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STOCK-BASED COMPENSATION - Schedule of Valuation Assumptions (Details) - Share-based Payment Arrangement, Option
9 Months Ended
Sep. 30, 2021
$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Weighted-average fair value of options granted (in USD per share) $ 5.21
Expected volatility 117.64%
Expected life (in years) 5 years 9 months 14 days
Risk-free interest rate 0.90%
Expected dividend yield 0.00%