ATLL is an aggressive malignancy caused by HTLV-1. ATLL cannot be cured by conventional chemotherapy thus urging the development of new therapeutic strategies. HDAC inhibitors are broadly active anti-neoplastic agents that can be exploited for the treatment of ATLL as it has been demonstrated that pharmacologic inhibition of HDACs promotes acetylation of nucleosomes and chromatin unwinding at the HTLV-1 5' long terminal repeat (LTR), which results in transcription of the viral genome.