APL variants cell lines were generated by lentiviral vector-transfecting ZBTB16-RARA(NB4ZBTB16/RARA), STAT5b-RARA(NB4STAT5b/RARA) and NPM-RARA(NB4NPM/RARA) fusion gene into APL-derived NB4 cells, respectively, as well as primary cells from patients with APL variants....HDACi inhibited proliferation, induced apoptosis and differentiation in APL variant cells in vitro....Taken together, our data demonstrated that a novel HDACi chidamide inhibited proliferation and induced apoptosis by activation of FoxO3a in refractory and relapsed APL variants and might promote the poor outcome.