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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Registrant Name	ORIC PHARMACEUTICALS, INC.
Trading Symbol	ORIC
Entity Central Index Key	0001796280
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		29,903,039
Entity File Number	001-39269
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-1787157
Entity Address, Address Line One	240 E. Grand Ave
Entity Address, Address Line Two	2nd Floor
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	388-5600
Document Quarterly Report	true
Document Transition Report	false

BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 79,442	$ 89,159
Prepaid expenses and other current assets	788	840
Total current assets	80,230	89,999
Property and equipment, net	2,096	2,241
Deferred offering costs	2,413	1,343
Other assets	317	510
Total assets	85,056	94,093
Current liabilities:
Accounts payable	770	152
Accrued other liabilities	4,010	5,202
Total current liabilities	4,780	5,354
Deferred rent - long term	635	765
Total liabilities	5,415	6,119
Commitments and Contingencies (Note 9)
Stockholders' deficit:
Additional paid-in capital	3,145	2,606
Accumulated deficit	(101,562)	(92,690)
Total stockholders' deficit	(98,417)	(90,084)
Total liabilities and stockholders' deficit	85,056	94,093
Series A Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	15,431	15,431
Series B Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	53,906	53,906
Series C Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	53,172	53,172
Series D Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock	$ 55,549	$ 55,549

BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Convertible preferred stock, authorized	20,348,788
Convertible preferred stock, issued	19,278,606
Convertible preferred stock, outstanding	19,278,606
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	26,750,000	26,750,000
Common stock, shares, issued	1,997,655	1,984,222
Common stock, shares, outstanding	1,997,655	1,984,222
Series A Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	3,862,500	3,862,500
Convertible preferred stock, issued	3,862,500	3,862,500
Convertible preferred stock, outstanding	3,862,500	3,862,500
Aggregate liquidation preference	$ 15,450	$ 15,450
Series B Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	6,750,000	6,750,000
Convertible preferred stock, issued	6,749,999	6,749,999
Convertible preferred stock, outstanding	6,749,999	6,749,999
Aggregate liquidation preference	$ 54,000	$ 54,000
Series C Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	4,448,788	4,448,788
Convertible preferred stock, issued	4,448,780	4,448,780
Convertible preferred stock, outstanding	4,448,780	4,448,780
Aggregate liquidation preference	$ 53,385	$ 53,385
Series D Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	5,287,500	5,287,500
Convertible preferred stock, issued	4,217,327	4,217,327
Convertible preferred stock, outstanding	4,217,327	4,217,327
Aggregate liquidation preference	$ 55,669	$ 55,669

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
Research and development	$ 7,254	$ 5,212
General and administrative	1,925	1,134
Total operating expenses	9,179	6,346
Loss from operations	(9,179)	(6,346)
Other income:
Interest income, net	241	261
Other income	66	70
Total other income	307	331
Net loss and comprehensive loss	$ (8,872)	$ (6,015)
Net loss per share, basic and diluted	$ (4.46)	$ (3.32)
Weighted-average shares outstanding, basic and diluted	1,988,861	1,809,323

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Unaudited) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C Convertible Preferred Stock	Series D Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning Balance at Dec. 31, 2018		$ 15,431	$ 53,906	$ 37,929
Beginning Balance (in shares) at Dec. 31, 2018		3,862,500	6,749,999	3,177,271
Beginning Balance (in shares) at Dec. 31, 2018						1,802,134
Beginning Balance at Dec. 31, 2018	$ (64,426)						$ 1,381	$ (65,807)
Issuance of preferred stock, net of issuance costs				$ 15,243
Issuance of preferred stock, net of issuance costs (in shares)				1,271,509
Exercise of stock options	21						21
Exercise of stock options, shares						26,159
Stock-based compensation expense	191						191
Net loss	(6,015)							(6,015)
Ending Balance at Mar. 31, 2019		$ 15,431	$ 53,906	$ 53,172
Ending Balance (in shares) at Mar. 31, 2019		3,862,500	6,749,999	4,448,780
Ending Balance at Mar. 31, 2019	$ (70,229)						1,593	(71,822)
Ending Balance (in shares) at Mar. 31, 2019						1,828,293
Beginning Balance at Dec. 31, 2019		$ 15,431	$ 53,906	$ 53,172	$ 55,549
Beginning Balance (in shares) at Dec. 31, 2019		3,862,500	6,749,999	4,448,780	4,217,327
Beginning Balance (in shares) at Dec. 31, 2019	1,984,222					1,984,222
Beginning Balance at Dec. 31, 2019	$ (90,084)						2,606	(92,690)
Exercise of stock options	$ 12						12
Exercise of stock options, shares	13,433					13,433
Stock-based compensation expense	$ 527						527
Net loss	$ (8,872)							(8,872)
Ending Balance at Mar. 31, 2020		$ 15,431	$ 53,906	$ 53,172	$ 55,549
Ending Balance (in shares) at Mar. 31, 2020	19,278,606	3,862,500	6,749,999	4,448,780	4,217,327
Ending Balance at Mar. 31, 2020	$ (98,417)						$ 3,145	$ (101,562)
Ending Balance (in shares) at Mar. 31, 2020	1,997,655					1,997,655

