Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Total revenue	$ 5,991	$ 2,646
Operating expenses:
Research and development	23,045	25,212
General and administrative	11,507	13,113
Total operating expenses	34,552	38,325
Operating loss	(28,561)	(35,679)
Other income (expense), net:
Interest income	297	87
Interest expense	(1,047)	(1,048)
Change in fair value of warrant liability	16,566	0
Other income, net	72	19
Total other income (expense), net	15,888	(942)
Net loss	(12,673)	(36,621)
Comprehensive loss	$ (12,673)	$ (36,621)
Net loss per share, basic and diluted (in USD per share)	$ (0.49)	$ (2.29)
Weighted-average common shares outstanding, basic and diluted (in shares)	25,795,721	15,981,247
License and collaboration revenue
Total revenue	$ 5,982	$ 2,271
Research and development services revenue
Total revenue	$ 9	$ 375