CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (3,963)	$ (6,061)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	49	82
Stock-based compensation expense	401	244
Change in fair value of warrant liability	0	(3)
(Gain) Loss from change in fair value of contingent consideration	(1,200)	1,500
Gain on sale of equipment	(5)	(76)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(236)	(127)
Accounts payable	486	(453)
Accrued expenses and other liabilities	85	123
Deferred revenue	0	(425)
Due to related party	0	1
Net cash used in operating activities	(4,383)	(5,195)
Investing activities
Sales of equipment	5	76
Net cash provided by investing activities	5	76
Financing activities
Proceeds from exercise of common stock options	0	40
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	9,376	0
Proceeds from sale of common stock pursuant to ESPP	10	5
Net cash provided by financing activities	9,386	45
Net increase (decrease) in cash, cash equivalents and restricted cash	5,008	(5,074)
Cash, cash equivalents and restricted cash at beginning of period	14,690	25,352
Cash, cash equivalents and restricted cash at end of period	$ 19,698	$ 20,278