CTIM-12. A RETROLECTIVE ANALYSIS ON THE SAFETY, EFFICACY AND IMMUNOGENICITY OF 203 GLIOBLASTOMA PATIENTS TREATED WITH PERSONALIZED THERAPEUTIC CANCER VACCINES (PTCV)

Abstract BACKGROUND Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor. Despite of the current SoC, patients have a poor prognosis with a median OS of about 14-17 months.Method, RESULTS We report retrospectively analyzed data from 203 GBM patients (IDH wildtype) who added PTCV derived from patient individual tumor mutations to their treatment regimen in the setting of individual treatment attempts (ITA) in Germany. Data were analyzed re. vaccine induced T cell responses and safety acc. to CTCAE terminology version 5.0. Subsets of patients with and without hypermethylation of the MGMT promoter were further evaluated re. efficacy. Treated patients had a median age of 53 years at diagnosis, started vaccination after a median of 11 months after diagnosis, received a median of 8 immunizations with a median of 20 neoepitope peptides, and had a median follow-up time since first vaccination of 21 months. They usually received SoC (Stupp scheme), often accompanied by additional therapies. In general, the PTCV was well tolerated, and most patients experienced only Grade 1 and 2 AEs. Most frequently injection site reactions were observed (67%). Seven patients developed Grade 3 allergic or anaphylactic reactions after 7 or more vaccinations. For 119 patients T-cell responses against the vaccinated neoepitopes were investigated. Almost all patients developed vaccine induced T-cell responses (97%). 71% of patients showed both CD4+ and CD8+ T-cell responses towards vaccinated peptides. Immune responses usually increased over time peaking within 3-6 months. Median OS of the whole cohort was 26 mo (95% CI 24, 31). Primary GBM patients without recurrence events before the start of vaccination and with or without hypermethylated MGMT promoter status showed a mOS of 41 months (95% CI: 32, NA) or 23 months (95% CI: 20, NA), respectively. CONCLUSION The retrospective data analysis from a real-world cohort of GBM patients suggests that PTCV are safe, immunogenic, and may prolong the survival of patients.