Metformin/aPD-L1 Co-delivered Liposomal Nanoparticles for Combination Immunotherapy against Tumor

Immunotherapy targeting the PD-1/PD-L1 axis has improved lung cancer treatment, yet its clinical efficacy remains limited by suboptimal tumor delivery and an immunosuppressive tumor microenvironment. Metformin, a clinically safe and widely used drug, has been reported to regulate tumor metabolism, autophagy, and immune responses, making it a potential candidate for combination immunotherapy. Here, we developed a liposomal co-delivery system (LNP@Me-aPD-L1) that integrates metformin and anti-PD-L1 antibodies for combined therapeutic intervention in lung cancer. The liposomes displayed uniform particle size, good stability, and favorable biocompatibility. Surface-conjugated anti-PD-L1 enhanced nanoparticle uptake by PD-L1-expressing tumor cells, while metformin loading enabled intracellular drug delivery. In vitro experiments showed that LNP@Me-aPD-L1 reduced LLC cell viability, promoted autophagy-related responses, and decreased PD-L1 expression. In multiple Lewis lung carcinoma models, LNP@Me-aPD-L1 effectively suppressed tumor growth and prolonged survival. Immune analyses indicated increased CD8⁺ T-cell infiltration and modulation of the tumor immune microenvironment. Western blot and immunofluorescence results suggested involvement of AMPK activation and autophagy-associated pathways. Overall, this study presents a liposomal co-delivery strategy that combines metformin and anti-PD-L1 to enhance anti-tumor efficacy. The use of clinically relevant liposomal components and an FDA-approved drug highlights the potential translational value of this approach for lung cancer therapy. • LNP@Me-aPD-L1 enhances tumor targeting in LLC models, significantly improving nanoparticle accumulation at tumor sites via aPD-L1 incorporation. • Combination therapy with LNP@Me-aPD-L1 suppresses tumor growth and extends survival in subcutaneous, and orthotopic LLC models. • LNP@Me-aPD-L1 induces autophagy and downregulates PD-L1 expression through AMPK activation, mitigating immune evasion in lung cancer. • The formulation promotes a pro-inflammatory tumor microenvironment by enhancing CD8+ T-cell activity and reducing immunosuppressive cells. • In vitro and in vivo studies confirm LNP@Me-aPD-L1’s safety and efficacy, offering a promising strategy for overcoming PD-L1 therapy resistance.