Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenues
Grant revenue	$ 0	$ 375
Type of Revenue [Extensible List]	us-gaap:GrantMember	us-gaap:GrantMember
Total revenues	$ 0	$ 375
Operating expense
Research and development	10,984	22,563
General and administrative	7,775	7,559
Total operating expense	18,759	30,122
Loss from operations	(18,759)	(29,747)
Other income (expense)
Interest income	45	151
Interest expense	(164)	(29)
Loss on warrant issuance	0	(5,020)
Change in fair value of warrant liabilities	(223)	(16,501)
Change in fair value of convertible notes payable	0	(109)
Total other income (expense)	(342)	(21,508)
Net loss and comprehensive loss	$ (19,101)	$ (51,255)
Net loss per share basic and diluted	$ (0.43)	$ (2.52)
Weighted-average common shares outstanding basic and diluted	44,766,640	20,308,818