Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 710	$ 625	$ 479
Costs and expenses:
Cost of goods sold	358	517	690
Research and development	8,562	8,453	5,799
Selling, general and administrative	6,003	5,757	6,395
Total costs and expenses	14,923	14,727	12,884
Operating loss	(14,213)	(14,102)	(12,405)
Other income (expense):
Interest income	87	118	95
Gain on change in fair value of redemption feature embedded in convertible notes	52
Interest expense	(112)
Loss on extinguishment of convertible notes	(521)
Other expense	(2)	(3)	2
Total other income (expense)	(496)	115	97
Net loss	$ (14,709)	$ (13,987)	$ (12,308)
Net loss per share, basic and diluted (in dollars per share)	$ (2.61)	$ (3.28)	$ (2.90)
Weighted-average shares used in computing net loss per share, basic and diluted (in shares)	5,644,328	4,264,178	4,240,060
Product [Member]
Revenue:
Total revenue	$ 182	$ 282	$ 389
Collaboration Agreement [Member]
Revenue:
Total revenue	$ 528	$ 343	$ 90