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Series C Convertible Preferred Stock
Preferred stock, issuance costs	$ 15

STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (8,872)	$ (6,015)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	250	242
Share-based compensation expense	527	191
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	53	(289)
Accounts payable and accrued other liabilities	(237)	340
Net cash used in operating activities	(8,279)	(5,531)
Cash flows from investing activities:
Acquisitions of property and equipment	(4)	(100)
Proceeds from notes receivable	193
Net cash provided by (used in) investing activities	189	(100)
Cash flows from financing activities:
Proceeds from issuance of preferred stock		15,258
Issuance cost associated with preferred stock		(15)
Proceeds from stock option exercises	12	21
Payment of deferred offering costs	(1,639)
Net cash (used in) provided by financing activities	(1,627)	15,264
Net (decrease) increase in cash and cash equivalents	(9,717)	9,633
Cash and cash equivalents, beginning of period	89,159	42,636
Cash and cash equivalents, end of period	79,442	52,269
Supplemental disclosure of non-cash investing and financing activities:
Amounts accrued for property and equipment	101	$ 135
Amounts accrued for offering costs	$ 675

Description of the Business

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Description of the Business

1. Description of the Business

ORIC Pharmaceuticals, Inc. (ORIC or the Company) is a clinical-stage biopharmaceutical company dedicated to improving patients’ lives by Overcoming Resistance In Cancer. The Company was incorporated in Delaware in August 2014 and has offices in South San Francisco and San Diego, California.

Since inception, the Company has devoted its primary efforts to raising capital and research and development activities and has incurred significant operating losses and negative cash flows from operations. As of March 31, 2020, the Company had an accumulated deficit of $101.6 million and cash and cash equivalents of $79.4 million. From its inception through March 31, 2020, all of the Company’s financial support has been provided primarily from the sale of its convertible preferred stock.

As the Company continues its expansion, it may seek additional financing and/or strategic investments, however, there can be no assurance that any additional financing or strategic investments will be available to the Company on acceptable terms, if at all. If events or circumstances occur such that the Company does not obtain additional funding, it will most likely be required to reduce its plans and/or certain discretionary spending, which could have a material adverse effect on the Company’s ability to achieve its intended business objectives. The accompanying financial statements do not include any adjustments that might be necessary if it were unable to continue as a going concern. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date of the issuance of these unaudited interim financial statements.

Initial Public Offering and Related Transaction

On April 28, 2020, the Company completed an initial public offering (IPO) selling 8,625,000 shares of common stock, which includes the full exercise by the underwriters of their option to purchase up to 1,125,000 additional shares, at a price of $16.00 per share. Gross proceeds from the IPO, excluding underwriting discounts and commissions and other offering expenses, were $138.0 million. In addition, in connection with the IPO, all shares of convertible preferred stock outstanding at the time of the IPO converted into 19,278,606 shares of common stock. On April 21, 2020, the Company amended its certificate of incorporation to effect a one-for-four reverse stock split of its issued and outstanding common and convertible preferred stock. The accompanying financial statements and related notes give retroactive effect to the reverse stock split for all periods presented.

Basis of Presentation and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

2. Basis of Presentation and Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC) on Form 10-Q and Rule 10-01 of Regulation S-X. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP, have been omitted. The accompanying unaudited financial statements include all known adjustments necessary for a fair presentation of the results of interim periods as required by U.S. GAAP. These adjustments consist primarily of normal recurring accruals and estimates that impact the carrying value of assets and liabilities. Operating results for the three months ended March 31, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020, particularly in light of the novel coronavirus pandemic, or COVID-19, and its impact on domestic and global economies. To limit the spread of COVID-19, governments have taken various actions including the issuance of stay-at-home orders and physical distancing guidelines. Accordingly, businesses have adjusted, reduced or suspended operating activities. Beginning the week of March 16, 2020, the majority of the Company’s workforce began working from home. The effects of the stay-at-home orders and work-from-home policies may negatively impact productivity, disrupt the business and delay the development programs and regulatory timelines, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on the Company’s ability to conduct business in the ordinary course. As a result, research and development expenses and general and administrative expenses may vary significantly if there is an increased impact from COVID-19 on the costs and timing associated with the conduct of the clinical trials and other related business activities.

