Unaudited Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue
Operating expenses:
Research and development	8,531	11,637
General and administrative	2,838	3,132
Total operating expenses	11,369	14,769
Loss from operations	(11,369)	(14,769)
Other (expense) income:
Interest expense related to amortization of debt issuance costs and discount	(305)	(390)
Interest expense on principal	(1,229)	(1,442)
Fair value adjustment related to derivative and warrant liability	453	(9,741)
Interest and other income, net	151	115
Total other (expense) income	(930)	(11,458)
Loss before income taxes	(12,299)	(26,227)
Income tax benefit	8	8
Net loss	$ (12,291)	$ (26,219)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.46)	$ (1.77)
Weighted average number of shares of common stock outstanding:
Basic and diluted (in shares)	26,701,891	14,791,882