RAPT Therapeutics (RAPT) 10-Q 11 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 06, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
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	Yes
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		29,488,367
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	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 86,220	$ 24,918
Marketable securities	137,084	86,592
Prepaid expenses and other current assets	4,651	4,088
Total current assets	227,955	115,598
Property and equipment, net	2,737	2,982
Other assets	389	389
Total assets	231,081	118,969
Current liabilities:
Accounts payable	2,714	2,383
Accrued expenses	5,068	4,935
Deferred revenue, current	2,283	4,096
Other current liabilities	329	328
Total current liabilities	10,394	11,742
Deferred rent, net of current portion	2,141	2,185
Deferred revenue, non-current	967	863
Total liabilities	13,502	14,790
Commitments
Stockholders' equity:
Preferred stock
Common stock	3	2
Additional paid-in capital	465,179	319,196
Accumulated other comprehensive loss	(137)	(177)
Accumulated deficit	(247,466)	(214,842)
Total stockholders' equity	217,579	104,179
Total liabilities and stockholders' equity	$ 231,081	$ 118,969

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 869	$ 1,277	$ 2,091	$ 2,212
Operating expenses:
Research and development	13,190	10,986	26,961	21,669
General and administrative	3,760	2,802	7,772	6,091
Total operating expenses	16,950	13,788	34,733	27,760
Loss from operations	(16,081)	(12,511)	(32,642)	(25,548)
Other income (expense), net	(29)	391	18	526
Net loss before taxes	(16,110)	(12,120)	(32,624)	(25,022)
Provision for income taxes		267		504
Net loss	(16,110)	(12,387)	(32,624)	(25,526)
Other comprehensive income (loss):
Foreign currency translation adjustment	70	(199)	108	5
Unrealized gain (loss) on marketable securities	(18)	369	(68)	152
Total comprehensive loss	$ (16,058)	$ (12,217)	$ (32,584)	$ (25,369)
Net loss per share, basic and diluted	$ (0.63)	$ (0.51)	$ (1.29)	$ (1.08)
Weighted average number of shares used in computing net loss per share, basic and diluted	25,589,947	24,336,102	25,217,542	23,743,058

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF PREFERRED STOCK AND STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	At The Market	Public Offering	Common Stock	Common StockAt The Market	Common StockPublic Offering	Additional Paid-In Capital	Additional Paid-In CapitalAt The Market	Additional Paid-In CapitalPublic Offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 73,121			$ 2			$ 235,049			$ 20	$ (161,950)
Beginning balance, shares at Dec. 31, 2019				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
Issuances from employee stock plans	30						30
Issuances from employee stock plans, 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			7	(175,089)
Ending balance, shares at Mar. 31, 2020				24,334,007
Beginning balance at Dec. 31, 2019	73,121			$ 2			235,049			20	(161,950)
Beginning balance, shares at Dec. 31, 2019				21,833,037
Foreign currency translation adjustment	5
Unrealized gain (loss) on marketable securities	152
Net loss	(25,526)
Ending balance at Jun. 30, 2020	122,611			$ 2			309,908			177	(187,476)
Ending balance, shares at Jun. 30, 2020				24,442,842
Beginning balance at Mar. 31, 2020	131,929			$ 2			307,009			7	(175,089)
Beginning balance, shares at Mar. 31, 2020				24,334,007
Issuances from employee stock plans	864						864
Issuances from employee stock plans, shares				108,835
Stock-based compensation	2,035						2,035
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			177	(187,476)
Ending balance, shares at Jun. 30, 2020				24,442,842
Beginning balance at Dec. 31, 2020	104,179			$ 2			319,196			(177)	(214,842)
Beginning balance, shares at Dec. 31, 2020				24,773,361
Issuance of common stock, net of issuance costs		$ 1,180						$ 1,180
Issuance of common stock, net of issuance costs, shares					57,100
Issuances from employee stock plans	121						121
Issuances from employee stock plans, shares				31,620
Stock-based compensation	2,687						2,687
Foreign currency translation adjustment	38									38
Unrealized gain (loss) on marketable securities	(50)									(50)
Net loss	(16,514)										(16,514)
Ending balance at Mar. 31, 2021	91,641			$ 2			323,184			(189)	(231,356)
Ending balance, shares at Mar. 31, 2021				24,862,081
Beginning balance at Dec. 31, 2020	104,179			$ 2			319,196			(177)	(214,842)
Beginning balance, shares at Dec. 31, 2020				24,773,361
Foreign currency translation adjustment	108
Unrealized gain (loss) on marketable securities	(68)
Net loss	(32,624)
Ending balance at Jun. 30, 2021	217,579			$ 3			465,179			(137)	(247,466)
Ending balance, shares at Jun. 30, 2021				29,475,921
Beginning balance at Mar. 31, 2021	91,641			$ 2			323,184			(189)	(231,356)
Beginning balance, shares at Mar. 31, 2021				24,862,081
Issuance of common stock, net of issuance costs		$ 3,510	$ 134,582			$ 1		$ 3,510	$ 134,581
Issuance of common stock, net of issuance costs, shares					157,871	4,356,060
Issuances from employee stock plans	1,016						1,016
Issuances from employee stock plans, shares				99,909
Stock-based compensation	2,888						2,888
Foreign currency translation adjustment	70									70
Unrealized gain (loss) on marketable securities	(18)									(18)
Net loss	(16,110)										(16,110)
Ending balance at Jun. 30, 2021	$ 217,579			$ 3			$ 465,179			$ (137)	$ (247,466)
Ending balance, shares at Jun. 30, 2021				29,475,921

