RAPT Therapeutics (RAPT) 10-Q 16 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 10, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Trading Symbol	RAPT
Entity Registrant Name	RAPT Therapeutics, Inc.
Entity Central Index Key	0001673772
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	No
Entity Shell Company	false
Entity File Number	001-38997
Entity Tax Identification Number	47-3313701
Entity Address, Address Line One	561 Eccles Avenue
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	489-9000
Entity Common Stock, Shares Outstanding		24,555,259
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 20,229	$ 77,383
Marketable securities	102,557
Prepaid expenses and other current assets	2,722	3,123
Total current assets	125,508	80,506
Property and equipment, net	3,073	3,707
Other assets	389	389
Total assets	128,970	84,602
Current liabilities:
Accounts payable	4,405	1,143
Accrued expenses	5,669	3,642
Deferred revenue, current	5,128	4,000
Other current liabilities	389	471
Total current liabilities	15,591	9,256
Deferred rent, net of current portion	2,200	2,225
Deferred revenue, non-current	1,132
Commitments
Stockholders' equity:
Preferred stock
Common stock	2	2
Additional paid-in capital	312,078	235,049
Accumulated other comprehensive income	74	20
Accumulated deficit	(202,107)	(161,950)
Total stockholders' equity	110,047	73,121
Total liabilities and stockholders' equity	$ 128,970	$ 84,602

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 1,528,000		$ 3,740,000
Operating expenses:
Research and development	12,912,000	$ 8,582,000	34,581,000	$ 24,720,000
General and administrative	3,197,000	1,733,000	9,288,000	6,094,000
Total operating expenses	16,109,000	10,315,000	43,869,000	30,814,000
Loss from operations	(14,581,000)	(10,315,000)	(40,129,000)	(30,814,000)
Other income, net	237,000	344,000	763,000	1,033,000
Net loss before taxes	(14,344,000)	(9,971,000)	(39,366,000)	(29,781,000)
Provision for income taxes	287,000	0	791,000	0
Net loss	(14,631,000)	(9,971,000)	(40,157,000)	(29,781,000)
Other comprehensive income (loss):
Foreign currency translation adjustment	(70,000)	15,000	(65,000)	17,000
Unrealized gain (loss) on marketable securities	(33,000)		119,000
Total comprehensive loss	$ (14,734,000)	$ (9,956,000)	$ (40,103,000)	$ (29,764,000)
Net loss per share, basic and diluted	$ (0.60)	$ (12.41)	$ (1.67)	$ (40.15)
Weighted average number of shares used in computing net loss per share, basic and diluted	24,449,115	803,229	23,989,926	741,711

