Dr Porter on Mirvetuximab Soravtansine Plus Pembrolizumab in FRα+ pMMR/MSS Endometrial Cancer

Rebecca L. Porter, MD, PhD, physician, Dana-Farber Cancer Institute, assistant professor of medicine, Harvard Medical School, discusses data from a phase 2 trial (NCT03835819) evaluating mirvetuximab soravtansine-gynx (Elahere) in combination with pembrolizumab (Keytruda) for the treatment of patients with folate receptor α (FRα)–positive, mismatch repair–proficient (pMMR)/microsatellite stable (MSS) recurrent or persistent endometrial cancer.

At a median follow-up of 4.7 months, findings presented at the 2024 AACR Annual Meeting showed that the combination led to an overall response rate (ORR) of 37.5% in evaluable patients (n = 16), which was comprised of a confirmed complete response (CR) rate of 6.3%, a confirmed partial response (PR) rate of 18.8%, and an unconfirmed PR rate of 12.5%. Additionally, 31.3% of patients experienced stable disease, and 25.0% had progressive disease. One patient (6.3%) was not evaluable for response as they withdrew consent for non–adverse effect–related reasons after receipt of 3 doses of study treatment.

Prolonged responses were observed in 2 patients, including 1 patient who had a CR for more than 18 months; this patient was in ongoing clinical response after discontinuing treatment due to grade 2 pneumonitis and grade 3 adrenal insufficiency. The other patient achieved a PR for 11.3 months. Both patients did not have prior exposure to immune-oncology agents.

Furthermore, the 6-month progression-free survival rate was 16.2% (95% CI, 2.6%-40.2%).

The ORR was notable for patients with pMMR/MSS recurrent or persistent endometrial cancer, according to Porter, who underscores that there are several unmet needs for the treatment of this population. These findings support the rationale of investigating antibody-drug conjugates in combination with immunotherapy agents, she adds. However, improved biomarkers are needed to better identify patients with endometrial cancer who may benefit from treatment with combination therapies such as mirvetuximab soravtansine and pembrolizumab, Porter says. Tissue biopsies were not part of the phase 2 trial protocol, and gathering those samples will be important for future studies, she concludes.