Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended		127 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (9,711)	$ (12,799)	$ (350,542)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	124	199	3,437
Stock-based compensation	1,223	1,541	24,911
Change in fair value of warrants	(82)	(10,788)	(12,038)
Loss on disposal of fixed assets			641
Common stock issued in exchange for in-process research and development			36,151
(Increase) decrease in:
Receivables	118	(14)	(27)
Prepaid expenses and other current assets	359	2,078	(1,589)
Other noncurrent assets	11	258	(517)
Deposits			(128)
Increase (decrease) in:
Accounts payable	156	(526)	578
Accrued expenses	(605)	2,005	5,752
Deferred revenue	(200)	(200)	2,533
Deferred rent	(47)	3	1,016
Other noncurrent liabilities			20
Net cash used in operating activities	(8,654)	(18,243)	(289,802)
Cash flows from investing activities:
Purchases of property and equipment	(2)	(114)	(4,760)
Proceeds from sale of property and equipment			2
Net cash used in investing activities	(2)	(114)	(4,758)
Cash flows from financing activities:
Stockholders' capital contribution			500
Proceeds from exercise of stock options	969	851	3,298
Payments to employees for repurchase of common stock	(132)	(246)	(3,496)
Proceeds from exercise of warrants		101	13,278
Proceeds from issuance of common stock and warrants, net			324,605
Proceeds from issuance of preferred stock, net			16,760
Net cash provided by financing activities	837	706	354,945
Net increase (decrease) in cash and cash equivalents	(7,819)	(17,651)	60,385
Cash and cash equivalents, beginning of period	68,204	73,306
Cash and cash equivalents, end of period	60,385	55,655	60,385
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			764
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		$ 72	$ 9,789