Shelley Allen

A potential therapeutic target for FLT3-ITD AML: PIM1 Kinase

Patients with acute myeloid leukemia (AML) and a FLT3 internal tandem duplication (ITD) mutation have a poor prognosis, and FLT3 inhibitors are now under clinical investigation. PIM1, a serine/threonine kinase, is up-regulated in FLT3-ITD AML and may be involved in FLT3-mediated leukemogenesis. We employed a PIM1 inhibitor, AR00459339 (Array Biopharma Inc.), to investigate the effect of PIM1 inhibition in FLT3-mutant AML. Like FLT3 inhibitors, AR00459339 was preferentially cytotoxic to FLT3-ITD cells, as demonstrated in the MV4-11, Molm-14, and TF/ITD cell lines, as well as 12 FLT3-ITD primary samples. Unlike FLT3 inhibitors, AR00459339 did not suppress phosphorylation of FLT3, but did promote the de-phosphorylation of downstream FLT3 targets, STAT5, AKT, and BAD. Combining AR00459339 with a FLT3 inhibitor resulted in additive to mildly synergistic cytotoxic effects. AR00459339 was cytotoxic to FLT3-ITD samples from patients with secondary resistance to FLT3 inhibitors, suggesting a novel benefit to combining these agents. We conclude that PIM1 appears to be closely associated with FLT3 signaling, and that inhibition of PIM1 may hold therapeutic promise, either as monotherapy, or by overcoming resistance to FLT3 inhibitors.

The role of PIM kinases in human and mouse CD4+ T cell activation and inflammatory bowel disease.

PIM kinases are a family of three serine/threonine kinases expressed following T cell activation. Using potent selective small molecule antagonists of PIM-1/3 kinases, we demonstrate a potential role for these enzymes in naïve and effector CD4+ T cell activation. PIM-1/3 inhibition prevented CD4+ T cell proliferation by inducing a G0/G1 cell cycle arrest without affecting cellular survival. In the absence of PIM-1/3 kinase activity, naïve CD4+ T cells failed to fully differentiate into effector cells both in vitro and in vivo. Therapeutic dosing of a PIM-1/3 inhibitor was efficacious in a CD4+ T cell-mediated model of inflammatory bowel disease suggesting that PIM-1 and PIM-3 kinase activity contributes to sustained disease severity. These results demonstrate that PIM-1/3 kinases have an important role in CD4+ T cell responses and inhibition of this activity may provide a therapeutic benefit in T cell-mediated diseases.

Discovery of a Novel Class of Imidazo[1,2-a]Pyridines with Potent PDGFR Activity and Oral Bioavailability.

The in silico construction of a PDGFRβ kinase homology model and ensuing medicinal chemistry guided by molecular modeling, led to the identification of potent, small molecule inhibitors of PDGFR. Subsequent exploration of structure-activity relationships (SAR) led to the incorporation of a constrained secondary amine to enhance selectivity. Further refinements led to the integration of a fluorine substituted piperidine, which resulted in significant reduction of P-glycoprotein (Pgp) mediated efflux and improved bioavailability. Compound 28 displayed oral exposure in rodents and had a pronounced effect in a pharmacokinetic-pharmacodynamic (PKPD) assay.