A Phase I/II, Randomized, Open-label Platform Study Utilizing a Master Protocol to Study Belantamab Mafodotin (GSK2857916) as Monotherapy and in Combination With Anti-Cancer Treatments in Participants With Relapsed/Refractory Multiple Myeloma (RRMM) - DREAMM 5
B-cell maturation antigen (BCMA) is a target present on tumor cells in participants with multiple myeloma. Belantamab mafodotin (GSK2857916); is an antibody-drug conjugate (ADC) containing humanized anti-BCMA monoclonal antibody (mAb). This is a phase I/II, randomized, open-label, platform study designed to evaluate the effects of belantamab mafodotin in combination with other anti-cancer drugs in participants with relapsed/refractory multiple myeloma. The Platform design incorporates a single master protocol, where multiple treatment combinations, as sub-studies, will be evaluated simultaneously.
• Participant must be 18 years of age inclusive or older, at the time of signing the informed consent.
• Participants must have histologically or cytologically confirmed diagnosis of Multiple Myeloma (MM), as defined by the IMWG.
• Participants having at least 3 prior lines of prior anti-myeloma treatments including an immunomodulating agent (IMID) a proteasome inhibitor (PI) and an anti-CD38 monoclonal antibody.
• Participants with a history of autologous stem cell transplant are eligible for study participation when, transplant was \>100 days prior to study enrolment and with no active infection(s).
• Participants with Eastern Cooperative Oncology Group (ECOG) performance status of 0-1, unless ECOG less than equal to (\<=)2 is due solely to skeletal complications and/or skeletal pain due to MM.
• Participants with measurable disease defined as at least one of the following: Serum M-protein greater than equal to (\>=)0.5 gram per deciliter (\>=5 gram per liter) or Urine M-protein \>=200 milligrams (mg) per 24 hours or Serum free light chain (FLC) assay: Involved FLC level \>=10 mg per deciliter (\>=100 mg per Liter) and an abnormal serum FLC ratio (\<0.26 or \>1.65).
• Participants who have tested positive for Hepatitis B core antibody (HBcAb) can be enrolled if the following criteria are met: Serology result HBcAb+, Hepatitis B surface antigen (HBsAg)-; HBV deoxyribonucleic acid (DNA) undetectable during screening.
• Participants who are currently receiving physiological doses oral steroids (\<10 mg/day), inhaled steroids or ophthalmalogical steroids.
• Participants with contraception requirements specific to Sub-study 6, 7, and 8 respectively.
• Participants with platelets value for Adequate Organ System Function is ≥75 × 10\^9/L.
• In Japan, participants should reside in Japan and be Japanese as defined by having all biological Japanese grandparents. Similarly, in China, subjects should reside in China and be Chinese as defined by having all biological Chinese grandparents.