AS3MT and acute promyelocytic leukemia: In humans, iAsIII has found to be rapidly methylated to trivalent mono- and di- methylated metabolites (i.e., MMAIII and DMAIII) by arsenic methyltransferse (AS3MT) in liver (Fig. 1B), however, little is known about the therapeutic effects of intermediate metabolites of iAsIII on APL patients receiving As2O3 treatment.