Unaudited Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Temporary equity, Balance, shares at Dec. 31, 2018		85,093,688
Temporary equity, Balance at Dec. 31, 2018		$ 122,465
Balance, shares at Dec. 31, 2018			2,249,749
Balance at Dec. 31, 2018	$ (51,465)			$ 3,097	$ (53)	$ (54,509)
Stock-based compensation	1,442			1,442
Exercise of stock options	30			30
Exercise of stock options, shares			22,344
Vesting of early exercised stock options	75			75
Vesting of early exercised stock options, shares			161,548
Unrealized gain (loss) on available-for-sale securities, net	115				115
Net loss	(21,536)					(21,536)
Temporary equity, Balance, shares at Sep. 30, 2019		85,093,688
Temporary equity, Balance at Sep. 30, 2019		$ 122,465
Balance, shares at Sep. 30, 2019			2,433,641
Balance at Sep. 30, 2019	(71,339)			4,644	62	(76,045)
Temporary equity, Balance, shares at Jun. 30, 2019		85,093,688
Temporary equity, Balance at Jun. 30, 2019		$ 122,465
Balance, shares at Jun. 30, 2019			2,383,729
Balance at Jun. 30, 2019	(63,384)			4,134	62	(67,580)
Stock-based compensation	484			484
Vesting of early exercised stock options	26			26
Vesting of early exercised stock options, shares			49,912
Net loss	(8,465)					(8,465)
Temporary equity, Balance, shares at Sep. 30, 2019		85,093,688
Temporary equity, Balance at Sep. 30, 2019		$ 122,465
Balance, shares at Sep. 30, 2019			2,433,641
Balance at Sep. 30, 2019	$ (71,339)			4,644	62	(76,045)
Temporary equity, Balance, shares at Dec. 31, 2019	85,093,688	85,093,688
Temporary equity, Balance at Dec. 31, 2019	$ 122,465	$ 122,465
Balance, shares at Dec. 31, 2019	2,484,848		2,484,848
Balance at Dec. 31, 2019	$ (78,237)			5,164	41	(83,442)
Issuance of common stock from initial public offering, net of issuance costs	76,898		$ 1	76,897
Issuance of common stock from initial public offering, net of issuance costs, shares			6,540,000
Temporary equity, Conversion of preferred stock to common stock from completion of initial public offering, shares		(85,093,688)
Temporary equity, Conversion of preferred stock to common stock from completion of initial public offering		$ (122,465)
Conversion of preferred stock to common stock from completion of initial public offering, shares			16,685,014
Conversion of preferred stock to common stock from completion of initial public offering	122,465		$ 2	122,463
Conversion of convertible preferred stock warrant to common stock warrant	259			259
Stock-based compensation	3,151			3,151
Exercise of stock options	$ 69			69
Exercise of stock options, shares	54,266		54,266
Vesting of early exercised stock options	$ 73			73
Vesting of early exercised stock options, shares			145,360
Unrealized gain (loss) on available-for-sale securities, net	(27)				(27)
Net loss	$ (26,488)					(26,488)
Temporary equity, Balance, shares at Sep. 30, 2020	0
Balance, shares at Sep. 30, 2020	25,909,488		25,909,488
Balance at Sep. 30, 2020	$ 98,163		$ 3	208,076	14	(109,930)
Temporary equity, Balance, shares at Jun. 30, 2020		85,093,688
Temporary equity, Balance at Jun. 30, 2020		$ 122,465
Balance, shares at Jun. 30, 2020			2,600,373
Balance at Jun. 30, 2020	(94,213)			6,584	79	(100,876)
Issuance of common stock from initial public offering, net of issuance costs	76,898		$ 1	76,897
Issuance of common stock from initial public offering, net of issuance costs, shares			6,540,000
Temporary equity, Conversion of preferred stock to common stock from completion of initial public offering, shares		(85,093,688)
Temporary equity, Conversion of preferred stock to common stock from completion of initial public offering		$ (122,465)
Conversion of preferred stock to common stock from completion of initial public offering, shares			16,685,014
Conversion of preferred stock to common stock from completion of initial public offering	122,465		$ 2	122,463
Conversion of convertible preferred stock warrant to common stock warrant	259			259
Stock-based compensation	1,791			1,791
Exercise of stock options	58			58
Exercise of stock options, shares			35,882
Vesting of early exercised stock options	24			24
Vesting of early exercised stock options, shares			48,219
Unrealized gain (loss) on available-for-sale securities, net	(65)				(65)
Net loss	$ (9,054)					(9,054)
Temporary equity, Balance, shares at Sep. 30, 2020	0
Balance, shares at Sep. 30, 2020	25,909,488		25,909,488
Balance at Sep. 30, 2020	$ 98,163		$ 3	$ 208,076	$ 14	$ (109,930)