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENT OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Series C-2 Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Related Party Promissory Notes for the Purchase of Common Stock	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2018		$ 161,111
Beginning balance, shares at Dec. 31, 2018		98,491,880
Beginning balance at Dec. 31, 2018	$ (97,113)			$ 1	$ 22,441	$ (598)	$ (118,953)	$ (4)
Beginning balance, shares at Dec. 31, 2018				878,413
Issuance of convertible preferred stock, net of issuance cost			$ 6,947
Issuance of convertible preferred stock, net of issuance cost, shares			3,039,908
Issuance of common stock upon exercise of stock options, net of repurchase	66				66
Issuance of common stock upon exercise of stock options, net of repurchase, shares				3,685
Repurchase of common stock from related party	109					109
Repurchase of common stock from related party, shares				(53,649)
Interest on promissory notes from related parties for purchase of common stock	(2)					(2)
Stock-based compensation	377				377
Net loss	(9,188)						(9,188)
Ending balance at Mar. 31, 2019		$ 168,058
Ending balance, shares at Mar. 31, 2019		101,531,788
Ending balance at Mar. 31, 2019	(105,751)			$ 1	22,884	(491)	(128,141)	(4)
Ending balance, shares at Mar. 31, 2019				828,449
Beginning balance at Dec. 31, 2018		$ 161,111
Beginning balance, shares at Dec. 31, 2018		98,491,880
Beginning balance at Dec. 31, 2018	(97,113)			$ 1	22,441	(598)	(118,953)	(4)
Beginning balance, shares at Dec. 31, 2018				878,413
Foreign currency translation adjustment	17
Net loss	(29,781)
Ending balance at Sep. 30, 2019		$ 175,490
Ending balance, shares at Sep. 30, 2019		104,803,325
Ending balance at Sep. 30, 2019	(124,797)			$ 1	23,923		(148,734)	13
Ending balance, shares at Sep. 30, 2019				935,040
Beginning balance at Mar. 31, 2019		$ 168,058
Beginning balance, shares at Mar. 31, 2019		101,531,788
Beginning balance at Mar. 31, 2019	(105,751)			$ 1	22,884	(491)	(128,141)	(4)
Beginning balance, shares at Mar. 31, 2019				828,449
Issuance of convertible preferred stock, net of issuance cost			$ 7,451
Issuance of convertible preferred stock, net of issuance cost, shares			3,271,537
Issuance of common stock upon exercise of stock options, net of repurchase	34				34
Issuance of common stock upon exercise of stock options, net of repurchase, shares				13,996
Repurchase of common stock from related party	65					65
Repurchase of common stock from related party, shares				29,686
Paydown of promissory notes from related parties for purchase of common stock	73					73
Forgiveness of promissory notes from related parties for purchase of common stock	353					$ 353
Stock-based compensation	347				347
Foreign currency translation adjustment	2							2
Net loss	(10,622)						(10,622)
Ending balance at Jun. 30, 2019		$ 175,509
Ending balance, shares at Jun. 30, 2019		104,803,325
Ending balance at Jun. 30, 2019	(115,499)			$ 1	23,265		(138,763)	(2)
Ending balance, shares at Jun. 30, 2019				812,759
Issuance cost related to convertible preferred stock			$ (19)
Issuance of common stock upon exercise of stock options, net of repurchase	227				227
Issuance of common stock upon exercise of stock options, net of repurchase, shares				122,281
Stock-based compensation	431				431
Foreign currency translation adjustment	15							15
Net loss	(9,971)						(9,971)
Ending balance at Sep. 30, 2019		$ 175,490
Ending balance, shares at Sep. 30, 2019		104,803,325
Ending balance at Sep. 30, 2019	(124,797)			$ 1	23,923		(148,734)	13
Ending balance, shares at Sep. 30, 2019				935,040
Beginning balance at Dec. 31, 2019	$ 73,121			$ 2	235,049		(161,950)	20
Beginning balance, shares at Dec. 31, 2019	21,833,037			21,833,037
Issuance of common stock, net of issuance costs	$ 69,842				69,842
Issuance of common stock, net of issuance costs, shares				2,500,000
Issuance of common stock upon exercise of stock options, net of repurchase	30				30
Issuance of common stock upon exercise of stock options, net of repurchase, shares				970
Stock-based compensation	2,088				2,088
Foreign currency translation adjustment	204							204
Unrealized gain (loss) on marketable securities	(217)							(217)
Net loss	(13,139)						(13,139)
Ending balance at Mar. 31, 2020	131,929			$ 2	307,009		(175,089)	7
Ending balance, shares at Mar. 31, 2020				24,334,007
Beginning balance at Dec. 31, 2019	$ 73,121			$ 2	235,049		(161,950)	20
Beginning balance, shares at Dec. 31, 2019	21,833,037			21,833,037
Foreign currency translation adjustment	$ (65)
Unrealized gain (loss) on marketable securities	119
Net loss	(40,157)
Ending balance at Sep. 30, 2020	$ 110,047			$ 2	312,078		(202,107)	74
Ending balance, shares at Sep. 30, 2020	24,495,525			24,495,525
Beginning balance at Mar. 31, 2020	$ 131,929			$ 2	307,009		(175,089)	7
Beginning balance, shares at Mar. 31, 2020				24,334,007
Issuance of common stock upon exercise of stock options, net of repurchase	453				453
Issuance of common stock upon exercise of stock options, net of repurchase, shares				68,485
Stock-based compensation	2,035				2,035
Issuance of common stock under the employee stock purchase plan	411				411
Issuance of common stock under the employee stock purchase plan, shares				40,350
Foreign currency translation adjustment	(199)							(199)
Unrealized gain (loss) on marketable securities	369							369
Net loss	(12,387)						(12,387)
Ending balance at Jun. 30, 2020	122,611			$ 2	309,908		(187,476)	177
Ending balance, shares at Jun. 30, 2020				24,442,842
Issuance of common stock upon exercise of stock options, net of repurchase	165				165
Issuance of common stock upon exercise of stock options, net of repurchase, shares				52,683
Stock-based compensation	2,005				2,005
Foreign currency translation adjustment	(70)							(70)
Unrealized gain (loss) on marketable securities	(33)							(33)
Net loss	(14,631)						(14,631)
Ending balance at Sep. 30, 2020	$ 110,047			$ 2	$ 312,078		$ (202,107)	$ 74
Ending balance, shares at Sep. 30, 2020	24,495,525			24,495,525

