Polyinosinic/Polycytidylic\nLipid Nanoparticles Enhance\nImmune Cell Infiltration and Improve Survival in the Glioblastoma\nMouse Model

Glioblastoma (GBM) immunotherapy is particularly challenging\ndue\nto the pro-tumorigenic microenvironment, marked by low levels and\ninactive immune cells. Toll-like receptor (TLR) agonists have emerged\nas potent immune adjuvants but failed to show improved outcomes in\nclinical trials when administered as a monotherapy. We hypothesize\nthat a combined nanoparticulate formulation of TLR agonist and immunogenic\ncell death-inducing drug (doxorubicin) will synergize to induce improved\nGBM immunotherapy. Lipid nanoparticle (LNP) formulations of the TLR\nagonists CpG and polyinosinic/polycytidylic (pIpC), with and without\nDox, were first prepared, achieving an encapsulation efficiency >75%\nand a size <140 nm. In vitro studies identified that LNP pIpC was\nsuperior to CpG at activating bone marrow-derived immune cell populations\n(dendritic cells and macrophages) with minimal toxicity. It was also\nobserved that the pIpC formulation can skew macrophage polarization\ntoward the antitumorigenic M1 phenotype and increase macrophage phagocytosis\nof cancer cells. Upon intratumoral administration, pIpC Dox LNPs led\nto significant immune cell infiltration and activation. In survival\nmodels, the inclusion of Dox into pIpC LNP improved mice survival\ncompared to control. However, addition of Dox did not show significant\nimprovement in mice’s survival compared to singly formulated\npIpC LNP. This study has illustrated the potential of pIpC LNP formulations\nin prospective GBM immunotherapeutic regimes. Future studies will\nfocus on optimizing dosage regimen and/or combination with other modalities,\nincluding the standard of care (temozolomide), immune checkpoint blockade,\nor cancer vaccines.