Therefore, anti-CD4 antibodies were investigated emphasizing CD4 as an interesting target.28, 29 Tregalizumab (BT-061) is a non-depleting IgG1 monoclonal antibody, which binds to a unique epitope of CD4 and represents the first humanized anti-CD4 monoclonal antibody that selectively induces Treg activation.30 As a new therapeutic approach, Tregalizumab has been investigated in eight clinical trials, including healthy subjects, RA and psoriasis patients. Here, CD4 is linked to rheumatoid arthritis.