Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (unaudited) - USD ($)	Total	Initial Public Offering	Series A Redeemable Convertible Preferred Stock	Series A Redeemable Convertible Preferred Stock Initial Public Offering	Series B Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock Initial Public Offering	Common Stock	Common Stock Initial Public Offering	Common Stock License Agreement with Stanford	Additional Paid in Capital	Additional Paid in Capital Initial Public Offering	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ (2,218,000)											$ (2,218,000)
Net loss and comprehensive loss	(141,000)											(141,000)
Ending balance at Mar. 31, 2020	(2,359,000)											(2,359,000)
Beginning balance at Dec. 31, 2019	$ (2,218,000)											(2,218,000)
Common stock shares issued upon early exercise of options, Shares	236,660
Net loss and comprehensive loss	$ (4,837,000)
Ending balance at Sep. 30, 2020	(4,788,000)									$ 2,267,000		(7,055,000)
Temporary equity, Ending balance, Shares at Sep. 30, 2020			15,019,945
Temporary equity, Ending balance at Sep. 30, 2020			$ 11,513,000
Ending balance, Shares at Sep. 30, 2020							9,618,160
Beginning balance at Mar. 31, 2020	(2,359,000)											(2,359,000)
Common shares issued to founders and investor							8,548,517
Issuance of restricted common shares, Shares							832,983
Issuance of redeemable convertible preferred stock upon conversion of outstanding related party convertible note and accrued interest			$ 5,020,000
Issuance of redeemable convertible preferred stock upon conversion of outstanding related party convertible note and accrued interest, Shares			5,019,945
Related party convertible note and accrued interest cancellation	2,225,000									2,225,000
Issuance of redeemable convertible preferred stock for cash			$ 6,493,000
Issuance of redeemable convertible preferred stock for cash, Shares			10,000,000
Stock-based compensation expense	1,000									1,000
Net loss and comprehensive loss	(1,312,000)											(1,312,000)
Ending balance at Jun. 30, 2020	(1,445,000)									2,226,000		(3,671,000)
Temporary equity, Ending balance, Shares at Jun. 30, 2020			15,019,945
Temporary equity, Ending balance at Jun. 30, 2020			$ 11,513,000
Ending balance, Shares at Jun. 30, 2020							9,381,500
Stock-based compensation expense	$ 36,000									36,000
Common stock shares issued upon early exercise of options, Shares	236,660						236,660
Vesting of early exercised stock options	$ 5,000									5,000
Net loss and comprehensive loss	(3,384,000)											(3,384,000)
Ending balance at Sep. 30, 2020	(4,788,000)									2,267,000		(7,055,000)
Temporary equity, Ending balance, Shares at Sep. 30, 2020			15,019,945
Temporary equity, Ending balance at Sep. 30, 2020			$ 11,513,000
Ending balance, Shares at Sep. 30, 2020							9,618,160
Beginning balance at Dec. 31, 2020	(65,408,000)									5,183,000		(70,591,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2020			30,019,945
Temporary equity, Beginning balance at Dec. 31, 2020	55,608,000		$ 55,608,000
Beginning balance, Shares at Dec. 31, 2020							10,279,102
Issuance of redeemable convertible preferred stock for cash			$ 14,997,000		$ 150,524,000
Issuance of redeemable convertible preferred stock for cash, Shares			15,000,000		29,792,487
Stock-based compensation expense	1,033,000									1,033,000
Common stock shares issued upon early exercise of options, Shares							918,825
Vesting of early exercised stock options	7,000									7,000
Reclassification of tranche liability upon settlement			$ 39,403,000
Net loss and comprehensive loss	(19,709,000)											(19,709,000)
Ending balance at Mar. 31, 2021	(84,077,000)									6,223,000		(90,300,000)
Temporary equity, Ending balance, Shares at Mar. 31, 2021			45,019,945		29,792,487
Temporary equity, Ending balance at Mar. 31, 2021			$ 110,008,000		$ 150,524,000
Ending balance, Shares at Mar. 31, 2021							11,197,927
Beginning balance at Dec. 31, 2020	(65,408,000)									5,183,000		(70,591,000)
Temporary equity, Beginning balance, Shares at Dec. 31, 2020			30,019,945
Temporary equity, Beginning balance at Dec. 31, 2020	55,608,000		$ 55,608,000
Beginning balance, Shares at Dec. 31, 2020							10,279,102
Net loss and comprehensive loss	(51,830,000)
Ending balance at Sep. 30, 2021	400,132,000						$ 1,000			522,552,000		(122,421,000)
Temporary equity, Ending balance, Shares at Sep. 30, 2021			0
Ending balance, Shares at Sep. 30, 2021							58,079,002
Beginning balance at Mar. 31, 2021	(84,077,000)									6,223,000		(90,300,000)
Temporary equity, Beginning balance, Shares at Mar. 31, 2021			45,019,945		29,792,487
Temporary equity, Beginning balance at Mar. 31, 2021			$ 110,008,000		$ 150,524,000
Beginning balance, Shares at Mar. 31, 2021							11,197,927
Issuance of common stock		$ 218,177,000									$ 218,177,000
Issuance of common stock, Shares								14,000,000	640,861
Repurchase of common shares in connection with License Agreement with Stanford, Shares									(624,845)
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering		260,532,000						$ 1,000			260,531,000
Temporary equity, Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering, Shares				(45,019,945)		(29,792,487)
Temporary equity, Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering				$ (110,008,000)		$ (150,524,000)
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering, Shares								30,761,676
Stock-based compensation expense	2,018,000									2,018,000
Common stock shares issued upon early exercise of options	21,000						$ 3,383			21,000
Vesting of early exercised stock options	42,000									42,000
Net loss and comprehensive loss	(17,529,000)											(17,529,000)
Ending balance at Jun. 30, 2021	379,184,000						$ 1,000			487,012,000		(107,829,000)
Ending balance, Shares at Jun. 30, 2021							55,979,002
Issuance of common stock		$ 33,146,000									$ 33,146,000
Issuance of common stock, Shares								2,100,000
Stock-based compensation expense	2,374,000									2,374,000
Vesting of early exercised stock options	20,000									20,000
Net loss and comprehensive loss	(14,592,000)											(14,592,000)
Ending balance at Sep. 30, 2021	$ 400,132,000						$ 1,000			$ 522,552,000		$ (122,421,000)
Temporary equity, Ending balance, Shares at Sep. 30, 2021			0
Ending balance, Shares at Sep. 30, 2021							58,079,002