CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
License and contract revenues	$ 0	$ 416	$ 0	$ 1,056
Operating costs and expenses:
Research and development	6,199	6,356	9,463	11,528
General and administrative	3,797	5,053	8,264	10,259
Restructuring expenses	0	0	0	794
Other operating expenses	0	0	4,200	0
Total operating costs and expenses	9,996	11,409	21,927	22,581
Loss from operations	(9,996)	(10,993)	(21,927)	(21,525)
Non-operating income (expense):
Interest income	43	347	162	727
Interest expense	(137)	(269)	(304)	(563)
Amortization of debt discount and issuance costs	(130)	(130)	(260)	(260)
Foreign exchange (loss) gain	(6)	69	(83)	(169)
Loss on dissolution of majority-owned subsidiary	(3,774)	0	(3,774)	0
Total non-operating (expense) income, net	(4,004)	17	(4,259)	(265)
Net loss before noncontrolling interest	(14,000)	(10,976)	(26,186)	(21,790)
Noncontrolling interest	0	5	0	5
Net loss	$ (14,000)	$ (10,971)	$ (26,186)	$ (21,785)
Basic and diluted net loss per common share (in dollars per share)	$ (0.19)	$ (0.19)	$ (0.38)	$ (0.38)
Shares used in calculation of basic and diluted net loss per common share (in shares)	73,685	57,973	68,073	57,973