Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended		121 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Cash flows from operating activities:
Net loss	$ (48,203)	$ (65,907)	$ (331,927)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	582	466	3,156
Stock-based compensation	2,482	3,482	22,663
Change in fair value of warrants	(2,979)	2,516	(13,750)
Loss on disposal of fixed assets	194	48	251
Common stock issued in exchange for in-process research and development			36,151
(Increase) decrease in:
Receivables	(391)	66	(449)
Prepaid expenses and other current assets	3,717	(5,922)	(3,195)
Other noncurrent assets	262	(47)	(739)
Deposits	5	(42)	(129)
Increase (decrease) in:
Accounts payable	(618)	2,521	891
Accrued expenses	(4,943)	5,861	11,573
Deferred revenue	(600)	(600)	2,933
Deferred rent	8	226	447
Other liabilities	20		20
Net cash used in operating activities	(50,464)	(57,332)	(272,104)
Cash flows from investing activities:
Purchases of property and equipment	(119)	(1,482)	(4,745)
Proceeds from sale of property and equipment	1		2
Net cash used in investing activities	(118)	(1,482)	(4,743)
Cash flows from financing activities:
Stockholders' capital contribution			500
Proceeds from exercise of stock options	956	30	2,329
Payments to employees for repurchase of common stock	(250)	(96)	(3,117)
Proceeds from exercise of warrants	201	330	13,280
Proceeds from issuance of common stock and warrants, net		49,170	270,726
Proceeds from issuance of preferred stock, net			16,760
Net cash provided by financing activities	907	49,434	300,478
Net increase (decrease) in cash and cash equivalents	(49,675)	(9,380)	23,631
Cash and cash equivalents, beginning of period	73,306	104,713
Cash and cash equivalents, end of period	23,631	95,333	23,631
Supplementary disclosure of cash flow information:
Cash paid for interest
Cash paid for income taxes
Supplementary disclosure of noncash investing and financing activities:
Warrants issued to placement agents and investors			47,276
Exercise of liability-classified warrants to common shares		412	352
Convertible Preferred Stock
Supplementary disclosure of noncash investing and financing activities:
Preferred stock conversion/exercise of equity-classified warrants to common stock			16,760
Warrants
Supplementary disclosure of noncash investing and financing activities:
Preferred stock conversion/exercise of equity-classified warrants to common stock	$ 142	$ 269	$ 9,466