A tumor‐targeting nanomedicine carrying the p53 gene crosses the blood–brain barrier and enhances anti‐PD‐1 immunotherapy in mouse models of glioblastoma

Despite its anticipated clinical potential, anti‐PD‐1 immunotherapy has only yielded poor outcomes in recent clinical trials for glioblastoma patients. Strategies combining anti‐PD‐1 antibody with other treatment modalities are being explored to alter the immunosuppressive microenvironment that appears to characterize these anti‐PD‐1‐insensitive tumors. Here, we evaluated whether introducing wild‐type p53 gene via a tumor‐targeting nanomedicine (termed SGT‐53) could provide immune stimulation and augment anti‐PD‐1 therapy in mouse syngeneic GL261 tumor models (either subcutaneous or intracranial). In both models, anti‐PD‐1 monotherapy had no demonstrable therapeutic effect. However, combining anti‐PD‐1 with our investigational nanomedicine SGT‐53 was very effective in inhibiting tumor growth, inducing tumor cell apoptosis and increasing intratumoral T‐cell infiltration. A significant survival benefit was observed in mice bearing intracranial glioblastoma receiving combination treatment. Importantly, SGT‐53 upregulated PD‐L1 expression both in vitro and in vivo. Transcriptome analysis revealed modulation of genes linked to either cancer progression or immune activation after combination treatment. Our data suggest that SGT‐53 can boost antitumor immunity and sensitize glioblastoma to anti‐PD‐1 therapy by converting immunologically “cold” tumors into “hot” tumors. Combining SGT‐53 with anti‐PD‐1 might benefit more patients from anti‐PD‐1 immunotherapy and our data support evaluation of this combination in patients with glioblastoma.