Statements of Cash Flows (Unaudited) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net loss	$ (26,568,382)	$ (23,222,678)	$ (18,818,435)
Non-cash items included in net loss:
Depreciation and amortization	281,489	169,358	165,480
Change in fair value of common stock warrant liability	4,117,534	(81,733)	(573,760)
Stock based compensation - options	1,084,326	1,036,337	1,295,382
Stock based compensation – restricted stock	59,438	171,549	357,678
Shares issued out of treasury	57,239	60,360
Amortization of patent license fee	7,500	7,500	7,500
Shares issued in exchange for services	49,810	71,550	18,060
Change in deferred rent liability	55,256	65,467
Net changes in:
Refundable income taxes			806,255
Prepaid expenses and other	585,595	(393,676)	340,837
Deposits and other assets	61,936	4,167	20,286
Accounts payable	(1,344,379)	(538,383)	2,357,629
Other accrued liabilities	(776,955)	(92,255)	655,699
Net cash used in operating activities	(22,329,593)	(22,742,437)	(13,367,389)
Cash flows from investing activities:
Purchases of investment securities	(16,208,958)	(10,659,238)	(11,844,356)
Proceeds from sale and maturity of investment securities	18,478,591	395,556	17,057,726
Security deposit on letter of credit		(250,000)
Purchases of property and equipment	(613,390)	(573,406)	(6,745)
Net cash provided by (used in) investing activities	1,656,243	(11,087,088)	5,206,625
Cash flows from financing activities:
Proceeds from sale of 8% Series A Redeemable, Convertible Preferred Stock, net of issuance costs		4,324,080
Proceeds from sale of common stock equity, net of issuance costs		48,082,025	2,484,536
Proceeds from exercise of common stock warrants	10,106,557	428,337
Proceeds from exercise of common stock options	697,220
Proceeds from note payable	4,825,494	144,448
Principal payments on note payable	(110,287)	(142,427)	(108,332)
Net cash provided by financing activities	15,518,984	52,836,463	2,376,204
(Decrease) increase in cash and cash equivalents	(5,154,366)	19,006,938	(5,784,560)
Cash and cash equivalents at beginning of period	20,145,854	1,138,916	6,923,476
Cash and cash equivalents at end of period	14,991,488	20,145,854	1,138,916
Cash paid for:
Interest	$ 359,413	$ 501,855	$ 31,517