Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue—related party	$ 17,903	$ 995	$ 8,181
Operating expenses:
Research and development	34,334	23,691	14,717
General and administrative	22,760	8,692	8,428
Total operating expenses	57,094	32,383	23,145
Loss from operations	(39,191)	(31,388)	(14,964)
Interest income	785	938	543
Interest expense	(134)
Other income (expense), net	(953)	2,331	4,533
Loss before income tax benefit	(39,493)	(28,119)	(9,888)
Income tax expense (benefit)	(2,815)	19	(589)
Net loss	$ (36,678)	$ (28,138)	$ (9,299)
Net loss per share attributable to common stockholders, basic and diluted	$ (5.01)	$ (13.15)	$ (4.78)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	7,319,977	2,138,973	1,946,976
Other comprehensive income (loss):
Unrealized gain (loss) on marketable debt securities, net of tax	$ 1	$ 36	$ (13)
Total other comprehensive income (loss)	1	36	(13)
Comprehensive loss	$ (36,677)	$ (28,102)	$ (9,312)