ImmunoGen Presents Final Data From Phase 1b FORWARD II Triplet Cohort Evaluating Mirvetuximab Soravtansine in Combination With Carboplatin and Avastin at ESMO

ImmunoGen, Inc., (Nasdaq: IMGN) a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced final data from the FORWARD II triplet cohort evaluating mirvetuximab soravtansine in combination with carboplatin and Avastin (bevacizumab) in patients with folate receptor alpha (FRα)-positive recurrent, platinum-sensitive ovarian cancer at the European Society for Medical Oncology (ESMO) 2020 Virtual Congress.

“Although there have been advances in the treatment of platinum-sensitive disease with targeted and maintenance therapies, there remains a significant need for additional active, well-tolerated combinations in the platinum-sensitive setting,” said David O'Malley, MD, Professor, Director of Gynecologic Oncology and Co-Director, Gynecologic Oncology Phase 1 Program at The Ohio State University and the James Cancer Center, and FORWARD II Principal Investigator. “The efficacy outcomes demonstrated by combining full dose mirvetuximab with bevacizumab and carboplatin in more heavily pretreated platinum-sensitive ovarian cancer patients is encouraging relative to current standard of care triplet regimens.”

In the FORWARD II triplet cohort Phase 1b trial, 41 patients with a median age of 63 years received the combination of full dose mirvetuximab with carboplatin and bevacizumab. Eligibility criteria included patients with recurrent platinum-sensitive ovarian cancer that expressed medium or high levels of FRα, who had been treated with up to two prior lines of therapy. 73% of patients had one prior line of therapy and 27% had two prior lines of therapy, while 42% of patients had received prior PARP inhibitors, and 24% had received prior treatment with bevacizumab.

Key Findings from FORWARD II Triplet Cohort

• In 41 patients with recurrent platinum-sensitive ovarian cancer with medium or high levels of FRα who have received up to two prior lines of therapy, the confirmed overall response rate (ORR) for the triplet was 83%, with a median duration of response (DOR) of 10.9 months and median progression free survival (PFS) of 12.8 months.
• These efficacy outcomes are encouraging relative to those reported in less heavily pretreated patient populations for other carboplatin and bevacizumab-based triplets.
• Mirvetuximab was readily combined and well tolerated with standard dosing of carboplatin and bevacizumab, with a manageable adverse event (AE) profile as anticipated for this triplet based on the side effect profiles of each agent. Thrombocytopenia, a common adverse event with carboplatin treatment, was the most common cause of drug-related discontinuations.
• Post-carboplatin (median 6 cycles), mirvetuximab soravtansine and bevacizumab continuation/maintenance was well tolerated.

“Having generated a wealth of data demonstrating encouraging efficacy and favorable tolerability, mirvetuximab continues to show promise in combination – not only as a triplet but also when combined with bevacizumab or carboplatin as a doublet. In the future, we look forward to defining a formal path to registration for mirvetuximab in combination with approved agents with the goal of expanding use into earlier lines of therapy and becoming the combination agent of choice in ovarian cancer,” said Anna Berkenblit, MD, Senior Vice President and Chief Medical Officer of ImmunoGen.