Evaluation of Efficacy and Safety of Belantamab Mafodotin, Bortezomib and Dexamethasone Versus Daratumumab, Bortezomib and Dexamethasone in Participants With Relapsed/Refractory Multiple Myeloma

Inclusion Criteria:

Confirmed diagnosis of multiple myeloma as defined by the International Myeloma Working Group (IMWG) criteria.
Previously treated with at least 1 prior line of multiple myeloma (MM) therapy, and must have documented disease progression during or after their most recent therapy.
Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.

Must have at least 1 aspect of measurable disease, defined as one of the following;

Urine M-protein excretion >=200 mg per 24-hour, or
Serum M-protein concentration >=0.5 grams per deciliter (g/dL), or
Serum free light chain (FLC) assay: involved FLC level >=10 mg per dL (>=100 mg per liter) and an abnormal serum free light chain ratio (<0.26 or >1.65).
All prior treatment-related toxicities (defined by National Cancer Institute Common Toxicity Criteria for Adverse Events [NCI-CTCAE] version 5.0) must be <=Grade 1 at the time of enrollment, except for alopecia.
Adequate organ function

Exclusion Criteria:

Intolerant to daratumumab.
Refractory to daratumumab or any other anti-CD38 therapy (defined as progressive disease during treatment with anti-CD38 therapy, or within 60 days of completing that treatment).
Intolerant to bortezomib, or refractory to bortezomib (defined as progressive disease during treatment with a bortezomib-containing regimen of 1.3 mg/m^2 twice weekly, or within 60 days of completing that treatment). Note: participants with progressive disease during treatment with a weekly bortezomib regimen are allowed.
Ongoing Grade 2 or higher peripheral neuropathy or neuropathic pain.
Prior treatment with anti-B-cell maturation antigen (anti-BCMA) therapy.
Prior allogenic stem cell transplant.
Any serious and/or unstable pre-existing medical, psychiatric disorder or other conditions, including renal, liver, cardiovascular, or certain prior malignancies.
Corneal epithelial disease.