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss	$ (32,624)	$ (25,526)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of premium on marketable securities	430	51
Depreciation and amortization	536	595
Stock-based compensation expense	5,575	4,123
Gain on foreign currency translation	108	5
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(563)	(4)
Accounts payable, accrued expenses, and other current liabilities	471	1,811
Deferred revenue	(1,709)	3,788
Deferred rent	(50)	(15)
Net cash used in operating activities	(27,826)	(15,172)
Investing activities
Purchase of marketable securities	(118,705)	(111,892)
Proceeds from maturities of marketable securities	67,715	8,000
Purchase of property and equipment	(291)	(98)
Net cash used in investing activities	(51,281)	(103,990)
Financing activities
Proceeds from issuance of common stock under the employee stock plans	1,137	894
Net cash provided by financing activities	140,409	70,736
Net increase (decrease) in cash and cash equivalents	61,302	(48,426)
Cash and cash equivalents at beginning of period	24,918	77,383
Cash and cash equivalents at end of period	86,220	28,957
Supplemental disclosures of non-cash investing and financing information
Issuance costs related to public offering included in accrued expenses	403	0
Public Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs	134,582	69,842
At The Market
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 4,690	$ 0

Organization

Organization	6 Months Ended
	Jun. 30, 2021
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. The Company is located in South San Francisco, California. Equity Financings During the six months ended June 30, 2021, the Company sold 214,971 shares of common stock in “at the market” offerings pursuant to a Controlled Equity Offering SM In June 2021, pursuant to the shelf registration statement on Form S-3 that was declared effective by the Securities and Exchange Commission (“SEC”) on November 16, 2020, the Company completed a public offering (“2021 Public Offering”) of 4,356,060 shares of common stock, including 568,181 shares of the common stock issued in connection with the exercise by the underwriters of their over-allotment option, at a public offering price of $33.00 per share. The Company received approximately $134.6 million in net proceeds from the 2021 Public Offering, after deducting underwriting discounts and other offering-related costs.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
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. 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 The fair value of restricted stock awards granted after the Company’s initial public offering (“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. In February 2016, the FASB issued Accounting Standard Update (“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	6 Months Ended
	Jun. 30, 2021
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. 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 on 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 — Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. 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 June 30, 2021 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 84,393 $ — $ — $ 84,393 Corporate debt Level 2 72,797 9 (28 ) 72,778 Commercial paper Level 2 45,530 — — 45,530 U.S. government agency securities Level 2 18,773 3 — 18,776 Total $ 221,493 $ 12 $ (28 ) $ 221,477 As of December 31, 2020 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 21,333 $ — $ — $ 21,333 Corporate debt Level 2 32,164 48 — 32,212 Asset-backed securities Level 2 12,367 2 (1 ) 12,368 Commercial paper Level 2 28,962 — — 28,962 U.S. government agency securities Level 2 13,047 3 — 13,050 Total $ 107,873 $ 53 $ (1 ) $ 107,925 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 June 30, 2021 were temporary in nature. The following table presents the remaining contractual maturities of the Company’s marketable securities as of June 30, 2021 (in thousands): June 30, 2021 Due in less than one year $ 169,222 Due in more than one year 52,255 Total $ 221,477

