Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (22,053,726)	$ (22,461,084)
Depreciation and amortization	1,022,829	424,966
Change in fair value of earn-out milestone liability	(733,186)	257,702
Change in fair value of common stock warrant liability		61,246
Stock-based compensation	1,511,023	1,849,811
Shares issued out of treasury	101,491	86,730
Amortization of deferred finance charges and debt discount associated with note payable	236,666	438,717
Amortization of patent license fee	5,625	7,500
Change in deferred rent liability	(35,245)	(29,810)
Loss (gain) realized on sale of investment securities	532	(264)
Interest receivable on investments	22,721	183,301
Other current assets	(14,855)	246,401
Accounts payable	48,751	(859,183)
Deferred revenue	(500,000)	(500,000)
Other accrued liabilities	563,987	(536,596)
Net cash used in operating activities	(18,379,364)	(20,830,563)
Cash flows from investing activities:
Purchases of investment securities	(4,511,784)	(21,074,871)
Proceeds from sale and maturity of investment securities	13,635,000	34,460,825
Refund on security for letter of credit		50,000
Purchases of property and equipment	(62,503)	(109,341)
Net cash provided by investing activities	9,060,713	13,326,613
Cash flows from financing activities:
Proceeds from sale of common stock equity, net of issuance costs	6,775,016	7,736,443
Proceeds from exercise of common stock warrants	2,500
Principal payments on note payable	(4,099,847)	(3,654,230)
Net cash provided by financing activities	2,677,669	4,082,213
Decrease in cash and cash equivalents	(6,640,982)	(3,421,737)
Cash and cash equivalents at beginning of period	9,265,144	12,686,881
Cash and cash equivalents at end of period	2,624,162	9,265,144
Cash paid for:
Interest	486,327	918,465
Income taxes
In-Process Research and Development [Member]
Cash flows from operating activities:
Impairment of in-process research and development	$ 1,444,023