Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Grant	$ 0	$ 0	$ 3,888
Type of revenue [extensible list]	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 59,638	$ 64,600	$ 36,719
General and administrative	21,843	15,734	12,632
Total operating expenses	81,481	80,334	49,351
Loss from operations	(81,481)	(80,334)	(45,463)
Other income (expense):
Interest income	593	2,143	1,172
Other expense, net	(5)	(63)	(57)
Total other income	588	2,080	1,115
Net loss	$ (80,893)	$ (78,254)	$ (44,348)
Net loss per share, basic and diluted	$ (1.52)	$ (2.45)	$ (2.13)
Weighted-average common shares outstanding, basic and diluted	53,371,730	31,949,633	20,822,560