Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues
Revenues	$ 0	$ 103	$ 0	$ 2,010
Operating expenses
Research and development	8,140	14,331	30,346	51,211
General and administrative	4,163	9,209	12,095	24,263
Total operating expenses	12,303	23,540	42,441	75,474
Gain on dispositions, net	0	0	(3,761)	0
Loss from operations	(12,303)	(23,437)	(38,680)	(73,464)
Other income (expense):
Interest income	10	323	392	1,044
Interest expense	(725)	(1,079)	(2,473)	(3,237)
Change in fair value of warrant and private placement option liabilities	12,131	(4,850)	14,256	(4,850)
Other expense	0	(2,989)	0	(2,989)
Total other income (expense)	11,416	(8,595)	12,175	(10,032)
Net loss	$ (887)	$ (32,032)	$ (26,505)	$ (83,496)
Net loss per common share attributable to common shareholders, basic and diluted (in shares)	$ (0.18)	$ (6.79)	$ (5.25)	$ (18.21)
Weighted-average shares outstanding, basic and diluted (in shares)	5,059,779	4,720,895	5,050,603	4,584,592
Other comprehensive income (loss):
Unrealized (loss) gain on available-for-sale securities, net of tax	$ 0	$ (8)	$ 0	$ 48
Foreign currency translation adjustment	36	(23)	(26)	(41)
Comprehensive loss	(851)	(32,063)	(26,531)	(83,489)
Grants
Revenues
Revenues	$ 0	$ 103	$ 0	$ 2,010