Final MIRASOL Trial Analysis Confirms Consistent Efficacy of Mirvetuximab Soravtansine

The phase 3 MIRASOL trial (NCT04209855) final analysis demonstrated that mirvetuximab soravtansine-gynx (Elahere; AbbVie) continued to deliver superior clinical benefits in patients with folate receptor alpha-positive, platinum-resistant ovarian cancer.

These results were presented in a late-breaking session at the Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer on Saturday by investigator Toon Van Gorp, MD, PhD. In an interview with The American Journal of Managed Care^®, Van Gorp elaborated on the similarities between the primary and final analyses of the MIRASOL trial.

This transcript has been lightly edited for clarity; captions were auto-generated.

Transcript

To start, can you summarize the key findings of the MIRASOL primary analysis?

The primary analysis was already presented in 2023 by doctor Kathleen Moore [MD, MS]. The primary analysis showed that there was a clear benefit of using mirvetuximab over the investigator's choice of chemotherapy.

The median overall survival with mirvetuximab was 16.5 months, compared with 12.8 months with the investigator's choice of chemotherapy. This was with a hazard ratio of 0.67, so a reduction of 33% for the risk of death.

How do the primary analysis results of the MIRASOL trial differ from the primary analysis results? Were there any unexpected findings?

Back then, when we did the primary analysis, we had a follow-up of 13.1 months. We wanted to extend this follow-up to a longer duration. For the final analysis, we had a follow-up of 30.5 months. This was, of course, to see whether the benefit that we saw with mirvetuximab was maintained.

Also, we wanted to know whether there were any long-term safety concerns that we had to know about because we were using, of course, a new drug, which is an ADC [antibody-drug conjugate], compared with the chemotherapy that we already have known for quite a long time.

The overall survival data were approximately the same. We had a median overall survival for the mirvetuximab arm of 16.9 months and 13.3 months for the investigator's choice of chemotherapy, which gave a hazard ratio of 0.68. It was 0.67 [in the primary analysis], so it's almost the same in the final analysis.

The same was true for progression-free survival. The median was a little bit less than 6 months for mirvetuximab and a little bit less than 4 months for the investigator's choice of chemotherapy. Also, there was a hazard ratio of 0.63, so, again, approximately the same result as what we saw in the primary analysis.

I can continue with the objective response rate. Also, there, we saw the same. We had an objective response rate of 42% for mirvetuximab and 16% for the investigator's choice of chemotherapy, which is a huge difference.

I was also very impressed, also, with the PFS2, so the second progression-free survival after the first progression. There, we also see that the benefit of mirvetuximab was maintained even after the first progression. The PFS2 for mirvetuximab was 11 months vs 7.8 months for the investigator's choice of chemotherapy.

Overall, I think we can really say that the efficacy benefit was maintained for all the end points that we investigated, and there were actually no surprises that we saw. When we look at the safety data, there were no new safety signals. When you look at the figure that we showed during the presentation and you compare it to the first figure that we showed during the primary analysis, it is almost exactly the same. So, no new safety signals.