Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Grant revenue	$ 1,147	$ 106	$ 1,366	$ 181
Expenses:
Research and development	5,483	8,316	11,896	18,676
General and administrative	1,804	1,783	3,726	5,440
Total operating expense	7,287	10,099	15,622	24,116
Operating loss	(6,140)	(9,993)	(14,256)	(23,935)
Change in fair value of common stock warrant liability				223
Other income / (expense):
Interest income	3	5	6	12
Interest expense	(615)	(637)	(1,226)	(1,259)
Other income		1		434
Other income / (expense), net	(612)	(631)	(1,220)	(813)
Net loss	(6,752)	(10,624)	(15,476)	(24,525)
Deemed dividend on Series A preferred stock	(532)		(4,136)
Net loss attributable to common shareholders	$ (7,284)	$ (10,624)	$ (19,612)	$ (24,525)
Net loss per common share
Basic and diluted (in dollars per share)	$ (0.76)	$ (1.29)	$ (2.10)	$ (2.99)
Weighted average number of common shares outstanding
Basic and diluted (in shares)	9,634	8,238	9,317	8,215