Condensed 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	$ 30,877	$ 6,505	$ 51,112	$ 13,168
General and administrative	5,311	4,384	11,122	8,617
Total operating expenses	36,188	10,889	62,234	21,785
Operating loss	(36,188)	(10,889)	(62,234)	(21,785)
Other income (expense):
Interest income	270	116	504	212
Other income	139	84	153	189
Net loss	$ (35,779)	$ (10,689)	$ (61,577)	$ (21,384)
Net loss per share applicable to common stockholders - basic and diluted	$ (0.95)	$ (0.40)	$ (1.65)	$ (0.92)
Weighted-average number of common shares used in net loss per share applicable to common stockholders—basic and diluted	37,811,056	26,614,671	37,342,324	23,340,590
Comprehensive loss:
Net loss	$ (35,779)	$ (10,689)	$ (61,577)	$ (21,384)
Other comprehensive income (loss) - unrealized gain (loss) on securities	63	(19)	37	(27)
Comprehensive loss	$ (35,716)	$ (10,708)	$ (61,540)	$ (21,411)