Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Net product revenue	$ 389,000	$ 517,000	$ 860,000
Collaboration agreement revenue	90,000	59,000	44,000
Total revenue	479,000	576,000	904,000
Costs and expenses:
Cost of goods sold	690,000	746,000	1,061,000
Research and development	5,799,000	3,330,000	1,518,000
Selling, general and administrative	6,395,000	4,108,000	3,734,000
Total costs and expenses	12,884,000	8,184,000	6,313,000
Operating loss	(12,405,000)	(7,608,000)	(5,409,000)
Other income (expense):
Interest income	95,000
Interest expense	0	(1,736,000)	(1,386,000)
Write-off of deferred offering costs			(1,634,000)
Change in fair value of convertible preferred stock warrant liability		250,000	274,000
Change in fair value of maturity date preferred stock warrant liability		10,000	87,000
Change in fair value of convertible shareholder notes derivative liability		(1,224,000)	1,373,000
Other income (expense)	2,000	(2,000)	(2,000)
Total other income (expense), net	97,000	(2,702,000)	(1,288,000)
Net loss	$ (12,308,000)	$ (10,310,000)	$ (6,697,000)
Net loss per share, basic and diluted (in dollars per share)	$ (0.32)	$ (1.23)	$ (4.29)
Weighted-average shares used in computing net loss per share, basic and diluted (in shares)	38,160,543	8,368,284	1,560,293