Study of Single Agent Belantamab Mafodotin Versus Pomalidomide Plus Low-dose Dexamethasone (Pom/Dex) in Participants With Relapsed/Refractory Multiple Myeloma (RRMM)

Inclusion Criteria: * Capable of giving signed informed consent. * Participants must be 18 or older, at the time of signing the informed consent. In Republic of Korea, participants must be over 19 years of age inclusive, at the time of signing informed consent. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. * Histologically or cytologically confirmed diagnosis of Multiple myeloma (MM) as defined according to IMWG, and : Has undergone autologous stem cell transplant (SCT), or is considered transplant ineligible; Has received at least 2 prior lines of anti-myeloma treatments, including at least 2 consecutive cycles of both lenalidomide and a proteasome inhibitor (given separately or in combination), and must have documented disease progression on, or within 60 days of, completion of the last treatment or must be non-responsive while on last treatment, where non-responsive is defined as not achieving at least Minimal Response (MR) after 2 complete treatment cycles. In such cases lack of achieving of at least MR must be determined no earlier than at least 4 weeks after the last treatment. * Has measurable disease with at least one of the following: Serum M-protein \>=0.5 gram per deciliter (g/dL) (\>=5 gram per Liter); Urine M-protein \>=200 mg/24 hours; Serum free light chain (FLC) assay: Involved FLC level \>=10 milligram per deciliter (mg/dL) (\>=100 mg/L) and an abnormal serum FLC ratio (\<0.26 or \>1.65). * Participants with a history of autologou…