Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 643,978	$ 2,634,393	$ 5,225,600	$ 7,742,514
Operating expenses:
Research and development	8,729,697	4,728,726	14,892,464	15,394,616
General and administrative	2,187,661	1,963,733	6,485,960	7,345,651
Impairment charges	1,000,000		1,000,000	490,676
Total operating expenses	11,917,358	6,692,459	22,378,424	23,230,943
Loss from operations	(11,273,380)	(4,058,066)	(17,152,824)	(15,488,429)
Other income (expense):
Changes in fair value of warrant liability	76,000	806,224	30,000	(2,874,484)
Changes in fair value of embedded derivatives		185,768		183,638
Interest expense	(756)	(166,946)	(2,244)	(169,737)
Interest income	224,058	21,100	649,268	78,306
Other income (expense)	(23,734)	31,378	(6,206)	289,053
Total other income (expense)	275,568	877,524	670,818	(2,493,224)
Net loss before income tax benefit	(10,997,812)	(3,180,542)	(16,482,006)	(17,981,653)
Income tax benefit	58,500	829,393	58,500	3,318,124
Net loss	(10,939,312)	(2,351,149)	(16,423,506)	(14,663,529)
Other comprehensive income (loss) – foreign currency translation adjustments				(463,177)
Other comprehensive income (loss) – unrealized gains on investments	18,953		18,953
Comprehensive loss	(10,920,359)	(2,351,149)	(16,404,553)	(15,126,706)
Net loss	(10,939,312)	(2,351,149)	(16,423,506)	(14,663,529)
Preferred stock accretion and other deemed dividends		64,139	(452,925)	(2,527,275)
Net loss attributed to common stockholders	$ (10,939,312)	$ (2,287,010)	$ (16,876,431)	$ (17,190,804)
Weighted-average common shares outstanding, basic and diluted	14,768,931	1,321,289	12,481,494	983,651
Net loss per share attributed to common stockholders, basic and diluted	$ (0.74)	$ (1.73)	$ (1.35)	$ (17.48)