Targeted protein degradation via chimeric antigen receptor (CAR)-mediated antigen endocytosis in T cells

Targeted protein degradation (TPD) holds significant therapeutic potential over conventional biologics. However, existing platforms are constrained by their reliance on host protein degradation machinery and limited durability, rendering them inadequate for chronic diseases requiring sustained treatment. Here, we constructed a chimeric antigen receptor (CAR) incorporating the TNFR1 ectodomain as the antigen-binding domain (TNFR1T cells) and used CRISPR-mediated knockout of BCOR and ZC3H12A to generate persistent TNFR1T_IF cells. TNF binding, endocytosis, and degradation were assessed in vitro by flow cytometry and immunofluorescence. Immunocompetent syngeneic, Tnf ^-/-, and hTNF-tg rheumatoid arthritis (RA) mice (n = 4-9) were used in vivo to evaluate engraftment, persistence, and disease severity (clinical scoring and grip strength), with adalimumab (Humira, 1 or 10 mg/kg) as a comparator. Safety was assessed by intravenous Listeria monocytogenes challenge (1 × 10⁴ colony-forming units [CFU], n = 6) and Thy1.1-based depletion (0.25 mg, n = 3). We found that TNFR1T cells specifically bound, endocytosed, and degraded soluble TNF in vitro. Without lymphodepletion preconditioning, TNFR1T_IF cells expanded and persisted for one year in immunocompetent mice. A single infusion into hTNF-tg mice reduced serum hTNF to near wild-type levels, preventing and treating all stages of RA with superior efficacy and durability than the repeated high-dose adalimumab. Antibacterial defense remained uncompromised, and anti-Thy1.1 antibody efficiently eliminated TNFR1T_IF cells in vivo. This approach extends CAR-T cell targeting from cellular antigens to soluble extracellular proteins, establishing a host-machinery-independent, durable cellular-TPD platform for chronic inflammatory diseases.