CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net loss	$ (12,921)	$ (13,377)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	101	174
Stock-based compensation expense	686	566
Change in fair value of warrant liability	0	(5)
Loss from change in fair value of contingent consideration	2,700	3,700
Gain on sale of equipment	(5)	(79)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(426)	(200)
Accounts payable	403	(422)
Accrued expenses and other liabilities	(517)	359
Deferred revenue	0	(425)
Due to related party	0	4
Net cash used in operating activities	(9,979)	(9,705)
Investing activities
Sales of equipment	5	69
Net cash provided by investing activities	5	69
Financing activities
Proceeds from exercise of common stock options	29	40
Proceeds from issuance of common stock and the issuance and exercise of common stock warrants, net of issuance costs	58,226	0
Proceeds from sale of common stock pursuant to ESPP	10	5
Net cash provided by financing activities	58,265	45
Net increase (decrease) in cash, cash equivalents and restricted cash	48,291	(9,591)
Cash, cash equivalents and restricted cash at beginning of period	14,690	25,352
Cash, cash equivalents and restricted cash at end of period	$ 62,981	$ 15,761