PIM1 is a member of the PIM family of proteins which are proto-oncogenes, serine-threonine kinases with increased expression in a variety of malignancies. PIM1 expression appears to be up-regulated by STAT5, and has been found to be over-expressed in primary AML blast samples. In particular, PIM1 has associated with FLT3 mediated leukemogenesis in FLT3-ITD AML. PIM1 expression was noted to be 25-fold higher than in FLT3-ITD samples, as compared to wild type FLT3 (WT) AML samples. The PIM kinases, therefore, represent potential therapeutic targets in AML, particularly in those cases harboring FLT3-ITD mutations. According to one study, the small molecule inhibitor of PIM1, AR00459339, alone and in combination with a FLT3 inhibitor (AR00454200), resulted in significant cytotoxicity in FLT3-ITD cell lines and patient samples that strikingly parallels the effects of FLT3 inhibition. A variety of mutations have been reported throughout PIM1 in various types of malignancy including hematopoietic tumors, but PIM1 mutations appear to be extremely rare in acute myeloid leukemia and myelodysplasia.