The accompanying unaudited financial statements should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2019, which are included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b)(4) on April 24, 2020 under the Securities Act of 1933, as amended (the Securities Act).

Use of Estimates

The preparation of the Company’s financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially from these estimates.

Concentration of Credit Risk

Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company is exposed to credit risk in the event of default by the financial institutions holding our cash and cash equivalents that are recorded on our balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits its exposure. The Company has not experienced any losses since inception.

The carrying amounts of cash and cash equivalents, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items.

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents primarily represent funds invested in readily available checking and money market funds.

Research and Development Expenses and Accrued Research and Development Expenses

The Company is required to estimate its expenses resulting from its obligations under contracts with vendors, consultants, contract research organizations (CRO), and contract manufacturing organizations (CMO) in connection with conducting research and development activities. The financial terms of these contracts vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts.

Research and development costs are expensed in the periods in which they are incurred. External costs consist primarily payments to outside CROs, CMOs, clinical trial sites and central laboratories in connection with the Company’s discovery and preclinical activities, process development, clinical manufacturing and clinical development activities. External expenses are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers or its estimate of the level of service that has been performed at each reporting date. The Company allocates external costs by the stage of program, clinical or preclinical. Internal costs consist primary of employee-related costs, laboratory supplies, facilities, depreciation and costs related to compliance with regulatory requirements. The Company does not allocate internal costs by stage of program because these costs are deployed across multiple programs and, as such, are not separately classified. Research and development expenses amounted to $7.3 million and $5.2 million during the three months ended March 31, 2020 and 2019, respectively.

Deferred Offering Costs

The Company capitalizes costs that are directly associated with in-process equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the IPO. Should an in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statement of operations and comprehensive loss. The Company recorded $2.4 million and $1.3 million of deferred offering costs as of March 31, 2020 and December 31, 2019, respectively.

Net Loss Per Share

Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts).

	Three Months Ended March 31,
	2020			2019
Numerator
Net loss	$	(8,872	)	$	(6,015	)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic and diluted		1,988,861			1,809,323
Net loss per share, basic and diluted	$	(4.46	)	$	(3.32	)

The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive:

	Three Months Ended March 31,
	2020		2019
Options to purchase common stock		2,658,953		1,974,884
Convertible preferred stock		19,278,606		15,061,279
Total		21,937,559		17,036,163

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) under its accounting standard codifications (ASC) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below.

New Accounting Pronouncements Not Yet Adopted

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASC 842), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. ASC 842 provides a lessee with an option to not account for leases with a term of 12 month or less as leases in the scope of the new standard. ASC 842 supersedes the previous leases standard, ASC 840 Leases. For public business entities, this ASU is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years, and should be applied through a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. For all other entities, this ASU is effective for fiscal years beginning after December 15, 2020 and interim periods within fiscal years beginning after December 15, 2021. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU No. 2016-02 is effective for the Company for the year ended December 31, 2021, and all interim periods within. In July 2018, the FASB issued supplemental adoption guidance and clarification to ASC 842 within ASU No. 2018-10, Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements. ASU No. 2018-11 provides another transition method in addition to the existing modified retrospective transition method by allowing entities to initially apply the new leasing standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of accumulated deficit in the period of adoption. The Company is currently evaluating the impact the adoption of these ASUs will have on financial statements and related disclosures. The Company expects to recognize a right-of-use asset and corresponding lease liability for its real estate operating leases upon adoption. See Note 9 for more information related to the Company’s lease obligations, which are presented on an undiscounted basis therein.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) (ASC 326): Measurement of Credit Losses on Financial Instruments, which introduced the expected credit losses methodology for the measurement of credit losses on financial assets measured at amortized cost basis, replacing the previous incurred loss methodology. The amendments in Update 2016-13 added Topic 326, Financial Instruments—Credit Losses, and made several consequential amendments to the Codification. Update 2016-13 also modified the accounting for available-for-sale debt securities, which must be individually assessed for credit losses when fair value is less than the amortized cost basis, in accordance with Subtopic 326-30, Financial Instruments— Credit Losses—Available-for-Sale Debt Securities. Effective for fiscal years beginning after December 15, 2019. Since the Company has elected to use the extended transition period under the JOBS Act available to emerging growth companies (EGCs), the ASU is effective for the Company for fiscal years beginning after December 15, 2020. The Company expects to adopt the new standard in the first quarter of 2021. The Company is currently evaluating the impact the adoption of these ASUs will have on its financial statements and related disclosures.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12), which eliminates certain exceptions to the general principles in Topic 740 and simplifies other areas of the existing guidance. For non-EGCs, ASU 2019-12 is effective for fiscal years beginning after December 15, 2020. For EGCs, the standard is effective for fiscal years beginning after December 15, 2021. The Company expects to adopt the new standard in the first quarter of 2022. The Company is currently evaluating the impact the adoption of ASU 2019-12 will have on its financial statements and related disclosures.

