Otelixizumab (also known as TRX4 or ChAglyCD3) is a humanized, Fc-engineered monoclonal antibody that targets the CD3 epsilon (ε) chain of the T-cell receptor (TCR) complex. Its Fc region is engineered to reduce binding to Fcγ receptors, thereby minimizing T-cell activation and cytokine release syndrome (CRS) compared to earlier anti-CD3 antibodies like muromonab-CD3 (OKT3). By binding to CD3, otelixizumab modulates T-cell function, inducing transient T-cell depletion, anergy, or immune tolerance.