Study to Investigate Alternative Dosing Regimens of Belantamab Mafodotin in Participants With Relapsed or Refractory Multiple Myeloma

This study aims to evaluate alternative dosing regimens of single-agent belantamab mafodotin in participants with relapsed or refractory multiple myeloma (RRMM) to determine if an improved overall benefit/risk profile can be achieved by modifying the belantamab mafodotin dose, schedule, or both.

Inclusion Criteria: * Participant must be 18 years of age inclusive at the time of signing the informed consent form (ICF). * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. * Histologically or cytologically confirmed diagnosis of MM and a. Has undergone stem cell transplant or is considered transplant ineligible, and b. Has failed at least 3 prior lines of anti-myeloma therapies, including an anti-cluster of differentiation (CD)38 antibody (e.g., daratumumab) alone or in combination and is refractory to an immunomodulatory agent (e.g., lenalidomide, pomalidomide) and a proteasome inhibitor (e.g., bortezomib, ixazomib, carfilzomib). * France specific: participants have failed at least 4 prior lines of anti-myeloma therapies * Participant has measurable disease per modified IMWG criteria. * Life expectancy of at least 6 months, in the opinion of the investigator. * Male and female participants agree to abide by protocol-defined contraceptive requirements. * Participant is capable of giving signed informed consent. * Participant meets country-specific inclusion criteria described in the protocol. Exclusion Criteria: * Symptomatic amyloidosis, active POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, myeloma protein, and skin changes), or active plasma cell leukemia at the time of screening. * Current corneal epithelial disease, except nonconfluent superficial punctate keratitis (SPK). * Evidence of active mucosal or internal bleeding. * Presence of an active renal condition. * Any serious and/or unstable pre-existing medical condition, psychiatric disorder, or other conditions that could interfere with the participant's safety, obtaining informed consent, or compliance with the study procedures. * Malignancies other than the disease under study, except for any other malignancy from which the participant has been disease free for \>2 years and, will not affect the evaluation of the effects of the study treatment on the currently targeted malignancy (MM). Participants with curatively treated non-melanoma skin cancer may be enrolled without a 2-year restriction. * Evidence of cardiovascular risk as per the protocol criteria. * Pregnant or lactating female. * Active infection requiring antibiotic, antiviral, or antifungal treatment. * Known human immunodeficiency virus (HIV) infection, unless the criteria in protocol can be met. * Hepatitis B and C will be excluded unless the criteria in protocol can be met. * Cirrhosis or current unstable liver or biliary disease. * Alanine aminotransferase (ALT) \>2.5× upper limit of normal (ULN). * Total Bilirubin \>1.5×ULN. * Systemic anti-MM therapy within \<=14 days or 5 half-lives, whichever is shorter. * Systemic therapy with high dose steroids within \<=14 days before the first dose of study treatment. * Prior allogenic stem cell transplant. * Prior treatment with a monoclonal antibody \<=30 days before the first dose of study treatment. Use of monoclonal antibodies for serious conditions unrelated to multiple myeloma, such as COVID, may be permitted. * Prior treatment with an anti-B cell maturation antigen (BCMA) targeted therapy or hypersensitivity reactions to any components of the study treatment. * Treatment with an antibody-drug conjugate. * Participant has received any major surgery \<=4 weeks before the first dose of study treatment. An exception may be allowed for bone stabilizing surgery. * Inadequate bone marrow reserve or organ functions as demonstrated by any of the following: a. Absolute neutrophil count \<1.0×10\^9/L, b. Hemoglobin \<8 gram/deciliter (g/dL), c. Platelet count \<50×10\^9/L, d. Spot urine (albumin/creatinine ratio) \>500 milligram/gram (mg/g), e. Estimated glomerular filtration rate (eGFR) \<30 milliliter per minute per 1.73 meter square (mL/min/1.73m\^2). * UK specific: a. Absolute neutrophil count \<1.5×10\^9/L, c. Platelet count \<75×10\^9/L