Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues
Revenues	$ 0	$ 1,391	$ 0	$ 1,907
Operating expenses
Research and development	11,758	20,032	22,206	36,880
General and administrative	3,761	7,518	7,932	15,054
Total operating expenses	15,519	27,550	30,138	51,934
Gain on dispositions, net	(3,761)	0	(3,761)	0
Loss from operations	(11,758)	(26,159)	(26,377)	(50,027)
Other income (expense):
Interest income	28	311	382	721
Interest expense	(763)	(1,088)	(1,748)	(2,158)
Change in fair value of warrant and private placement option liabilities	(30,701)	0	2,125	0
Total other (expense) income	(31,436)	(777)	759	(1,437)
Net loss	$ (43,194)	$ (26,936)	$ (25,618)	$ (51,464)
Net loss per common share attributable to common shareholders, basic and diluted (in shares)	$ (8.55)	$ (5.85)	$ (5.08)	$ (11.40)
Weighted-average shares outstanding, basic and diluted (in shares)	5,052,234	4,605,234	5,045,965	4,515,311
Other comprehensive income (loss):
Unrealized gain on available-for-sale securities, net of tax	$ 0	$ 5	$ 0	$ 56
Foreign currency translation adjustment	(49)	(46)	(62)	(18)
Comprehensive loss	(43,243)	(26,977)	(25,680)	(51,426)
Grants
Revenues
Revenues	$ 0	$ 1,391	$ 0	$ 1,907