Retrospective pooled analysis of IMGN 853 in ovarian cancer presented at 23rd Congress of the European Society of Gynaecological Oncology.- ImmunoGen

The analysis is titled: CHARACTERIZATION OF EXTENDED TREATMENT BENEFIT FROM THREE PHASE I AND III CLINICAL TRIALS EXAMINING PATIENTS WITH FOLATE RECEPTOR ALPHA–POSITIVE RECURRENT OVARIAN CANCER TREATED WITH SINGLE-AGENT MIRVETUXIMAB SORAVTANSINE by Ana Oaknin, poster: #PA-048.

A retrospective pooled analysis of patients who achieved ETB with mirvetuximab monotherapy was conducted across three studies - the Phase I IMGN853-0401 trial, the Phase III FORWARD I trial, and the Phase III SORAYA trial. ETB was defined as progression-free survival (PFS) for more than 12 months per investigator assessment. FRalpha expression levels were evaluated by immunohistochemistry (IHC).

The trial key findings include the following: i. In a pooled analysis of 466 patients, mirvetuximab monotherapy demonstrated ETB in 40 patients (9%).a. Most patients with ETB had stage III disease (83%), 1 prior line of therapy (55%), and prior Avastin (bevacizumab) exposure (60%).b. EBT occurred in patients with a wide range of FRalpha expression, but did so predominantly among those with high FRalpha expression.ii. Patients with ETB had an objective response rate (ORR) of 77.5% (31 out of 40 patients), with 10 (25%) achieving a complete response and 21 (52.5%) achieving a partial response. The remaining 8 patients (20%) with ETB had a best response of stable disease and one patient was not evaluable. iii. Median duration of response (DOR) in patients with ETB was 22.1 months (95% CI, 13.8-60.0).iv. Median PFS in patients with ETB was 17.0 months (95% CI, 16.4-23.1).

In patients with ETB, the overall adverse event (AE) profile was consistent with the previously reported integrated safety summary (ISS) of 464 patients, with no new safety signals identified and minimal cumulative toxicities. AEs were primarily low-grade gastrointestinal and ocular events that generally resolved with supportive care or, if needed, dose modifications. These findings were highlighted in a poster presentation at the 23rd Congress of the European Society of Gynaecological Oncology (ESGO) in Berlin, Germany. A trial in progress poster from the mirvetuximab program will also be presented.