Safety and Efficacy of Bispecific Antibody Treatment in Relapsed/Refractory Multiple Myeloma: A Systematic Review and Meta-Analysis of Proportions from Clinical Trials.

: Multiple myeloma (MM) is an incurable plasma cell dyscrasia with particularly adverse prognosis in relapsed, multi-drug refractory settings. The management of those patients is challenging as treatment options are limited. In this context, bispecific antibodies (BsAbs) have recently emerged as promising therapeutic agents, and several have gained regulatory approval. To better understand their impact in MM landscape, we performed a systematic review and meta-analysis assessing their efficacy and safety in patients with relapsed/refractory MM (RRMM). : A systematic search was conducted in the PubMed, ScienceDirect, Scopus and ClinicalTrials.gov databases for clinical trials investigating BsAbs for RRMM. Pooled estimates in terms of proportions along with 95% confidence intervals were calculated with random-effects models. The present meta-analysis was performed following PRISMA guidelines and was registered in PROSPERO (ID: CRD420251028553). : Based on data from six clinical trials involving 850 patients, the pooled overall response and complete response or better rates were 69% and 42%, respectively, whereas the pooled rate of duration of response for at least one year was 71%. The estimated one-year progression-free survival and overall survival were 56% and 72%, respectively. Neutropenia was the most frequently observed severe hematological toxicity, with a pooled incidence of 46%. Grade ≥3 infections occurred in 29%, while any-grade CRS occurred in 69%, as per pooled analysis. Finally, an exploratory minimal residual disease (MRD) analysis in four of the six studies yielded a pooled MRD-negativity rate of 24%. : BsAbs demonstrated commendable efficacy in heavily pretreated RRMM patients, in terms of response rates and survival outcomes. However, notable rates of hematologic toxicity, infections, and CRS were recorded. These findings support the clinical utility of BsAbs in RRMM, while highlighting the need for comprehensive toxicity management.