Perales-Linares, Renzo F.

Abstract Glioblastoma is a highly lethal malignancy with dismal overall survival and near universal recurrence despite maximal multimodal therapy. Patients with unmethylated O6-methylguanine methyltransferase (MGMT) promoters do not derive survival benefit from adjuvant temozolomide. Immunotherapies have revolutionized cancer care; however, this modality has yet to translate into survival benefits in glioblastoma in part due to both local and systemic immunosuppressive states. Here, we report the results of a phase 1 clinical trial (NCT04015700) evaluating the safety and feasibility of GNOS-PV01, a personalized DNA vaccination platform that safely immunized against up to 40 patient-specific neoantigens in a clinically relevant timescale following surgical resection and radiation for MGMT-unmethylated glioblastoma patients. Multisector tumor sampling at time of resection enabled personalized and spatially representative neoantigen identification through an established pipeline. In the nine participants receiving vaccines, there were no unexpected toxicities or serious adverse events with a median vaccine delivery time of 10 weeks post-radiation. The vaccination was strongly immunogenic and induced activation and expansion of both local infiltrating CD8+ and CD4+ T-cells and circulating peripheral T-cells. T-cell receptor sequencing revealed both expanded pre-existing populations as well as novel neoantigen-specific populations, suggesting that vaccination both reinvigorates pre-existing immunity and generates novel immune reactivity. We developed a new technology to profile T-cells at single-nuclei resolution from frozen tissue revealing that vaccination altered gene expression signatures involved in inflammatory response and lymphocyte activation in the tumor microenvironment. Exposure to dexamethasone greatly suppressed immune reactivity, while PD-1 blockade enhanced local immune responses. With respect to efficacy, one third of patients survived longer than 24 months with one long-term survivor living >40 months from time of diagnosis, exceeding survival of recently published trials. Thus, our study demonstrates the safety, feasibility, and preliminary clinical efficacy of a personalized multivalent neoantigen vaccination platform in a devastating cancer.