Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (33,864)	$ (26,339)	$ (24,013)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation	274	292	270
Increase in warrant liabilities	2,608
Amortization of deferred loan costs	193	238	198
Amortization of debt discount	3,644	3,739	1,635
Interest expense added to loan principal	9,269	7,636	8,237
Interest added to lease liability	964	755
Loss on debt conversion	58	1,234
Loss on early extinguishment of debt and debt refinancing	3,501	2,250
Compensation charge for stock awards and share options	2,304	1,296	1,116
Changes in operating assets and liabilities:
Decrease in accounts receivable	3	148	52
Decrease (increase) in prepaid expenses and other	2,980	(3,082)	37
Increase in other assets	(444)	(185)	(186)
(Decrease) increase in accounts payable	(79)	130	9
(Decrease) increase in accrued liabilities	(1,877)	2,374	77
Net cash used for operating activities	(10,466)	(9,514)	(12,568)
Cash flows from investing activities:
Additions to property, plant and equipment	(1,006)		(906)
Net cash used for investing activities	(1,006)		(906)
Cash flows from financing activities:
Net proceeds from issuance of common stock		10,510
Up-front payment related to lease liability		12,000
Net proceeds from issuance of long-term debt	57,253	8,000
Debt issuance costs		(960)
Principal payments on long-term debt	(44,923)	(10,554)	(42)
Net cash provided by (used for) financing activities	12,330	18,996	(42)
Net increase (decrease) in cash and cash equivalents	858	9,482	(13,516)
Cash and cash equivalents, beginning of period	12,172	2,690	16,206
Cash and cash equivalents, end of period	$ 13,030	$ 12,172	$ 2,690