Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended		100 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (5,103)	$ (13,326)	$ (87,012)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	195	167	1,540
Non-cash derivatives loss		10,449	31,410
Non-cash interest expense			985
Non-cash loss from modification of warrants			765
Common stock issued to 401(k) plan	41	53	366
Common stock issued for services	282		516
Share-based compensation expense	835	432	7,004
Changes in operating assets and liabilities:
Restricted cash	231		(371)
Prepaid expenses	(425)	(63)	(456)
Other assets	1	1	(194)
Accounts payable	(195)	(70)	704
Accrued interest payable			(15)
Accrued expenses	(56)	(312)	1,236
Net cash used in operating activities	(4,194)	(2,669)	(43,522)
Cash flows from investing activities:
Purchases of property and equipment	(35)	(410)	(3,555)
Net cash used in investing activities	(35)	(410)	(3,555)
Cash flows from financing activities:
Proceeds from issuance of note payable			150
Repayment of note payable	(18)		(75)
Proceeds from issuance of convertible notes payable			4,181
Proceeds from convertible bridge notes			500
Principal payments on capital lease obligation	(3)	(8)	(94)
Proceeds from loan payable		222	2,241
Repayment of loan payable			(321)
Proceeds from exercise of options and warrants	116	341	50,341
Net cash provided by financing activities	95	555	56,923
Increase in cash and cash equivalents	(4,134)	(2,524)	9,846
Cash and cash equivalents at beginning of period	13,980	12,825
Cash and cash equivalents at end of period	9,846	10,301	9,846
Supplemental disclosure of cash flow information and non-cash transactions:
Cash paid for interest	32	27	313
Conversion of convertible notes payable and accrued interest into common stock			4,672
Conversion of convertible bridge note payable and accrued interest into common stock			505
Asset acquired through capital lease obligation			94
Beneficial conversion feature on convertible and bridge notes payable			134
Fair value of warrants issued with bridge notes payable			179
Fair value of warrants issued in connection with loan agreement			42
Reclassification of derivative warrant liability to additional paid-in capital		$ 476	$ 38,104