ImmunoGen touts a PhIII comeback in ovarian cancer, eyeing a 2022 accelerated approval
When ImmunoGen’s lead antibody-drug conjugate flunked a Phase III study in ovarian cancer a couple years ago, the company clung to hope that it would perform better in a subgroup of patients with high folate receptor alpha (FRα) expression.
On Tuesday, researchers uncorked topline Phase III results suggesting it was right — and investors cheered on the news with a 40% boost to ImmunoGen’s stock price $IMGN. CEO Mark Enyedy says he’s going after an accelerated approval and plans to file in the first quarter of 2022.
A total of 106 platinum-resistant ovarian cancer patients who had taken a median of three prior therapies — at least one of them being Genentech’s Avastin — enrolled in the SORAYA study. ImmunoGen’s drug, called mirvetuximab soravtansine, shrank tumors in 32.4% of patients at a median follow-up of 8.1 months. And five of those patients achieved a complete response.
“Any CR is groundbreaking,” co-principal investigator Rob Coleman said in a call with investors on Tuesday. “Remember, these are patients who have progressed through our best therapies multiple times, and they have actual visible tumor that went away.”
The median duration of response was 5.9 months, with nearly half of responders continuing on the therapy, according to ImmunoGen — though the company expects to have more data on DOR at a medical conference next quarter.
While ImmunoGen says mirvetuximab was well-tolerated, 41% of patients experienced blurred vision related to the treatment (though only 6% experienced cases Grade 3 or higher). Keratopathy, a disease of the cornea, occurred in 35% of patients and 29% experienced nausea.
“Compared to other toxicities that we deal with, with other types of therapies, this one is very straightforward to deal with,” co-principal investigator Ursula Matulonis said of the vision problems. “I’ve been working with this drug for many years now, and we have a set group of ophthalmologists we refer patients to, and patients are given lubricating eye drops, steroid eye drops.”
The ocular toxicities are reversible, she said, adding they “really did not result in very many patients dropping out of the study.”
Beyond SORAYA, ImmunoGen expects to read out topline data from a confirmatory study called MIRASOL in the third quarter of 2022 in the hopes of winning a full approval for mirvetuximab.
In antibody-drug conjugates, a cancer-killing toxin is attached to a specific antibody using a biodegradable linker. ImmunoGen has been a longtime player in the ADC field, but a Phase III failure for mirvetuximab back in 2019 sent shares spiraling.
Patients in that trial, dubbed FORWARD I, were given either mirvetuximab or the physician’s choice of single-agent chemotherapy. Although the overall response rate was higher for mirvetuximab than chemotherapy, the drug did not induce a statistically significant improvement in progression-free survival, which was the main goal. It also failed to significantly improve overall survival. Two months later, the FDA batted back an attempt at an accelerated approval based on a secondary endpoint.
At the end of 2019, ImmunoGen announced it was launching SORAYA in patients with high FRα expression, which it said could support accelerated approval of the drug.
Enyedy is already prepping a commercial launch, which he says could take off next year if all goes well.