The FDA-approved CCR4 monoclonal antibody, mogamulizumab, had modest activity in clinical trials against ATLL and CTCL (11, 83), and CCR4 CAR T cells showed in vitro and in vivo activity against some but not all malignant T cell lines expressing high levels of CCR4 in preclinical studies (84). This evidence concerns the gene CCR4 and primary cutaneous T-cell non-Hodgkin lymphoma.