Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	$ (25,494,273)	$ (8,251,358)	$ (26,568,382)
Non-cash items included in net loss:
Depreciation and amortization	369,327	339,229	281,489
Change in fair value of common stock warrant liability	(204,279)	(8,090,636)	4,117,534
Change in fair value of earn-out milestone liability	(213,949)
Cash received for non-refundable research and development fee		5,000,000
Deferred revenue	(500,000)	(500,000)
Stock based compensation	2,585,132	1,235,437	1,143,764
Shares issued out of treasury	64,483	98,046	107,049
Amortization of deferred finance charges and debt discount associated with note payable	437,994	336,387	43,215
Amortization of patent license fee	7,500	7,500	7,500
Change in deferred rent liability	(24,375)	(18,940)	55,256
Loss realized on sale of investment securities	24,727	92,364	7,580
Net changes in:
Interest receivable on investments	2,018	(146,123)	177,820
Prepaid expenses and other current assets	77,468	(121,235)	585,595
Deposits and other assets	1,932	(116,181)	18,721
Accounts payable	1,764,563	(887,332)	(1,344,379)
Other accrued liabilities	(251,288)	1,497,566	(776,955)
Net cash used in operating activities	(21,353,020)	(9,525,276)	(22,144,193)
Cash flows from investing activities:
Purchases of investment securities	(29,825,918)	(66,323,059)	(16,394,358)
Proceeds from sale and maturity of investment securities	42,812,300	37,194,375	18,478,591
Cash used in acquisition of EGEN, Inc., net of cash received	(2,820,649)
Refund on security for letter of credit	50,000	50,000
Purchases of property and equipment	(672,256)	(57,494)	(613,390)
Net cash provided by (used in) by investing activities	9,543,477	(29,136,178)	1,470,843
Cash flows from financing activities:
Proceeds from sale of preferred stock, net of issuance costs		13,616,432
Proceeds from sale of common stock equity, net of issuance costs	13,788,811	15,622,955
Proceeds from exercise of common stock warrants	0	261,944	10,106,557
Proceeds from exercise of common stock options	0	184,047	697,220
Proceeds from note payable	5,000,000	4,763,803	4,825,494
Principal payments on note payable	(10,891)	(5,060,711)	(110,287)
Net cash provided by financing activities	18,777,920	29,388,470	15,518,984
Increase (decrease) in cash and cash equivalents	6,968,377	(9,272,984)	(5,154,366)
Cash and cash equivalents at beginning of period	5,718,504	14,991,488	20,145,854
Cash and cash equivalents at end of period	12,686,881	5,718,504	14,991,488
Cash paid for:
Interest	$ 892,600	$ 637,183	$ 359,413