Mirvetuximab Soravtansine Stakes Claim as SOC in FRα+ Platinum-Resistant Ovarian Cancer

Toon Van Gorp, MD, PhD

Mirvetuximab soravtansine-gynx (Elahere) maintained its significant activity and tolerability benefits over chemotherapy after a median follow-up of 30.5 months, solidifying its place as a standard of care for patients with folate receptor α (FRα)–positive, platinum-resistant ovarian cancer, according to Toon Van Gorp, MD, PhD.

During 2025 SGO Annual Meeting on Women’s Cancer, Van Gorp presented data from the final analysis of the phase 3 MIRASOL trial (NCT04209855).1 Findings showed that patients who received mirvetuximab soravtansine (n = 227) achieved a median overall survival (OS) of 16.85 months (95% CI, 14.36-19.78) compared with 13.34 months (95% CI, 11.37-15.15) among those who received investigator’s choice of chemotherapy (n = 226; HR, 0.68; 95% CI, 0.54-0.84; P = .0004).

Additionally, the median investigator-assessed progression-free survival (PFS) was 5.59 months (95% CI, 4.34-5.88) vs 3.98 months (95% CI, 2.86-4.47) in the investigational vs control arm, respectively (HR, 0.63; 95% CI, 0.51-0.79; P < .0001). The investigator-assessed objective response rate (ORR) was 41.9% (95% CI, 35.4%-48.6%) compared with 15.9% (95%, 11.4%-21.4%), respectively (OR, 3.75; 95% CI, 2.4-5.85). Notably, 5.7% of patients in the mirvetuximab soravtansine arm achieved a complete response.

“We looked at OS, PFS, and all the other efficacy end points, and it was clear that the benefit that we saw during the primary analysis in 2023 [with mirvetuximab soravtansine vs chemotherapy] was maintained [after long-term follow-up],” Van Gorp said in an interview with OncLive®.

In November 2022, mirvetuximab soravtansine received accelerated approval from the FDA for the treatment of adult patients with FRα-positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer, who previously received 1 to 3 systemic treatment regimens.2 In March 2024, the agent was fully approved by the FDA for the same indication; the approval was supported by prior data from MIRASOL.3

In the interview, Van Gorp discussed findings from MIRASOL he presented during the meeting and potential future directions of mirvetuximab soravtansine research. Van Gorp is a gynecologic oncologist at Universitair Ziekenhuis Leuven in Belgium.

OncLive: What were the key characteristics of the patient population examined in MIRASOL?

Van Gorp: [The study included] patients with high-grade serous ovarian cancer who had platinum-resistant disease [and] they were able to have received 1 to 3 prior lines of therapy. One of the most important inclusion criteria was FRα expression; more than 75% of the [tumor] cells had to be 2+ by immunohistochemistry [staining]. That [represents] approximately 35% of the whole population [with ovarian cancer].

What were the efficacy data updates you presented during the SGO Annual Meeting on Women’s Cancer?

We [performed an analysis with] longer follow-up [and] the study was closed in the meantime. The final analysis was done with 30.5 months [of follow-up], which is very long for [patients with] platinum-resistant disease. In most studies, the follow-up is much shorter.

We saw a HR of 0.68 [for OS] to the benefit of mirvetuximab soravtansine [over chemotherapy]. [As] the median OS was 16.9 months for mirvetuximab soravtansine and 13.3 months for investigator’s choice chemotherapy, [there was] a clear benefit. Looking at the curves, they split and are still separated; even after 2 to 3 years, we saw a separation of the curves. This means that the effect of mirvetuximab soravtansine continues after the next treatments that these patients [receive].

Were there any subgroups who especially benefited from treatment with mirvetuximab soravtansine?

It’s important to mention that when you look at the forest plot for OS across all subgroups, whether patients had [disease] recurrence after 1 or 3 [prior] lines [of treatment], or had prior [exposure to] PARP inhibitors or bevacizumab [Avastin], it didn’t matter. They all benefited from this treatment. I don’t believe we need to do another subselection in this population.

Were there any new safety signals with longer follow-up?

There were no new safety signals at all. Looking at all the adverse effects [AEs] which we saw, especially the serious AEs [SAEs] and the grade 3 or higher treatment-emergent AEs, the [rates] stayed the same as seen in the primary analysis in 2023. We had less SAEs, less grade 3 or higher AEs, and less discontinuations with mirvetuximab soravtansine [vs chemotherapy], which is important. Patients are able to continue treatment for a longer time.

What is the clinical significance of these updated findings?

This is a patient population with a poor prognosis. As soon as a patient has platinum-resistant disease, we know that the prognosis is very bad; [the life expectancy] is usually approximately 12 to 13 months. This [agent] is giving hope to these patients. With this efficacy and this safety profile, [data are] reaffirming that the use of mirvetuximab soravtansine, even after a very long follow-up time, is definitely the best treatment to give to these patients.

What are the next steps for the investigation of mirvetuximab soravtansine?

This is not the final end point for mirvetuximab soravtansine. We need to [move the agent] into earlier lines of therapy, [including in] platinum-sensitive disease and possibly even frontline [therapy]. There are studies ongoing looking at this, and I believe it’s such a good molecule that we have to look at these different populations. We have to move it to the frontline. At the moment, only approximately 35% of the population can use mirvetuximab soravtansine. I hope that we will also be able to [evaluate it in] patients who have a lower FRa expression, but that’s something we will have to show in studies.

References

1. Van Gorp T, Angelergues A, Konecny G, et al. Final overall survival analysis among patients with FRa-positive, platinum-resistant ovarian cancer (PROC) treated with mirvetuximab soravtansine (MIRV) vs investigator’s choice chemotherapy (ICC) in the phase 3 MIRASOL (GOG 3045/ENGOT-ov55) study. Presented at: 2025 SGO Annual Meeting on Women’s Cancer; March 14-17, 2025; Seattle, WA. Abstract 939696.
2. ImmunoGen announces FDA accelerated approval of Elahere (mirvetuximab soravtansine-gynx) for the treatment of platinum-resistant ovarian cancer. News release. ImmunoGen Inc. November 14, 2022. Accessed March 21, 2025. https://news.abbvie.com/2022-11-14-ImmunoGen-Announces-FDA-Accelerated-Approval-of-ELAHERE-TM-mirvetuximab-soravtansine-gynx-for-the-Treatment-of-Platinum-Resistant-Ovarian-Cancer
3. FDA approves mirvetuximab soravtansine-gynx for FRα positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer. FDA. March 22, 2024. Accessed March 21, 2025. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-mirvetuximab-soravtansine-gynx-fra-positive-platinum-resistant-epithelial-ovarian