Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (20,402,176)	$ (22,053,726)
Non-cash items included in net loss:
Depreciation and amortization	553,010	1,022,829
Change in fair value of earn-out milestone liability	(649,701)	(733,186)
Impairment of in-process research and development	2,520,000	1,444,023
Stock-based compensation	1,105,245	1,511,023
Shares issued to satisfy certain obligations	235,072
Shares issued out of treasury		101,491
Amortization of deferred finance charges and debt discount associated with note payable	35,370	236,666
Amortization of patent license fee		5,625
Change in deferred rent liability	59,358	(35,245)
Loss realized on sale of investment securities		532
Net changes in:
Interest receivable on investments	(50,432)	22,721
Other current assets	115,222	(14,855)
Accounts payable - trade	537,885	48,751
Deferred revenue	(500,000)	(500,000)
Other accrued liabilities	(200,929)	563,987
Net cash used in operating activities	(16,642,076)	(18,379,364)
Cash flows from investing activities:
Purchases of investment securities	(12,734,184)	(4,511,784)
Proceeds from sale and maturity of investment securities	1,680,000	13,635,000
Refund on security for letter of credit	100,000
Purchases of property and equipment	(38,629)	(62,503)
Net cash (used in) provided by investing activities	(10,992,813)	9,060,713
Cash flows from financing activities:
Proceeds from sale of common stock equity, net of issuance costs	17,910,401	6,775,016
Proceeds from exercise of common stock warrants	21,140,304	2,500
Principal payments on note payable	(2,595,923)	(4,099,847)
Net cash provided by financing activities	36,454,782	2,677,669
Increase (decrease) in cash and cash equivalents	8,819,893	(6,640,982)
Cash and cash equivalents at beginning of period	2,624,162	9,265,144
Cash and cash equivalents at end of period	11,444,055	2,624,162
Cash paid for:
Interest	56,386	486,327
Income taxes