Engineering BiTE-inspired IPSC-exosomes to potentiate CAR-T cell therapy against lung cancer

Chimeric antigen receptor T (CAR-T) cell therapy faces critical barriers in solid tumors, including poor infiltration, T cell exhaustion, and immunosuppressive microenvironments, resulting in response rates below 10%. Herein, we engineered an inhalable nanoplatform using induced pluripotent stem cell-derived exosomes (IEXOs) displaying bispecific PD-1/mesothelin (MSLN) single-chain variable fragments (scFv) and loaded with indole-3-propionic acid (IPA) for metabolic reprogramming. IEXOs demonstrated high yield and intrinsic antitumor properties, inhibiting Lewis lung carcinoma (LLC) cell proliferation and migration. The bispecific exosomes loaded with IPA (BIEXO@IPA) achieved efficient pulmonary delivery via nebulization with 79.3% tumor cell-specific uptake versus 47.9% for liposomes in orthotopic lung cancer models. BIEXO@IPA treatment reduced tumor burden by 87.9% and achieved 80% survival at 80 days. Mechanistically, BIEXO@IPA bridged PD-1⁺ T cells to MSLN⁺ tumor cells through bispecific engagement while expanding progenitor exhausted T (Tpex) cells and reducing regulatory T cells. When combined with CAR-T cells, BIEXO@IPA achieved 66.7% complete remission with 100% survival at 80 days and 83.3% resistance to tumor rechallenge. Safety assessments revealed minimal toxicity. This BIEXO@IPA platform represents a scalable, clinically translatable strategy that addresses fundamental CAR-T limitations in solid tumors through synergistic multimodal immunomodulation.