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (40,157)	$ (29,781)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of premium on marketable securities	268	0
Depreciation and amortization	858	1,011
Stock-based compensation expense	6,128	1,155
Loss on disposal of capital equipment	0	9
Gain (loss) on foreign currency translation	(65)	17
Noncash interest income, net	0	20
Changes in operating assets and liabilities:
Prepaid expenses and other long-term assets	401	(4,404)
Accounts payable and accrued liabilities	5,207	2,187
Deferred revenue	2,260	0
Deferred rent	(25)	0
Net cash used in operating activities	(25,125)	(29,786)
Investing activities
Purchase of marketable securities	(122,706)	0
Proceeds from maturities of marketable securities	20,000	0
Purchase of property and equipment	(224)	(863)
Net cash used in investing activities	(102,930)	(863)
Financing activities
Proceeds from public offering, net of issuance costs	69,842	0
Proceeds from the sale of convertible preferred stock, net of issuance costs	0	14,379
Proceeds from issuance of common stock under the employee stock purchase plan	411	0
Proceeds from issuance of common stock, net of repurchases	648	782
Net cash provided by financing activities	70,901	15,161
Net decrease in cash and cash equivalents	(57,154)	(15,488)
Cash and cash equivalents at beginning of period	77,383	63,798
Cash and cash equivalents at end of period	20,229	48,310
Supplemental disclosures of non-cash investing and financing information
Deferred offering costs included in accounts payable and accrued expenses	0	454
Forgiveness of promissory notes from related party for purchase of common stock	$ 0	$ 382

Organization

Organization	9 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Description of the Business RAPT Therapeutics, Inc. (“RAPT” or the “Company”) is a clinical-stage, immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in oncology and inflammatory diseases. Utilizing its proprietary drug discovery and development engine, the Company develops highly selective small molecules that are designed to modulate the critical immune responses underlying these diseases. In May 2019, the Company changed its name from FLX Bio, Inc. to RAPT Therapeutics, Inc. The Company is located in South San Francisco, California. Equity Financing In February 2020, the Company completed an underwritten public offering (the “Follow‑on Offering”) of 2,500,000 shares of common stock at an offering price of $30.00 per share. The Company received approximately $69.8 million in net proceeds from the Follow-on Offering, after deducting underwriting discounts and other offering-related costs.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ( “ ” ’ The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its wholly-owned subsidiary, RAPT Therapeutics Australia Pty Ltd., which was established in 2018. All intercompany balances and transactions have been eliminated in consolidation. Revenue License and collaborative agreement revenue consists of license, milestone and royalty payments generated through agreements with strategic partners for the development and commercialization of certain product candidates. The terms of an agreement may include a non-refundable upfront fee, payments based upon achievement of milestones and royalties on net product sales. If a portion of the nonrefundable upfront fee or other payments received is allocated to continuing performance obligations under the terms of an agreement, such portion is recorded as deferred revenue and recognized as revenue when or as the underlying performance obligation is satisfied. The Company recognizes revenue when it transfers promised goods or services to customers or counterparties in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized, the Company performs the following steps: (i) identification of the promised goods or services in the agreement; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the agreement; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to performance obligations based on estimated selling prices; and (v) recognition of revenue when or as the Company satisfies each performance obligation. Licenses: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an agreement, the Company will recognize revenue from the nonrefundable, upfront fee allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. If a license is bundled with other performance obligations, the Company utilizes judgment to assess the nature of the combined performance obligations to determine whether the combined performance obligations are satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: If an agreement includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered likely to be achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is unlikely that a significant revenue reversal would occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become likely to be achieved. Royalties: If an agreement includes sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied. Stock-Based Compensation The Company measures stock-based compensation expense for all employee and non-employee stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Stock-based compensation expense related to restricted stock awards is determined using the estimated fair value of the Company’s common stock on the date of grant for the period prior to the Company’s initial public offering (“IPO”) in November 2019. The fair value of restricted stock awards granted after the IPO is determined based on the stock price on the date of grant. The estimated fair value is amortized as compensation expense over the service period of the award. Stock-based compensation expense related to the Company’s employee stock purchase plan is recognized based on the fair value of each award estimated on the first day of the offering period using the Black‑Scholes option-pricing model and recorded as expense over the service period using the straight‑line method. 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 during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares outstanding during the period plus the number of potential dilutive securities outstanding during the period calculated in accordance with the treasury stock method. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of including potential dilutive securities is anti-dilutive. Marketable securities Marketable securities primarily consist of commercial paper, corporate bonds and U.S. government agency securities Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (the “FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on our condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act. Adopted Accounting Pronouncements In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-Employee Share-Based Payment Accounting in the first quarter of 2020 using a modified retrospective method and there was an insignificant impact to the Company’s financial position and results of operations related to this adoption. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurements (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement in the first quarter of 2020 and there was no impact to the Company’s financial position or results of operations related to this adoption. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Recently Issued Accounting Pronouncement Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments—Credit Losses, Topic 326 Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates Codification Improvements to Topic 326, Financial Instruments—Credit Losses

