Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (22,461,084)	$ (25,494,273)	$ (8,251,358)
Non-cash items included in net loss:
Depreciation and amortization	424,966	369,327	339,229
Change in fair value of earn-out milestone liability	257,702	(213,949)
Change in fair value of common stock warrant liability	61,246	(204,279)	(8,090,636)
Cash received for non-refundable research and development fee			5,000,000
Deferred revenue	(500,000)	(500,000)	(500,000)
Stock based compensation	1,849,811	2,585,132	1,235,437
Shares issued out of treasury	86,730	64,483	98,046
Amortization of deferred finance charges and debt discount associated with note payable	438,717	437,994	336,387
Amortization of patent license fee	7,500	7,500	7,500
Change in deferred rent liability	(29,810)	(24,375)	(18,940)
(Gain) loss realized on sale of investment securities	(264)	24,727	92,364
Net changes in:
Interest receivable on investments	183,301	2,018	(146,123)
Prepaid expenses and other current assets	246,401	77,468	(121,235)
Deposits and other assets		1,932	(116,181)
Accounts payable	(859,183)	1,764,563	(887,332)
Other accrued liabilities	(536,596)	(251,288)	1,497,566
Net cash used in operating activities	(20,830,563)	(21,353,020)	(9,525,276)
Cash flows from investing activities:
Purchases of investment securities	(21,074,871)	(29,825,918)	(66,323,059)
Proceeds from sale and maturity of investment securities	34,460,825	42,812,300	37,194,375
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	50,000
Purchases of property and equipment	(109,341)	(672,256)	(57,494)
Net cash provided by (used in) by investing activities	13,326,613	9,543,477	(29,136,178)
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	7,736,443	13,788,811	15,622,955
Proceeds from exercise of common stock warrants	0	0	261,944
Proceeds from exercise of common stock options	0	0	184,047
Proceeds from note payable		5,000,000	4,763,803
Principal payments on note payable	(3,654,230)	(10,891)	(5,060,711)
Net cash provided by financing activities	4,082,213	18,777,920	29,388,470
(Decrease) increase in cash and cash equivalents	(3,421,737)	6,968,377	(9,272,984)
Cash and cash equivalents at beginning of period	12,686,881	5,718,504	14,991,488
Cash and cash equivalents at end of period	9,265,144	12,686,881	5,718,504
Cash paid for:
Interest	$ 918,465	$ 892,600	$ 637,183