CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Convertible Preferred Stock
Temporary Equity, Beginning Balance at Dec. 31, 2018						$ 12,709
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2018						6,170,349
Temporary Equity, Ending Balance at Mar. 31, 2019						$ 12,709
Temporary Equity, Ending Balance, Shares at Mar. 31, 2019						6,170,349
Beginning Balance at Dec. 31, 2018	$ (5,396)	$ 1	$ 187	$ (5,584)
Beginning Balance, Shares at Dec. 31, 2018		1,231,840
Vesting of shares of common stock subject to repurchase	20		20
Vesting of shares of common stock subject to repurchase, Shares		134,601
Share-based compensation expense	67		67
Net loss	(3,083)			(3,083)
Ending Balance at Mar. 31, 2019	(8,392)	$ 1	274	(8,667)
Ending Balance, Shares at Mar. 31, 2019		1,366,441
Temporary Equity, Beginning Balance at Dec. 31, 2018						$ 12,709
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2018						6,170,349
Temporary Equity, Ending Balance at Sep. 30, 2019						$ 54,356
Temporary Equity, Ending Balance, Shares at Sep. 30, 2019						24,987,848
Beginning Balance at Dec. 31, 2018	(5,396)	$ 1	187	(5,584)
Beginning Balance, Shares at Dec. 31, 2018		1,231,840
Net loss	(10,589)
Ending Balance at Sep. 30, 2019	(15,573)	$ 1	599	(16,173)
Ending Balance, Shares at Sep. 30, 2019		1,565,859
Temporary Equity, Beginning Balance at Mar. 31, 2019						$ 12,709
Temporary Equity, Beginning Balance, Shares at Mar. 31, 2019						6,170,349
Temporary equity, Beneficial conversion feature upon issuance of convertible promissory notes						$ 261
Temporary Equity, Ending Balance at Jun. 30, 2019						$ 12,970
Temporary Equity, Ending Balance, Shares at Jun. 30, 2019						6,170,349
Beginning Balance at Mar. 31, 2019	(8,392)	$ 1	274	(8,667)
Beginning Balance, Shares at Mar. 31, 2019		1,366,441
Vesting of shares of common stock subject to repurchase	5		5
Vesting of shares of common stock subject to repurchase, Shares		96,030
Share-based compensation expense	88		88
Net loss	(4,838)			(4,838)
Ending Balance at Jun. 30, 2019	(13,137)	$ 1	367	(13,505)
Ending Balance, Shares at Jun. 30, 2019		1,462,471
Temporary equity, reacquisition of beneficial conversion feature upon settlement of promissory notes						$ (145)
Temporary equity, issuance of Series B second tranche convertible preferred stock, net of issuance cost						$ 44,326
Temporary equity, issuance of Series B second tranche convertible preferred stock, net of issuance costs, Shares						18,817,499
Temporary equity, Series B or preferred stock purchase right (liability) reversal upon issuance of convertible preferred stock						$ (2,795)
Temporary Equity, Ending Balance at Sep. 30, 2019						$ 54,356
Temporary Equity, Ending Balance, Shares at Sep. 30, 2019						24,987,848
Vesting of shares of common stock subject to repurchase	5		5
Vesting of shares of common stock subject to repurchase, Shares		97,054
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		6,334
Share-based compensation expense	227		227
Net loss	(2,668)			(2,668)
Ending Balance at Sep. 30, 2019	(15,573)	$ 1	599	(16,173)
Ending Balance, Shares at Sep. 30, 2019		1,565,859
Temporary Equity, Beginning Balance at Dec. 31, 2019	59,815					$ 59,815
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019						27,283,973
Temporary Equity, Ending Balance at Mar. 31, 2020						$ 59,815
Temporary Equity, Ending Balance, Shares at Mar. 31, 2020						27,283,973
Beginning Balance at Dec. 31, 2019	(25,482)	$ 1	1,179	(26,660)	$ (2)
Beginning Balance, Shares at Dec. 31, 2019		1,600,601
Vesting of shares of common stock subject to repurchase	14		14
Vesting of shares of common stock subject to repurchase, Shares		17,494
Issuance of common stock upon exercise of stock option, net of repurchase	1		1
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		2,871
Share-based compensation expense	482		482
Unrealized gain (loss) on short-term investments	(1)				(1)
Net loss	(8,706)			(8,706)
Ending Balance at Mar. 31, 2020	(33,692)	$ 1	1,676	(35,366)	(3)
Ending Balance, Shares at Mar. 31, 2020		1,620,966
Temporary Equity, Beginning Balance at Dec. 31, 2019	59,815					$ 59,815
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019						27,283,973
Temporary Equity, Ending Balance, Shares at Sep. 30, 2020						0
Beginning Balance at Dec. 31, 2019	(25,482)	$ 1	1,179	(26,660)	(2)
Beginning Balance, Shares at Dec. 31, 2019		1,600,601
Net loss	(73,464)
Ending Balance at Sep. 30, 2020	334,981	$ 3	435,098	(100,124)	4
Ending Balance, Shares at Sep. 30, 2020		32,568,332
Temporary Equity, Beginning Balance at Mar. 31, 2020						$ 59,815
Temporary Equity, Beginning Balance, Shares at Mar. 31, 2020						27,283,973
Temporary Equity, Ending Balance at Jun. 30, 2020						$ 59,815
Temporary Equity, Ending Balance, Shares at Jun. 30, 2020						27,283,973
Beginning Balance at Mar. 31, 2020	(33,692)	$ 1	1,676	(35,366)	(3)
Beginning Balance, Shares at Mar. 31, 2020		1,620,966
Vesting of shares of common stock subject to repurchase	12		12
Vesting of shares of common stock subject to repurchase, Shares		19,110
Issuance of common stock upon exercise of stock option, net of repurchase	285		285
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		110,425
Share-based compensation expense	566		566
Unrealized gain (loss) on short-term investments	4				4
Net loss	(51,065)			(51,065)
Ending Balance at Jun. 30, 2020	(83,890)	$ 1	2,539	(86,431)	1
Ending Balance, Shares at Jun. 30, 2020		1,750,501
Temporary equity, issuance of Series B second tranche convertible preferred stock, net of issuance cost						$ 64,321
Temporary equity, issuance of Series B second tranche convertible preferred stock, net of issuance costs, Shares						27,066,206
Reclassification of preferred stock purchase right liability to equity upon issuance of convertible preferred stock						$ 41,641
Temporary equity, conversion of convertible preferred stock to common stock						$ (165,777)
Conversion of convertible preferred stock to common stock, Shares						(54,350,179)
Temporary Equity, Ending Balance, Shares at Sep. 30, 2020						0
Conversion of convertible preferred stock to common stock	165,777	$ 1	165,776
Conversion of convertible preferred stock to common stock, Shares		14,689,215
Issuance of common stock upon initial public offering, net of issuance cost	265,130	$ 1	265,129
Issuance of common stock upon initial public offering, net of issuance cost, Shares		16,100,000
Vesting of shares of common stock subject to repurchase	9		9
Vesting of shares of common stock subject to repurchase, Shares		18,246
Issuance of common stock upon exercise of stock option, net of repurchase	36		36
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		10,370
Share-based compensation expense	1,609		1,609
Unrealized gain (loss) on short-term investments	3				3
Net loss	(13,693)			(13,693)
Ending Balance at Sep. 30, 2020	$ 334,981	$ 3	$ 435,098	$ (100,124)	$ 4
Ending Balance, Shares at Sep. 30, 2020		32,568,332