The present invention relates to pharmaceutical compositions for use in the treatment of chemoresistant acute myeloid leukemia (AML). The inventors have established a powerful preclinical model to screen in vivo responses to conventional genotoxics and to mimic the chemoresistance and minimal residual disease as observed in AML patients after chemotherapy. The inventors showed that cytarabine-resistance mechanism involves the CD39-dependent crosstalk between energetic niche and AML mitochondrial functions through CD39-P2Y13-cAMP-PKA signaling axis. In particular, the present invention relates to an inhibitor of the CD39-P2Y13-cAMP-PKA signaling axis for use in a method of treating chemoresistant acute myeloid leukemia (AML) in a patient in need thereof comprising administering to the patient a therapeutically effective amount of said inhibitor.