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually). Financial instruments such as cash and cash equivalents, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the balance sheet are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 — Level 2 — Level 3 — To date, the Company has not recorded any impairment charges on marketable securities due to other-than-temporary declines in market value. In determining whether a decline is other than temporary, the Company considers various factors, including the length of time and extent to which the market value has been less than amortized cost, the financial condition and near-term prospects of the issuer and the Company’s intent and ability to retain its investment in the issuer for a period of time sufficient to allow for any anticipated recovery in market value. The Company estimates the fair values of investments in corporate debt securities, commercial paper and U.S. government agency securities Cash equivalents and marketable securities, all of which are classified as available-for-sale securities and measured at fair value on a recurring basis, consisted of the following (in thousands): As of September 30, 2020 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 19,087 $ — $ — $ 19,087 Corporate debt Level 2 51,413 111 — 51,524 Commercial paper Level 2 18,458 — — 18,458 U.S. government agency securities Level 2 32,568 8 — 32,576 Total $ 121,526 $ 119 $ — $ 121,645 As of December 31, 2019, the financial assets subject to fair value measurement on a recurring basis consisted of money market funds with a fair value of $77.4 million. As of September 30, 2020, the Company’s marketable securities had remaining contractual maturities of less than one year. The Company does not intend to sell the securities that are in an unrealized loss position, and the Company believes it is more likely than not that the investments will be held until recovery of the amortized cost bases. The Company has determined that the gross unrealized losses on marketable securities as of September 30, 2020 were temporary in nature.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): September 30, December 31, 2020 2019 Laboratory equipment $ 5,835 $ 5,752 Leasehold improvements 3,294 3,294 Computer equipment 416 326 Furniture and fixtures 394 394 Total property and equipment 9,939 9,766 Less accumulated depreciation and amortization (6,866 ) (6,059 ) Property and equipment, net $ 3,073 $ 3,707 Depreciation and amortization expense was $0.3 million for each of the three months ended September 30, 2020 and 2019, and $0.9 million and $1.0 million for the nine months ended September 30, 2020 and 2019, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): September 30, December 31, 2020 2019 Accrued clinical expenses $ 2,149 $ 1,353 Accrued compensation 3,156 1,779 Accrued professional and consulting services 270 192 Accrued lab supplies 34 29 Other 60 289 Total accrued expenses $ 5,669 $ 3,642

Collaboration Agreements

Collaboration Agreements	9 Months Ended
	Sep. 30, 2020
Collaboration Agreements [Abstract]
Collaboration Agreements	6. Collaboration Agreements Collaboration and License Agreement with Hanmi In December 2019, the Company entered into a Collaboration and License Agreement with Hanmi (the “Hanmi Agreement”), pursuant to which the Company granted Hanmi an exclusive license to develop, manufacture and commercialize FLX475 and related compounds and products with respect to human cancers in the Republic of Korea, the Republic of China (Taiwan) and the People’s Republic of China, including the special administrative regions of Macau and Hong Kong (the “Hanmi Territory”), and certain sublicense In consideration of the rights granted under the Hanmi Agreement, the Company was entitled to $10.0 million in an upfront payment of $4.0 million and a near-term milestone payment of $6.0 million. The milestone payment was received in April 2020. Additionally, the Company will be eligible to receive contingent payments of up to $108.0 million upon the achievement of specified milestones, as well as double-digit royalties on future net sales of FLX475 in the Hanmi Territory. The transaction price as of September 30, 2020 was $10.0 million, consisting of the upfront fee of $4.0 million and the near-term milestone payment of $6.0 million, which was consistent with the transaction price as of December 31, 2019. The Company recognizes revenue for the performance obligation by applying the cost-based input method over the estimated service period. The Company determined that this method most faithfully depicts the transfer of its performance obligations to Hanmi as it reflects the progress made towards providing Hanmi with the necessary know-how to continue developing FLX475 in the Hanmi Territory. For the three and nine months ended September 30, 2020, the Company recognized $1.5 million and $3.7 million, respectively, as revenue pursuant to the Hanmi Agreement. As of September 30, 2020 and December 31, 2019, deferred revenue related to the Hanmi Agreement was $6.3 million and $4.0 million, respectively. The deferred revenue is expected to be recognized over the remaining period of the Company’s Phase 1/2 clinical trial of FLX475.

