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

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.