Pivotal Trial of Mirvetuximab Soravtansine in Advanced Ovarian Cancer Levels Likely in 2020

ImmunoGen is planning to open an open-label, pivotal clinical trial of mirvetuximab soravtansine in platinum-resistant ovarian cancer patients with high levels of the folate receptor alpha (FRα) protein early next year, the company announced.

Results could lead to the treatment’s accelerated, and conditional, approval by the U.S. Food and Drug Administration (FDA), the company announced in a press release.

To be called SORAYA, the trial will enroll about 100 patients previously given one to three therapies, including bevacizumab. It will enroll concurrently with a longer and larger Phase 3 trial in a similar patient group, called MIRASOL, that will serve as a confirmatory study.

“We have engaged in constructive discussions with FDA and evaluated all avenues to bring mirvetuximab to patients more quickly,” Mark Enyedy, the president and CEO of ImmunoGen, said in the release. If SORAYA’s results support the treatment’s efficacy, it “would enable us to submit an application for accelerated approval during the second half of 2021.”

Mirvetuximab soravtansine is an antibody-drug conjugate (ADC), meaning it consists of an antibody bound to a cell-killing agent. When the antibody binds to its target — the folate receptor alpha (FRα), a protein found at medium-to-high levels in about 60% of ovarian cancers — it releases the toxic compound, killing the cancer cell without harming healthy cells.

The investigational treatment was awarded fast track designation by the FDA, and previous Phase 3 trial results suggest it could be effective in ovarian cancers that are resistant to traditional, platinum-based chemotherapies, particularly in cases where the tumor expresses high levels of FRα.

To request regulatory approval for this indication, ImmunoGen had planned one new Phase 3 clinical trial — MIRASOL — in 430 people with FRα-high ovarian cancer also given up to three prior treatment regimens. Those enrolled will be randomly assigned to treatment with either mirvetuximab soravtansine or a single-agent chemotherapy.

MIRASOL’s primary goal is to determine if mirvetuximab extends the time patients live without seeing signs of cancer worsening compared to a placebo, and key secondary objectives include overall response rate, overall survival, and patient-reported outcomes.

But after discussions with the FDA, ImmunoGen has decided to also initiate SORAYA, expected to speed the approval of mirvetuximab soravtansine.

SORAYA plans to enroll 100 women with FRα-high ovarian cancer, who received up to three previous treatment regimens — including bevacizumab, a treatment that works by reducing blood flow in the tumor, effectively starving cancer cells.

Unlike in MIRASOL, all participants in SORAYA will be treated with mirvetuximab soravtansine, and the primary goal is to determine the proportion of patients responding to treatment and the duration of such responses — two measures on which accelerated approvals are usually based on.

Then, MIRASOL will serve as a confirmatory trial, supporting the use of mirvetuximab soravtansine over standard treatment, and potentially its full approval for ovarian cancer patients.

Anna Berkenblit, MD, senior vice president and chief medical officer of ImmunoGen, said that the efficacy results from previous clinical trials show a 31.4% response rate to mirvetuximab in patients that would be eligible for SORAYA, which compares “quite favorably to the [12%] response rate seen with single agent chemotherapy in platinum resistant disease.”

“Replicating these data in SORAYA would support an application for accelerated approval in advance of the completion of MIRASOL, which would thereafter provide the randomized data needed for conversion to full approval,” Berkenblit added. “We are delighted to advance both studies as soon as possible.”

Enrollment for SORAYA is expected to begin in early 2020, with initial results possibly available in mid-2021.