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DEBT - Additional Information (Details) - Hercules and Silicon Valley Bank [Member] - USD ($) |  | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 01, 2022 | Sep. 30, 2020 | Dec. 31, 2020
Debt Instrument [Line Items] |  |  |
Maximum borrowing capacity under term loan |  | $ 75,000,000 |
Description of maturity date terms for term loan |  |  | The Term Loan matures on October 1, 2024, or the Loan Maturity Date, and may be extended up to an additional 12 months upon the achievement of certain clinical, regulatory and financial milestones.
Term loan interest rate description |  |  | The Term Loan bears interest at a floating rate per annum equal to the greater of either (i) 9.0% or (ii) 9.0% plus the prime rate as reported in The Wall Street Journal (3.25% as of December 31, 2020) less 3.25%.
Term loan maturity date |  | Oct. 01, 2024 |
Percentage added to prime rate for debt instrument interest rate |  | 9.00% |
End of term charge for loan, percentage |  | 6.55% |
Minimum amount of prepayment allowed under debt instrument |  | $ 5,000,000 |
Prepayment charge (as a percentage) |  | 1.50% |
Description of term loan payment terms |  | At our option, upon at least five business days’ prior written notice to Hercules, we may prepay all or any portion greater than or equal to $5,000,000 of the outstanding loan by paying the entire principal balance (or portion thereof) and all accrued and unpaid interest. Such prepayment is subject to a prepayment charge of 1.5% of the prepayment amount, if the prepayment is made in any of the first 36 months following the Closing Date. Thereafter, any prepayment is not subject to a prepayment charge. |
Debt covenant minimum cash balance upon licensing transaction |  | $ 30,000,000 |
Debt covenant minimum cash balance upon regulatory milestone achievement |  | $ 20,000,000 |
Additional percentage of interest on past due amounts |  | 5.00% |
Scenario Forecast [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Debt covenant minimum cash balance | $ 25,000,000 |  |
Tranche A [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maximum borrowing capacity under term loan |  | $ 35,000,000 |
Principal amount outstanding under term loan |  | 25,000,000 | $ 25,000,000
Unused amount under Tranche A term loan |  | $ 10,000,000 |
Expiration date to borrow under a tranche for a debt instrument |  | Jun. 15, 2021 |
Minimum interest rate (as a percentage) |  |  | 9.00%
Carrying value of term loan, net |  |  | $ 24,042,000
Unamortized debt discount and issuance costs |  |  | 1,063,000
Accrued end of term charge |  |  | 105,000
Tranche B [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maximum borrowing capacity under term loan |  | $ 15,000,000 |
Principal amount outstanding under term loan |  |  | 0
Expiration date to borrow under a tranche for a debt instrument |  | Dec. 15, 2021 |
Start date to borrow under a tranche for a debt instrument |  | Jan. 01, 2021 |
Tranche C [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Maximum borrowing capacity under term loan |  | $ 25,000,000 |
Principal amount outstanding under term loan |  |  | $ 0
Expiration date to borrow under a tranche for a debt instrument |  | Dec. 31, 2022 |

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