Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net loss	$ (2,876)	$ (1,496)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	13	10
Change in fair value of convertible preferred stock warrant liability		(53)
Change in fair value of maturity date preferred stock warrant liability		1
Change in fair value of convertible shareholder notes derivative liability		(78)
Share-based compensation	622	30
Non-cash interest expense on convertible shareholder notes		550
Changes in operating assets and liabilities:
Accounts receivable	(47)	(4)
Inventory	(9)	42
Prepaid expenses	104	28
Accounts payable	(249)	103
Accrued liabilities excluding accrued interest on convertible note	176	86
Deferred revenue	1	40
Deferred rent	6	(7)
Grant liability	(19)
Net cash used in operating activities	(2,278)	(748)
Investing activities:
Purchase of property and equipment	(64)
Net cash used in investing activities	(64)
Financing activities:
Proceeds from the exercise of stock options	22
Net cash provided by financing activities	22
Net decrease in cash and cash equivalents	(2,320)	(748)
Cash and cash equivalents at beginning of period	21,352	3,557
Cash and cash equivalents at end of period	19,032	2,809
Supplemental disclosures for noncash investing activity:
Accounts payable recognized for the purchase of equipment	$ 15