Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Collaboration revenue	$ 8,976	$ 8,967	$ 24,979	$ 8,967
Revenue from Contract with Customer, Product and Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses
Research and development	$ 15,503	$ 10,025	$ 42,048	$ 27,647
General and administrative	5,186	3,938	14,830	11,384
Total operating expenses	20,689	13,963	56,878	39,031
Loss from operations	(11,713)	(4,996)	(31,899)	(30,064)
Interest income and other income (expense), net	131	70	349	704
Net loss	(11,582)	(4,926)	(31,550)	(29,360)
Change in unrealized losses on marketable securities	(46)	(22)	(57)	(30)
Comprehensive loss	$ (11,628)	$ (4,948)	$ (31,607)	$ (29,390)
Net loss per common share, basic and diluted	$ (0.31)	$ (0.17)	$ (0.92)	$ (1.26)
Weighted average number of common shares outstanding used in computing net loss per share, basic and diluted	37,769,910	28,396,670	34,157,578	23,235,218