All Japanese Population: Belantamab Mafodotin Plus Pomalidomide and Dexamethasone (Pd) Versus Bortezomib Plus Pd in Relapsed/Refractory Multiple Myeloma

Prior treatment

• Prior allogeneic SCT.
• Systemic anti-myeloma therapy (including chemotherapy and systemic steroids) within 14 days or five half-lives (whichever is shorter) preceding the first dose of study drug; prior treatment with a monoclonal antibody drug within 30 days of receiving the first dose of study drugs.
• Plasmapheresis within 7 days prior to the first dose of study drug.
• Received prior treatment with or intolerant to pomalidomide.
• Received prior Beta cell maturation antigen (BCMA) targeted therapy.
• Any major surgery within the last 4 weeks.
• Previous or concurrent invasive malignancy other than multiple myeloma, except:
  • The disease must be considered medically stable for at least 2 years; or
  • The participant must not be receiving active therapy, other than hormonal therapy for this disease.
• Ongoing Grade 2 peripheral neuropathy with pain within 14 days prior to randomization or ≥Grade 3 peripheral neuropathy.

Other illness

• Active plasma cell leukemia, symptomatic amyloidosis or active polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma proliferative disorder, and skin changes (POEMS) syndrome at the time of screening.
• Intolerant to bortezomib or refractory to bortezomib (for example; participant experienced progressive disease during treatment, or within 60 days of completing treatment, with a bortezomib-containing regimen of 1.3 mg/meter square \[m\^2\] twice weekly).
• Evidence of cardiovascular risk including any of the following;
  • Evidence of current clinically significant untreated arrhythmias, including clinically significant electrocardiogram abnormalities including second degree (Mobitz type II) or third degree atrioventricular (AV) block.
  • Recent history within (3 months of screening) of myocardial infarction, acute coronary syndromes (including unstable angina), coronary angioplasty, or stenting or bypass grafting .
  • Class III or IV heart failure as defined by the New York Heart Association (NYHA) functional classification system
  • Uncontrolled hypertension.
• Known immediate or delayed hypersensitivity reaction or idiosyncratic reaction to belantamab mafodotin or drugs chemically related to belantamab mafodotin, or any of the components of the study treatment.
• Evidence of active mucosal or internal bleeding.
• Cirrhosis or current unstable liver or biliary disease per investigator assessment defined by the presence of ascites, encephalopathy, coagulopathy, hypoalbuminemia, esophageal or gastric varices, persistent jaundice.
• Active infection requiring treatment.
• Known or active human immunodeficiency virus (HIV) infection, hepatitis B or hepatitis C will be excluded unless the protocol-defined criteria are met.
• Presence of active renal conditions (such as infection, severe renal impairment requiring dialysis or any other condition that could affect participant's safety).
• Active or history of venous and arterial thromboembolism within the past 3 months.
• Current corneal disease except for mild punctate keratopathy.

Lab values

• Any serious and/or unstable pre-existing medical, psychiatric disorder or other conditions (including laboratory abnormalities) that could interfere with participant's safety, obtaining informed consent or compliance to the study procedures.

Other

• Contraindications to or unwilling to undergo protocol-required anti-thrombotic prophylaxis.
• Pregnant or lactating female.

• Capable of giving signed informed consent.
• Male or female, 18 years or older.
• Have a confirmed diagnosis of multiple myeloma (MM) as defined by the International Myeloma Working Group (IMWG) criteria.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Have been previously treated with at least 1 prior line of MM therapy including a lenalidomide-containing regimen and must have documented disease progression during or after their most recent therapy. (Participants treated with lenalidomide ≥10 mg daily for at least 2 consecutive cycles are eligible).
• Must have at least 1 aspect of measurable disease defined as one of the following;
  • Urine M-protein excretion greater than or equal to (≥)200 milligrams (mg) per 24-hour, or
  • Serum M-protein concentration ≥0.5 grams/deciliters (g/dL) (≥5.0 g/liter \[L\]), or
  • Serum free light chain (FLC) assay: involved FLC level ≥10 mg/dL (≥100 mg/L) and an abnormal serum free light chain ratio (less than \[\<\]0.26 or greater than \[\>\]1.65) only if participant has no measurable urine or serum M spike.
• Have undergone autologous stem cell transplant (ASCT) or are considered transplant ineligible. Participants with a history of ASCT are eligible for study participation provided the following eligibility criteria are met: a. ASCT was \>100 days prior to the first dose of study medication. b. No active bacterial, viral, or fungal infection(s) present
• All prior treatment-related toxicities (defined by National Cancer Institute Common Terminology Criteria for Adverse Events \[NCI-CTCAE\] version 5.0) must be less than or equal to (≤)Grade 1 at the time of enrolment, except for alopecia.
• Adequate organ system functions as mentioned in the protocol.
• Male and female participants agree to abide by protocol-defined contraceptive requirements.
• In Japan, Hepatitis B participants who are hepatitis B surface antigen (HbsAg)- (e.g. HBsAb+/HbsAg-, HBcAb+/HbsAg-, HBcAb+/HBsAb+/HbsAg-) are eligible for inclusion in this study if hepatitis B virus (HBV) DNA is undetectable. A patient with HBsAg+ is eligible if HBV DNA is undetectable after assessing hepatitis B e antigen (HBeAg), hepatitis B e antibody (HBeAb) and HBV DNA, and if a hepatologist agrees with the participation into this study.