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2020
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	7. Convertible Preferred Stock Immediately prior to the closing of the Company’s IPO on November 4, 2019, all outstanding shares of convertible preferred stock converted into 17,467,184

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Common Stock	8. Common Stock As of September 30, 2020 and December 31, 2019, 24,495,525 shares and 21,833,037 shares of common stock were outstanding, respectively, which includes shares subject to repurchase of 11,097 and 51,098, respectively, as a result of early exercise of stock options not yet vested. The holders of common stock have one vote for each share of common stock held by them. Holders of shares of common stock are entitled to dividends when, as and if declared by the board of directors. No dividends had been declared as of September 30, 2020. As of September 30, 2020, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 1,517,965 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 56,500 Options available for future grants 2,420,840 Shares reserved under the 2019 Employee Stock Purchase Plan 199,986 Total 4,195,291

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	9. Stock-based Compensation In 2019, the Company adopted the 2019 Equity Incentive Plan (the “2019 Plan”) for eligible employees, officers, directors, advisors and consultants, which provides for the grant of incentive and non-statutory stock options and restricted stock units (“RSUs”) of common stock Stock option activity under the 2019 Plan is set forth below for the nine months ended September 30, 2020: Weighted Average Number of Exercise Shares Shares Price Per Available Outstanding Share Balances at December 31, 2019 1,874,759 1,313,468 $ 9.77 Stock options authorized 873,321 — Stock options granted (343,621 ) 343,621 34.75 Stock options exercised — (122,743 ) 4.62 Stock options forfeited 16,381 (16,381 ) 11.61 Balances at September 30, 2020 2,420,840 1,517,965 $ 15.66 RSU activity under the 2019 Plan is set forth below for the nine months ended September 30, 2020: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2019 — $ — RSUs granted 56,500 44.66 RSUs vested and settled — — RSUs forfeited — — Balances at September 30, 2020 56,500 $ 44.66 Stock-based compensation expense Total stock-based compensation expense recognized for options and RSUs granted to both employees and non-employees and for the employee stock purchase plan was as follows (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 1,125 $ 212 $ 3,450 $ 611 General and administrative 880 219 2,678 544 Total stock-based compensation expense $ 2,005 $ 431 $ 6,128 $ 1,155 As of September 30, 2020, unrecognized stock-based compensation expense related to outstanding unvested stock options and RSUs that are expected to vest was $12.4 million. This unrecognized stock-based compensation expense is expected to be recognized over 2.19 years. 2019 Employee Stock Purchase Plan In October 2019, the Company adopted the 2019 Employee Stock Purchase Plan (the “2019 ESPP”). The Company reserved 240,336 shares of common stock pursuant to purchase rights to be granted to the Company’s employees. The 2019 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1 of each calendar year, beginning January 1, 2020, by the lesser of (1) 1.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, (2) 240,336 shares or (3) a number determined by the board of directors that is less than (1) and (2). Under the 2019 ESPP, eligible employees are granted rights to purchase shares of common stock, which can be funded through payroll deductions that cannot exceed 15% of each employee’s compensation. The 2019 ESPP generally provides for a 24-month offering period, which includes four six-month purchase periods. At the end of each purchase period, eligible employees are permitted to purchase shares of common stock at 85% of the lower of fair market value at the beginning of the offering period or fair market value at the end of the purchase period. The 2019 ESPP is considered a compensatory plan and the Company recorded stock-based compensation expense of $0.7

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The Company recorded provisions for income taxes of $0.3 million and $0.8 million for the three and nine months ended September 30, 2020, respectively, related to Korean withholding taxes on the near-term milestone payment the Company received pursuant to the Hanmi Agreement. No provision had been recorded for the three and nine months ended September 30, 2019. In addition, the Company’s deferred tax assets continue to be subject to a full valuation allowance. On March 27, 2020, President Trump signed into U.S. federal law the CARES Act, which provides emergency assistance and health care for individuals, families and businesses affected by the COVID-19 pandemic. The CARES Act did not have a material impact on the Company’s condensed consolidated financial statements as of September 30, 2020; however, the Company continues to examine the impacts the CARES Act may have on its business, results of operations, financial condition and liquidity.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net Loss Per Share Net loss per share The following table sets forth the computation of the basic and diluted net loss per share for the three and nine months ended September 30, 2020 and 2019 (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (14,631 ) $ (9,971 ) $ (40,157 ) $ (29,781 ) Denominator: Weighted average common shares outstanding 24,474,157 838,961 24,019,746 822,644 Less: weighted-average unvested restricted common stock subject to repurchase — (19,097 ) — (45,451 ) Less: weighted-average unvested common shares subject to repurchase (25,042 ) (16,635 ) (29,820 ) (35,482 ) Weighted-average shares used to compute net loss per share, basic and diluted 24,449,115 803,229 23,989,926 741,711 Net loss per share, basic and diluted $ (0.60 ) $ (12.41 ) $ (1.67 ) $ (40.15 ) Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of September 30, 2020 2019 Convertible preferred stock — 104,803,325 Common stock options issued and outstanding 1,517,965 943,610 Estimated shares issuable under the employee stock purchase plan 39,830 — RSUs subject to future vesting 56,500 — Total 1,614,295 105,746,935

