Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating expenses:
Research and development	$ (7,097)	$ (7,615)
General and administrative	(2,869)	(2,522)
Loss from operations	(9,966)	(10,137)
Interest expense	(876)
Interest income	172	69
Net loss	$ (10,670)	$ (10,068)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.40)	$ (0.38)
Weighted-average number of shares outstanding—basic and diluted	26,986,318	26,423,394