Anti-FAP CAR T cells produced in vivo reduce fibrosis and restore liver homeostasis in metabolic dysfunction–associated steatohepatitis

Hepatic fibrosis is a key predictor of mortality in liver disease, driven by fibrogenic hepatic stellate cells (HSCs). Targeting these fibrogenic cells may therefore offer a therapeutic approach for hepatic fibrosis. We previously showed that in vivo-generated chimeric antigen receptor (CAR) T cells targeting fibroblast activation protein alpha (FAP) reduced murine cardiac fibrosis. Here, we explored the antifibrotic potential of this in vivo-generated anti-FAP CAR T cell therapy in metabolic dysfunction-associated steatohepatitis (MASH), a highly prevalent disease with no approved antifibrotic therapies. We first established that FAP expression in both human and murine MASH is specific to HSCs. We then used flow cytometry, Sirius Red morphometry, digital pathology analysis, and single nuclear RNA sequencing to assess the impact of anti-FAP CAR T cell therapy on murine MASH. Anti-CD5-targeted lipid nanoparticles carrying anti-FAPCAR messenger RNA transiently generated activated anti-FAP CAR T cells, which substantially reduced fibrosis by depleting profibrogenic HSCs. They also modulated immune cells, endothelial cells, and hepatocytes in a non-cell autonomous manner to mitigate inflammation and restore hepatic homeostasis. These findings highlight the potential of in vivo CAR T therapy to attenuate a highly morbid and pervasive liver disease, not only by directly reducing fibrosis but also through indirect effects on other cell types.