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment consisted of the following (in thousands): June 30, December 31, 2021 2020 Laboratory equipment $ 6,251 $ 5,966 Leasehold improvements 3,294 3,294 Computer equipment 404 447 Furniture and fixtures 394 357 Total property and equipment 10,343 10,064 Less accumulated depreciation and amortization (7,606 ) (7,082 ) Property and equipment, net $ 2,737 $ 2,982 Depreciation and amortization expense was $0.2 million and $0.4 million for the three months ended June 30, 2021 and 2020, and $0.5 million and $0.6 million for the six months ended June 30, 2021 and 2020, respectively.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): June 30, December 31, 2021 2020 Accrued research and development expenses $ 2,136 $ 1,576 Accrued compensation 2,272 2,967 Accrued professional and consulting services 620 129 Other 40 263 Total accrued expenses $ 5,068 $ 4,935

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 2021
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 (the “Hanmi Agreement”) with Hanmi Pharmaceutical Ltd. (“Hanmi”), 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 June 30, 2021 was $10.4 million, consisting of the upfront fee of $4.0 million, the near-term milestone payment of $6.0 million, and $0.4 million related to the supply of FLX475 to Hanmi. 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 six months ended June 30, 2021, the Company recognized $0.9 million and $2.1 million, respectively, as revenue pursuant to the Hanmi Agreement. As of June 30, 2021 and December 31, 2020, deferred revenue related to the Hanmi Agreement was $3.3 million and $5.0 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.

Common Stock

Common Stock	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common Stock	7. Common Stock As of June 30, 2021, 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 1,984,626 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 40,500 Options available for future grants under the 2019 Equity Incentive Plan 2,782,334 Shares reserved under the 2019 Employee Stock Purchase Plan 342,214 Total 5,149,674

Stock-based Compensation

Stock-based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	8. Stock-based Compensation Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the six months ended June 30, 2021: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2020 1,481,100 $ 16.13 8.36 $ 11,123 Stock options authorized — Stock options granted 679,895 19.73 Stock options exercised (66,271 ) 8.91 Stock options forfeited (110,098 ) 20.53 Balances at June 30, 2021 1,984,626 $ 17.36 8.43 $ 30,488 As of June 30, 2021, 2,782,334 shares remained available for issuance under the 2019 Plan. Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the six months ended June 30, 2021: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2020 56,500 $ 44.66 RSUs granted — — RSUs vested and settled (14,125 ) 44.66 RSUs forfeited (1,875 ) 44.66 Balances at June 30, 2021 40,500 $ 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 June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Research and development $ 1,627 $ 1,243 $ 3,101 $ 2,325 General and administrative 1,261 792 2,474 1,798 Total stock-based compensation expense $ 2,888 $ 2,035 $ 5,575 $ 4,123 As of June 30, 2021, unrecognized stock-based compensation expense related to outstanding unvested stock options and RSUs that are expected to vest was $17.0 million. This unrecognized stock-based compensation expense is expected to be recognized over 2.8 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

