T-cell-targeted fusogenic nanovesicles generate CAR-T cells in vivo for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic autoimmune disease in which pathogenic B cells drive persistent inflammation and joint damage. Although CD19-targeted CAR-T cell therapy enables effective B-cell depletion, conventional ex vivo manufacturing and viral vector-based genetic modification limit its scalability and clinical application. Strategies that allow efficient CAR-T cell generation directly in vivo may therefore provide a more practical approach to sustained immune modulation. We developed FuNV CAR , a T cell-targeted fusogenic nanovesicle system that delivers preformed αCD19 CAR proteins to T cells via membrane fusion. FuNV CAR was characterized for size, composition, and fusion specificity. CAR-T cell generation, persistence, and cytotoxic function were evaluated in vitro. In vivo CAR-T induction, B-cell depletion, therapeutic efficacy, and tissue-level outcomes were assessed in a collagen-induced arthritis (CIA) mouse model. FuNV CAR selectively fused with CD3⁺ T cells and enabled dose-dependent surface display of functional αCD19 CAR proteins without genetic modification. FuNV CAR -generated CAR-T cells exhibited antigen-specific cytotoxicity against CD19⁺ B cells in vitro. In vivo administration induced measurable CAR-T cell generation in blood and spleen, resulting in effective B-cell depletion, reduced autoantibody levels, attenuation of joint inflammation, and preservation of cartilage and bone architecture in CIA mice. FuNV CAR showed favorable tolerability with no overt organ toxicity. These findings demonstrate that FuNV CAR enables functional in vivo CAR-T cell generation and sustained disease modification in experimental arthritis. FuNV CAR represents a mechanistically distinct and scalable platform for CAR-T-based immunotherapy in RA and other B cell-driven autoimmune diseases.