THE MECHANISM OF ACTION OF OMACETAXINE MEPESUCCINATE HAS NOT BEEN FULLY ELUCIDATED BUT INCLUDES INHIBITION OF PROTEIN SYNTHESIS AND IS INDEPENDENT OF DIRECT BCR-ABL BINDING. OMACETAXINE MEPESUCCINATE BINDS TO THE A-SITE CLEFT IN THE PEPTIDYL-TRANSFERASE CENTER OF THE LARGE RIBOSOMAL SUBUNIT FROM A STRAIN OF ARCHAEABACTERIA. IN VITRO, OMACETAXINE MEPESUCCINATE REDUCED PROTEIN LEVELS OF THE BCR-ABL ONCOPROTEIN AND MCL-1, AN ANTI-APOPTOTIC BCL-2 FAMILY MEMBER. OMACETAXINE MEPESUCCINATE SHOWED ACTIVITY IN MOUSE MODELS OF WILD-TYPE AND T315I MUTATED BCR-ABL CML.