Bringing Mezigdomide Into Practice: Efficacy, Safety, and Clinical Implications
Key Points
- The SUCCESSOR-2 trial enrolled approximately 660 patients with relapsed or refractory multiple myeloma across 26 countries and evaluated mezigdomide plus carfilzomib/dexamethasone versus carfilzomib/dexamethasone alone.
- The study achieved its primary end point, demonstrating a median progression-free survival of 18 months versus 8.3 months.
- Benefits were observed consistently across multiple high-risk subgroups, including patients with extramedullary disease, high-risk cytogenetics, prior B-cell maturation antigen (BCMA) exposure, and pomalidomide-refractory disease.
- Safety findings were predictable and manageable, with neutropenia representing the principal toxicity and low rates of serious opportunistic infections.
At a Rapid Reactions discussion coinciding with the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, Rahul Gosain, MD, MBA, of Wilmot Cancer Institute, spoke with Paul Richardson, MD, of Dana-Farber Cancer Institute. Dr. Richardson reviewed the pivotal phase 3 SUCCESSOR-2 trial, which enrolled roughly 660 patients with relapsed or refractory multiple myeloma worldwide and included broad representation from North America, Europe, Asia, and Latin America. Following dose optimization in the initial stage of the study, patients were randomized to receive mezigdomide combined with carfilzomib and dexamethasone or carfilzomib/dexamethasone alone. The trial was designed to reflect real-world clinical practice while satisfying regulatory requirements.
The study met its primary end point, delivering a median progression-free survival (PFS) of 18 months with the mezigdomide-based triplet compared with 8.3 months for the control arm. Dr. Richardson noted that the hazard ratio of 0.48 represents a substantial reduction in the risk of progression or death. Importantly, PFS 2 analyses suggested that earlier use of mezigdomide did not compromise subsequent treatment opportunities, while overall survival trends also favored the investigational arm despite relatively immature follow-up.
Safety outcomes were considered highly manageable. Neutropenia remained the most common adverse event, but Dr. Richardson emphasized that proactive growth factor support can effectively address this toxicity. Rates of opportunistic infections were low, intravenous immunoglobulin utilization was limited, and no unexpected safety signals emerged. Thromboprophylaxis and Pneumocystis jirovecii pneumonia prophylaxis were highlighted as important supportive care considerations when treating patients with mezigdomide.
The conversation concluded with a discussion of the broader implications of SUCCESSOR-2. Dr. Richardson highlighted the consistency of benefit across numerous high-risk patient subsets, including those with extramedullary disease, prior BCMA-directed therapy, high-risk cytogenetics, and refractory disease. Comparing outcomes with those reported for chimeric antigen receptor T-cell therapy and bispecific antibodies, he suggested that mezigdomide provides an important additional option that can be used strategically across the treatment continuum while preserving future cellular therapy opportunities.