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DEBT - Additional Information (Details) - Hercules and Silicon Valley Bank [Member] - USD ($) |  | 9 Months Ended |  |
--- | --- | --- | --- | ---
Aug. 12, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Jun. 15, 2021
Debt Instrument [Line Items] |  |  |  |
Maximum borrowing capacity under term loan |  | $ 75,000,000 |  |
Minimum |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt covenant minimum cash balance |  | 25,000,000 |  |
Debt covenant max cash upon licensing transaction |  | 30,000,000 |  |
Maximum |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt covenant minimum cash balance | $ 30,000,000 |  |  |
Debt covenant max cash upon licensing transaction | $ 35,000,000 |  |  |
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 | $ 35,000,000 |
Remaining amount drawn down under Tranche A term loan |  |  |  | $ 10,000,000
Carrying value of term loan, net |  |  | 34,669,000 |
Unamortized debt discount and issuance costs |  |  | 836,000 |
Accrued end of term charge |  |  | $ 505,000 |
Tranche B [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum borrowing capacity under term loan |  | $ 15,000,000 |  |
Start date to borrow under a tranche for a debt instrument |  | Jan. 01, 2021 |  |
Expiration date to borrow under a tranche for a debt instrument |  | Dec. 15, 2021 |  |
Tranche C [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum borrowing capacity under term loan |  | $ 25,000,000 |  |
Expiration date to borrow under a tranche for a debt instrument |  | Dec. 31, 2022 |  |

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