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	9. 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 six months ended June 30, 2021 and 2020 (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Numerator: Net loss $ (16,110 ) $ (12,387 ) $ (32,624 ) $ (25,526 ) Denominator: Weighted average common shares outstanding 25,589,947 24,376,891 25,217,542 23,788,944 Less: weighted-average unvested common shares subject to repurchase — (40,789 ) — (45,886 ) Weighted-average shares used to compute net loss per share, basic and diluted 25,589,947 24,336,102 25,217,542 23,743,058 Net loss per share, basic and diluted $ (0.63 ) $ (0.51 ) $ (1.29 ) $ (1.08 ) Potential dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: As of June 30, 2021 2020 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 1,984,626 1,525,827 Estimated shares issuable under the 2019 ESPP 9,965 16,457 RSUs subject to future vesting 40,500 56,500 Total 2,035,091 1,598,784

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
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. 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.
Stock-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 The fair value of restricted stock awards granted after the Company’s initial public offering (“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. In February 2016, the FASB issued Accounting Standard Update (“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)	6 Months Ended
	Jun. 30, 2021
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 June 30, 2021 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 84,393 $ — $ — $ 84,393 Corporate debt Level 2 72,797 9 (28 ) 72,778 Commercial paper Level 2 45,530 — — 45,530 U.S. government agency securities Level 2 18,773 3 — 18,776 Total $ 221,493 $ 12 $ (28 ) $ 221,477 As of December 31, 2020 Fair Value Hierarchy Level Amortized Cost Unrealized Gains Unrealized Losses Fair Value Financial assets: Money market funds—classified as cash equivalents Level 1 $ 21,333 $ — $ — $ 21,333 Corporate debt Level 2 32,164 48 — 32,212 Asset-backed securities Level 2 12,367 2 (1 ) 12,368 Commercial paper Level 2 28,962 — — 28,962 U.S. government agency securities Level 2 13,047 3 — 13,050 Total $ 107,873 $ 53 $ (1 ) $ 107,925
Schedule of Remaining Contractual Maturities of Marketable Securities	The following table presents the remaining contractual maturities of the Company’s marketable securities as of June 30, 2021 (in thousands): June 30, 2021 Due in less than one year $ 169,222 Due in more than one year 52,255 Total $ 221,477

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): June 30, December 31, 2021 2020 Laboratory equipment $ 6,251 $ 5,966 Leasehold improvements 3,294 3,294 Computer equipment 404 447 Furniture and fixtures 394 357 Total property and equipment 10,343 10,064 Less accumulated depreciation and amortization (7,606 ) (7,082 ) Property and equipment, net $ 2,737 $ 2,982

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): June 30, December 31, 2021 2020 Accrued research and development expenses $ 2,136 $ 1,576 Accrued compensation 2,272 2,967 Accrued professional and consulting services 620 129 Other 40 263 Total accrued expenses $ 5,068 $ 4,935

Common Stock (Tables)

Common Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	As of June 30, 2021, 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 1,984,626 Restricted stock units issued and outstanding under the 2019 Equity Incentive Plan 40,500 Options available for future grants under the 2019 Equity Incentive Plan 2,782,334 Shares reserved under the 2019 Employee Stock Purchase Plan 342,214 Total 5,149,674

Stock-based Compensation (Table

Stock-based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	Stock option activity under the 2019 Equity Incentive Plan (the “2019 Plan”) is set forth below for the six months ended June 30, 2021: Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Shares Price Per Term Value Outstanding Share (Years) (in thousands) Balances at December 31, 2020 1,481,100 $ 16.13 8.36 $ 11,123 Stock options authorized — Stock options granted 679,895 19.73 Stock options exercised (66,271 ) 8.91 Stock options forfeited (110,098 ) 20.53 Balances at June 30, 2021 1,984,626 $ 17.36 8.43 $ 30,488
Summary of RSU Activity	Restricted stock unit (“RSU”) activity under the 2019 Plan is set forth below for the six months ended June 30, 2021: Weighted Average Number of Grant Date Shares Fair Value Outstanding Per Share Balances at December 31, 2020 56,500 $ 44.66 RSUs granted — — RSUs vested and settled (14,125 ) 44.66 RSUs forfeited (1,875 ) 44.66 Balances at June 30, 2021 40,500 $ 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 June 30, For the Six Months Ended June 30, 2021 2020 2021 2020 Research and development $ 1,627 $ 1,243 $ 3,101 $ 2,325 General and administrative 1,261 792 2,474 1,798 Total stock-based compensation expense $ 2,888 $ 2,035 $ 5,575 $ 4,123

