CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses:
Research and development	$ 12,376	$ 22,005	$ 18,916
General and administrative	6,667	6,237	5,516
Loss from operations	(19,043)	(28,242)	(24,432)
Interest income	324	128	64
Interest expense	(159)	(464)	(475)
Other income (expense)	(20)	(65)	(7)
Net loss	$ (18,898)	$ (28,643)	$ (24,850)
Per share information:
Net loss per share of common stock-basic and diluted (in dollars per share)	$ (0.80)	$ (1.47)	$ (1.67)
Basic and diluted weighted average shares outstanding (in shares)	23,540,748	19,498,143	14,919,783
Net loss	$ (18,898)	$ (28,643)	$ (24,850)
Other comprehensive loss:
Unrealized loss on available-for-sale securities	(96)
Total comprehensive loss	$ (18,994)	$ (28,643)	$ (24,850)