MIRASOL: Mirvetuximab Soravtansine Improves PFS, OS in Certain Women With Recurrent Ovarian Cancer

For certain women with recurrent ovarian cancer, results presented early today at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago confirm that mirvetuximab soravtansine offers improved progression-free survival (PFS) and overall survival (OS) with fewer side effects.

Results from MIRASOL (NCT04209855) offer positive results for this newly approved treatment, described as an antibody microtubule inhibitor conjugate—the first in ovarian cancer. Mirvetuximab soravtansine (Elahere, Immunogen) received accelerated FDA approval in November 2022 based on results from SORAYA for women with platinum-resistant, advanced high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancers with high folate receptor-alpha expression. The indication was for women with 1-3 prior treatments.

“MIRASOL is the confirmatory, global randomized phase 3 trial that is poised to result in global approvals,” said lead investigator Kathleen N. Moore, MD, MS, associate director of clinical research and co-director of the Cancer Therapeutics Program at the Stephenson Cancer Center at the University of Oklahoma in Oklahoma City.

Speaking in a press briefing ahead of her presentation this morning, Moore said MIRASOL showed that mirvetuximab soravtansine offered patients improved levels of both survival and safety compared with previous standards of care.

“We’ll show you there were less grade 3 or higher treatment emergent adverse events, less serious adverse events, and markedly fewer discontinuations from assigned therapy,” she said. “We see no alopecia and less peripheral neuropathy than seen with the closest comparative, which would be paclitaxel,” a standard chemotherapy.

Study results. MIRASOL evaluated 453 women patients with platinum-resistant, advanced high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancers with high folate receptor-alpha expression. After a median follow-up of 13.1 months, results showed:

• Among 281 women who had previously received bevacizumab, PFS was 36% better (HR, 0.64 [0.492-0.842]) and OS was 26% better (HR, 0.74 [0.535-1.036]) for women who received mirvetuximab soravtansin vs physician’s choice of chemotherapy.
• Among the 172 women who had not previously received bevacizumab, PFS was 34% better (HR 0.66 [0.459-0.942]) and OS was 49% better (0.51, [0.306-0.860]) for those receiving mirvetuximab soravtansin vs the physician’s choice of standard chemotherapy.
• AEs were consistent with earlier studies and mostly low-grade ocular and gastrointestinal events.
• 14% of the women taking mirvetuximab soratansine were still taking the drug, vs 3% receiving chemotherapy.

Mirvetuximab soravtansine targets folate receptor-alpha, which is overexpressed on a variety of epithelial-derived cancer cells. The drug binds to the receptor, leading to cell death. “This is the first antibody drug conjugate approved in ovarian cancer, the only biomarker selected therapy available for platinum resistant ovarian cancer, and only the second biomarker directed therapy, after PARP inhibitors, for ovarian cancer,” Moore said. “These are data we consider to be practice changing,” she said.

Moore’s enthusiasm stems in part from the grim statistics that surround ovarian cancer. In 2023, there will be an estimated 19,710 new cases and 13,270 deaths from ovarian cancer just in the United States. If the cancer spreads to distant sites, as was the case with MIRASOL, then 5-year survival rates are 30%. Due to the lack of a widespread screening method, more than 70% of people annually are diagnosed at this advanced stage.

The therapy is being evaluated in earlier lines of treatment, Moore said.

An ASCO commentator shared her assessment of the importance of the results. “Mirvetuximab soravtansine has fewer serious side effects, especially those that can lead to stopping treatment, compared to standard chemotherapies for patients with platinum-resistant ovarian cancer. This, coupled with the overall survival advantage, demonstrates progress and offers hope for these patients,” said Merry Jennifer Markham, MD, of the University of Florida.

Reference

Moore KN, Angelergues A, Konecny GE, et al. Phase III MIRASOL (GOG 3045/ENGOT-ov55) study: Initial report of mirvetuximab soravtansine vs. investigator's choice of chemotherapy in platinum-resistant, advanced high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancers with high folate receptor-alpha expression. J Clin Oncol. 2023;41 (suppl 17):abstr LBA5507.