), the Company adjusts its accruals accordingly on a prospective basis. Revisions to contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain.

Accrued research and development expenses totaled $2.8 million and $3.6 million as of December 31, 2019 and 2018, respectively, and are a component of accounts payable and accrued expenses in the Consolidated Balance Sheets.

Australian Tax Incentive

CAPL is eligible to obtain a cash refund from the Australian Taxation Office for eligible research and development expenditures under the Australian R&D Tax Incentive Program (the “Australian Tax Incentive”). The Australian Tax Incentive is recognized as a reduction to R&D expense when there is reasonable assurance that the relevant expenditure has been incurred, the amount can be reliably measured and that the Australian Tax Incentive will be received. The Company recognized reductions to R&D expense of $1.0 million, $1.2 million and $0.5 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Stock-Based Compensation

Stock-based compensation expense represents the estimated grant date fair value of the Company’s equity awards, consisting of stock options and shares issued under the Company’s Employee Stock Purchase Plan, recognized over the requisite service period of such awards (usually the vesting period) on a straight-line basis. The Company estimates the fair value of equity awards using the Black-Scholes option pricing model on the date of grant and recognizes forfeitures as they occur. For stock awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable, or the performance condition has been achieved.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements. Under this method, deferred tax assets and liabilities are determined based on the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense, and any accrued interest and penalties would be included within the related tax liability. No such costs were recorded during the three years ended December 31, 2019.

Comprehensive Loss

Comprehensive loss is comprised of the Company’s net loss and the unrealized gains on the Company’s investment securities for all periods presented.

Net Loss Per Share

Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Dilutive common stock equivalents are comprised of convertible preferred stock, common stock subject to repurchase, and options outstanding under the Company’s stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive securities would be antidilutive.

Recently Adopted Accounting Pronouncements

ASU 2016-02

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) which requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use (“ROU”) model that requires a lessee to recognize a ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. ASU 2016-02 also requires disclosures to meet the objective of enabling users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. On January 1, 2019, the Company adopted ASU 2016-02, and the related ASUs, using the modified retrospective transition method. Under this transition method, the Company recognized and measured leases that existed at the adoption date in the consolidated balance sheet as of January 1, 2019.

ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. Operating lease ROU assets and operating lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term, discounted at the rate implicit in the lease. If the rate implicit in the lease cannot be determined, Topic 842 requires the use of the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term for a similar amount to the lease payments in a similar economic environment. The operating lease ROU asset is also adjusted for any prepaid or accrued lease payments and any lease incentives received. Operating lease terms may include options to extend or terminate the lease when it is reasonably certain that these options will be exercised. Further, the Company has elected to recognize short-term lease payments on a straight-line basis over the associated lease term and variable lease payments in the period in which the obligation for those payments is incurred. Short-term and variable lease payments were not material in the first half of 2019.

In connection with the adoption of ASU 2016-02, the Company elected the package of practical expedients requiring no reassessment of whether any expired or existing contracts contain leases, the lease classification of any expired or existing leases, or initial direct costs for any existing leases. The Company also made accounting policy elections not to apply the recognition requirements under ASU 2016-02 to any short-term leases and to account for each separate lease and associated non-lease components as a single lease component for the Company’s leases.

Adoption of ASU 2016-02 resulted in recognition of a ROU asset of $2.8 million and an operating lease liability of $6.2 million, related to the lease of office and laboratory space; and the derecognition of deferred rent of $3.4 million for certain lease incentives received previously. Adoption of ASU 2016-02 also resulted in recognition of a deferred tax asset and a corresponding deferred tax liability) of $0.7 million. The comparative prior period information continues to be reported under the accounting standards in effect during those periods.

ASU 2018-07

In June 2018, the FASB issued ASU 2018-07, “Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting”, which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees and 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. This ASU was adopted by the Company on January 1, 2019 using the modified retrospective transition method with no impact on the consolidated financial statements. As a result of adopting this ASU, the estimated fair values of awards issued to non-employees are determined at issuance and are no longer subject to revaluation over their vesting terms.

Recent Accounting Pronouncements

ASU 2016-13

In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (“Topic 326”). Topic 326 amends guidance on reporting credit losses for assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, Topic 326 eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current GAAP, however Topic 326 will require that credit losses be presented as an allowance rather than as a write-down. This ASU update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. This update is effective for the company for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements.

