SUMMARY: Multiple Myeloma is a clonal disorder of plasma cells in the bone marrow and the American Cancer Society estimates that in the United States, 35,780 new cases will be diagnosed in 2024 and 12,540 patients are expected to die of the disease. Multiple Myeloma is a disease of the elderly, with a median age at diagnosis of 69 years and characterized by intrinsic clonal heterogeneity. Almost all patients eventually will relapse, and patients with a high-risk cytogenetic profile, extramedullary disease or refractory disease have the worst outcomes. The introduction of Proteasome Inhibitors, Immunomodulatory agents and CD38 targeted therapies has resulted in higher Response Rates, as well as longer Progression Free Survival (PFS) and Overall Survival (OS), with the median survival for patients with myeloma approaching 10 years or more. Nonetheless, multiple myeloma in 2023 remains an incurable disease.
Patients with newly diagnosed multiple myeloma often receive triplet and quadruplet regimens that incorporate proteasome inhibitors, immunomodulators, and anti-CD38 antibodies as first line therapy, as these regimens are associated with prolonged Progression Free Survival and Overall Survival. However, most patients relapse and frontline use of Lenalidomide therapy has increased the number of patients with Lenalidomide-refractory disease at the time of the first relapse. New novel combinations are needed for patients who have relapsed or refractory myeloma, after disease progression during frontline therapy.
B-Cell Maturation Antigen (BCMA) is a member of the Tumor Necrosis Factor superfamily of proteins. It is a transmembrane signaling protein primarily expressed by malignant and normal plasma cells and some mature B cells. BCMA is involved in JNK and NF-kB signaling pathways that induce B-cell development and autoimmune responses. BCMA has been implicated in autoimmune disorders, as well as B-lymphocyte malignancies, Leukemia, Lymphomas, and multiple myeloma. B-Cell Maturation Antigen is therefore an established target in myeloma.
Belantamab mafodotin (BLENREP®) is a BCMA-targeting antibody-drug conjugate comprising a humanised B-cell maturation antigen monoclonal antibody conjugated to the cytotoxic agent auristatin F via a non-cleavable linker. Among patients with relapsed or refractory myeloma, data from a Phase I-II trial involving Belantamab mafodotin, Pomalidomide, and Dexamethasone (BPd) showed some safety concerns but promising clinical activity.
The DREAMM-8 is an ongoing, global, open-label, randomized, multicenter Phase III trial, conducted to evaluate the efficacy and safety of Belantamab mafodotin in combination with Pomalidomide and Dexamethasone (BPd) compared to the standard of care, Pomalidomide, Bortezomib, and Dexamethasone (PVd), in patients with relapsed or refractory multiple myeloma (RRMM) who had received at least one prior line of therapy, including a Lenalidomide-containing regimen, and experienced disease progression. In this study, 302 patients were randomized 1:1 to BPd regimen (N=155) or PVd regimen (N=147). Patients in the BPd group received Belantamab mafodotin 2.5 mg/kg IV on Day 1 of Cycle 1, then 1.9 mg/kg on Day 1 of subsequent cycles, plus Pomalidomide 4 mg orally daily on Days 1-21 of each cycle, and Dexamethasone 40 mg orally weekly on Day 1 of each cycle. Patients in the PVd group received Pomalidomide 4 mg orally daily on Days 1-14 of each 21-day cycle, Bortezomib 1.3 mg/m² subcutaneously on Days 1, 4, 8, 11 (Cycles 1-8) and Days 1, 8 (Cycle 9+), and Dexamethasone 20 mg orally on the day of and day after Bortezomib. The median age was 67 years, 86% were Caucasian, 33% had high risk cytogenetics, 28% had previous anti-CD38 antibodies and approximately 60% of patients had Autologous Stem-Cell Transplantation (ASCT). The Primary Endpoint was Progression-Free Survival (PFS) evaluated by an Independent Review Committee (IRC) and Secondary Endpoints included Overall Survival (OS), Overall Response Rate (ORR) defined as the proportion of patients achieving Partial Response (PR) or better according to the International Myeloma Working Group (IMWG) criteria, Duration of Response and Safety.
At a median follow-up of 21.8 months, the median PFS was not reached (NR) in the BPd arm versus 12.7 months in the PVd arm (HR=0.52; P<0.001). The 12-month estimated PFS rate was 71% with BPd versus 51% with PVd. The ORR in the BPd group was 77% and in the PVd group was 72%. The Complete Response (CR) or better was 40% in the BPd group and 16% in the PVd group, and the median Duration of Response was Not Reported with BPd versus 17.5 months with PVd. With regards to Overall Survival, a positive trend favoring BPd was observed (HR 0.77; 95% CI 0.53-1.14), although data were immature at the time of analysis. Follow-up for OS is ongoing.
Adverse Events occurred in more than 99% of patients in the BPd arm and 96% in the PVd arm. Ocular adverse events were common with BPd (89%, Grade 3/4 in 43%) versus PVd (30%, Grade 3/4 in 2%). These adverse events were mitigated by Belantamab mafodotin dose modifications. Treatment was discontinued due to adverse events in 9% of patients in the BPd arm versus none in the PVd arm.
In summary, the DREAMM-8 trial provides robust evidence of the clinical efficacy and safety of Belantamab mafodotin in combination with Pomalidomide and Dexamethasone for relapsed or refractory multiple myeloma patients, addressing the critical need for effective therapies post-Lenalidomide exposure. Despite higher rates of ocular adverse events with Belantamab mafodotin, these toxicities can be effectively managed with dose adjustments, ensuring continued patient safety and treatment compliance.
Results from the randomized phase 3 DREAMM-8 study of belantamab mafodotin plus pomalidomide and dexamethasone (BPd) vs pomalidomide plus bortezomib and dexamethasone (PVd) in relapsed/refractory multiple myeloma (RRMM). Trudel S, Beksac M, Pour L, et al. J Clin Oncol 42, 2024 (suppl 17; abstr LBA105). DOI: 10.1200/JCO.2024.42.17_suppl.LBA105
