Statements of Cash Flows (USD $)	6 Months Ended		119 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013
Cash flows from operating activities
Net loss	$ (10,956,284)	$ (3,015,223)	$ (30,297,302)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,861,999	132,027	5,061,666
Non-cash interest expense	82,389	50,038	379,339
Mark to market of put option liability	(30,415)	(12,460)	(111,420)
Beneficial conversion of convertible notes	422,648		422,648
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(863,090)	212,285	(1,162,179)
Accounts payable and accrued expenses	1,377,172	917,115	4,172,723
Net cash used in operating activities	(7,105,581)	(1,716,218)	(21,534,525)
Cash flows from investing activities
Purchase of marketable securities			(20,545,087)
Redemption of marketable securities			20,545,087
Cash flows from financing activities
Proceeds from issuance of preferred stock, net			12,500,000
Redemption of preferred stock			(750,000)
Proceeds from issuance of common stock, net	97,708,506		101,550,788
Proceeds from exercise of stock options	57,649		57,649
Proceeds from issuance of convertible notes		322,000	862,000
Net cash provided by financing activities	97,766,155	322,000	114,220,437
Net increase (decrease) in cash and cash equivalents	90,660,574	(1,394,218)	92,685,912
Cash and cash equivalents at beginning of period	2,025,338	5,829,886
Cash and cash equivalents at end of period	92,685,912	4,435,668	92,685,912
Supplemental disclosure of non-cash transactions
Discount on redemption of preferred stock			12,921,765
Issuance of common stock on redemption of preferred stock			1,200,000
Accretion of preferred stock dividend			$ 2,591,165