Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Type of revenue [extensible list]	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 11,855	$ 14,562
General and administrative	6,354	4,460
Total operating expenses	18,209	19,022
Loss from operations	(18,209)	(19,022)
Other income (expense):
Interest income	22	300
Total other income (expense)	(9)	294
Other expense, net	(31)	(6)
Net loss	$ (18,218)	$ (18,728)
Net loss per share, basic and diluted	$ (0.28)	$ (0.57)
Weighted-average common shares outstanding, basic and diluted	65,604,336	33,097,736