Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$ 23,748	$ 16,367	$ 9,900
General and administrative	9,071	5,354	2,478
Total operating expenses	32,819	21,721	12,378
Loss from operations	(32,819)	(21,721)	(12,378)
Interest income, net	175	9	1
Net loss	$ (32,644)	$ (21,712)	$ (12,377)
Net loss per share, basic and diluted	$ (1.81)	$ (4.67)	$ (131.53)
Weighted average common shared used to compute net loss per share, basic and diluted	18,045	4,652	94