Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net loss	$ (15,611)	$ (7,553)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss from discontinued operations	6	283
Depreciation and amortization	147	137
Stock-based compensation	3,773	1,097
Amortization of debt discount	262	64
Changes in operating assets and liabilities:
Accounts receivable		110
Prepaid expenses and other current assets	(89)	(96)
Accounts payable	980	274
Accrued expenses	(352)	710
Deferred revenue		(272)
Net cash used in operating activities	(10,884)	(5,246)
Cash flows from investing activities:
Purchases of property and equipment	(546)	(126)
Net cash used in investing activities	(546)	(126)
Cash flows from financing activities:
Proceeds from sale of common stock, net of issuance costs	50,491
Proceeds from sale of units of common stock and warrants, net of issuance costs		22,772
Proceeds from convertible note financing	3,000	1,500
Proceeds from the issuance of shares under the Employee Stock Purchase Plan	13	10
Net cash provided by financing activities	53,504	24,282
Net increase in cash and cash equivalents	42,074	18,910
Cash and cash equivalents, beginning of period	17,974	2,109
Cash and cash equivalents, end of period	$ 60,048	$ 21,019