Consolidated 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	$ 4,935	$ 1,848	$ 14,105	$ 4,598
Operating expenses:
Research and development	17,077	15,640	50,789	42,897
General and administrative	8,628	5,312	20,811	15,525
Total operating expenses	25,705	20,952	71,600	58,422
Loss from operations	(20,770)	(19,104)	(57,495)	(53,824)
Other income, net	54	142	132	725
Net loss	$ (20,716)	$ (18,962)	$ (57,363)	$ (53,099)
Net loss per share, basic and diluted	$ (0.57)	$ (0.70)	$ (1.71)	$ (2.16)
Weighted-average common shares outstanding, basic and diluted	36,606	27,261	33,603	24,621
Comprehensive loss:
Net loss	$ (20,716)	$ (18,962)	$ (57,363)	$ (53,099)
Other comprehensive (loss) gain:
Unrealized (loss) gain on marketable securities	(78)	(50)	(85)	31
Total other comprehensive (loss) gain	(78)	(50)	(85)	31
Comprehensive loss	$ (20,794)	$ (19,012)	$ (57,448)	$ (53,068)