Intraperitoneal programming of tailored CAR macrophages via mRNA lipid nanoparticle to boost cancer immunotherapy.

Therapeutic strategies for peritoneal metastasis in solid tumors are urgently needed. Programming chimeric antigen receptor macrophages (CAR-Ms) in situ offers opportunities for an unmet demand. However, potential intracellular domains (ICDs) for CAR design and their antitumor mechanisms for macrophage empowerment remain to be explored systematically. By developing a macrophage-targeted mRNA lipid nanoparticle (mRNA-LNP) system, we evaluate 36 CAR formats in CAR-Ms. Tailored CAR-Ms with CD3ζ TLR4 ICDs elicit robust adaptive immune activation and significantly synergize with PD-1/L1 therapy. Single-cell RNA sequencing (scRNA-seq) reveals that CAR-Ms reshape the immunosuppressive tumor microenvironment (TME) and boost the TCF1(+)PD-1(+) progenitor-exhausted CD8(+) T cells (Tpex) population. Mechanistically, CAR-Ms maintain a proinflammatory phenotype and simultaneously upregulate MHC-I and PD-L1 by perturbing NF-κB pathways. Collectively, this approach enables intraperitoneal programming of tailored CAR-Ms and broadens understanding of both regulatory and feedback mechanisms for CAR-M therapies against solid tumors.