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2021
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 six months ended June 30, 2021 and 2020 (in thousands, except share and per share data): Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Numerator: Net loss $ (16,110 ) $ (12,387 ) $ (32,624 ) $ (25,526 ) Denominator: Weighted average common shares outstanding 25,589,947 24,376,891 25,217,542 23,788,944 Less: weighted-average unvested common shares subject to repurchase — (40,789 ) — (45,886 ) Weighted-average shares used to compute net loss per share, basic and diluted 25,589,947 24,336,102 25,217,542 23,743,058 Net loss per share, basic and diluted $ (0.63 ) $ (0.51 ) $ (1.29 ) $ (1.08 )
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 June 30, 2021 2020 Stock options issued and outstanding under the 2019 Equity Incentive Plan and 2015 Stock Plan 1,984,626 1,525,827 Estimated shares issuable under the 2019 ESPP 9,965 16,457 RSUs subject to future vesting 40,500 56,500 Total 2,035,091 1,598,784

Organization - Additional Infor

Organization - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020
Class Of Stock [Line Items]
Total shares reserved	5,149,674	5,149,674
Sales Agreement | 2021 Public Offering
Class Of Stock [Line Items]
Shares issued during period	4,356,060
Net proceeds received after deducting underwriting discounts and other offering related costs	$ 134,600
Shares issued, price per share	$ 33	$ 33
At The Market
Class Of Stock [Line Items]
Net proceeds received after deducting underwriting discounts and other offering related costs		$ 4,690	$ 0
At The Market | Sales Agreement
Class Of Stock [Line Items]
Shares issued during period		214,971
Net proceeds received after deducting underwriting discounts and other offering related costs		$ 4,700
At The Market | Sales Agreement | Maximum
Class Of Stock [Line Items]
Total shares reserved	90,900,000	90,900,000
Underwriters | Sales Agreement | 2021 Public Offering
Class Of Stock [Line Items]
Shares issued during period	568,181

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) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 221,493	$ 107,873
Unrealized Gains	12	53
Unrealized Losses	(28)	(1)
Fair Value	221,477	107,925
Level 1 | Money Market Funds | Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	84,393	21,333
Fair Value	84,393	21,333
Level 2 | Corporate Debt
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	72,797	32,164
Unrealized Gains	9	48
Unrealized Losses	(28)
Fair Value	72,778	32,212
Level 2 | Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		12,367
Unrealized Gains		2
Unrealized Losses		(1)
Fair Value		12,368
Level 2 | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	45,530	28,962
Fair Value	45,530	28,962
Level 2 | U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	18,773	13,047
Unrealized Gains	3	3
Fair Value	$ 18,776	$ 13,050

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Remaining Contractual Maturities of Marketable Securities (Details) $ in Thousands	Jun. 30, 2021USD ($)
Investments Debt And Equity Securities [Abstract]
Due in less than one year	$ 169,222
Due in more than one year	52,255
Total	$ 221,477

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 10,343	$ 10,064
Less accumulated depreciation and amortization	(7,606)	(7,082)
Property and equipment, net	2,737	2,982
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	6,251	5,966
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	404	447
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	$ 394	$ 357

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 200	$ 400	$ 536	$ 595

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 2,136	$ 1,576
Accrued compensation	2,272	2,967
Accrued professional and consulting services	620	129
Other	40	263
Total accrued expenses	$ 5,068	$ 4,935

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Apr. 30, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized	$ 869,000	$ 1,277,000	$ 2,091,000	$ 2,212,000
Collaboration and License Agreement | Hanmi Pharmaceutical Co., LTD
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront and near-term milestone payment	10,400,000		10,400,000				$ 10,000,000
Upfront fee	4,000,000		4,000,000				4,000,000
Milestone payment	6,000,000		6,000,000			$ 6,000,000
Milestone payment related to supply	400,000		400,000
Revenue recognized	900,000		2,100,000
Deferred revenue	$ 3,300,000		$ 3,300,000		$ 5,000,000
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

