Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities:
Net loss	$ (6,184,000)	$ (9,707,000)
Adjustments required to reconcile net loss to net cash used in operating activities:
Change in fair value of derivative liabilities	77,000	(2,034,000)
Impairment charges		5,800,000
Stock-based compensation	246,000	470,000
Deferred taxes		(1,302,000)
Depreciation	178,000	170,000
Amortization of patents	15,000	15,000
Other non-cash adjustments, net		18,000
Changes in operating assets and liabilities:
Accounts payable and accrued expenses	28,000	(12,000)
Prepaid expenses and other current assets	(69,000)	352,000
Net cash used in operating activities	(5,709,000)	(6,230,000)
Investing activities:
Purchases of property and equipment	(31,000)	(7,000)
Net cash used in investing activities	(31,000)	(7,000)
Financing activities:
Proceeds from sale of common stock and related warrants, net of offering costs	6,203,000	9,690,000
Proceeds from exercises of warrants	198,000
Proceeds from stock issuance under employee stock purchase plan	5,000	3,000
Principal payment on note payable		(205,000)
Net cash provided by financing activities	6,406,000	9,488,000
Net increase in cash and cash equivalents	666,000	3,251,000
Cash and cash equivalents, beginning of period	5,132,000	5,711,000
Cash and cash equivalents, end of period	5,798,000	8,962,000
Supplemental schedule of non-cash financing activities:
Offering costs included in accounts payable	$ 44,000	$ 339,000