Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Collaboration revenue	$ 4,789	$ 750
Operating expenses:
Research and development	16,334	14,482
General and administrative	5,498	5,064
Total operating expenses	21,832	19,546
Loss from operations	(17,043)	(18,796)
Other income, net	44	344
Net loss	$ (16,999)	$ (18,452)
Net loss per share, basic and diluted	$ (0.54)	$ (0.81)
Weighted-average common shares outstanding, basic and diluted	31,510	22,719
Comprehensive loss:
Net loss	$ (16,999)	$ (18,452)
Other comprehensive loss:
Unrealized loss on marketable securities	(2)	(53)
Total other comprehensive loss	(2)	(53)
Comprehensive loss	$ (17,001)	$ (18,505)