Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Product revenue	$ 438	$ 441	$ 913	$ 857
Collaboration revenue				42
Total revenue	438	441	913	899
Costs and operating expenses:
Cost of product revenue	104	105	219	204
Research and development	8,117	6,978	14,846	14,051
Selling and marketing	6,832	1,492	12,859	2,881
General and administrative	3,724	2,973	7,000	5,379
Total costs and operating expenses	18,777	11,548	34,924	22,515
Loss from operations	(18,339)	(11,107)	(34,011)	(21,616)
Other income (expense):
Interest income	113	80	205	167
Interest expense	(468)	(418)	(911)	(836)
Total other expense, net	(355)	(338)	(706)	(669)
Net loss	$ (18,694)	$ (11,445)	$ (34,717)	$ (22,285)
Net loss per share, basic and diluted	$ (0.64)	$ (0.46)	$ (1.22)	$ (0.90)
Weighted average common shares outstanding, basic and diluted	29,026,259	24,770,059	28,352,348	24,761,498
Comprehensive loss:
Net loss	$ (18,694)	$ (11,445)	$ (34,717)	$ (22,285)
Other comprehensive income (loss):
Unrealized gain on marketable securities	9	10	5	78
Total other comprehensive income	9	10	5	78
Total comprehensive loss	$ (18,685)	$ (11,435)	$ (34,712)	$ (22,207)