Property and Equipment, Net

3 Months Ended

Mar. 31, 2020

Property Plant And Equipment [Abstract]

Property and Equipment, Net

3. Property and Equipment, net

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

	March 31, 2020			December 31, 2019
Lab equipment	$	3,855		$	3,748
Leasehold improvements		1,710			1,710
Computer hardware and software		156			158
Furniture and fixtures		140			140
Total property and equipment, gross		5,861			5,756
Less accumulated depreciation		(3,765	)		(3,515	)
Total property and equipment, net	$	2,096		$	2,241

Accrued Other Liabilities

3 Months Ended

Mar. 31, 2020

Accrued Liabilities Current [Abstract]

Accrued Other Liabilities

4. Accrued Other Liabilities

Accrued other liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
Accrued compensation	$	1,019	$	1,883
Accrued deferred financing costs		675		1,244
Deferred rent - short-term		509		495
Accrued clinical development costs		877		484
Accrued manufacturing costs		369		479
Accrued professional fees		157		175
Accrued legal fees		93		163
Share purchase liability		36		39
Other accruals		275		240
Total accrued other liabilities	$	4,010	$	5,202

Fair Value Measurements

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. 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 nonrecurring 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; and

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

At March 31, 2020 and December 31, 2019, the carrying amounts of the Company’s financial instruments, which include cash and cash equivalents, accounts payable and accrued expenses, approximate fair value because of their short maturities. Included in cash and cash equivalents at March 31, 2020 and December 31, 2019 are money market funds with a carrying value and fair value of $79.4 million and $88.1 million, respectively, based upon a Level 1 fair value assessment.

As of March 31, 2020 and December 31, 2019, the Company did not hold any Level 2 or Level 3 financial assets.

- 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

Convertible Preferred Stock

3 Months Ended

Mar. 31, 2020

Temporary Equity Disclosure [Abstract]

Convertible Preferred Stock

6. Convertible Preferred Stock

Issued and outstanding convertible preferred stock and its principal terms as of March 31, 2020 and December 31, 2019 were as follows (in thousands, except share and per share amounts):

	Shares Authorized		Shares Issued and Outstanding		Issue Period	Issue Price per Share		Dividend Annual Rate per Share		Aggregate Liquidation Preference
Series A		3,862,500		3,862,500	2014- 2015	$	4.00	$	0.32	$	15,450
Series B		6,750,000		6,749,999	2015 - 2016	$	8.00	$	0.64	$	54,000
Series C		4,448,788		4,448,780	2018 - 2019	$	12.00	$	0.96	$	53,385
Series D		5,287,500		4,217,327	2019	$	13.20	$	1.056	$	55,669
Total		20,348,788		19,278,606

Holders of the convertible preferred stock, in preference to any distributions to the holders of common stock, shall be entitled to receive dividends at an annual rate. Such dividends shall be payable only when and if declared by the Company’s Board of Directors and shall not be cumulative. No such dividends have been declared or paid through March 31, 2020.

Following the closing of the IPO, all outstanding shares of the convertible preferred stock converted into 19,278,606 shares of common stock and the related carrying value was reclassified to common stock and additional paid-in capital. There were no shares of convertible preferred stock outstanding as of the closing of the IPO on April 28, 2020.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

2014 Incentive Plan

In October 2014, the Company approved the 2014 Equity Incentive Plan (the 2014 Plan). The 2014 Plan provides for the issuance of 16,035,400 shares of common stock to officers, directors, employees, non-employee directors, and consultants of the Company. The 2014 Plan allows for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock unit awards and other stock awards. As of March 31, 2020 and December 31, 2019, there were 214,751 and 203,696, respectively, options remaining available for future issuance under the 2014 Plan.

The options that were granted from the 2014 Plan are exercisable at various dates as determined upon grant and will expire no more than ten years from their date of grant. Stock options generally vest over a four-year term. The exercise price of each option shall be determined by the Company’s Board of Directors, although generally options have an exercise price equal to the fair market value of the Company’s stock on the date of the option grant. In the case of incentive stock options, the exercise price shall not be less than 100% of the fair market value of the Company’s common stock at the time the option is granted. For holders of more than 10% of the Company’s total combined voting power of all classes of stock, incentive stock options may not be granted at less than 110% of the fair market value of the Company’s common stock at the date of grant and for a term not to exceed five years.

