Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ 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	$ 2,163	$ 1,746	$ 7,474	$ 4,645
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 24,831	$ 9,455	$ 68,214	$ 23,983
General and administrative	6,612	3,757	18,764	8,646
Total operating expenses	31,443	13,212	86,978	32,629
Loss from operations	(29,280)	(11,466)	(79,504)	(27,984)
Other income (expense):
Interest income	17	27	49	188
Interest expense	0	0	0	(209)
Change in fair value of preferred warrant liability	0	0	0	(75)
Other expense	(11)	0	(16)	0
Total other income (expense)	6	27	33	(96)
Net loss	(29,274)	(11,439)	(79,471)	(28,080)
Other comprehensive income (loss):
Net unrealized (losses) gains on marketable securities	(1)	0	4	0
Comprehensive loss	$ (29,275)	$ (11,439)	$ (79,467)	$ (28,080)
Net loss per share, basic and diluted	$ (0.68)	$ (0.31)	$ (2.01)	$ (1.72)
Weighted-average shares outstanding, basic and diluted	43,265	37,420	39,477	16,361