RTID-02. PERSONALIZED PEPTIDE VACCINATION AMONG 173 PATIENTS WITH GLIOBLASTOMA

Abstract Current treatment outcome of patients with glioblastoma (GBM) remains poor. Following standard therapy, recurrence is universal with limited survival. GBM tumors from 173 patients were analyzed for somatic mutations to generate a personalized peptide vaccine targeting tumor-specific neoepitopes. In agreement with their treating physician, patients added a personalized peptide vaccine to their treatment as an individual healing attempt. Patients were monitored from October 2015 until August 2023. We retrospectively evaluated their clinical courses and the results of their immune monitoring data. Among all patients, including 70 treated prior to progression (primary) and 103 treated after progression (recurrent), the median overall survival from first diagnosis was 31.9 months (95% CI: 25.0-36.5). Adverse events were infrequent and were predominantly grade 1 or 2. An immune response to at least one of the vaccinated peptides was detected in blood samples of 87 of 97 (90%) monitored patients. T-cell responses to vaccinated neoepitope peptides were durable in most patients. Significantly prolonged survival was observed for patients with multiple vaccine-induced immune responses (53 months) compared to those with no/low induced responses (27 months; P=0.03). Altogether, our results highlight that the application of personalized neoantigen-targeting peptide vaccine is feasible and represents a promising potential treatment option for GBM patients. This is the largest real-world observation involving GBM patients safely treated with a personalized peptide vaccine to date. This real-world observation will be translated into a clinical trial to evaluate the specific contribution of the neoantigen vaccine.