Abstract B270: Profiling the biochemical and cellular activities of TAK-901, a potent multi-targeted Aurora-B kinase inhibitor

Abstract

Abstract Aurora A, B, and C comprise a family of serine-threonine protein kinases that are key cell cycle regulators ensuring an orderly and accurate execution of mitosis and cell division. Aurora A localizes to centrosomes and spindle poles and is required for mitotic spindle assembly and centrosome maturation, whereas Aurora B is a chromosome passenger protein essential for phosphorylation of histone H3, chromosome segregation, and cytokinesis. Aurora A and B are overexpressed in many malignancies, making them attractive therapeutic targets. Derived from the azacarboline scaffold representing a unique kinase hinge-binder chemotype, TAK-901 is a novel inhibitor of Aurora A, B, and C kinases with IC50 values in the low nanomolar range. It potently inhibits Aurora A-TPX2 and Aurora B-INCENP (IC50 = 21 and 15 nM, respectively) and is a time-dependent, tight binding inhibitor of Aurora B-INCENP. Dissociation of TAK-901 from Aurora B-INCENP was slow with a t1/2 of 920 minutes, and the affinity constant for TAK-901 binding to Aurora B-INCENP was determined to be 0.02 nM. TAK-901 induced inhibition of cell proliferation in cultured human cancer cell lines from different tissues with IC50s ranging from 40 to 500 nM. Consistent with Aurora B inhibition, TAK-901 treatment produced polyploidy in human PC3 prostate cancer and HL60 acute myeloid leukemia cells as measured by immunofluorescence and flow cytometry. Examination of a broad panel of kinases revealed that multiple kinases, including FLT3, FGFR and the Src family kinases, were inhibited by TAK-901 with IC50 values similar to those for Aurora A and B. In cells, TAK-901 suppressed the Flt3 and FGFR2 autophosphorylation with IC50 values close to that of Aurora B as measured by cellular histone H3 phosphorylation, whereas the IC50s for inhibition of cellular Src and BcrAbl were 20-fold weaker. In a panel of pathway specific reporter-based cell models, TAK-901 inhibited the NFkB and JAK/STAT pathways with submicromolar potency. However, phosphorylation or subcellular localization of the signaling mediators NFkB and STAT5 were unaffected by TAK-901 treatment. The expression of a subset of NFkB-regulated genes was altered by TAK-901. Furthermore, TAK-901 treated human PBMCs exhibited multiple differentially expressed genes, as identified using gene expression profiling by microarray analysis, which were subsequently confirmed by quantitative RT-PCR. The mechanism by which TAK-901 alters expression of these genes remains unknown and is under investigation. Altogether, these findings have led to increased understanding of the biological activities of TAK-901 and identification of potential novel biomarkers for clinical use. TAK-901 is currently in Phase I clinical trials. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B270.