Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Product revenue	$ 447	$ 22
Cost of product revenue	461	18
Gross profit (loss)	(14)	4
Expenses
Research and development	1,772	878
Sales and marketing	538	260
General and administrative	1,939	1,292
Total expenses	4,249	2,430
Operating loss	(4,263)	(2,426)
Interest and other income (expense)
Interest expense, net	0	(1)
Change in fair value of warrants liabilities (expense)	1,170	(6,174)
Cease-use expense	(94)	0
Other expense	(2)	0
Inducement charge for Series C warrants	0	(3,050)
Interest and other income (expense), net	1,074	(9,225)
Net loss	$ (3,189)	$ (11,651)
Basic and diluted net loss per common share (in dollars per share)	$ (0.22)	$ (1.67)
Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share (in shares)	14,796,119	6,965,483