Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating activities
Net loss	$ (18,328)	$ (29,298)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	325	445
Stock-based compensation expense	2,178	2,728
Amortization of debt issuance costs	220	137
Change in fair value of foreign currency derivative	959	2,340
Changes in operating assets and liabilities:
Receivables from collaborations	747	14,266
Prepaid expenses and other current assets	105	745
Deferred collaboration expense	1,984	977
Accounts payable and accrued expenses	(2,575)	(8,031)
Interest payable	2,100	1,318
Interest reserve		(3,000)
Deferred collaboration revenue	(6,305)	(425)
Net cash used in operating activities	(18,590)	(17,798)
Investing activities
Acquisitions of furniture and equipment	(109)	(53)
Change in restricted cash	(1,605)	(791)
Purchases of investments	(14,534)	(27,676)
Sales and maturities of investments	25,811	26,189
Net cash provided by (used in) investing activities	9,563	(2,331)
Financing activities
Exercise of stock options	510	238
Employee stock purchase plan sales	148	170
Purchases of treasury stock		(61)
Sale of common stock,net	15,339	(73)
Issuance of non-recourse notes payable		25,691
Payment of foreign currency derivative collateral	(1,490)	(2,450)
Net cash provided by financing activities	14,507	23,515
Increase in cash and cash equivalents	5,480	3,386
Cash and cash equivalents at beginning of period	16,444	13,622
Cash and cash equivalents at end of period	$ 21,924	$ 17,008