Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product revenue	$ 3,440	$ 1,747	$ 599
Research revenue	1,226	2,333	2,214
Total revenue	4,666	4,080	2,813
Costs and expenses:
Cost of product revenue	12,028	6,872	1,740
Research and development	23,733	24,009	25,362
Selling, general and administrative	22,757	24,077	19,094
Total costs and expenses	58,518	54,958	46,196
Loss from operations	(53,852)	(50,878)	(43,383)
Interest expense, net	(8,907)	(4,098)	(1,967)
Other income, net	331	172	60
Net loss and comprehensive loss	$ (62,428)	$ (54,804)	$ (45,290)
Net loss per share — basic and diluted	$ (1.94)	$ (2.11)	$ (2.21)
Weighted-average number of common shares used in computing net loss per share — basic and diluted	32,131,512	26,015,751	20,501,748