Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development	$ 29,075	$ 17,478	$ 78,752	$ 48,981
General and administrative	8,989	6,604	25,033	17,057
Total operating expenses	38,064	24,082	103,785	66,038
Loss from operations	(38,064)	(24,082)	(103,785)	(66,038)
Interest income, net	275	53	717	115
Other expense, net	(7)	(6)	(18)	(10)
Net loss	$ (37,796)	$ (24,035)	$ (103,086)	$ (65,933)
Net loss per share—basic and diluted	$ (1.15)	$ (0.84)	$ (3.20)	$ (2.40)
Weighted average common shares outstanding—basic and diluted	32,975,897	28,737,743	32,218,204	27,430,275
Comprehensive loss:
Net loss	$ (37,796)	$ (24,035)	$ (103,086)	$ (65,933)
Other comprehensive items:
Unrealized loss on marketable securities	(74)		(35)
Total other comprehensive loss	(74)		(35)
Total comprehensive loss	$ (37,870)	$ (24,035)	$ (103,121)	$ (65,933)