ACCRUED EXPENSES AND OTHER LIABILITIES - Accrued Expenses and Other Liabilities (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Research and development costs and other accrued expenses	$ 976,635	$ 1,880,552
Accrued bonus	601,264
Professional fees	227,874	140,981
Vacation pay	76,478
Accrued severance		31,876
Accrued expenses and other liabilities	$ 1,882,251	$ 2,053,409