Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue—related party	$ 3,028	$ (7,047)	$ 12,493	$ (974)
Operating expenses:
Research and development	8,942	6,331	24,651	17,168
General and administrative	7,741	1,847	17,684	6,069
Total operating expenses	16,683	8,178	42,335	23,237
Loss from operations	(13,655)	(15,225)	(29,842)	(24,211)
Interest income	153	276	704	561
Interest expense	(50)		(84)
Other income (expense), net	(1,224)	171	(1,174)	2,091
Loss before income tax expense (benefit)	(14,776)	(14,778)	(30,396)	(21,559)
Income tax expense (benefit)	3		(2,676)	1
Net loss	$ (14,779)	$ (14,778)	$ (27,720)	$ (21,560)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.84)	$ (6.87)	$ (8.69)	$ (10.10)
Weighted-average common shares used in computing net loss per share attributable to common stockholders, basic and diluted	5,208,887	2,149,986	3,190,557	2,133,645
Other comprehensive income:
Unrealized (loss) gain on marketable debt securities, net of tax	$ (114)	$ (5)	$ 60	$ 11
Total other comprehensive (loss) income	(114)	(5)	60	11
Comprehensive loss	$ (14,893)	$ (14,783)	$ (27,660)	$ (21,549)