To Evaluate Safety, Tolerability, and Clinical Activity of the Antibody-drug Conjugate, GSK2857916 Administered in Combination With Lenalidomide Plus Dexamethasone (Arm A), or in Combination With Bortezomib Plus Dexamethasone (Arm B) in Participants With Relapsed/Refractory Multiple Myeloma (RRMM)

DLT is an adverse event (AE) that is considered by the investigator to be clinically relevant and attributed to the study therapy during the 28 day DLT period and meets at least one of the DLT criteria: Grade 3 or greater febrile neutropenia lasting >48 hours (h) despite adequate treatment; Grade 4 thrombocytopenia <25,000/mm^3 accompanied by significant bleeding; any Grade 3 or greater non-hematologic laboratory value (if laboratory abnormality persist >48 h despite supportive treatment or abnormality leading to hospitalisation); non-hematologic toxicity which does not resolve with appropriate supportive treatment within 48 h, Grade 4 corneal adverse events; and other organ specific toxicities (liver toxicity that causes discontinuation of treatment).

DLT is an adverse event (AE) that is considered by the investigator to be clinically relevant and attributed to the study therapy during the 21 day DLT period and meets at least one of the DLT criteria: Grade 3 or greater febrile neutropenia lasting >48 hours (h) despite adequate treatment; Grade 4 thrombocytopenia <25,000/mm^3 accompanied by significant bleeding; any Grade 3 or greater non-hematologic laboratory value (if laboratory abnormality persist >48 h despite supportive treatment or abnormality leading to hospitalisation); non-hematologic toxicity which does not resolve with appropriate supportive treatment within 48 h, Grade 4 corneal adverse events; and other organ specific toxicities (liver toxicity that causes discontinuation of treatment).

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of a study treatment, whether or not considered related to the study treatment. 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 or Is a congenital anomaly/birth defect, Other situations which involve medical or scientific judgment or is associated with liver injury and impaired liver function. SAEs are subset of AEs. A summary of number of participants with any AEs and SAEs are presented. AEs were coded using the Medical Dictionary for Regulatory Affairs (MedDRA dictionary).

12-lead electrocardiogram (ECGs) were obtained using an automated ECG machine that automatically calculated the QTcF intervals. QTc values are categorized into the clinical concern ranges which are specific to changes in QTc: 31-60 milliseconds (msec), and >60 msec, and >530msec. An increase is defined relative to Baseline. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Data of number of participants with worst-case increase post baseline is presented.

Blood samples were collected for analysis of following hematology parameters: Hemoglobin (hemoglobin increased and anemia), Lymphocytes (lymphocyte count increased and lymphocyte count decreased), Neutrophils, Platelets and Leukocytes (leukocytosis and white blood cells decreased). The laboratory parameters were graded according to Common Terminology Criteria for Adverse Events (CTCAE) version (v) 4.03. Grade (G) 1: mild; G2: moderate; G3: severe or medically significant; G4: life-threatening consequences. Higher grade indicates greater severity and increase in grade was defined relative to Baseline grade. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Any worst-case post baseline increases in grade along with any increase to a maximum G3 and a maximum G4 are presented.

Blood samples were collected for the analysis of following hematology parameters: basophils, eosinophils, hematocrit, mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV), monocytes, erythrocytes and reticulocyte. The summaries of worst-case change from baseline with respect to normal range was analyzed for only those laboratory tests that were not gradable by CTCAE version 4.03. The number of participants with decreases to low from baseline, changes to normal or no changes from baseline, and increases to high values from baseline have been presented. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits.

Blood samples were collected for analysis of following clinical chemistry parameters: Hyperglycemia, Hypoglycemia, Albumin, Alkaline Phosphatase, Alanine Aminotransferase (ALT), Aspartate Aminotransferase, (AST), Bilirubin, Creatine Kinase (CK), Creatinine, Gamma Glutamyl Transferase (GGT), Hyperkalemia, Hypokalemia, Hypermagnesemia, Hypomagnesemia, Phosphate, Hypernatremia, Hyponatremia, Urate, Hypercalcemia and Hypocalcemia. Laboratory parameters were graded according to CTCAE v4.03. Grade (G) 1: mild; G2: moderate; G3: severe or medically significant; G4: life-threatening consequences. Higher grade indicates greater severity and increase in grade was defined relative to Baseline grade. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Any worst-case post baseline increases in grade along with any increase to a maximum G3 and a maximum G4 are presented.

Blood samples were collected for analysis of following clinical chemistry parameters: Direct Bilirubin (DB), Calcium, Chloride, Carbon Dioxide (CO2), lactate dehydrogenase (LDH) and Protein. The summaries of worst-case change from baseline with respect to normal range was analyzed for only those laboratory tests that were not gradable by CTCAE version 4.03. The number of participants with decreases to low from baseline, changes to normal or no changes from baseline, and increases to high values from baseline have been presented. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits.

