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This Phase 1 GT-20 trial tested a personalized DNA neoantigen vaccine in 9 patients with newly diagnosed MGMT-unmethylated glioblastoma (GBM). Unlike other neoantigen vaccine approaches, GT-20 sequenced multiple regions of each tumor rather than just one and incorporated up to 40 patient-specific neoantigens into each vaccine.
The vaccine was generally well tolerated and generated measurable immune responses in six of seven evaluable patients, with evidence that vaccine-induced T cells entered the tumor microenvironment. The study was not designed to evaluate efficacy, but investigators reported a median overall survival of 16.3 months and a two-year survival rate of 33%. Patients receiving dexamethasone had weaker immune responses, consistent with findings from other immunotherapy studies.
While several neoantigen vaccine programs have successfully generated anti-tumor immune responses in GBM, the key question remains whether those responses can translate into meaningful clinical benefit, either alone or in combination with other therapies.