Mirvetuximab soravtansine-gynx (Elahere) has achieved significant milestones with approvals from both the European Commission and the FDA for the treatment of folate receptor alpha (FRα)-positive, platinum-resistant ovarian cancer. These approvals mark a pivotal advancement in the treatment landscape, offering a targeted therapy for patients who have undergone one to three prior systemic treatments. The global phase 3 MIRASOL trial (NCT04209855) served as the foundation for these regulatory decisions, demonstrating the drug's superiority over traditional chemotherapy options.
Efficacy and Clinical Data
The MIRASOL trial, a randomized, controlled study, evaluated mirvetuximab soravtansine against investigator's choice of chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan) in patients with platinum-resistant, high-grade serous ovarian cancer expressing high levels of FRα. The trial's results, published in The New England Journal of Medicine, showcased a significant improvement in progression-free survival (PFS) for patients treated with mirvetuximab soravtansine, with a median PFS of 5.62 months (95% CI, 4.34-5.95) compared to 3.98 months (95% CI, 2.86-4.47) with chemotherapy (P < .001).
Overall survival (OS) also favored mirvetuximab soravtansine, with a median OS of 16.46 months (95% CI, 14.46-24.57) versus 12.75 months (95% CI, 10.91-14.36) in the chemotherapy arm. The objective response rate (ORR) was notably higher in the mirvetuximab soravtansine group at 42.3% (95% CI, 35.8%-49.0%) compared to 15.9% (95% CI, 11.4%-21.4%) in the chemotherapy group (P < .001).
Kathleen N. Moore, MD, MS, from the University of Oklahoma College of Medicine, emphasized the drug's efficacy, stating that the MIRASOL data proved mirvetuximab soravtansine is a highly efficacious medication and superior to standard of care options.
Safety and Tolerability
While mirvetuximab soravtansine offers significant clinical benefits, it is associated with specific adverse effects (AEs). Common AEs include blurred vision, nausea, diarrhea, and fatigue. Ocular toxicities, such as keratopathy and dry eye, are particularly noteworthy and require careful management. Ritu Salani, MD, director of Gynecologic Oncology at UCLA, stressed the importance of consulting eye specialists to manage these ocular toxicities effectively.
The MIRASOL trial reported fewer grade 3 or higher AEs with mirvetuximab soravtansine (41.7%) compared to chemotherapy (54.1%). Similarly, serious AEs of any grade were less frequent with the antibody-drug conjugate (23.9%) versus chemotherapy (32.9%), as were events leading to discontinuation (9.2% vs 15.9%).
The Role of FRα Testing
Given that mirvetuximab soravtansine targets FRα, identifying patients with high FRα expression is crucial. The VENTANA FOLR1 (FOLR1-2.1) RxDx Assay is used to confirm FRα expression in tumor samples. Experts recommend performing immunohistochemistry testing at the time of diagnosis to determine folate receptor status for potential future use.
Impact on Treatment Paradigm
The approvals of mirvetuximab soravtansine represent a significant advancement in the treatment of platinum-resistant ovarian cancer. As Toon Van Gorp, MD, professor of gynecological oncology at the University of Leuven in Belgium, noted, it has been 10 years since a new treatment for platinum-resistant ovarian cancer was approved in the EU, and now oncologists have an effective, new, targeted treatment option for these patients.
With its demonstrated improvements in PFS, OS, and ORR, mirvetuximab soravtansine is poised to become a key component of the treatment algorithm for FRα-positive, platinum-resistant ovarian cancer. Ongoing research aims to further optimize its use and sequencing with other therapies to improve survival and, ultimately, achieve higher cure rates.
