Maintenance Belantamab Mafodotin (Blenrep®) After B-cell Maturation Antigen-Directed Chimeric Antigen Receptor T-cell Therapy in Patients With Relapsed and/or Refractory Multiple Myeloma

Inclusion Criteria

• •1. Diagnosis of multiple myeloma with measurable disease (serum M-protein ≥ 0.5 g/dL or urine M-protein ≥200 mg/24 hour or involved serum-free light chain ≥10 mg/dL provided that the ratio of involved/uninvolved light chain is abnormal) prior to receiving CAR-T. Patients with no biochemically measurable disease before CAR-T may be enrolled if bidirectionally measurable plasmacytomas or bone marrow plasmacytomas \>10% are present prior to CAR-T infusion (sites must explicitly identify these patients to the Medical College of Wisconsin Multisite Team upon enrollment, as only four of these patients will be permitted on study, after which no future patients will be permitted to be enrolled).
• •2. Received at least three prior therapies (including a PI, immunomodulatory drugs (IMiD), and anti-cluster of differentiation 38 antibody (anti-CD38 antibody) ) given before CAR-T, and has not progressed/relapsed after receiving CAR-T therapy.
• •3. Achieved at least stable disease (SD) to CAR-T therapy and remained progression free after anti-BCMA CAR-T administration until enrollment (this requirement is also necessary prior administration of first study drug).
• •4. Voluntary consent (per single Institutional Review Board (sIRB) requirements) must be given before performance of any study-related procedure not part of standard medical care, with the understanding that consent may be withdrawn by the subject at any time without prejudice to future medical care.
• •5. Age ≥ 18 years.
• •6. Life expectancy ≥ six months.
• •7. Eastern Cooperative Oncology Group (ECOG) performance status 0-2.
• •8. Creatinine clearance (CrCl) ≥ 30 mL/minute, either measured or calculated using a standard formula (e.g., Modification of Diet in Renal Disease (MDRD) Study equation; Cockcroft and Gault).
• •9. Adequate hepatic function evidenced by aspartate aminotransferase (AST) and aspartate aminotransferase (ALT) ≤ 2.5 x ULN, bilirubin ≤ 1.5 x upper limit of the normal range (ULN) (isolated bilirubin ≥1.5 x ULN is acceptable if bilirubin is fractionated and direct bilirubin \<35%).
• •10. Adequate bone marrow function evidenced by hemoglobin ≥8 g/dL, platelets ≥75,000/mm3 (without transfusion of platelets in the prior seven days) and absolute neutrophil count ≥1,500/mm\^3 (growth factors are allowed during screening, but not within seven days prior to obtaining this result).
• •17. Participant must not use contact lenses while participating in this study.
• •18. Participant must not have used an investigational drug or approved systemic anti-myeloma therapy (including systemic steroids) within 14 days or five half-lives, whichever is shorter, preceding enrollment (this requirement is also necessary prior administration of first study drug).
• •19. Participant must not have had plasmapheresis within seven days prior to enrollment (this requirement is also necessary prior administration of first study drug).
• •20. Participant must not have received prior treatment with a monoclonal antibody within 30 days of enrollment (this requirement is also necessary prior administration of first study drug).
• •21. Participant must not have had major surgery ≤ four weeks prior to enrollment (this requirement is also necessary prior administration of first study drug).
• •22. Participant must not have any evidence of active mucosal or internal bleeding.
• •23. Participant must not have known immediate or delayed hypersensitivity reaction or idiosyncratic reactions to belantamab mafodotin or drugs chemically related to belantamab mafodotin, or any of the components of the study treatment.
• •24. Participant must not have known HIV infection.
• •25. Participant must not have presence of hepatitis B surface antigen (HBsAg), or hepatitis B core antibody (HBcAb) at screening or within three months prior to first dose of study treatment. Note: presence of hepatitis B surface antibody (HBsAb) indicating previous vaccination will not exclude a participant.
• •26. Participant must not have positive hepatitis C antibody test result or positive hepatitis C RNA test result at screening or within three months prior to first dose of study treatment.
• •Note: Participants with positive hepatitis C antibody due to prior resolved disease can be enrolled, only if a confirmatory negative hepatitis C RNA test is obtained.
• •Note: Hepatitis RNA testing is optional and participants with negative hepatitis C antibody test are not required to also undergo hepatitis C RNA testing.
• •27. Participant must not have invasive malignancies other than disease under study, unless the second malignancy has been medically stable for at least two years and, in the opinion of the principal investigators, will not affect the evaluation of the effects of clinical trial treatments on the currently targeted malignancy. Participants with curatively treated non-melanoma skin cancer may be enrolled without a two-year restriction.
• •28. Prior allogenic stem cell transplant within one year before enrollment, or current evidence of GvHD, or on systemic immunosuppressive therapy for GvHD at least six weeks before enrollment. Note - Participants who have undergone syngeneic transplant will be allowed, only if no history of GvHD
• •29. Symptomatic amyloidosis, active POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma proliferative disorder, skin changes) or active plasma cell leukemia at the time of screening.
• •30. Any serious and/or unstable pre-existing medical, psychiatric disorder or other conditions (including lab abnormalities) that could interfere with participant's safety, obtaining informed consent or compliance to the study procedures.
• •31. Administration of live or live-attenuated vaccines are contraindicated 30 days prior to the first dose of study treatment. Killed or inactivated vaccines may be administered; however, the response to such vaccines cannot be predicted.