INNV-07. IVOSIDENIB AND BEVACIZUMAB IN HEAVILY PRETREATED PATIENTS WITH IDH1 MUTANT GLIOMAS

Abstract Isocitrate dehydrogenase 1 (IDH1) inhibitors are transforming the treatment of patients with non-enhancing IDH1 mutant gliomas that have only undergone surgical resection. Questions remain on the utility of IDH1 inhibitors in patients that have received prior therapies such as radiation therapy (RT) and chemotherapy (e.g. temozolomide (TMZ)) and have progressive disease. We evaluated the safety and efficacy of ivosidenib, an oral IDH1 inhibitor, in combination with bevacizumab (BEV), a monoclonal antibody targeting VEGF-A, in IDH1 mutant glioma patients that were heavily pretreated. Fourteen patients received combination ivosidenib and bevacizumab starting between February 2021 to July 2023. In our small cohort, patient age range was 26 to 73 years with seven female patients and seven male patients. Diagnoses represented were astrocytoma, IDH1 mutant (n=10) and oligodendroglioma, IDH1 mutant (n=4). At the time of IDH1 therapy initiation, the majority of patients (n=10) had a grade 3 tumor. All patients (n=14) had canonical IDH1 mutation (p.Arg132His) and had enhancing disease. Therapies initiated prior to ivosidenib therapy included: prior RT (n=12), prior TMZ (n=14) and prior BEV (n=10). The median number of progressions prior to initiation of ivosidenib combination therapy was 3 (range 2 to 6). All patients received ivosidenib dosed at 500 mg daily with bevacizumab doses varying from 5 to 15 mg/kg IV dosed every 2 to 3 weeks. Combination therapy was well tolerated with minimal patients experiencing toxicities requiring dose interruptions; diarrhea (n=2), creatine phosphokinase elevations (n=1), QTc prolongation (n=1), and thrombocytopenia (n=1). The median treatment duration on ivosidenib combination therapy was 4.42 months (range 0.69 to 11.4 months). In this cohort, the combination of ivosidenib and bevacizumab was well tolerated. More information is needed on the benefit of ivosidenib in combination with other therapies and in heavily pretreated patients with IDH1 mutant gliomas.