Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 1,021	$ 1,158
Operating expenses:
Research and development	13,108	6,876
General and administrative	3,170	2,301
Total operating expenses	16,278	9,177
Loss from operations	(15,257)	(8,019)
Interest income	191
Other income (expense), net	(30)	28
Net loss	(15,096)	(7,991)
Accruing dividends on preferred stock		(1,378)
Net loss attributable to common stockholders	$ (15,096)	$ (9,369)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.60)	$ (0.87)
Weighted average common shares outstanding—basic and diluted	25,020,337	10,766,722