Consolidated 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]
Collaboration revenue	$ 4,381	$ 2,000	$ 9,170	$ 2,750
Operating expenses:
Research and development	17,378	12,775	33,712	27,257
General and administrative	6,685	5,149	12,183	10,213
Total operating expenses	24,063	17,924	45,895	37,470
Loss from operations	(19,682)	(15,924)	(36,725)	(34,720)
Other income, net	34	239	78	583
Net loss	$ (19,648)	$ (15,685)	$ (36,647)	$ (34,137)
Net loss per share, basic and diluted	$ (0.60)	$ (0.66)	$ (1.14)	$ (1.47)
Weighted-average common shares outstanding, basic and diluted	32,636	23,854	32,076	23,287
Comprehensive loss:
Net loss	$ (19,648)	$ (15,685)	$ (36,647)	$ (34,137)
Other comprehensive (loss) gain:
Unrealized (loss) gain on marketable securities	(5)	134	(7)	81
Total other comprehensive (loss) gain	(5)	134	(7)	81
Comprehensive loss	$ (19,653)	$ (15,551)	$ (36,654)	$ (34,056)