Personalized drug screening aims to improve the survival of glioblastoma (GBM) patients by identifying effective patient-individual drugs. Therefore, we conducted an automated high-throughput drug screening (aHTS) on standardized patient-derived glioblastoma tumor organoids (TOs). Robot-assisted aHTS was performed on TOs from 11 GBM patients. TOs fully compacted after two days, and the size remained stable over 10 days. TOs proliferated over time, and immunofluorescence stainings (GFAP, Tenascin C) confirmed tissue-like architecture. Anti-glioma effects with the lowest drug concentrations were achieved for proteasome inhibitors (carfilzomib, bortezomib, ixazomib), and HDAC inhibitors (panobinostat, romidepsin). Plasma C_max-based drug levels (C_max/IC₅₀ > 1) used as a surrogate were only achieved for the three proteasome inhibitors and the HDACi romidepsin. The impact of their drug targets PSMB5 and HDAC1/2 on the growth of GBM cells was successfully validated by RNAi experiments. We established an aHTS platform for GBM TOs, and identified proteasome and HDAC inhibitors as promising drugs for the treatment of GBMs.

The clonal glioma driver mutation IDH1^R132H gives rise to a major histocompatibility class II-restricted neoepitope. A multicenter, first-in-human phase 1 trial met its prespecified primary endpoints by demonstrating safety and immunogenicity of an IDH1-R132H peptide vaccine (IDH1-vac) integrated into standard of care in 33 participants with newly diagnosed grade III and IV (World Health Organization classification 2007) IDH1-R132H⁺ astrocytomas (NOA16). Here we report on the clinical and immunological long-term follow-up of this trial as secondary and translational endpoints. The 8-year progression-free and overall survival (OS) rates were 0.42 months (confidence interval (CI): 0.24-0.59) and 0.66 months (CI: 0.46-0.79), respectively. For participants with grade IV astrocytoma, median OS was 106.1 months (CI: 39.6-not estimable (NE)), comparing favorably to the published median OS in this population ranging from 31.6-56.4 months. Within the responder group, sustained antibody responses to IDH1-R132H were associated with a favorable long-term clinical course. IDH1-vac-induced T cell responses were detected in the inflamed brain lesion of an IDH1-vac-associated pseudoprogression, whereas no IDH1-vac-induced T cells were found in participants with early progressive disease. The favorable long-term outcome of the NOA16 cohort supports investigating IDH1-vac in persons with newly diagnosed grade 3 and 4 (World Health Organization classification 2021) IDH-mutant astrocytomas in a randomized phase 2 trial (ClinicalTrials.gov identifier: NCT02454634 ).