Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 1,779	$ 2,413	$ 4,660	$ 6,372
General and administrative	1,768	2,318	3,594	5,404
Restructuring Charges		416	0	416
Total operating expenses	3,547	5,147	8,254	12,192
Loss from operations	(3,547)	(5,147)	(8,254)	(12,192)
Other income (expense)
Interest income	63	101	101	198
Interest expense		(320)		(689)
Change in fair value of warrants		22		29
Total other income (expense), net	63	(197)	101	(462)
Loss before benefit from income taxes	(3,484)	(5,344)	(8,153)	(12,654)
Benefit from income taxes				477
Net loss	$ (3,484)	$ (5,344)	$ (8,153)	$ (12,177)
Net loss per share (basic and diluted) (in dollars per share)	$ (0.08)	$ (0.16)	$ (0.20)	$ (0.36)
Weighted-average common shares (basic and diluted) (in shares)	43,776,549	34,277,601	40,560,259	34,253,515