SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accrued Expenses (Details) - USD ($) |
Jun. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Accounting Policies [Abstract] | ||
| Accrued compensation and benefits | $ 1,105,521 | $ 574,332 |
| Accrued clinical expenses | 1,995,441 | 4,143,269 |
| Other accrued expenses | 183,133 | 30,150 |
| Total | $ 3,284,095 | $ 4,747,751 |