Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating Activities:
Net loss	$ (18,786)	$ (29,391)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	500	479
Amortization of premium/discount on marketable securities	692	1,237
Stock-based compensation	4,011	5,982
Changes in operating assets and liabilities:
Interest receivable	20	(205)
Accounts receivable	(2,585)	(787)
Prepaid expenses and other assets	(364)	(264)
Accounts payable and accrued liabilities	(3,770)	(3,188)
Accrued compensation and employee benefits	159
Deferred revenues	11,818	240
Net cash used in operating activities	(8,305)	(25,897)
Investing Activities:
Purchases of investments	(70,570)	(82,526)
Maturities of investments	75,155	57,874
Proceeds from sales of investments		10,139
Purchases of property and equipment	(363)	(371)
Net cash provided by (used in) investing activities	4,222	(14,884)
Financing Activities:
Proceeds from issuance of common stock	1,041	51,664
Net cash provided by financing activities	1,041	51,664
Net increase/ (decrease) in cash and cash equivalents	(3,042)	10,883
Cash and cash equivalents, beginning of period	16,766	10,784
Cash and cash equivalents, end of period	$ 13,724	$ 21,667