CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
License and contract revenues	$ 3,345	$ 26,290
Operating costs and expenses:
Research and development	24,107	36,467
Selling, general and administrative	19,155	22,062
Restructuring expenses	794	660
Total operating costs and expenses	44,056	59,189
Loss from operations	(40,711)	(32,899)
Non-operating income (expense):
Interest income	1,172	1,219
Interest expense	(1,002)	(1,209)
Amortization of debt discount and issuance costs	(521)	(525)
Foreign exchange loss	(281)	(233)
Other non-operating income	1,320	4,295
Total non-operating income, net	688	3,547
Net loss before noncontrolling interest	(40,023)	(29,352)
Noncontrolling interest	3	32
Net loss	(40,020)	(29,320)
Deemed dividends on preferred stock	0	(80)
Net loss attributable to common stockholders	$ (40,020)	$ (29,400)
Basic and diluted net loss per common share (in USD per share)	$ (0.69)	$ (0.52)
Shares used in calculation of basic and diluted net loss per common share (in shares)	57,974	56,073