Researchers reported a technique using intraperitoneal delivery of mRNA lipid nanoparticles to program CAR macrophages in vivo, enhancing anti‑tumor activity against peritoneal cancers. The approach enables transient, cell‑type‑selective CAR expression without ex vivo cell manufacturing, showing improved tumor control in preclinical models. This method reduces the logistical burden and cost associated with conventional ex vivo CAR cell therapies and offers a route to rapidly generate tumor‑targeting myeloid effector cells within patients. The work, presented by the research team, frames a potential clinical pathway for solid tumor immunotherapy that bypasses complex manufacturing.