Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (20,410)	$ (24,092)
Adjustment to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	55	88
Change in fair value of warrant liabilities	(1,597)	(1,628)
Stock compensation expense	1,147	1,710
Gain on dissolution of GBO and other	(824)
Changes in assets and liabilities:
Receivables	24	(28)
Prepaid expenses and other current assets	60	768
Other assets	(137)
Accounts payable	(1,454)	863
Accrued expenses and other current liabilities	838	(1,047)
Deferred revenue	(398)	(454)
Net cash used in operating activities	(22,696)	(23,820)
Financing activities:
Proceeds from the sale of common stock and warrants, net of costs	35,068	6,360
Proceeds from the exercise of stock options	589
Net cash provided by financing activities	35,657	6,360
Effect of foreign currency translation on cash	(15)	34
Net increase (decrease) in cash and cash equivalents	12,946	(17,426)
Cash and cash equivalents at beginning of period	4,024	21,450
Cash and cash equivalents at end of period	$ 16,970	$ 4,024