At the 2026 Annual Meeting of the American Society of Clinical Oncology (ASCO) David Reardon, MD, director of the Center for Neuro-Oncology at Dana-Farber, presents findings from a phase 1 clinical trial showing that patients with newly diagnosed glioblastoma who were treated with a personalised neoantigen peptide vaccine (NeoVax) plus pembrolizumab achieved vaccine-stimulated anti-tumor activity that was still evident in some patients after one year and extended survival compared to historical observations of survival for similar patients.

The team, co-led by Catherine Wu, MD, chief of the Division of Stem Cell Transplantation and Cell Therapies at Dana-Farber, observed these results across many patients.

Glioblastoma is an aggressive and fatal form of adult brain cancer.

In a previous study, Reardon and Wu showed that the vaccine generated measurable tumor-specific immune responses.

Building on that work, this study excluded the use of dexamethasone, an immune suppressant, and added an immune checkpoint inhibitor, pembrolizumab, to enhance anti-tumor activity of the vaccine.

Three of the four cohorts of patients had MGMT-unmethylated tumors, which are not sensitive to chemotherapy, and received pembrolizumab at different timepoints in the vaccine administration schedule.

The fourth cohort had MGMT-methylated tumors and received pembrolizumab, the vaccine, and chemotherapy.

Of 39 enrolled patients, 37 have initiated the NeoVax regimen to date.

Median overall survival was 36.9 months for MGMT-methylated patients and 19.0 months for MGMT-unmethylated patients, compared to the 25.3 and 16.7 months historically observed with standard of care.

T-cell responses measured through analyses of blood from vaccinated patients were evident and comparable across all cohorts of patients, including the ten patients who received chemotherapy, suggesting that this potentially immune-weakening therapy was not detrimental.

This study also confirmed that vaccine-specific T cells had migrated into the brain and tumors following vaccination.

The timing of pembrolizumab administration did not appear to affect the stimulation of an immune response, but starting pembrolizumab before NeoVax priming may result in longer overall survival.

“The median survival for MGMT-methylated patients is remarkable compared to what we typically observe in glioblastoma. This is encouraging but has to be very cautiously interpreted as this study was not a direct comparison,” said Reardon.

“We've got a lot of challenges to overcome for immunotherapy to have a meaningful effect in brain cancer, but this vaccine-based approach to immunotherapy treatments does provide some hope that immunotherapy can have an impact in this disease.”

Source: Dana-Farber Cancer Institute