Oral Mezigomab Overcomes Limitations of CAR-T Therapy, Demonstrates Doubled Survival in Phase 3 Trial for Multiple Myeloma
Background
The treatment landscape for multiple myeloma is rapidly changing with the emergence of T-cell redirecting therapies. Chimeric antigen receptor (CAR) T-cell therapies and bispecific antibodies (BsAbs) targeting B-cell maturation antigen (BCMA) have demonstrated excellent efficacy in patients with refractory disease. However, patient access is often limited due to the practical barriers associated with advanced biologics, including complex logistics and the need for hospitalization in specialized medical centers to manage severe adverse events. Consequently, many patients do not receive adequate treatment due to disparities in healthcare access. There is a critical need for an oral therapy that is both convenient to administer in an outpatient setting and highly effective.
Key Findings
The SUCCESSOR-2 phase 3 clinical trial, published in The Lancet, clearly demonstrates the clinical utility of mezigomab, a next-generation cereblon E3 ligase modulator (CELMoD). The trial included patients with relapsed or refractory multiple myeloma (RRMM). Patients were randomized to receive mezigomab in combination with carfilzomib and dexamethasone (MeziKd) or carfilzomib and dexamethasone alone (Kd). 92.1% of patients had prior exposure to key therapies, 85.8% were refractory to anti-CD38 monoclonal antibodies, and 75.8% were high-risk patients with lenalidomide-resistant disease.
The median progression-free survival (PFS) in the MeziKd arm was 18.0 months, more than double that of the control arm (8.3 months). This resulted in a 52% reduction in the risk of disease progression or death (hazard ratio 0.48, p<0.0001). The overall response rate (ORR) was 80.2% in the MeziKd arm and 53.4% in the control arm. The proportion of patients achieving a complete response (CR) or better was also significantly higher in the MeziKd arm (26.7%) compared to the control arm (8.9%).
However, the incidence of grade 3 or higher adverse events was higher in the MeziKd arm (83.7%) compared to the control arm (56.0%). The most common adverse events were neutropenia (61%), and the incidence of grade 3 or higher infections was also higher in the MeziKd arm (34%) compared to the control arm (16%). Careful monitoring and proactive management of adverse events by healthcare professionals will be essential to ensure patient safety.
Implications and Future Directions
These findings provide a new treatment option for patients with relapsed disease who have limited alternatives. Existing CAR-T therapies have long manufacturing times, which can delay treatment for patients with rapidly progressing disease. Furthermore, these therapies require specialized infrastructure, which can limit access for patients in rural areas. In contrast, mezigomab, an oral drug, can be administered quickly and easily, which can improve access to treatment.
The increased risk of serious infections observed in the safety profile is an important consideration for future development. Further studies are needed to optimize the dose and schedule of mezigomab to minimize the risk of adverse events. In addition, studies are needed to determine the optimal sequencing of mezigomab with other therapies, such as cellular therapies. The U.S. Food and Drug Administration (FDA) has accepted the application for approval of the combination therapy and has set a target review date of May 2027. The approval of this therapy could significantly change the treatment landscape for multiple myeloma.
The treatment landscape for relapsed or refractory multiple myeloma is rapidly evolving with the introduction of T-cell redirecting therapies.1–3 Recent randomised clinical trials have shown the superiority of anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapies and bispecific antibodies over standard-of-care regimens when used in earlier lines of therapy, leading to regulatory approvals around the world. However, access to these therapies might be restricted due to the need for specialised care and logistical considerations.
The study results are expected to provide a concrete opportunity to shift the multiple myeloma treatment environment, which is currently concentrated in large medical institutions, to a community-based model. For example, patients living in rural areas must endure the inconvenience of waiting for a bed to become available in a large hospital in the metropolitan area in order to receive CAR-T therapy. If the tumor worsens during the waiting period, they may lose the opportunity for treatment. On the other hand, if the triple combination therapy with mezigomab is approved, patients can easily receive a prescription and take the medication by visiting the outpatient clinic of a local hospital near their residence. From the perspective of the pharmaceutical industry, oral small-molecule compounds, which are easy to mass-produce and have lower distribution costs compared to complex autologous cell therapies, are advantageous for building a global supply chain. This will pave the way for expanding the treatment area to countries with poor cold chain logistics.