Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue
Product revenue	$ 245		$ 255
Research revenue	804		1,547
Total revenue	1,049		1,802
Costs and expenses:
Cost of product revenue	829		832
Research and development	6,204	$ 4,803	18,724	$ 14,572
Selling, general and administrative	5,181	2,984	14,086	7,271
Total costs and expenses	12,214	7,787	33,642	21,843
Loss from operations	(11,165)	(7,787)	(31,840)	(21,843)
Interest expense, net	(501)	(304)	(1,455)	(471)
Other income (expense), net	22		37	(1)
Net loss	(11,644)	(8,091)	(33,258)	(22,315)
Comprehensive loss	(11,644)	(8,091)	(33,258)	(22,315)
Reconciliation of net loss to net loss applicable to common stockholders:
Net loss	(11,644)	(8,091)	(33,258)	(22,315)
Accretion of redeemable convertible preferred stock to redemption value		(758)		(4,570)
Net loss applicable to common stockholders	$ (11,644)	$ (8,849)	$ (33,258)	$ (26,885)
Net loss per share applicable to common stockholders - basic and diluted	$ (0.57)	$ (0.71)	$ (1.64)	$ (5.25)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders - basic and diluted	20,331,274	12,379,337	20,225,056	5,120,977