INCOME TAXES - Net Deferred Tax Assets (Liabilities) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 15,049,549	$ 18,265,530
Research and development tax credits	145,115	145,115
Capitalized research and development costs	22,072,598	14,858,509
Stock-based compensation	5,532,341	4,180,651
Deferred start-up and license costs	5,929,901	6,532,419
Deferred Revenue	11,249,174	3,053,174
Other		129,082
Net deferred tax assets	59,978,678	47,164,480
Valuation allowance	(54,687,950)	(41,878,528)
Net deferred tax assets	5,290,728	5,285,952
Deferred tax liabilities:
In-process research and development	(9,343,440)	(9,343,440)
Other	(4,776)
Net deferred tax liabilities	$ (4,057,488)	$ (4,057,488)