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events On November 4, 2020, the Company filed a shelf registration statement on Form S-3 with the SEC covering (a) up to $350 million of the Company’s securities, including up to $100 million of shares of common stock that may be offered and sold from time to time in one or more “at-the-market” offerings pursuant to a Controlled Equity Offering SM

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ( “ ” ’ The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP and include the consolidated accounts of the Company and its wholly-owned subsidiary, RAPT Therapeutics Australia Pty Ltd., which was established in 2018. All intercompany balances and transactions have been eliminated in consolidation.
Revenue	Revenue License and collaborative agreement revenue consists of license, milestone and royalty payments generated through agreements with strategic partners for the development and commercialization of certain product candidates. The terms of an agreement may include a non-refundable upfront fee, payments based upon achievement of milestones and royalties on net product sales. If a portion of the nonrefundable upfront fee or other payments received is allocated to continuing performance obligations under the terms of an agreement, such portion is recorded as deferred revenue and recognized as revenue when or as the underlying performance obligation is satisfied. The Company recognizes revenue when it transfers promised goods or services to customers or counterparties in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized, the Company performs the following steps: (i) identification of the promised goods or services in the agreement; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the agreement; (iii) measurement of the transaction price, including any constraint on variable consideration; (iv) allocation of the transaction price to performance obligations based on estimated selling prices; and (v) recognition of revenue when or as the Company satisfies each performance obligation. Licenses: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an agreement, the Company will recognize revenue from the nonrefundable, upfront fee allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. If a license is bundled with other performance obligations, the Company utilizes judgment to assess the nature of the combined performance obligations to determine whether the combined performance obligations are satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: If an agreement includes event-based or milestone payments, the Company evaluates whether the events or milestones are considered likely to be achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is unlikely that a significant revenue reversal would occur, the value of the associated event-based or milestone payments is included in the transaction price. Event-based or milestone payments that are not within the control of the Company are not included in the transaction price until they become likely to be achieved. Royalties: If an agreement includes sales-based royalties and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied or partially satisfied.
Share-Based Compensation	Stock-Based Compensation The Company measures stock-based compensation expense for all employee and non-employee stock-based awards based on their grant date fair value using the Black-Scholes option-pricing model. Subsequent to the adoption of ASU 2018-07, Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting Stock-based compensation expense related to restricted stock awards is determined using the estimated fair value of the Company’s common stock on the date of grant for the period prior to the Company’s initial public offering (“IPO”) in November 2019. The fair value of restricted stock awards granted after the IPO is determined based on the stock price on the date of grant. The estimated fair value is amortized as compensation expense over the service period of the award. Stock-based compensation expense related to the Company’s employee stock purchase plan is recognized based on the fair value of each award estimated on the first day of the offering period using the Black‑Scholes option-pricing model and recorded as expense over the service period using the straight‑line method.
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 during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares outstanding during the period plus the number of potential dilutive securities outstanding during the period calculated in accordance with the treasury stock method. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of including potential dilutive securities is anti-dilutive.
Marketable Securities	Marketable securities Marketable securities primarily consist of commercial paper, corporate bonds and U.S. government agency securities
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (the “FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on our condensed consolidated financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company and has elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act.
Adopted Accounting Pronouncements	Adopted Accounting Pronouncements In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-Employee Share-Based Payment Accounting in the first quarter of 2020 using a modified retrospective method and there was an insignificant impact to the Company’s financial position and results of operations related to this adoption. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurements (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement in the first quarter of 2020 and there was no impact to the Company’s financial position or results of operations related to this adoption. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncement Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments—Credit Losses, Topic 326 Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates Codification Improvements to Topic 326, Financial Instruments—Credit Losses

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Cash Equivalents and Marketable Securities Classified as Available-for-Sale Securities Measured at Fair Value on Recurring Basis	Cash equivalents and marketable securities, all of which are classified as available-for-sale securities and measured at fair value on a recurring basis, consisted of the following (in thousands): As of September 30, 2020 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 19,087 $ — $ — $ 19,087 Corporate debt Level 2 51,413 111 — 51,524 Commercial paper Level 2 18,458 — — 18,458 U.S. government agency securities Level 2 32,568 8 — 32,576 Total $ 121,526 $ 119 $ — $ 121,645

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): September 30, December 31, 2020 2019 Laboratory equipment $ 5,835 $ 5,752 Leasehold improvements 3,294 3,294 Computer equipment 416 326 Furniture and fixtures 394 394 Total property and equipment 9,939 9,766 Less accumulated depreciation and amortization (6,866 ) (6,059 ) Property and equipment, net $ 3,073 $ 3,707

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): September 30, December 31, 2020 2019 Accrued clinical expenses $ 2,149 $ 1,353 Accrued compensation 3,156 1,779 Accrued professional and consulting services 270 192 Accrued lab supplies 34 29 Other 60 289 Total accrued expenses $ 5,669 $ 3,642

