Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Total revenue	$ 10,765	$ 8,925	$ 25,618	$ 16,805
Cost of sales	6,229	3,133	11,127	6,796
Gross profit	4,536	5,792	14,491	10,009
Operating expenses:
Research and development	6,773	6,427	13,253	12,816
General and administrative	3,329	2,793	6,548	5,638
Sales and marketing	1,713	1,361	3,079	2,219
Total operating expenses	11,815	10,581	22,880	20,673
Loss from operations	(7,279)	(4,789)	(8,389)	(10,664)
Interest expense	(222)	(176)	(433)	(406)
Other income, net	132	24	176	43
Loss on extinguishment of debt		(246)		(246)
Net loss and comprehensive loss	$ (7,369)	$ (5,187)	$ (8,646)	$ (11,273)
Net loss per common share, basic and diluted	$ (0.44)	$ (0.42)	$ (0.55)	$ (0.91)
Weighted-average shares used to compute net loss per common share, basic and diluted	16,635,261	12,413,524	15,717,248	12,357,066
Product sales
Total revenue	$ 9,449	$ 7,200	$ 18,814	$ 13,848
Licensing, royalty and other revenue
Total revenue	$ 1,316	$ 1,725	$ 6,804	$ 2,957