Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research and development	$ (14,193)	$ (31,985)
General and administrative	(12,544)	(9,894)
Loss from operations	(26,737)	(41,879)
Interest expense	(3,579)	(1,418)
Interest income	819	443
Net loss	$ (29,497)	$ (42,854)
Net loss per share attributable to common stockholders—basic and diluted	$ (4.36)	$ (6.41)
Weighted-average number of shares outstanding—basic and diluted	6,765,451	6,683,794