Condensed Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses
Research and development	$ 5,587	$ 6,103	$ 12,751	$ 12,798
General and administrative	2,464	2,248	5,443	4,251
Change in fair value of contingent consideration	3,034	2,842	2,047	3,426
Total operating expenses	11,085	11,193	20,241	20,475
Operating loss	(11,085)	(11,193)	(20,241)	(20,475)
Other income
Change in fair value of warrants liabilities	56	3,808	257	7,221
Interest income	41	1	42	12
Total other income	97	3,809	299	7,233
Net loss	$ (10,988)	$ (7,384)	$ (19,942)	$ (13,242)
Net loss per common share, basic and diluted	$ (0.14)	$ (0.16)	$ (0.25)	$ (0.29)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share	79,747,506	46,236,209	79,721,290	45,458,034