Comparing Lower Versus Standard Doses of Belantamab Mafodotin With Pomalidomide and Dexamethasone in Relapsed or Refractory Multiple Myeloma.

This study is testing whether a lower dose of belantamab mafodotin used together with pomalidomide and dexamethasone can provide similar effectiveness with fewer side effects compared with the standard dose in patients with relapsed or refractory multiple myeloma. Participants will be randomly assigned to receive either a reduced dose or a standard dose of belantamab mafodotin in combination with pomalidomide and dexamethasone. The study will evaluate treatment response, side effects, and minimal residual disease (MRD), which is a measure of the number of myeloma cells that remain after treatment. The goal is to determine whether treatment can be optimized while maintaining disease control and reducing treatment-related toxicity.

Inclusion Criteria: 1. Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form and in the REBEL study protocol. 2. Male or female, 18 years or older (at the time consent is obtained). 3. Have a confirmed diagnosis of MM as defined by the IMWG criteria. 4. Eastern Cooperative Oncology Group performance status of 0-2. 5. Have been previously treated with at least 1 prior line of MM therapy, including a lenalidomide-containing regimen (lenalidomide must have been administered for at least 2 consecutive cycles), and must have documented disease progression during or after their most recent therapy. 6. Must have at least ONE aspect of measurable disease, defined as one the following: 1. Urine M-protein excretion ≥200 mg/24 h, or 2. Serum M-protein concentration ≥0.5 g/dL (≥5.0 g/L), or 3. Serum free light chain (FLC) assay: involved FLC level ≥10 mg/dL (≥100 mg/L) and an abnormal serum free light chain ratio (\1.65) only if the patient has no measurable urine or serum M spike. 7. Have undergone autologous stem cell transplant (autoSCT) or are considered transplant ineligible. Participants with a history of autoSCT are eligible for study participation provided the following eligibility criteria are met: 1. AutoSCT was \>100 days prior to the first dose of study medication 2. No active bacterial, viral, or fungal infection(s) present 8. All prior treatment-related toxicities (defined by National Cancer Institute Common Toxicity Criteria for Adverse Events v5.0) must be Grade ≤1 at the time of enrolment, except for alopecia and Grade ≤ 2 peripheral neuropathy. 9. Compliance with contraceptive precautions in accordance with the protocol. 10. Organ System Function - adequate organ system functions as defined by the laboratory assessments * Hematologic: * Absolute neutrophil count - ≥1.5× 10 9/L (Without growth factor support for the past 14 days, excluding erythropoietin) * Hemoglobin - ≥8.0 g/dL * Platelets - ≥75 × 10 9/L * Hepatic: * Total bilirubin - ≤1.5 × ULN; (isolated bilirubin \>1.5 × ULN is acceptable if bilirubin is fractionated and direct bilirubin is \