ORGANIZATION, BASIS OF PRESENTATION, AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll	$ 122	$ 264
Accrued patient treatment costs	1,159	675
Accrued clinical research costs	703	841
Accrued manufacturing costs	104	434
Accrued professional services	368	207
Accrued other	31	56
Total accrued expenses and other current liabilities	$ 2,487	$ 2,477