Influence of PPM1D Mutations on Response and Survival Outcomes Following Bispecific Antibody Therapy in Relapsed and Refractory Multiple Myeloma Patients

Background/Objectives: Therapeutic options for patients with relapsed and refractory multiple myeloma (RRMM) have advanced substantially in recent years. In particular, T-cell-engaging therapies, including chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies (bsAbs), have emerged as highly effective treatment modalities. However, data on predictive biomarkers for response to these therapies remain limited. Patients currently receiving T-cell-engaging therapies are typically heavily pretreated and frequently exhibit clonal hematopoiesis. Clonal hematopoiesis, especially involving PPM1D mutations, may adversely affect the efficacy of T-cell-engaging therapies. Methods: We conducted a retrospective, single-center study including 27 patients with RRMM who were treated with bsAbs (teclistamab, elranatamab, or talquetamab) between June 2022 and September 2025 and for whom genetic material was available before bsAB treatment. We evaluated the impact of PPM1D mutations on treatment response, progression-free survival (PFS), and overall survival (OS). Results: The prevalence of PPM1D mutations in our cohort was 27%. Compared with patients without PPM1D mutations, mutation carriers showed a trend toward less deep remissions and demonstrated significantly inferior 6-month PFS (43% vs. 85%, p = 0.0272) and 6-month OS (57% vs. 90%, p = 0.0473). Conclusions: These findings suggest that PPM1D mutations may represent a promising biomarker in patients with RRMM treated with bsAbs. Larger, prospective studies are warranted to validate and further elucidate these observations.