Anti-CCR4 monoclonal antibody (mAb) mogamulizumab is approved for adult T cell leukemia/lymphoma and cutaneous T cell lymphomas...Kinetic analyses using flow cytometry showed that Ks of CMab-1 for CHO/mCCR4, P388, and J774-1 cells were 4.2 × 10 M, 5.4 × 10 M, and 1.1 × 10 M, respectively. CMab-1 could be a valuable tool for elucidating mCCR4-related biological responses.