Common Stock - Summary of Reser

Common Stock - Summary of Reserved Shares of Common Stock for Future Issuance (Detail)	Jun. 30, 2021shares
Class Of Stock [Line Items]
Total shares reserved	5,149,674
2019 Equity Incentive Plan and 2015 Stock Plan | Options Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	1,984,626
2019 Equity Incentive Plan | Restricted Stock Units Issued and Outstanding
Class Of Stock [Line Items]
Total shares reserved	40,500
2019 Equity Incentive Plan | Options Available for Future Grants
Class Of Stock [Line Items]
Total shares reserved	2,782,334
2019 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total shares reserved	342,214

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Stock Option Activity (Details) - 2019 Plan - Share-based Payment Arrangement, Option - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	1,481,100
Number of Shares Outstanding, Stock options granted	679,895
Number of Shares Outstanding, Stock options exercised	(66,271)
Number of Shares Outstanding, Stock options forfeited	(110,098)
Number of Shares Outstanding, Ending Balance	1,984,626	1,481,100
Weighted Average Exercise Price Per Share, Beginning Balance	$ 16.13
Weighted Average Exercise Price Per Share, Stock options granted	19.73
Weighted Average Exercise Price Per Share, Stock options exercised	8.91
Weighted Average Exercise Price Per Share, Stock options forfeited	20.53
Weighted Average Exercise Price Per Share, Ending Balance	$ 17.36	$ 16.13
Average Remaining Contractual Term (Years), Balance	8 years 5 months 4 days	8 years 4 months 9 days
Aggregate Intrinsic Value	$ 30,488	$ 11,123

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Oct. 31, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest		$ 17,000		$ 17,000
Unrecognized stock-based compensation cost, expected period to be recognized				2 years 9 months 18 days
Stock-based compensation expense		2,888	$ 2,035	$ 5,575	$ 4,123
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		$ 1,000	$ 800	$ 1,800	$ 1,300
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares remained available for issuance		2,782,334		2,782,334

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of RSU Activity (Details) - 2019 Plan - Restricted Stock Unit ("RSU")	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance | shares	56,500
Number of Shares Outstanding, RSUs vested and settled | shares	(14,125)
Number of Shares Outstanding, RSUs forfeited | shares	(1,875)
Number of Shares Outstanding, Ending Balance | shares	40,500
Weighted Average Grant Date Fair Value Per Share, Beginning Balance | $ / shares	$ 44.66
Weighted Average Grant Date Fair Value Per Share, RSUs vested and settled | $ / shares	44.66
Weighted Average Grant Date Fair Value Per Share, RSUs forfeited | $ / 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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,888	$ 2,035	$ 5,575	$ 4,123
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,627	1,243	3,101	2,325
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,261	$ 792	$ 2,474	$ 1,798

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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (16,110)	$ (16,514)	$ (12,387)	$ (13,139)	$ (32,624)	$ (25,526)
Denominator:
Weighted average common shares outstanding	25,589,947		24,376,891		25,217,542	23,788,944
Less: weighted-average unvested common shares subject to repurchase			(40,789)			(45,886)
Weighted-average shares used to compute net loss per share, basic and diluted	25,589,947		24,336,102		25,217,542	23,743,058
Net loss per share, basic and diluted	$ (0.63)		$ (0.51)		$ (1.29)	$ (1.08)

Net Loss Per Share - Potential

Net Loss Per Share - Potential Dilutive Securities not Included in Diluted per Share Calculations (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	2,035,091	1,598,784
Stock Options Issued And Outstanding Equity Incentive Plan And Under 2019 Equity Incentive Plan And 2015 Stock Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	1,984,626	1,525,827
Estimated Shares Issuable Under Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	9,965	16,457
RSUs Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities	40,500	56,500