Intratumoral administration of lipid nanoparticles carrying mRNA encoding for IL-21, IL-7, and 4-1BBL induces anti-tumor immunity in preclinical tumor models.

Local delivery of mRNA-based immunotherapy offers a promising avenue for personalized medicine as it enables the production of specific immunomodulatory proteins that can stimulate the immune system to recognize and eliminate cancer cells, showcasing encouraging results in preclinical tumor models while minimizing systemic side effects. Nonetheless, efficient mRNA delivery is challenging due to its rapid degradation by ribonucleases and limited cellular uptake. Here, we developed and employed ionizable lipid nanoparticles (LNPs) to intratumorally deliver an mRNA mixture encoding the cytokines IL-21 and IL-7 and the immunostimulatory molecule 4-1BB ligand (Triplet LNP). The Triplet LNP led to a profound increase in the frequency of tumor-infiltrating granzyme B+ CD8+ T cells and their capacity to secrete IFN-γ, leading to tumor eradication in a CD8+ T cell-dependent manner. Ultimately, the Triplet LNP showed superior therapeutic efficacy to anti-PD1 against the orthotopic triple-negative breast carcinoma model E0771, highlighting the therapeutic potential of the Triplet LNP in multiple murine tumor models.