Condensed Statements of Cash Flows (USD $)	3 Months Ended		52 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013
Operating activities
Net loss	$ (6,253,233)	$ (9,174,109)	$ (65,873,235)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	3,417	3,727	38,544
Amortization of premiums and discounts on short-term investments	2,959	37,092	159,435
Gain on sales of short-term investments			(779)
Warrant interest expense	4,394,500		5,086,722
Stock based compensation	214,675	150,219	1,578,954
Changes in assets and liabilities:
Other assets	(1,407,712)		(1,727,602)
Prepaid and other current assets	(286,513)	(1,325,080)	(447,816)
Accounts payable and accrued expenses	(617,318)	(815,553)	4,864,001
Net cash used in operating activities	(3,949,225)	(11,123,704)	(56,321,776)
Investing activities
Purchase of property and equipment	(1,432,749)	(2,733)	(1,489,852)
Purchases of short-term investments		(399,090)	(19,472,734)
Maturities and sales of short-term investments		4,600,000	19,316,311
Net cash (used in) provided by investing activities	(1,432,749)	4,198,177	(1,646,275)
Financing activities
Secured convertible notes	17,298,074		19,798,074
Proceeds from the issuance of convertible preferred stock, net of issuance costs		(10,280)	52,586,953
Proceeds from sale of common stock			4,200
Net cash provided by (used in) financing activities	17,298,074	(10,280)	72,389,227
Net increase (decrease) in cash and cash equivalents	11,916,100	(6,935,807)	14,421,176
Cash and cash equivalents at beginning of period	2,505,076	10,869,129
Cash and cash equivalents at end of period	14,421,176	3,933,322	14,421,176
Non-cash financing activities:
Conversion of note payable and related warrants to convertible Series B Preferred Stock			$ 3,209,444