The following table summarizes the option activity:

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		2,683,441		$	3.75		9.0
Granted		-			-		-
Exercised		(13,433	)		1.24		7.7
Forfeited and cancelled		(11,055	)		1.60		8.5
Outstanding at March 31, 2020		2,658,953		$	3.76		8.8	$	29,929
Exercisable at March 31, 2020		820,963		$	2.40		8.4	$	10,349

Certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying balance sheets and will be transferred into common stock and additional paid-in capital as the shares vest. As of March 31, 2020 and December 31, 2019, there were 26,056 shares and 29,579 shares subject to repurchase by the Company, respectively. As of March 31, 2020 and December 31, 2019, the Company recorded less than $0.1 million of liabilities associated with shares issued with repurchase rights.

Fair Value of Common Stock

Prior to the Company’s IPO, the fair value of the Company’s common stock underlying the stock options was determined by the Board of Directors with assistance from management and, in part, on input from an independent third-party valuation firm. The Board of Directors determines the fair value of common stock by considering a number of objective and subjective factors, including valuations of comparable companies, sales of convertible preferred stock, operating and financial performance, the lack of liquidity of the Company’s common stock and the general and industry-specific economic outlook. Subsequent to the Company’s IPO, the fair value of the Company’s common stock is determined based on its closing market price.

The fair value of stock options was estimated using the Black-Scholes Merton option pricing model with the following assumptions:

	Three Months Ended March 31,
	2020	2019
Stock price	-	$	1.60
Risk-free interest rate	-	2.58%
Expected volatility	-	100.5%
Expected term (in years)	-		6.1
Expected dividend yield	-	0%

The Company recognized stock-based compensation expense of $0.5 million and $0.2 million for the three months ended March 31, 2020 and 2019, respectively. The total unrecognized compensation expense related to outstanding unvested stock-based awards as of March 31, 2020 and 2019 was $6.3 million and $2.4 million, respectively, which is expected to be recognized over a weighted-average remaining service period for 3.2 years for 2019 and 2020.

Income Taxes

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

8. Income Taxes

No income tax expense or benefit was recorded for the three months ended March 31, 2020 and 2019, due to the full valuation allowance on the Company’s net deferred tax assets. The full valuation is based on the Company’s assessment that it is more likely than not that the benefits of those deferred tax assets will not be realized.

Commitment and Contingencies

3 Months Ended

Mar. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Operating Leases

Rent expense is recorded on a straight-line basis over the term of the respective lease. Total rent expense for South San Francisco and San Diego locations was $0.3 million for the three months ended March 31, 2020 and 2019.

Future minimum lease payments under non-cancelable operating leases as of March 31, 2020 were as follows (in thousands):

	Operating Leases
2020 remaining nine months	$	1,427
2021		1,871
2022		686
Total minimum lease payments	$	3,984

Litigation

From time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no threatened litigation or litigation pending that could have, individually or in the aggregate, a material adverse effect on the Company’s financial position, results of operations or cash flows.

Employee Benefit Plan

3 Months Ended

Mar. 31, 2020

Postemployment Benefits [Abstract]

Employee Benefit Plan

10. Employee Benefit Plan

The Company has a defined-contribution 401(k) plan for employees. Employees are eligible to participate in the plan beginning on the first day of the month following date of hire. Under the terms of the plan, employees may make voluntary contributions as a percentage of compensation and the Company has the option to make a discretionary match as determined by the Company’s Board of Directors, within prescribed limits. There were no employer contributions to the plan during the period ended March 31, 2020 or March 31, 2019.

Subsequent Events

3 Months Ended

Mar. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

11. Subsequent Events

On April 21, 2020, the Company amended its certificate of incorporation to effect a one-for-four reverse stock split of its issued and outstanding capital stock. The accompanying financial statements and related notes give retroactive effect to the reverse stock split for all periods presented.

On April 22, 2020, the 2014 Plan terminated, and the Company will not grant any additional awards under the 2014 Plan. On April 22, 2020, the Company’s 2020 Equity Incentive Plan (the 2020 Plan) and the Company’s 2020 Employee Stock Purchase Plan (the 2020 ESPP) became effective. The 2020 Plan authorizes 2,656,500 shares plus the number of shares (not to exceed 3,000,000 shares) that remain unissued under the 2014 Plan as of the effective date of the 2020 Plan and the shares subject to or issued pursuant to awards granted under the 2014 Plan that subsequently expire or otherwise terminate without having been exercised or issued in full, are tendered or withheld by the Company for payment of an exercise price or for tax withholding obligations, or are forfeited to or repurchased by the Company due to failure to vest. The 2020 Plan also provides for certain automatic increases in the number of shares of common stock reserved for issuance under the 2020 Plan. Under the 2020 ESPP, 290,000 shares of common stock are reserved for future issuance. The 2020 ESPP also provides for certain automatic increases in the number of shares of common stock reserved for future issuance under the 2020 ESPP.

