CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended			86 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
Cash Flows From Operating Activities:
Net loss	$ (39,444)	$ (14,467)	$ (15,221)	$ (109,053)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2	2	2	10
Loss on disposal of property and equipment	2			2
Stock-based compensation expense	2,515	822	712	5,484
Accretion of discount/premium on investment securities	(86)			(86)
Purchased in-process research and development				28,157
Change in fair value of derivative instruments-warrants	1,933	(5,257)	(297)	(3,621)
Changes in operating assets and liabilities:
Security deposit	(5)			(20)
Accounts payable and accrued expenses	4,442	(2,265)	3,286	6,467
Prepaid expenses and other current assets	(484)	(66)	64	(1,547)
Total Adjustments	8,319	(6,764)	3,767	34,846
Net Cash used in Operating Activities	(31,125)	(21,231)	(11,454)	(74,207)
Cash Flows From Investing Activities:
Net cash paid on Exchange Transaction				(155)
(Loans to) /Repayment from related parties	(1,764)	133	(702)	(3,306)
Purchases of available-for-sale securities	(20,000)			(20,000)
Additions to property and equipment	(28)			(42)
Net Cash (used in) /provided by Investing Activities	(21,792)	133	(702)	(23,503)
Cash Flows From Financing Activities:
Capital contribution by shareholders				9
Issuance of common stock				2
Proceeds of sale of common stock	55,862	34,369	7,179	116,406
Proceeds from exercise of warrants		415		415
Proceeds from sale of unregistered common stock to founders				18
Fees and expenses related to sale of common stock	(3,774)	(2,148)	(468)	(6,724)
Net Cash provided by Financing Activities	52,088	32,636	6,711	110,126
Net increase (decrease) in cash and cash equivalents	(829)	11,538	(5,445)	12,416
Cash and cash equivalents at beginning of period	13,245	1,707	7,152
Cash and cash equivalents at end of period	12,416	13,245	1,707	12,416
Supplementary disclosure of cash flow information:
Cash paid for taxes	50	38	31	140
Supplementary disclosure of non-cash investing and financing activities:
Value of warrants classified to derivative liability-net		5,094	3,785	8,879
Value of common stock issued to induce stockholders to extend lock-up agreements			$ 3,235	$ 3,235