CTNI-15. A PERIOPERATIVE STUDY OF SAFUSIDENIB IN PATIENTS WITH IDH1 MUTATED GLIOMA

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Abstract BACKGROUND IDH mutations cause aberrant accumulation of (R)-2-hydroxyglutarate (2-HG), an oncometabolite that promotes tumorigenesis through abnormal hypermethylation of histones and DNA as well as suppression of normal cellular differentiation. IDH inhibition significantly improves progression free survival in patients with IDH mutant WHO grade 2 glioma, however most patients progress, and there is a lack of understanding on mechanistic reasons for failure. METHODS We tested Safusidenib, an oral, blood brain barrier penetrant IDH1 R132X enzyme inhibitor in a single arm, open label perioperative study. Patients with IDH1 mutated glioma, treatment naïve to radiation or chemotherapy, received Safusidenib (250 mg BID) for four weeks following surgical biopsy and prior to definitive resection (Part A). After resection patients continued Safusidenib until toxicity or progression (Part B). Translational endpoints include paired whole genome transcriptome sequencing (WGTS), single nuclei RNA sequencing (snRNAseq), spatial transcriptomics and spatial metabolomics as well as longitudinal sampling of blood and CSF for circulating tumour DNA (ctDNA). Here we are reporting Part A of the study. RESULTS As of May/27/2024 10 patients (mean age 37, 40% female) have been enrolled: seven with astrocytoma, three with oligodendroglioma; six had prior surgical resection. Pharmacokinetic sampling showed a mean tumor concentration 2457 ng/mL (range 957.0 – 4810) with tumor:plasma ratio 0.33. Consistent with mechanism, tumor 2-HG reduced 86% from biopsy (mean 75.0μM, range 7.8-203) to surgery (10.3μM, range 2.3 – 30.8), as well as identification of novel biomarkers of response. Paired tumour snRNAseq reveals transcriptional shift with changing cell-to-cell communication, and increased immune infiltration post-treatment, validated by spatial transcriptomics. Additionally, we find reduced heterogeneity consistent with a more differentiated tumour state. Treatment was well tolerated with ongoing follow-up. CONCLUSIONS This innovative trial facilitates intra-patient comparisons and confirmation of the on-target effects of Safusidenib, enhancing understanding of the mechanisms of response and resistance. The approach serves as a proof of concept for advancing drug development in glioma through perioperative trials.

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