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	As of September 30, 2020, the Company had reserved the following shares of common stock for future issuance: Options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 1,517,965 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 56,500 Options available for future grants 2,420,840 Shares reserved under the 2019 Employee Stock Purchase Plan 199,986 Total 4,195,291

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	Stock option activity under the 2019 Plan is set forth below for the nine months ended September 30, 2020: Weighted Average Number of Exercise Shares Shares Price Per Available Outstanding Share Balances at December 31, 2019 1,874,759 1,313,468 $ 9.77 Stock options authorized 873,321 — Stock options granted (343,621 ) 343,621 34.75 Stock options exercised — (122,743 ) 4.62 Stock options forfeited 16,381 (16,381 ) 11.61 Balances at September 30, 2020 2,420,840 1,517,965 $ 15.66
Summary of RSU Activity	RSU activity under the 2019 Plan is set forth below for the nine months ended September 30, 2020: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2019 — $ — RSUs granted 56,500 44.66 RSUs vested and settled — — RSUs forfeited — — Balances at September 30, 2020 56,500 $ 44.66
Summary of Stock-based Compensation Expense	Total stock-based compensation expense recognized for options and RSUs granted to both employees and non-employees and for the employee stock purchase plan was as follows (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 1,125 $ 212 $ 3,450 $ 611 General and administrative 880 219 2,678 544 Total stock-based compensation expense $ 2,005 $ 431 $ 6,128 $ 1,155

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
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 for the three and nine months ended September 30, 2020 and 2019 (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (14,631 ) $ (9,971 ) $ (40,157 ) $ (29,781 ) Denominator: Weighted average common shares outstanding 24,474,157 838,961 24,019,746 822,644 Less: weighted-average unvested restricted common stock subject to repurchase — (19,097 ) — (45,451 ) Less: weighted-average unvested common shares subject to repurchase (25,042 ) (16,635 ) (29,820 ) (35,482 ) Weighted-average shares used to compute net loss per share, basic and diluted 24,449,115 803,229 23,989,926 741,711 Net loss per share, basic and diluted $ (0.60 ) $ (12.41 ) $ (1.67 ) $ (40.15 )
Potential Dilutive Securities not Included in Diluted per Share Calculations	Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of September 30, 2020 2019 Convertible preferred stock — 104,803,325 Common stock options issued and outstanding 1,517,965 943,610 Estimated shares issuable under the employee stock purchase plan 39,830 — RSUs subject to future vesting 56,500 — Total 1,614,295 105,746,935

Organization - Additional Infor

Organization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Feb. 29, 2020	Sep. 30, 2020	Sep. 30, 2019
Class Of Stock [Line Items]
Net proceeds received after deducting underwriting discounts and other offering related costs		$ 69,842	$ 0
Follow-on Offering
Class Of Stock [Line Items]
Shares issued during period	2,500,000
Shares issued, price per share	$ 30
Net proceeds received after deducting underwriting discounts and other offering related costs	$ 69,800

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	Sep. 30, 2020
ASU 2018-07
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
ASU 2018-13
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, immaterial effect	true
ASU 2019-12
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, immaterial effect	true

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Cash Equivalents and Marketable Securities Classified as Available-for-Sale Securities Measured at Fair Value on Recurring Basis (Details) $ in Thousands	Sep. 30, 2020USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 121,526
Unrealized Gains	119
Fair Value	121,645
Level 1 | Money Market Funds | Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	19,087
Fair Value	19,087
Level 2 | Corporate Debt
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	51,413
Unrealized Gains	111
Fair Value	51,524
Level 2 | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	18,458
Fair Value	18,458
Level 2 | U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	32,568
Unrealized Gains	8
Fair Value	$ 32,576

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities remaining contractual term	1 year
Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market fund, fair value		$ 77.4

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 9,939	$ 9,766
Less accumulated depreciation and amortization	(6,866)	(6,059)
Property and equipment, net	3,073	3,707
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	5,835	5,752
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	3,294	3,294
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	416	326
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	$ 394	$ 394

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 300	$ 300	$ 858	$ 1,011

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued clinical expenses	$ 2,149	$ 1,353
Accrued compensation	3,156	1,779
Accrued professional and consulting services	270	192
Accrued lab supplies	34	29
Other	60	289
Total accrued expenses	$ 5,669	$ 3,642

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Apr. 30, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized	$ 1,528,000	$ 3,740,000
Collaboration and License Agreement | Hanmi Pharmaceutical Co., LTD
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront and near-term milestone payment	10,000,000	10,000,000		$ 10,000,000
Upfront fee receivable	4,000,000	4,000,000		4,000,000
Milestone payment	6,000,000	6,000,000	$ 6,000,000
Revenue recognized	1,500,000	3,700,000
Deferred revenue	$ 6,300,000	$ 6,300,000		4,000,000
Collaboration and License Agreement | Hanmi Pharmaceutical Co., LTD | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments upon Achievement of specified milestones				$ 108,000,000