On April 28, 2020, the Company completed an IPO selling 8,625,000 shares of common stock, which includes the full exercise by the underwriters of their option to purchase up to 1,125,000 additional shares, at a price of $16.00 per share. Gross proceeds from the IPO, excluding underwriting discounts and commissions and other offering expenses, were $138.0 million. In addition, in connection with the IPO, all shares of convertible preferred stock outstanding at the time of the IPO converted into 19,278,606 shares of common stock.

Basis of Presentation and Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Concentration of Credit Risk

Cash and Cash Equivalents

Research and Development Expenses and Accrued Research and Development Expenses

Deferred Offering Costs

Net Loss Per Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts).

	Three Months Ended March 31,
	2020			2019
Numerator
Net loss	$	(8,872	)	$	(6,015	)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic and diluted		1,988,861			1,809,323
Net loss per share, basic and diluted	$	(4.46	)	$	(3.32	)

	Three Months Ended March 31,
	2020		2019
Options to purchase common stock		2,658,953		1,974,884
Convertible preferred stock		19,278,606		15,061,279
Total		21,937,559		17,036,163

Recent Accounting Pronouncements

New Accounting Pronouncements Not Yet Adopted

Basis of Presentation and Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Summary of Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts).

	Three Months Ended March 31,
	2020			2019
Numerator
Net loss	$	(8,872	)	$	(6,015	)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic and diluted		1,988,861			1,809,323
Net loss per share, basic and diluted	$	(4.46	)	$	(3.32	)

Summary of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share

	Three Months Ended March 31,
	2020		2019
Options to purchase common stock		2,658,953		1,974,884
Convertible preferred stock		19,278,606		15,061,279
Total		21,937,559		17,036,163

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2020

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

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

	March 31, 2020			December 31, 2019
Lab equipment	$	3,855		$	3,748
Leasehold improvements		1,710			1,710
Computer hardware and software		156			158
Furniture and fixtures		140			140
Total property and equipment, gross		5,861			5,756
Less accumulated depreciation		(3,765	)		(3,515	)
Total property and equipment, net	$	2,096		$	2,241

Accrued Other Liabilities (Tables)

3 Months Ended

Mar. 31, 2020

Accrued Liabilities Current [Abstract]

Schedule of Accrued Other Liabilities

Accrued other liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
Accrued compensation	$	1,019	$	1,883
Accrued deferred financing costs		675		1,244
Deferred rent - short-term		509		495
Accrued clinical development costs		877		484
Accrued manufacturing costs		369		479
Accrued professional fees		157		175
Accrued legal fees		93		163
Share purchase liability		36		39
Other accruals		275		240
Total accrued other liabilities	$	4,010	$	5,202

Convertible Preferred Stock (Tables)

3 Months Ended

Mar. 31, 2020

Temporary Equity Disclosure [Abstract]

Schedule of Issued and Outstanding Convertible Preferred Stock and its Principal Terms

Issued and outstanding convertible preferred stock and its principal terms as of March 31, 2020 and December 31, 2019 were as follows (in thousands, except share and per share amounts):

	Shares Authorized		Shares Issued and Outstanding		Issue Period	Issue Price per Share		Dividend Annual Rate per Share		Aggregate Liquidation Preference
Series A		3,862,500		3,862,500	2014- 2015	$	4.00	$	0.32	$	15,450
Series B		6,750,000		6,749,999	2015 - 2016	$	8.00	$	0.64	$	54,000
Series C		4,448,788		4,448,780	2018 - 2019	$	12.00	$	0.96	$	53,385
Series D		5,287,500		4,217,327	2019	$	13.20	$	1.056	$	55,669
Total		20,348,788		19,278,606

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Option Activity

The following table summarizes the option activity:

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		2,683,441		$	3.75		9.0
Granted		-			-		-
Exercised		(13,433	)		1.24		7.7
Forfeited and cancelled		(11,055	)		1.60		8.5
Outstanding at March 31, 2020		2,658,953		$	3.76		8.8	$	29,929
Exercisable at March 31, 2020		820,963		$	2.40		8.4	$	10,349

Summary of Fair Value of Stock Options Estimated Using Black-Scholes Merton Option Pricing Model Assumptions

The fair value of stock options was estimated using the Black-Scholes Merton option pricing model with the following assumptions:

	Three Months Ended March 31,
	2020	2019
Stock price	-	$	1.60
Risk-free interest rate	-	2.58%
Expected volatility	-	100.5%
Expected term (in years)	-		6.1
Expected dividend yield	-	0%

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Summary of Future Minimum Lease Payments under Non-cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases as of March 31, 2020 were as follows (in thousands):

	Operating Leases
2020 remaining nine months	$	1,427
2021		1,871
2022		686
Total minimum lease payments	$	3,984

