ImmunoGen Presents Initial 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 initial safety and overall response data from the Phase 1b FORWARD II triplet cohort evaluating mirvetuximab in combination with carboplatin and Avastin (bevacizumab) in patients with recurrent, platinum-sensitive ovarian cancer at the European Society for Medical Oncology (ESMO) 2019 Congress in Barcelona, Spain.

“The initial results from the triplet combining mirvetuximab with both bevacizumab and carboplatin build nicely off of the encouraging data previously generated when mirvetuximab was paired individually with each of these agents,” said David O'Malley, M.D., 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 anti-tumor responses observed with this combination compare favorably to those of other triplets and I look forward to reporting longer-term efficacy data, as we seek to provide new treatment options for patients with recurrent, FRα-positive platinum-sensitive ovarian cancer.”

Key Findings from FORWARD II Triplet Cohort

• In 41 patients with recurrent platinum-sensitive disease with medium or high folate receptor alpha (FRα) expression levels who have received up to two prior lines of therapy, the confirmed overall response rate (ORR) for the triplet was 83%, with a complete response (CR) rate of 17%.
• In a subset of 31 patients with only 1 prior line, the confirmed ORR was 90%, with a CR rate of 19%.
• These efficacy outcomes are encouraging relative to those reported in similar patient populations for other carboplatin and bevacizumab-based triplets.
• With a median follow up of 9.3 months, progression-free survival (PFS) data are maturing.
• The combination of full dose mirvetuximab, carboplatin and bevacizumab is well tolerated.
• No new safety signals were seen; adverse events observed with the triplet were as expected based on the side effect profiles of each agent, with thrombocytopenia as the most common cause of drug-related discontinuations.
• Post-carboplatin (median 6 cycles), mirvetuximab and bevacizumab continuation/maintenance is well tolerated.

“We are encouraged by the initial safety and overall response data from our triplet cohort, demonstrating that full-dose mirvetuximab can be combined safely with the standard dosing for both bevacizumab and carboplatin,” said Anna Berkenblit, M.D., Vice President and Chief Medical Officer of ImmunoGen. “We are continuing to follow patients for progression-free survival and look forward to initiating the next set of studies to support a path to registration in platinum-sensitive ovarian cancer.”