ASU 2018-13

In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement,” which improves the effectiveness of the disclosures required under ASC 820, “Fair Value Measurements and Disclosures” and modifies the disclosure requirements on fair value measurements, including the consideration of costs and benefits. The new standard is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. FAIR VALUE MEASUREMENTS

The Company holds investment securities that consist of highly liquid, investment grade debt securities. The Company determines the fair value of its investment securities based upon one or more valuations reported by its investment accounting and reporting service provider. The investment service provider values the securities using a hierarchical security pricing model that relies primarily on valuations provided by an industry-recognized valuation service. Such valuations may be based on trade prices in active markets for identical assets or liabilities (Level 1 inputs) or valuation models using inputs that are observable either directly or indirectly (Level 2 inputs), such as quoted prices for similar assets or liabilities, yield curves, volatility factors, credit spreads, default rates, loss severity, current market and contractual prices for the underlying instruments or debt, and broker and dealer quotes, as well as other relevant economic measures.

Financial assets measured at fair value on a recurring basis as of December 31, 2019 and 2018 were as follows (in thousands):

	As of December 31, 2019
	Level 1		Level 2		Level 3		Total
Investment securities:
U.S. government and agency obligations	$	15,478	$	27,890	$	—	$	43,368
Certificates of deposit		—		5,982		—		5,982
Commercial paper		—		17,645		—		17,645
Corporate debt securities		—		11,071		—		11,071
Total assets measured at fair value	$	15,478	$	62,588	$	—	$	78,066

	As of December 31, 2018
	Level 1		Level 2		Level 3		Total
Investment securities:
U.S. government and agency obligations	$	22,275	$	19,989	$	—	$	42,264
Certificates of deposit		—		5,408		—		5,408
Commercial paper		—		47,686		—		47,686
Corporate debt securities		—		23,544		—		23,544
Total assets measured at fair value	$	22,275	$	96,627	$	—	$	118,902

The Company’s policy is to recognize transfers between levels of the fair value hierarchy on the date of the event or change in circumstances that caused the transfer. There were no transfers into or out of Level 3 during the years ended December 31, 2019 and 2018.

- Definition

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

+ References + Details

Equity Incentive Plans - Weighted Average Assumptions Used to Estimate Fair Value of Stock Options Granted to Employees (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	0.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option term	1 year 9 months 18 days	1 year 1 month 6 days
Expected volatility	65.00%	66.00%
Risk free interest rate	2.20%	2.40%
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option term	5 years 10 months 24 days	6 years	6 years
Expected volatility	78.00%	70.00%	71.00%
Risk free interest rate	2.30%	2.80%	2.10%

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Potentially Dilutive Securities (in Common Stock Equivalent Shares) not Included in Calculation of Diluted Net Loss Per Share

	Year ended December 31,
	2019		2018		2017
Convertible preferred stock outstanding		—		—		8,743
Common stock options		3,127		2,339		838
Unvested common stock subject to repurchase		33		127		527
Total		3,160		2,466		10,108

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Activity Under Stock Option Plans

Activity under the Company’s stock option plans during the year ended December 31, 2019 was as follows:

				Weighted-		Weighted-		Aggregate
				Average		Average		Intrinsic
	Options			Exercise		Remaining		Value
	Outstanding			Price		Term		(000’s)
Balance at December 31, 2018		2,339,157		$	6.40
Granted		900,175		$	23.96
Exercised		(90,322	)	$	1.40
Forfeited and expired		(21,619	)	$	17.35
Balance at December 31, 2019		3,127,391		$	11.52		8.4	$	42,777
Exercisable at December 31, 2019		1,236,908		$	6.96		7.9	$	22,510

Weighted Average Assumptions Used to Estimate Fair Value of Stock Options Granted to Employees

	Year ended December 31,
Stock Option Awards	2019			2018			2017
Expected option term	5.9 years			6.0 years			6.0 years
Expected volatility		78	%		70	%		71	%
Risk free interest rate		2.3	%		2.8	%		2.1	%
Expected dividend yield		—	%		—	%		—	%

	Year ended December 31,
ESPP	2019			2018			2017
Expected option term	1.8 years			1.1 years			N/A
Expected volatility		65	%		66	%	N/A
Risk free interest rate		2.2	%		2.4	%	N/A
Expected dividend yield		—	%		—	%	N/A

