Mogamulizumab was approved for the treatment of CCR4-positive ATLL caused by human T-lymphotropic virus type 1 (HTLV-1) and peripheral T cell lymphoma (PTCL) in Japan in 201228,35, and has also been tested for another HTLV-1-associated disease, HTLV-1-associated myelopathy-tropical spastic paraparesis (HAM-TSP)30. The gene discussed is CCR4; the disease is tropical spastic paraparesis.