ImmunoGen announces findings from MIRASOL trial

ImmunoGen announced findings from two subset analyses of the Phase 3 confirmatory MIRASOL trial evaluating the safety and efficacy of Elahere compared to chemotherapy in patients with folate receptor alpha, or FRa-positive platinum-resistant ovarian cancer, or PROC. The findings will be presented by Toon Van Gorp in an oral presentation at the 24th Congress of the European Society of Gynaecological Oncology, or ESGO, in Istanbul, Turkey. In addition to the top-line MIRASOL data previously disclosed and subsequently presented at the 2023 American Society of Clinical Oncology, or ASCO, annual meeting, the following new data are being presented at ESGO: Elahere demonstrated clinically meaningful improvement in PFS and ORR by investigator assessment and in OS compared to IC chemotherapy, regardless of prior PARPi exposure. In patients with prior PARPi, PFS hazard ratio was 0.58; in the PARPi-naive subset, PFS HR was 0.74. In patients with prior PARPi, ORR in the Elahere arm was 45%, including 7 CRs, compared to 17%, with no CRs, in the IC chemotherapy arm; in the PARPi-naive subset, ORR in the Elahere arm was 40%, including 5 CRs, compared to 14%, with no CRs, in the IC chemotherapy arm. In patients with prior PARPi, OS HR was 0.48; in the PARPi-naive subset, OS HR was 0.90. Elahere demonstrated clinically meaningful improvements in PFS and ORR by investigator assessment and in OS compared to IC chemotherapy, regardless of prior lines of therapy. In patients with 1 or 2 PLOT, the PFS HR was 0.61; in patients with 3 PLOT, PFS HR was 0.71. In patients with 1 or 2 PLOT, ORR in the ELAHERE arm was 46% (95% CI: 37%, 55%), including 10 complete responses, or CRs, compared to 15%, with no CRs, in the IC chemotherapy arm; in patients with 3 PLOT, ORR in the ELAHERE arm was 38%, including two CRs, compared to 18%, with no CRs, in the IC chemotherapy arm. In patients with 1 or 2 PLOT, OS HR was 0.66; in patients with 3 PLOT, OS HR was 0.65. Elahere demonstrated a tolerable safety profile compared to IC chemotherapy consisting predominantly of low-grade ocular and gastrointestinal events. In all patients, the frequency of grade 3+ treatment-emergent adverse events, or TEAEs, was 42% with Elahere and 54% with IC chemotherapy; the frequency of serious adverse events, or SAEs, was 24% with Elahere and 33% with IC chemotherapy; and the frequency of discontinuations due to a TEAE was 9% with Elahere and 16% with IC chemotherapy.