Summary of Stock-based Compensation Expense for the Equity Awards Issued to Employees and Non-Employees

Stock-based compensation expense for the equity awards issued by the Company to employees and non-employees for the periods presented below was as follows (in thousands):

	Year ended December 31,
	2019		2018		2017
Included in research and development	$	3,190	$	1,100	$	122
Included in general and administrative		3,104		1,220		149
Total stock-based compensation expense	$	6,294	$	2,320	$	271

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Temporary equity convertible preferred stock issuance costs	$ 225	$ 40
Issuance of common stock in initial public offering, issuance costs	$ 10,829

Operating Lease - Schedule of Future Minimum Payments Under Non-cancellable Operating Leases (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases [Abstract]
2020	$ 1,123
2021	1,173
2022	1,208
2023	1,244
2024	1,280
Thereafter	871
Total future minimum lease payments	6,899
Less imputed interest	1,326
Total operating lease liability	5,573
Less operating lease liability, current	724
Operating lease liability, non-current	$ 4,849

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Impairment losses of long-lived assets	$ 0	$ 0	$ 0
Operating lease right-of-use asset	2,510,000
Operating lease, liability	5,573,000
Recognition of deferred tax asset	0	0
ASU 2016-02
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use asset	2,800,000
Operating lease, liability	6,200,000
Deferred rent credit	3,400,000
Recognition of deferred tax asset	700,000
Recognition of deferred tax liabilities	700,000
Australian Research and Development Tax Incentive \| Australian Taxation Office
Summary Of Significant Accounting Policies [Line Items]
Tax incentive receivable, reductions to research and development expense	1,000,000	1,200,000	$ 500,000
Accounts Payable And Accrued Expenses
Summary Of Significant Accounting Policies [Line Items]
Accrued research and development expenses	$ 2,800,000	$ 3,600,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life	5 years

Stockholder's Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jul. 31, 2018	Oct. 31, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 20, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized			200,000	200,000
Common stock and paid-in capital, par value			$ 0.001	$ 0.001
Preferred stock, shares authorized			10,000	10,000
Preferred stock, par value			$ 0.001	$ 0.001
Stock-based compensation expenses			$ 6,294	$ 2,320	$ 271
Stock Restriction Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrestricted shares of common stock repurchased		1,914,893
Common stock repurchase rights lapsed		765,957
Common stock repurchase rights to be lapsed monthly thereafter till fully vested in October 2019				23,936
Stock-based compensation expenses				$ 400	$ 200
Initial Public Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares authorized						200,000,000
Common stock and paid-in capital, par value						$ 0.001
Preferred stock, shares authorized						10,000,000
Preferred stock, par value						$ 0.001
Proceeds from issuance initial public offering	$ 106,500
Initial Public Offering \| Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of common stock	6,900,000			6,900,000
Common stock price per share	$ 17.00

Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value assets transferred into level 3	$ 0	$ 0
Fair value assets transferred into level 3	0	0
Fair value assets transferred into level 3	0	0
Fair value assets transferred into level 3	$ 0	$ 0

Income Taxes - Schedule of Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Expected income tax benefit at federal statutory rate	$ (10,589)	$ (5,694)	$ (3,113)
State income tax benefit, net of federal benefit	(3,431)	(1,758)	(474)
Change in valuation allowance	16,064	7,724	2,112
R&D credit	(2,485)	(1,129)	(525)
Federal rate change	0	(52)	1,602
Australian tax incentive	307	362	176
Other	134	547	222
Provision for income taxes	$ 0	$ 0	$ 0

Investment Securities

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Investment Securities

3. INVESTMENT SECURITIES

Available-for-sale investment securities consisted of the following as of December 31, 2019 and 2018 (in thousands):

	As of December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Available-for-sale investment securities:
U.S. government and agency obligations	$	43,275	$	94	$	(1	)	$	43,368
Certificates of deposit		5,931		51		—			5,982
Commercial paper		17,645		—		—			17,645
Corporate debt securities		11,067		7		(3	)		11,071
Total	$	77,918	$	152	$	(4	)	$	78,066

	As of December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
Available-for-sale investment securities:
U.S. government and agency obligations	$	42,193	$	72	$	(1	)	$	42,264
Certificates of deposit		5,408		—		—			5,408
Commercial paper		47,686		—		—			47,686
Corporate debt securities		23,554		2		(12	)		23,544
Total	$	118,841	$	74	$	(13	)	$	118,902

All available-for-sale investment securities held at December 31, 2019 and 2018, had maturity dates of less than 24 months.

