Lung-targeted delivery of PTEN mRNA combined with anti-PD-1-mediated immunotherapy for In Situ lung cancer treatment.

mRNA-based protein replacement therapy has become one of the most widely applied forms of mRNA therapy, with lipid nanoparticles (LNPs) being extensively studied as efficient delivery platforms for mRNA. However, existing LNPs tend to accumulate in the liver or kidneys after intravenous injection, highlighting the need to develop vectors capable of targeting specific organs. In this study, we synthesized a small library of ionizable lipids and identified PPz-2R as a promising candidate, exhibiting lung-targeting capabilities, high mRNA transfection efficiency, and good stability through structure-activity relationship studies. In an in situ lung cancer model with PTEN deletion, precise delivery of PTEN mRNA to the lungs restored the cancer-suppressing function of the PTEN protein and successfully alleviated the immunosuppressive tumor microenvironment in the lungs by modulating immune cell activity and cytokine levels. Additionally, the upregulation of PD-L1 expression at the tumor site was triggered. Building on this, in vivo treatment with PTEN mRNA combined with anti-PD-1 therapy was tested in tumor-bearing mice. The results demonstrated that the combined treatment strategy effectively overcame immune escape, promoted T cell infiltration, improved survival rates over 60 days, and significantly inhibited tumor growth. Furthermore, the combination treatment was more effective than either therapy alone. This study presents an effective and practical strategy for the targeted treatment of lung diseases and relevant combination therapies. STATEMENT OF SIGNIFICANCE: Lipid nanoparticles (LNPs) have been extensively studied as efficient delivery vectors for mRNA. However, it remains essential to develop vectors that can specifically target distinct organs. In this study, we designed and synthesized a series of piperazine-containing ionizable lipids and their analogues, which were initially explored as lung-targeting vectors for PTEN mRNA delivery. Through screening in both in vitro and in vivo experiments, we found that the leading LNPs-assisted PTEN mRNA-mediated protein supplementation therapy effectively downregulated Treg expression and activated immune cells, thereby reversing the immunosuppressive tumor microenvironment in a mouse model of lung cancer. Furthermore, when combined with anti-PD-1-mediated immunotherapy, the combination therapy exhibited the strongest tumor growth inhibition. This approach offers a novel strategy for the targeted treatment of lung diseases and associated combination therapies.