CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (6,061)	$ (7,574)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	82	54
Non-cash interest expense	0	26
Stock-based compensation expense	244	586
Change in fair value of warrant liability	(3)	(115)
Loss from change in fair value of contingent consideration	1,500	0
Loss on extinguishment of debt	0	221
Gain on sale of equipment	(76)	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(127)	(162)
Restricted cash	0	(80)
Accounts payable	(453)	342
Accrued expenses and other liabilities	123	(1,645)
Deferred revenue	(425)	(203)
Due to related party	1	0
Net cash used in operating activities	(5,195)	(8,550)
Investing activities
Sales of property and equipment	76	0
Net cash provided by investing activities	76	0
Financing activities
Payments on notes payable	0	(14,124)
Proceeds from exercise of common stock options	40	14
Proceeds from sale of common stock pursuant to ESPP	5	0
Net cash provided by (used in) financing activities	45	(14,110)
Net decrease in cash and cash equivalents	(5,074)	(22,660)
Cash and cash equivalents at beginning of period	25,342	36,079
Cash and cash equivalents at end of period	20,268	13,419
Supplemental cash flow information
Cash paid for interest	$ 0	$ 663