Urine samples were collected to analyze presence of occult blood and protein in urine by dipstick method. Data for worst-case post baseline urinalysis results is presented. Result for urinalysis parameters were recorded as no change/decreased and increase to trace, 1+, 2+, 3+, >3+ indicating proportional concentrations in the urine sample. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits.

Urine samples were collected to analyze urine pH levels. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits.

Urine samples were collected to analyze urine specific gravity using dipstick method. Baseline (Day 1) was defined as latest pre-dose assessment with a non-missing value, including unscheduled visits.

Blood pressures (DBP and SBP) were measured after resting for at least 5 minutes in a supine or semi-recumbent position. Baseline (Day 1) was defined as latest pre-dose assessment with a non-missing value, including unscheduled visits. Change from Baseline was calculated as post-dose visit value minus Baseline value.

Pulse rate was measured after resting for at least 5 minutes in a supine or semi-recumbent position. Baseline (Day 1) was defined as latest pre-dose assessment with a non-missing value, including unscheduled visits. Change from Baseline was calculated as post-dose visit value minus Baseline value.

Temperature was measured after resting for at least 5 minutes in a supine or semi-recumbent position. Baseline (Day 1) was defined as latest pre-dose assessment with a non-missing value, including unscheduled visits. Change from Baseline was calculated as post-dose visit value minus Baseline value.

ORR was defined as the percentage of participants with a confirmed partial response (PR) or better (i.e., PR, very good partial response [VGPR], complete response [CR] and stringent complete response [sCR]), according to the International Myeloma Working Group (IMWG) Response Criteria. CR: negative immunofixation of serum and urine and disappearance of any soft tissue plasmacytomas and <5% plasmacytomas in the bone marrow; sCR: stringent complete response, CR as above plus normal serum free light-chain (FLC) assay ratio and absence of clonal cells in bone marrow by immunohistochemistry or immunofluorescence; VGPR: serum and urine M-component detectable by immunofixation but not on electrophoresis OR >= 90% reduction in serum M-component plus urine M-component <100 mg/24 h; PR: >=50% reduction of serum M-protein and reduction in 24-hour urinary M-protein by >=90% or to <200 mg/24 h. Confidence intervals were based on the exact method.

Blood samples were collected at indicated timepoints for pharmacokinetic (PK) analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods. Tlast is the time of last observed quantifiable concentration of belantamab mafodotin in Cycle 1 which extended beyond protocol defined duration for some participants across treatment groups.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods. AUC(0-1008h) was derived only for Belantamab mafodotin 1.9 mg/kg STRETCH + Bor/Dex, Belantamab mafodotin 2.5 mg/kg StepDown STRETCH + Bor/Dex and Belantamab mafodotin 2.5 mg/kg STRETCH + Bor/Dex cohorts.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods. Tlast is the time of last observed quantifiable concentration of belantamab mafodotin in Cycle 1 which extended beyond protocol defined duration for some participants across treatment groups.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods. AUC(0-1008) was derived only for Belantamab mafodotin 1.9mg/kg + Len/Dex STRETCH cohort.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods. AUC(0-1344) was derived only for Belantamab mafodotin 1.9mg/kg + Len/Dex STRETCH cohort.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods. Tlast is the time of last observed quantifiable concentration of belantamab mafodotin in Cycle 1 which extended beyond protocol defined duration for some participants across treatment groups.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected at indicated timepoints for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods. AUC(0-1008h) was derived only for Belantamab mafodotin 1.9 mg/kg STRETCH + Bor/Dex, Belantamab mafodotin 2.5 mg/kg StepDown STRETCH + Bor/Dex and Belantamab mafodotin 2.5 mg/kg STRETCH + Bor/Dex cohorts.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods. Tlast is the time of last observed quantifiable concentration of belantamab mafodotin in Cycle 1 which extended beyond protocol defined duration for some participants across treatment groups.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods. AUC (0-336h) was derived only for the Belantamab mafodotin 2.5mg/kg + Len/Dex SPLIT cohort.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods. Tlast is the time of last observed quantifiable concentration of belantamab mafodotin in Cycle 1 which extended beyond protocol defined duration for some participants across treatment groups.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Blood samples were collected for PK analysis. PK parameter was determined using standard non-compartmental methods.

Serum samples were collected and tested for the presence of antibodies against belantamab mafodotin using validated immunoassays.

Serum samples were collected and tested for the presence of antibodies against belantamab mafodotin using validated immunoassays. Confirmed positive ADA samples were further analyzed to obtain the titer of the antibodies. Titers of anti-drug antibodies against belantamab mafodotin is presented.

The OSDI is a 12-item questionnaire designed to assess both the frequency of dry eye symptoms and their impact on vision-related functioning. OSDI consist of three subscales (ocular symptoms: item 1-3; visual related function: item 4-9; environmental triggers: item 10-12). Each item will be graded on a scale of 0 (none of the time or lower disability) to 4 (all of the time or greater disability) with total scores ranging from 0 (no disability) to 100 (complete disability). The total OSDI score was calculated as (sum of scores for all questions answered*100) divided by (total number of questions answered*4). Higher scores indicated greater disability. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline was calculated by subtracting Baseline value from the post-dose visit value.

