STOCK AWARD PLAN AND STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense Included in the Company's Consolidated Statements of Operations (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 2,056,035	$ 2,221,189	$ 7,739,704	$ 7,003,280
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	813,443	651,835	2,189,595	2,005,816
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 1,242,592	$ 1,569,354	$ 5,550,109	$ 4,997,464