Description of the Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	Apr. 28, 2020 USD ($) $ / shares shares	Apr. 21, 2020	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 $ / shares
Description Of Business [Line Items]
Accumulated deficit \| $			$ 101,562	$ 92,690
Cash and cash equivalents \| $			$ 79,442	$ 89,159
Price per share of common stock \| $ / shares					$ 1.60
Subsequent Event \| Common Stock
Description Of Business [Line Items]
Gross proceeds from IPO excluding underwriting discounts and commissions and other offering expenses \| $	$ 138,000
Reverse stock split		one-for-four
Reverse stock split ratio		0.25
Subsequent Event \| Common Stock \| IPO
Description Of Business [Line Items]
Shares of common stock issued \| shares	8,625,000
Price per share of common stock \| $ / shares	$ 16.00
Convertible preferred stock outstanding converted into shares of common stock \| shares	19,278,606
Subsequent Event \| Common Stock \| Option to Purchase Additional Shares \| Maximum
Description Of Business [Line Items]
Shares of common stock issued \| shares	1,125,000

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accounting Policies [Abstract]
Research and development expenses	$ 7,254	$ 5,212
Deferred offering costs	$ 2,400		$ 1,300

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator
Net loss	$ (8,872)	$ (6,015)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic and diluted	1,988,861	1,809,323
Net loss per share, basic and diluted	$ (4.46)	$ (3.32)

- Definition

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

+ References + Details

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share	21,937,559	17,036,163
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share	2,658,953	1,974,884
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share	19,278,606	15,061,279

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 5,861	$ 5,756
Less accumulated depreciation	(3,765)	(3,515)
Total property and equipment, net	2,096	2,241
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	3,855	3,748
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,710	1,710
Computer Hardware and Software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	156	158
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 140	$ 140

Accrued Other Liabilities - Schedule of Accrued Other Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Accrued compensation	$ 1,019	$ 1,883
Accrued deferred financing costs	675	1,244
Deferred rent - short-term	509	495
Accrued clinical development costs	877	484
Accrued manufacturing costs	369	479
Accrued professional fees	157	175
Accrued legal fees	93	163
Share purchase liability	36	39
Other accruals	275	240
Total accrued other liabilities	$ 4,010	$ 5,202

Fair Value Measurements - Additional Information (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents, at carrying value	$ 79,442,000	$ 89,159,000
Level 1 \| Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents, at carrying value	79,400,000	88,100,000
Cash and cash equivalents, fair value	79,400,000	88,100,000
Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	0	0
Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 0	$ 0

Convertible Preferred Stock - Schedule of Issued and Outstanding Convertible Preferred Stock and its Principal Terms (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Shares Authorized	20,348,788
Shares Issued	19,278,606
Shares Outstanding	19,278,606
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	3,862,500	3,862,500
Shares Issued	3,862,500	3,862,500
Shares Outstanding	3,862,500	3,862,500	3,862,500	3,862,500
Issue Price per Share	$ 4.00
Dividend Annual Rate per Share	$ 0.32
Aggregate Liquidation Preference	$ 15,450	$ 15,450
Series A Convertible Preferred Stock \| Minimum
Temporary Equity [Line Items]
Issue Period	2014
Series A Convertible Preferred Stock \| Maximum
Temporary Equity [Line Items]
Issue Period	2015
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	6,750,000	6,750,000
Shares Issued	6,749,999	6,749,999
Shares Outstanding	6,749,999	6,749,999	6,749,999	6,749,999
Issue Price per Share	$ 8.00
Dividend Annual Rate per Share	$ 0.64
Aggregate Liquidation Preference	$ 54,000	$ 54,000
Series B Convertible Preferred Stock \| Minimum
Temporary Equity [Line Items]
Issue Period	2015
Series B Convertible Preferred Stock \| Maximum
Temporary Equity [Line Items]
Issue Period	2016
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	4,448,788	4,448,788
Shares Issued	4,448,780	4,448,780
Shares Outstanding	4,448,780	4,448,780	4,448,780	3,177,271
Issue Price per Share	$ 12.00
Dividend Annual Rate per Share	$ 0.96
Aggregate Liquidation Preference	$ 53,385	$ 53,385
Series C Convertible Preferred Stock \| Minimum
Temporary Equity [Line Items]
Issue Period	2018
Series C Convertible Preferred Stock \| Maximum
Temporary Equity [Line Items]
Issue Period	2019
Series D Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	5,287,500	5,287,500
Shares Issued	4,217,327	4,217,327
Shares Outstanding	4,217,327	4,217,327
Issue Period	2019
Issue Price per Share	$ 13.20
Dividend Annual Rate per Share	$ 1.056
Aggregate Liquidation Preference	$ 55,669	$ 55,669

