The PIM kinase family members have been shown to be oncogenic in mouse studies, and capable of driving the progression of haematological cancers in humans. Inhibition of all three PIM members has been proposed to be an effective treatment approach for haematological malignancies. A preclinical study in multiple-myeloma cells has shown that the potent and specific pan-PIM inhibitor, LGB321, was able to prevent inhibition of mTOR-C1 signalling and phosphorylation of the downsteam component BAD. In a xenograft mouse model of acute myeloid leukaemia, the LGB321 inhibitor demonstrated potent and selective pan-PIM single agent activity and was also shown to synergize with cytarabine—part of the standard treatment for this disease. These results support the further development of pan-PIM inhibitors for treating haematological malignancies.