Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities
Net loss	$ (3,112,000)	$ (14,493,000)
Adjustments required to reconcile net loss to net cash used in operating activities:
Change in fair value of warrant liability	(4,000)	4,690,000
Change in fair value of Series B preferred stock derivative liability	(1,402,000)	7,105,000
Warrants issued	204,000	213,000
Amortization of patents	8,000	8,000
Depreciation	73,000	58,000
Stock-based compensation	816,000	52,000
Changes in operating assets and liabilities: [Abstract]
Accounts receivable	111,000	100,000
Accounts payable, accrued expenses, deferred revenue and other	436,000	158,000
Accrued severance	(170,000)	(122,000)
Prepaid expenses and other current assets	(45,000)	(74,000)
Net cash used in operating activities	(3,085,000)	(2,305,000)
Investing activities:
Purchases of property and equipment	(112,000)	(35,000)
Net cash used in investing activities	(112,000)	(35,000)
Financing activities:
Proceeds from issuance of common stock, net		12,384,000
Net cash provided by financing activities		12,384,000
Net (decrease) increase in cash and cash equivalents	(3,197,000)	10,044,000
Cash and cash equivalents, beginning of period	9,370,000	6,581,000
Cash and cash equivalents, end of period	6,173,000	16,625,000
Supplemental schedule of non-cash financing activities:
Accretion of Series B redeemable convertible preferred stock	$ 1,725,000	338,000
Fair value of warrant liability upon issuance		$ 4,211,000