Convertible Preferred Stock - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Apr. 28, 2020
Temporary Equity [Line Items]
Dividends declared	$ 0
Dividends paid	$ 0
Convertible preferred stock, outstanding	19,278,606
Subsequent Event
Temporary Equity [Line Items]
Outstanding shares of convertible preferred stock converted into shares of common stock		19,278,606
Convertible preferred stock, outstanding		0

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Oct. 31, 2014	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares subject to repurchase		26,056		29,579
Stock-based compensation expense		$ 500,000	$ 200,000
Total unrecognized compensation expense related to outstanding unvested stock-based awards		$ 6,300,000	$ 2,400,000
Total unrecognized compensation expense related to outstanding unvested stock-based awards expected to be recognized over weighted-average remaining service period		3 years 2 months 12 days	3 years 2 months 12 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Liabilities with shares issued with repurchase rights		$ 100,000		$ 100,000
2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized for issuance	16,035,400
Number of shares available for future issuance		214,751		203,696
2014 Plan \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
2014 Plan \| Stock Options \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period	10 years
2014 Plan \| Incentive Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price as a percentage of fair market value	100.00%
Minimum percentage required for holders of combined voting power to be eligible for incentive stock options	10.00%
Percentage of options may not be granted at less than fair market value of the common stock at the date of grant	110.00%
Maximum term of options may not be granted at less than fair market value of the common stock at the date of grant	5 years

Stock-Based Compensation - Summary of Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, Beginning Balance	2,683,441
Options, Exercised	(13,433)
Options, Forfeited and cancelled	(11,055)
Options outstanding, Ending Balance	2,658,953	2,683,441
Options, Exercisable	820,963
Weighted Average Exercise Price, Options outstanding Beginning Balance	$ 3.75
Weighted Average Exercise Price, Exercised	1.24
Weighted Average Exercise Price, Forfeited and Cancelled	1.60
Weighted Average Exercise Price, Options outstanding Ending Balance	3.76	$ 3.75
Weighted Average Exercise Price, Exercisable	$ 2.40
Weighted Average Remaining Contractual Term (in years), Options outstanding	8 years 9 months 18 days	9 years
Weighted Average Remaining Contractual Term (in years), Exercised	7 years 8 months 12 days
Weighted Average Remaining Contractual Term (in years), Forfeited and cancelled	8 years 6 months
Weighted Average Remaining Contractual Term (in years), Exercisable	8 years 4 months 24 days
Aggregate Intrinsic Value, Options outstanding	$ 29,929
Aggregate Intrinsic Value, Exercisable	$ 10,349

Stock-Based Compensation - Summary of Fair Value of Stock Options Estimated Using Black-Scholes Merton Option Pricing Model Assumptions (Details)	3 Months Ended
	Mar. 31, 2019 $ / shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock price	$ 1.60
Risk-free interest rate	2.58%
Expected volatility	100.50%
Expected term (in years)	6 years 1 month 6 days
Expected dividend yield	0.00%

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense or benefit	$ 0	$ 0

Commitment and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
South San Francisco and San Diego Locations
Loss Contingencies [Line Items]
Total rent expense	$ 0.3	$ 0.3

Commitment and Contingencies - Summary of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020 remaining nine months	$ 1,427
2021	1,871
2022	686
Total minimum lease payments	$ 3,984

Employee Benefit Plan - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Postemployment Benefits [Abstract]
Employer contributions to the plan during period	$ 0	$ 0

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Millions	Apr. 28, 2020 USD ($) $ / shares shares	Apr. 21, 2020 shares	Mar. 31, 2019 $ / shares
Subsequent Event [Line Items]
Price per share of common stock \| $ / shares			$ 1.60
Subsequent Event \| 2020 ESPP
Subsequent Event [Line Items]
Number of shares authorized		2,656,500
Number of shares available for future issuance		290,000
Subsequent Event \| 2020 ESPP \| Maximum
Subsequent Event [Line Items]
Number of shares authorized		3,000,000
Subsequent Event \| Common Stock
Subsequent Event [Line Items]
Reverse stock split		one-for-four
Reverse stock split ratio		0.25
Gross proceeds from IPO excluding underwriting discounts and commissions and other offering expenses \| $	$ 138.0
Subsequent Event \| Common Stock \| IPO
Subsequent Event [Line Items]
Shares of common stock issued	8,625,000
Price per share of common stock \| $ / shares	$ 16.00
Convertible preferred stock outstanding converted into shares of common stock	19,278,606
Subsequent Event \| Common Stock \| Maximum \| Option to Purchase Additional Shares
Subsequent Event [Line Items]
Shares of common stock issued	1,125,000