A Study to Evaluate the Efficacy and Safety of Belantamab Mafodotin in Combination With Cyclophosphamide, Bortezomib, and Dexamethasone in Adult Participants With Newly Diagnosed Amyloid Light Chain (AL) Amyloidosis

Inclusion criteria:

• Participant is at least 18 years of age or the legal age of consent

• Has histologically confirmed newly diagnosed primary AL amyloidosis according to thefollowing criteria:

• Presence of an amyloid-related systemic syndrome as per consensus guidelines.

• Positive amyloid staining by Congo red stain with green birefringence onpolarized light microscopy in any tissue AND at least 1 of the following teststo confirm amyloid type as AL Characteristic appearance by electron microscopyor confirmatory immunohistochemistry or AL amyloidosis typing by massspectrometric proteomic analysis of the amyloid deposits or amyloid-typing byimmunofluorescence oEvidence of a monoclonal plasma cell proliferative disorder

• Measurable clonal disease as defined by at least 1 of the following:

• Serum monoclonal protein >=0.5 grams per deciliter (g/dL) by proteinelectrophoresis (routine serum protein electrophoresis and immunofixationperformed at central laboratory),

• Involved serum FLC >=5.0 milligram per deciliter (mg/dL) with an abnormalkappa:lambda ratio or the difference between involved and uninvolved lightchain, FLC concentrations (dFLC) >=5 mg/dL.

• Not considered candidate for high-dose chemotherapy with autologous stem celltransplantation (ASCT) as part of first line of therapy

• Is willing to use adequate contraception.

• Is capable of giving signed informed consent

• Has an Eastern Cooperative Oncology Group performance status of 0, 1 or 2

• Has adequate hematologic, hepatic and renal function

Exclusion criteria:

• Has a previous or current diagnosis of plasma cell dyscrasia with polyneuropathy,organomegaly, endocrinopathy, monoclonal protein and skin changes (POEMS) syndromeor symptomatic multiple myeloma (MM), as per International Myeloma Working Groupcriteria for MM including the presence of lytic bone disease , plasmacytomas, orclonal BM plasma cells >=60%.

• Has Immunoglobulin M (IgM)-related AL amyloidosis.

• Has any form of non-AL amyloidosis, including wild type or mutated (Transthyretinamyloidosis [ATTR]) amyloidosis.

• Has evidence of significant cardiovascular (CV) conditions as specified below:

• New York Heart Association (NYHA) classification IIIb or IV heart failure.

• Heart failure that in the opinion of the investigator is caused by ischemicheart disease (e.g., prior myocardial infarction with documented history ofcardiac enzyme elevation and electrocardiogram [ECG] changes) or uncorrectedvalvular disease and not primarily due to AL amyloidosis cardiomyopathy.

• In-participant admission to a hospital for unstable angina or myocardialinfarction within the last 3 months prior to screening or percutaneous cardiacintervention with recent stent within last 3 months prior to screening orcoronary artery bypass grafting within the last 3 months prior to screening

• Participants with current evidence of clinically significant untreatedarrhythmia(s), including clinically significant ECG abnormalities includingsecond-degree (Mobitz Type II) or third-degree atrioventricular block.

• Participants with a history of sustained ventricular tachycardia or abortedventricular fibrillation or with a history of atrioventricular nodal orsinoatrial nodal dysfunction for which a pacemaker/implantablecardioverter-defibrillator is indicated but not placed (participants who dohave a pacemaker/implantable cardioverter-defibrillator are allowed on thestudy).

• Screening 12-lead ECG showing a baseline QT interval as corrected byFridericia's formula (QTcF) >450 millisecond (msec) or >480 msec forparticipants with bundle branch block. Participants who have a pacemaker may beincluded regardless of calculated QTc interval.

• Supine systolic blood pressure <90 millimeters of mercury (mmHg), orsymptomatic orthostatic hypotension, defined as a decrease in systolic bloodpressure upon standing of >20 mmHg despite medical management (e.g., midodrine,fludrocortisones) in the absence of volume depletion.

• Uncontrolled hypertension.

• Has Mayo stage 3B disease

• Has a current corneal epithelial disease except for mild punctate keratopathy.

• Has previous or concurrent malignancies other than AL amyloidosis, except for anyother malignancy that has been considered medically stable for at least 2 yearsTheparticipant must not be receiving active therapy, other than hormonal therapy forthis disease.

• Has major surgery within 2 weeks prior to the first dose of study interventions orhas not recovered fully from surgery.

• Has any history of prior allogenic or autologous BM transplant or other solid organtransplant.

• Has known immediate or delayed hypersensitivity reaction or idiosyncratic reactionto drugs chemically related to belantamab mafodotin, cyclophosphamide, bortezomib,boron or mannitol

• Has active infection or active bleeding.

• Has intolerance or contraindications to antiviral prophylaxis.

• Has known Human immunodeficiency virus (HIV) infection, unless the participant canmeet all of the following criteria:

• Established anti-retroviral therapy (ART) for at least 4 weeks and HIV viralload <400 copies/milliliter (mL) Cluster of differentiation 4 plus (CD4+)T-cell (CD4+) counts >=350 cells/microliter.

• No history of acquired immunodeficiency syndrome (AIDS)-defining opportunisticinfections within the last 12 months.

• Has prior therapy for AL amyloidosis or MM, with the exception of 160 milligram (mg)dexamethasone (or equivalent corticosteroid) maximum exposure prior to enrollment.

• Has received any live or live-attenuated vaccine within 30 days prior to first doseof belantamab mafodotin

• Is currently enrolled or has participated in any other clinical study involving aninvestigational study intervention or any other type of interventional medicalresearch within 28 days before enrollment.

• Has an alanine aminotransferase (ALT) value >2.5upper limit of normal (ULN) or >3ULN if hepatic involvement of AL amyloidosis

• Has a total bilirubin value >1.5*ULN

• Has cirrhosis or current unstable liver or biliary disease per investigatorassessment Has documented presence of Hepatitis B surface antigen (HBsAg) and/orHepatitis B core antibody (HBcAb) at screening or within 3 months prior to the firstdose of study intervention, unless HBV DNA is undetectable at screening andparticipant receives antiviral prophylaxis or treatment.

• Has a positive hepatitis C antibody test result or positive hepatitis C ribonucleicacid (RNA) test result at screening or within 3 months prior to first dose of studyintervention unless the following criteria are met:

• RNA test negative.

• Successful antiviral treatment (usually 8 weeks duration), followed by anegative Hepatitis C virus RNA test after a washout period of at least 4 weeks.

• Chronic hepatitis B infection, with the presence of HBsAg and/or detectablehepatitis B virus deoxyribonucleic acid (HBV DNA), and hepatitis D co-infection,with hepatitis D antibody and/or RNA, within 3 months