Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net loss	$ (230,090)	$ (12,290,626)
Depreciation and amortization	153,750	107,910
Change in fair value of common stock warrant liability	(8,660,417)	369,723
Deferred revenue	(250,000)
Stock-based compensation	734,673	557,021
Treasury shares issued for services and 401(k) matching contribution	20,837	81,617
Change in deferred rent liability	(8,563)	62,914
Deferred finance charges	62,823
Cash received for non-refundable research and development fee	5,000,000
Net changes in:
Accrued interest on short term investments and other current assets	(166,666)	45,662
Accounts payable	(817,058)	295,457
Accrued liabilities	572,880	(141,522)
Net cash used in operating activities:	(3,587,831)	(10,911,844)
Cash flows from investing activities:
Purchases of investment securities	(39,804,383)	(11,366,148)
Proceeds from sale and maturity of investment securities	5,048,000	9,440,882
Refund of deposit for letter of credit	50,000
Purchases of property and equipment	(57,494)	(371,215)
Net cash used in investing activities	(34,763,877)	(2,296,481)
Cash flows from financing activities:
Proceeds from sale of preferred stock, net of issuance costs	13,616,442
Proceeds from sale of common stock equity, net of issuance costs	15,640,213
Proceeds from exercise of common stock warrants	200,000
Proceeds from exercise of options to purchase common stock	181,337	200,000
Proceeds from note payable		4,853,137
Principal payments on notes payable	(319,188)	(82,556)
Net cash provided by financing activities	29,380,748	4,770,581
Decrease in cash and cash equivalents	(8,970,960)	(8,437,744)
Cash and cash equivalents at beginning of period	14,991,488	20,145,854
Cash and cash equivalents at end of period	6,020,528	11,708,110
Supplemental disclosures of cash flow information:
Interest paid	247,899	16,275
Common Stock Warrants (Member)
Cash flows from financing activities:
Proceeds from exercise of common stock warrants	$ 261,944