Ivosidenib for the treatment of IDH1-mutant glioma, grades 2-4: Tolerability, predictors of response, and outcomes.

Background: Mutant isocitrate dehydrogenase (IDHm) inhibitors represent a novel targeted approach for treating IDHm glioma patients, yet their optimal use in clinical practice outside of clinical trials remains undefined. This study describes the real-world utilization of the mutant IDH1 inhibitor (IDHi), ivosidenib, in patients with IDHm glioma. Methods: We retrospectively reviewed clinical and radiographic data from patients with IDHm glioma treated with ivosidenib monotherapy from 2020 to 2024 at the Dana-Farber Cancer Institute and Massachusetts General Hospital. Results: This cohort included 74 patients with a median age of 39. There were 35 astrocytomas and 39 oligodendrogliomas, with 49, 23, and 2, grade 2, 3, and 4 tumors, respectively. Nineteen patients (26%) experienced an adverse event, although only 1 patient discontinued ivosidenib for adverse events. Median progression-free survival was 31 months and median overall survival was not reached. Seven patients (9%) had partial response, 3 (4%) had minor response, 47 (64%) had stable disease, and 17 (23%) had progressive disease. The presence of enhancing disease at ivosidenib initiation was associated with lower disease control rates (DCR) whereas DCR differences were not detected based on grade (grade 2 vs. 3), tumor histology, or age. Subsequent-line ivosidenib use had lower DCR although this may have been explained by enrichment of patients with enhancing disease. Conclusions: In this large cohort of IDHm glioma patients, ivosidenib was well tolerated. Our results support the use of IDHi therapy in patients with grade 2 or 3 astrocytoma or oligodendroglioma and highlight limited effectiveness in patients with enhancing disease.