An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of a study intervention, whether or not considered related to the study intervention.

All treated population included all eligible participants who received at least 1 dose of study treatment.

An SAE is defined as any untoward medical occurrence that, at any dose: results in death; is life threatening; requires inpatient hospitalization or prolongation of existing hospitalization; results in persistent disability/incapacity; is a congenital anomaly/birth defect; important medical events that may jeopardize the participant or may require medical or surgical intervention; is associated with liver injury and impaired liver function.

All treated population

An event was considered DLT if it occurred within 21 days of treatment and met any of the following criteria within same period:

• Any Grade (Gr.) 3 or greater non-hematologic toxicity as described in NCI-CTCAE Version 5.0, other than corneal events that persists for >48 hours despite supportive treatment or leads to hospitalization.
• Hematologic toxicity such as Gr. 3 or greater febrile neutropenia lasting >48 hours despite adequate treatment (Gr. 3 defined as absolute neutrophil count (ANC) <1000/millimeter cube (mm^3) at a single temperature >38.3 degree celsius or a sustained temperature >=38 degree celsius for more than 1 hour) and, Gr. 4 thrombocytopenia defined as platelet count <25000/mm^3 with clinically significant bleeding, or if platelet transfusion is required.
• Gr. 4 per the corneal grading scale.
• Liver toxicity meeting pre-specified by GSK liver stopping criteria.

DLT evaluable population included all the eligible participants who have received the 1st dose as planned and experienced a DLT during the cycle 1 or completed the cycle 1.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. AUC[0-t] was calculated using the linear trapezoidal rule for each incremental trapezoid and the log trapezoidal rule for each decremental trapezoid.

Pharmacokinetic (PK) population, was defined as those participants in the "All treated" population from whom at least one PK sample was obtained, analyzed, and was measurable.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. AUC[0-t] was calculated using the linear trapezoidal rule for each incremental trapezoid and the log trapezoidal rule for each decremental trapezoid.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. AUC[0-t] was calculated using the linear trapezoidal rule for each incremental trapezoid and the log trapezoidal rule for each decremental trapezoid.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. Maximum observed plasma concentration, determined directly from the concentration-time data for each cycle.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. Maximum observed plasma concentration, determined directly from the concentration-time data for each cycle.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis. Maximum observed plasma concentration, determined directly from the concentration-time data for each cycle.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Blood samples were collected at indicated time points for pharmacokinetic analysis of belantamab mafodotin. PK parameters were analyzed using standard non-compartmental analysis.

Pharmacokinetic (PK) population. Only those participants with data available at specified time points were analyzed.

Abnormal vital signs were defined as any abnormal findings in the vital signs parameters (temperature, blood pressure and pulse rate).

All treated population

Blood samples were collected at indicated time points to assess change from baseline in hemoglobin, lymphocytes, neutrophils, platelets, leukocytes. Worst case grade increase from baseline grade was provided for all the hematology tests that were gradable by National Cancer Institute Common Terminology Criteria (NCI CTCAE, Version 5.0, 2017). Grade 1 = Mild AE; Grade 2 = Moderate AE; Grade 3 = Severe AE; Grade 4 = Life-threatening or disabling AE. Data for any participants with worst-case grade changes (Increase to Grade 3 or Increase to Grade 4) post-baseline were presented. Baseline was defined as latest pre-dose assessment (day 1) with a non-missing value, including those from unscheduled visits.

All treated population

Blood samples were collected at indicated time points to assess change from baseline in albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, bilirubin, creatine kinase, gamma glutamyl transferase, potassium, lactate dehydrogenase, magnesium. Worst case grade (G) increase from baseline grade was provided for all the chemistry tests that were gradable by National Cancer Institute Common Terminology Criteria (NCI CTCAE, Version 5.0, 2017). Grade 1 = Mild AE; Grade 2 = Moderate AE; Grade 3 = Severe AE; Grade 4 = Life-threatening or disabling AE. Data for any participants with worst-case grade changes (Increase to Grade 3 or Increase to Grade 4) post-baseline were presented. Baseline was defined as latest pre-dose assessment (day 1) with a non-missing value, including those from unscheduled visits.

All treated population

ORR was defined as the percentage of participants with a confirmed partial response (PR) or better (i.e., very good partial response [VGPR], complete response [CR] and stringent complete response [sCR]) as assessed by International Myeloma Working Group (IMWG) Uniform Response Criteria for Multiple Myeloma 2016. PR=response greater than or equal to (>=) 50 percent (%) reduction of serum M-protein and reduction in 24-hour urinary M-protein by >=90% or to less than (<) 200 mg per 24 hours. CR=negative immunofixation of serum and urine and disappearance of any soft tissue plasmacytomas and <5% plasma cells in bone marrow aspirates. sCR=complete response below plus normal free light chain (FLC) ratio and absence of clonal plasma cells in bone marrow by immunohistochemistry or 8-color, 2 tube multiparametric flow cytometry. VGPR=Serum and urine M-protein detectable by immunofixation but not on electrophoresis or ≥90% reduction in serum M-protein plus urine M-component level <100 mg/24 h.

All treated population

Serum samples were analyzed for the presence of anti-belantamab mafodotin antibodies by a validated electro chemiluminescent immunoassay. All samples were tested in a screening assay to identify potentially positive samples.

All treated population

Samples were analyzed for the presence of anti-belantamab mafodotin antibodies by a validated electro chemiluminescent immunoassay. All samples were tested in a screening assay to identify potentially positive samples. Screened positive was further characterized for the antibody titer values.

All Treated Population. Only the participants who showed positive results for ADAs were analyzed.

The OSDI instrument measures vision-related function. The total OSDI score was calculated as (sum of scores for all questions answered*100) divided by (total number of questions answered*4). The 12 items questionnaire assessed ocular symptoms, visual-related functioning and environmental triggers. Scores ranged from 0 to 100, with higher scores indicating a worse status. Baseline was defined as latest pre-dose assessment (day 1) with a non-missing value, including those from unscheduled visits.

All treated population