Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:
Net loss	$ (12,136)	$ (15,442)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	994	1,628
Decrease in fair value of warrant liability		(106)
Non-employee stock option expense	41	2
Depreciation expense	106	201
Other	18	5
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(199)	111
Accounts payable, accrued expenses, and other liabilities	(1,499)	(2,194)
Net cash used in operating activities	(12,675)	(15,795)
Cash Flows from Investing Activities:
Purchases of property and equipment	(4)
Net cash used in investing activities	(4)
Cash Flows from Financing Activities:
Proceeds from equity financings	40,538
Dividends paid	(1,067)	(423)
Proceeds from exercise of common stock options and warrants and employee stock purchases	1,864	3
Payments on capital lease	(3)	(4)
Net cash provided by (used in) financing activities	41,332	(424)
Net increase (decrease) in cash and cash equivalents	28,653	(16,219)
Cash and cash equivalents, beginning of period	10,096	24,571
Cash and cash equivalents, end of period	$ 38,749	$ 8,352