SHARED-BASED COMPENSATION - Financial Statements (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Allocated share-based compensation expense $ 4,021,000 $ 852,000 $ 4,297,000 $ 1,378,000
Research and Development Expense        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Allocated share-based compensation expense 1,460,550 351,000 1,588,550 443,000
General and Administrative Expense        
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]        
Allocated share-based compensation expense $ 2,560,450 $ 501,000 $ 2,708,450 $ 935,000