ImmunoGen files ovarian cancer ADC with FDA, a week after scaring investors with iffy survival data

Last week ImmunoGen’s investors scattered on underwhelming survival data from a late-stage trial of its antibody-drug conjugate for ovarian cancer. But that was last week. This week, the company is filing an application for FDA approval based on that very study. 

The company has submitted a biologics license application with the U.S. agency under the accelerated review pathway for mirvetuximab soravtansine for heavily pre-treated patients with folate receptor alpha-high platinum-resistant ovarian cancer. The submission is based on results from the phase 3 Soraya trial, which just last week sent the biotech’s shares down 20% when survival data fell short of investor expectations.

But ImmunoGen sees a path forward for the med.

“Platinum-resistant ovarian cancer is an area with high unmet need, and we look forward to working with FDA to secure mirvetuximab’s first approval and bringing this novel therapy to patients as quickly as possible,” said President and CEO Mark Enyedy.

ImmunoGen's shares were up slightly, about 4% to $4.55 as the markets opened Tuesday morning. 

In November 2021, ImmunoGen reported top-line data from Soraya that showed the ADC shrank ovarian tumors in the 106-patient trial. The therapy, which is designed to launch a targeted chemotherapy attack on cancer cells that express high levels of folate receptor alpha, achieved a 32% objective response rate in a heavily pre-treated population. That data gave ImmunoGen high confidence to begin planning a regulatory filing.

But earlier this month, the company was brought back down to earth when the full readout revealed median progression-free survival of just 4.3 months when assessed by the investigator and 5.5 months when assessed by blinded independent central review. Analysts said that Genetech's Avastin, which most of the patients had received prior to receiving mirvetuximab, may be negatively affecting patients who achieved stable disease.

The FDA will now have 60 days to review the application to determine whether it is acceptable. ImmunoGen has asked for priority review, which would mean a swift decision within six months of the filing date.

If mirvetuximab were authorized under the accelerated approval pathway, ImmunoGen would need to present more efficacy evidence to win a full approval. The company is already working on the phase 3 Mirasol study to collect randomized data that could provide the drug worthy. Top-line data from that trial is expected in the third quarter of this year.

But given the survival data from Soraya, analysts said that Mirasol could be in trouble if the percentage of patients previously treated with Avastin is too high.

Mirvetuximab was granted an orphan drug designation by the FDA in 2015, followed by a fast-track designation in 2018.