Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating expenses:
Research and development	$ 26,096	$ 18,603	$ 49,677	$ 31,503
General and administrative	8,910	6,456	16,044	10,453
Total operating expenses	35,006	25,059	65,721	41,956
Loss from operations	(35,006)	(25,059)	(65,721)	(41,956)
Interest income, net	266	41	442	62
Other expense, net	(7)	(9)	(11)	(4)
Net loss	$ (34,747)	$ (25,027)	$ (65,290)	$ (41,898)
Net loss per share-basic and diluted	$ (1.08)	$ (0.90)	$ (2.05)	$ (1.57)
Weighted average shares outstanding-basic and diluted	32,062,298	27,860,332	31,835,194	26,765,705
Comprehensive loss:
Net loss	$ (34,747)	$ (25,027)	$ (65,290)	$ (41,898)
Other comprehensive items:
Unrealized gain on marketable securities	39		39
Total other comprehensive gain	39		39
Total comprehensive loss	$ (34,708)	$ (25,027)	$ (65,251)	$ (41,898)