Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Contract revenue	$ 399	$ 1,750
Operating expenses:
Research and development	11,555	5,958
General and administrative	9,262	9,594
Total operating expenses	20,817	15,552
Loss from operations	(20,418)	(13,802)
Interest and other income, net	3,473	518
Interest expense		(1,478)
Net loss	$ (16,945)	$ (14,762)
Net loss per common share, basic and diluted	$ (21.75)	$ (49.99)
Shares used to compute net loss per common share, basic and diluted	779,166	295,272