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	Nov. 04, 2019shares
Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock, common stock shares issued	17,467,184

Common Stock - Additional Infor

Common Stock - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)voteshares	Dec. 31, 2019shares
Equity [Abstract]
Common stock shares outstanding	24,495,525	21,833,037
Shares subject to repurchase as a result of early exercise of stock options not yet vested	11,097	51,098
Number of votes for each share of common stock	The holders of common stock have one vote for each share of common stock held by them
Number of votes per share | vote	1
Dividends declared | $	$ 0

Common Stock - Summary of Reser

Common Stock - Summary of Reserved Shares of Common Stock for Future Issuance (Details)	Sep. 30, 2020shares
Class Of Stock [Line Items]
Total shares reserved	4,195,291
Options Available for Future Grants
Class Of Stock [Line Items]
Total shares reserved	2,420,840
2019 Equity Incentive Plan and 2015 Stock Plan | Options Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	1,517,965
2019 Equity Incentive Plan | Restricted Stock Units Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	56,500
2019 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total shares reserved	199,986

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - 2019 Plan - Stock Option	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available, Beginning Balance	1,874,759
Shares Available, Stock options authorized	873,321
Shares Available, Stock options granted	(343,621)
Shares Available, Stock options forfeited	16,381
Shares Available, Ending Balance	2,420,840
Number of Shares Outstanding, Beginning Balance	1,313,468
Number of Shares Outstanding, Stock options granted	343,621
Number of Shares Outstanding, Stock options exercised	(122,743)
Number of Shares Outstanding, Stock options forfeited	(16,381)
Number of Shares Outstanding, Ending Balance	1,517,965
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 9.77
Weighted Average Exercise Price Per Share, Stock options granted | $ / shares	34.75
Weighted Average Exercise Price Per Share, Stock options exercised | $ / shares	4.62
Weighted Average Exercise Price Per Share, Stock options forfeited | $ / shares	11.61
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	$ 15.66

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of RSU Activity (Details) - 2019 Plan - Restricted Stock Unit ("RSU")	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, RSUs granted | shares	56,500
Number of Shares Outstanding, Ending Balance | shares	56,500
Weighted Average Grant Date Fair Value Per Share, RSUs granted | $ / shares	$ 44.66
Weighted Average Grant Date Fair Value Per Share, Ending Balance | $ / shares	$ 44.66

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,005	$ 431	$ 6,128	$ 1,155
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,125	212	3,450	611
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 880	$ 219	$ 2,678	$ 544

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		$ 2,005	$ 431	$ 6,128	$ 1,155
2019 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares reserved	240,336
Percentage of increase in shares reserved for issuance on common stock outstanding	1.00%
Increase in shares at the beginning of each calendar year	240,336
Maximum employee subscription rate on salary	15.00%
Offering period	24 months
Purchase period	6 months
Purchase price of common stock as percentage of fair market value	85.00%
Stock-based compensation expense		700		2,000
Outstanding Unvested Stock Options and RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 12,400		$ 12,400
Unrecognized stock-based compensation expense, expected period to be recognized				2 years 2 months 8 days

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 287,000	$ 0	$ 791,000	$ 0

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (14,631)	$ (12,387)	$ (13,139)	$ (9,971)	$ (10,622)	$ (9,188)	$ (40,157)	$ (29,781)
Denominator:
Weighted average common shares outstanding	24,474,157			838,961			24,019,746	822,644
Less: weighted-average unvested common stock subject to repurchase	(25,042)			(16,635)			(29,820)	(35,482)
Weighted-average shares used to compute net loss per share, basic and diluted	24,449,115			803,229			23,989,926	741,711
Net loss per share, basic and diluted	$ (0.60)			$ (12.41)			$ (1.67)	$ (40.15)
Restricted Stock
Denominator:
Less: weighted-average unvested common stock subject to repurchase				(19,097)				(45,451)

Net Loss Per Share - Potential

Net Loss Per Share - Potential Dilutive Securities not Included in Diluted per Share Calculations (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	1,614,295	105,746,935
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities		104,803,325
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	1,517,965	943,610
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	39,830
RSUs Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	56,500

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Millions	Nov. 04, 2020	Sep. 30, 2020
Subsequent Event [Line Items]
Total shares reserved		4,195,291
Subsequent Event | At-The-Market | Maximum
Subsequent Event [Line Items]
Securities that may be offered and sold	$ 350
Common stock that may be offered and sold, value	$ 100
Total shares reserved	1,000,000