None of the Company’s available-for-sale investment securities were in a material unrealized loss position at December 31, 2019. The Company reviewed its investment holdings as of December 31, 2019 and determined that its unrealized losses were not considered to be other-than-temporary based upon (i) the financial strength of the issuing institution and (ii) the fact that no securities have been in an unrealized loss position for twelve months or more. As such, the Company has not recognized any impairment in its financial statements related to its available-for-sale investment securities.

Balance Sheet Details - Components of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid research and development costs	$ 2,478	$ 8
Australian tax incentive receivable	929	1,016
SBIR grant receivable	225	568
Interest receivable	224	340
Prepaid expenses and other assets	1,091	876
Total	$ 4,947	$ 2,808

Quarterly Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summary of Quarterly Financial Data

	Year Ended December 31, 2019
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Grant revenues	$	367		$	—		$	505		$	321
Research and development expenses	$	7,255		$	10,285		$	11,823		$	12,143
General and administrative expenses	$	3,156		$	3,060		$	3,911		$	3,392
Total operating expenses	$	10,411		$	13,345		$	15,734		$	15,535
Net loss	$	(9,016	)	$	(12,427	)	$	(14,430	)	$	(14,549	)
Net loss per share – basic and diluted	$	(0.37	)	$	(0.51	)	$	(0.60	)	$	(0.60	)

	Year Ended December 31, 2018
	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Grant revenues	$	442		$	657		$	548		$	781
Research and development expenses	$	4,720		$	5,222		$	6,886		$	7,651
General and administrative expenses	$	1,248		$	1,118		$	1,732		$	2,561
Total operating expenses	$	5,968		$	6,340		$	8,618		$	10,212
Net loss	$	(5,464	)	$	(5,568	)	$	(7,588	)	$	(8,495	)
Net loss per share – basic and diluted	$	(2.92	)	$	(2.41	)	$	(0.38	)	$	(0.35	)

Balance Sheet Details

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Details

5. BALANCE SHEET DETAILS

Prepaid expenses and other current assets consisted of the following (in thousands):

	December 31, 2019		December 31, 2018
Prepaid research and development costs	$	2,478	$	8
Australian tax incentive receivable		929		1,016
SBIR grant receivable		225		568
Interest receivable		224		340
Prepaid expenses and other assets		1,091		876
Total	$	4,947	$	2,808

Property and equipment, net consisted of the following (in thousands):

	December 31, 2019		December 31, 2018
Leasehold improvements	$	3,494	$	3,494
Lab equipment		1,468		915
Office equipment		567		523
Computers and software		41		41
Property and equipment at cost		5,570		4,973
Less accumulated depreciation and amortization		1,624		741
Total	$	3,946	$	4,232

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Jul. 31, 2018	Feb. 28, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of options exercised			$ 2.0	$ 2.4
Dividend yield			0.00%
Weighted-average fair value of stock options granted to employees per share			$ 16.35	$ 4.66	$ 0.85
Unrecognized stock-based compensation cost			$ 17.7
Weighted-average period of unrecognized stock-based compensation cost expected to be recognized over remaining period			2 years 9 months 18 days
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum percentage of eligible compensation to purchase common stock through payroll deductions	20.00%
Weighted-average fair value of stock options granted to employees per share			$ 10.59	$ 8.15
Unrecognized stock-based compensation cost			$ 0.4
Weighted-average period of unrecognized stock-based compensation cost expected to be recognized over remaining period			1 year 2 months 12 days
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration period	2028-07
Plan expiration term	10 years
Vesting period	4 years
Plan expiration date			Jan. 01, 2028
Annual increase in the number of shares available for issuance			5.00%
Remaining shares available for issuance			2,217,222
2015 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration term		10 years
Vesting period		4 years
Shares issued under early-exercise provisions subject to repurchase			33,048
Unvested stock liability			$ 49,000.0	$ 202,000.0
Common Stock \| ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration date	Jan. 01, 2028
Shares reserved for issuance, authorized			423,137
Additional shares available for future issuance	242,961
Common Stock \| 2018 Plan \| Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares available for future issuance						1,214,804