The NEI-VFQ-25 consisted of a base set of 25 vision-targeted questions representing 11 vision-related constructs, plus an additional single-item general health rating question to assess the patient's perception of vision-related functioning and vision-related quality of life. Items were coded to a 0 to 100 scale and were averaged to calculate domains. The composite score ranges from 0 (worst score) to 100 (best score), with higher scores indicating better vision-related functioning. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline was calculated by subtracting Baseline value from the post-dose visit value.

The PRO-CTCAE is a patient-reported outcome measure developed to evaluate symptomatic toxicity in participants on cancer clinical trials. It included item library of 124 items representing 78 symptomatic toxicities drawn from the CTCAE like Anxious, Blurred Vision, Chills, Concentration, Constipation, Cough, Decreased Appetite, Discouraged, Dizziness, Fatigue, Heart Palpitations, Insomnia, Memory, Mouth/Throat Sores, Nausea, Nosebleed, Numbness & Tingling, Pain, Ringing In Ears, Shortness Of Breath, Vomiting and Watery Eyes. Number of participants with symptomatic AEs measured by PRO-CTCAEs are presented.

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. Number of participants with AESI for belantamab mafodotin (corneal events, thrombocytopenia and infusion related reactions) are presented.

BCVA score was assessed individually for each eye. BCVA score was calculated based on the Logarithm of the Minimum Angle of Resolution (logMAR score). Any worst-case change from baseline categories are presented for right and left eyes. BCVA test scores were categorized as no change/improved vision, possible worsened vision and definite worsened vision. No change/improved vision was defined as a change from baseline <0.12 logMAR score; a possible worsened vision was defined as a change from baseline >=0.12 to <0.3 logMAR score; a definite worsened vision was defined as a change from baseline >=0.3 logMAR score. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline was calculated by subtracting Baseline value from the post-dose visit value.

BCVA score was assessed individually for better seeing eye and worse seeing eye. BCVA score was calculated based on the Logarithm of the Minimum Angle of Resolution (logMAR score). Any worst-case change post baseline categories are presented for better seeing eye and worse seeing eye. BCVA test scores by Snellen results were categorized as improved BCVA, <= 2 lines decline in visual acuity from baseline, >= 3 lines decline in visual acuity from baseline. Number of lines change from baseline was defined as the following: Improved BCVA equates to a negative change in logMAR from baseline BCVA. <= 2 lines decline in visual acuity equates to logMAR change from baseline ≤0.37. >= 3 lines decline in visual acuity equates to logMAR change from baseline ≥0.38. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline was calculated by subtracting Baseline value from the post-dose visit value.

Number of participants with a Decline in BCVA to 'Light Perception (LP)' or 'No Light Perception (NLP)' due to a Corneal Event Anytime Post-Baseline are presented. BCVA score was assessed individually for each eye (Left and Right). Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Number of participants analyzed were who have any post-baseline BCVA score, where the Visual Acuity is due to corneal findings.

Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Corneal epithelium findings like active edema, active opacity, corneal neovascularization (CN), corneal ulcer, epithelial microcystic edema (EME) and subepithelial haze were performed using a slit lamp. Number of participants with shift in corneal epithelium findings from no (Baseline) to yes (worst post-Baseline) are presented.

Participants with worse grade punctate keratopathy findings post baseline at any ocular exam by right eye, left eye and worse eye are presented as none, mild, moderate and severe. Worse eye indicates the eye with the worst visual acuity. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits.

The EORTC QLQ-C30 includes 30-items with single and multi-item scales. These included five functional scales (physical functioning [PF], role functioning [RF], cognitive functioning [CF], emotional functioning [EF] and social functioning [SF]), three symptom scales (fatigue, pain and nausea/vomiting [N/V]), a global health status (GHS)/ Quality-of-Life (QoL) scale, and six single items (constipation, diarrhea, insomnia, dyspnea, appetite loss [AL] and financial difficulties [FD]). Response options are 1 to 4. Scores were averaged and transformed to 0 to 100, a high score for functional scales/ GHS/QoL represent better functioning ability or health-related quality-of-life (HRQoL), whereas a high score for symptom scales/ single items represent significant symptomatology. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline (CFB) was calculated by subtracting Baseline value from the post-dose visit value.

The EORTC QLQ-MY20 is a supplement to the QLQ-C30 instrument used in participants with multiple myeloma. The module comprised of 20 questions that addressed four myeloma-specific HRQoL domains: disease symptoms (DS), side effects of treatment (SET), future perspective (FP) and body image (BI). Responses are 1 to 4. Scores were averaged and scales were transformed to 0 to 100 scale. A high score for disease symptoms and side effects of treatment represented a high level of symptomatology or problems, whereas a high score for future perspective and body image represented better outcomes. Baseline (Day 1) was defined as latest pre-dose assessment with non-missing value, including unscheduled visits. Change from Baseline was calculated by subtracting Baseline value from the post-dose visit value.