Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net loss	$ (18,006,096)	$ (15,625,405)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	471,710	478,343
Share-based compensation	997,232	420,600
Amortization of investment premium or discount	372,147	381,128
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(807,520)	249,251
Accounts receivable	73,252	(2,735)
Accounts payable and other liabilities	(277,621)	(71,387)
Accrued expenses	(380,042)	564,823
Deferred revenue	(87,500)	(112,500)
Net cash used in operating activities	(17,644,438)	(13,717,882)
Cash flows from investing activities:
Purchases of property and equipment	(69,415)	(83,650)
Purchases of investments	(55,000,666)	(17,701,210)
Proceeds from maturities of investments	27,906,979	28,826,000
Net cash (used in) provided by investing activities	(27,163,102)	11,041,140
Cash flows from financing activities:
Payments on promissory notes and capital leases	(340,971)	(231,286)
Proceeds from the exercise of stock options and warrants	2,020,132	677,479
Proceeds from the issuance of common stock	50,807,000
Public offering expenses	(247,473)
Net cash provided by financing activities	52,238,688	446,193
Increase (decrease) in cash and cash equivalents	7,431,148	(2,230,549)
Cash and cash equivalents at beginning of period	8,554,151	11,290,332
Cash and cash equivalents at end of period	15,985,299	9,059,783
Supplemental cash flow information:
Interest paid	14,304	31,398
Non-cash financing activities:
Issuance of common stock from cashless warrant exercises	$ 173,019