A tumor-responsive nanoplatform orchestrating multiplexed macrophage engagers and immune checkpoint blockade for triple-negative breast cancer immunotherapy

Introduction Triple‐negative breast cancer (TNBC) remains a formidable clinical challenge due to its profound inter‐ and intra‐tumoral heterogeneity and highly immunosuppressive tumor microenvironment (TME), which severely limit the efficacy of standard immune checkpoint blockade (ICB) therapies. To overcome these multifactorial barriers, we engineered a dual‐responsive, targeted lipid nanoparticle platform, denoted as R‐DCPA‐GPL‐LNP@mET, designed to holistically orchestrate innate and adaptive anti‐tumor immunity. Methods This multifunctional nanoplatform co-delivers multiplexed mRNAs encoding bispecific macrophage engagers that simultaneously target Epidermal Growth Factor Receptor (EGFR) and Trophoblast cell-surface antigen 2 (TROP2), ensuring comprehensive engagement of heterogeneous TNBC cells. The nanocarrier utilizes a pH-responsive charge-reversal lipid (DCPA) to accelerate robust endosomal escape in the acidic TME, alongside a glutathione (GSH)-cleavable anti-PD-L1 antibody tethered to the surface for tumor-selective ICB release. Results Upon systemic administration, the translated bispecific engagers physically bridge tumor-associated macrophages (TAMs) with TNBC cells, reprograming TAMs toward a tumoricidal M1 phenotype, triggering highly efficient phagocytosis, and neutralizing oncogenic PI3K/AKT/mTOR signaling pathways. Concurrently, the localized release of anti-PD-L1 synergizes with this innate immune activation to profoundly remodel the TME, driving the extensive infiltration of cytotoxic T lymphocytes and Natural Killer cells while depleting immunosuppressive myeloid-derived suppressor cells. In an orthotopic 4T1 TNBC murine model, this multiplexed, spatiotemporal intervention induced marked tumor regression with a favorable preliminary safety profile over the 22-day observation period. Discussion Collectively, these preclinical findings support further development of this multiplexed, dual-responsive nanoplatform as a promising strategy for heterogeneous and immunosuppressive solid tumors.