Condensed 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 — related party	$ 1,789	$ 3,600	$ 3,963	$ 32,538
Operating expenses:
Research and development	(19,218)	(17,536)	(37,745)	(31,455)
General and administrative	(5,475)	(3,040)	(12,041)	(7,051)
Total operating expenses	(24,693)	(20,576)	(49,786)	(38,506)
Loss from operations	(22,904)	(16,976)	(45,823)	(5,968)
Interest and other income (expense), net	73	(25)	136	(4)
Net loss	(22,831)	(17,001)	(45,687)	(5,972)
Net loss attributable to common stockholders	$ (22,831)	$ (17,001)	$ (45,687)	$ (5,972)
Net loss per share, attributable to common stockholders:
Basic (USD per share)	$ (0.64)	$ (1.39)	$ (1.28)	$ (0.85)
Diluted (USD per share)	$ (0.64)	$ (1.39)	$ (1.28)	$ (0.85)
Shares used in computing net loss per share attributable to common stockholders:
Basic (in shares)	35,746,922	12,253,943	35,726,393	7,062,780
Diluted (in shares)	35,746,922	12,253,943	35,726,393	7,062,780
Comprehensive loss:
Net loss	$ (22,831)	$ (17,001)	$ (45,687)	$ (5,972)
Net unrealized gain (loss) on short-term investments	(12)	(89)	2	(29)
Total other comprehensive income (loss)	(12)	(89)	2	(29)
Comprehensive loss	$ (22,843)	$ (17,090)	$ (45,685)	$ (6,001)