PHA-680632, a Novel Aurora Kinase Inhibitor with Potent Antitumoral Activity

Abstract

Purpose: Aurora kinases play critical roles during mitosis in chromosome segregation and cell division. The aim of this study was to determine the preclinical profile of a novel, highly selective Aurora kinase inhibitor, PHA-680632, as a candidate for anticancer therapy. Experimental Design: The activity of PHA-680632 was assayed in a biochemical ATP competitive kinase assay. A wide panel of cell lines was evaluated for antiproliferative activity. Cell cycle analysis. Immunohistochemistry, Western blotting, and Array Scan were used to follow mechanism of action and biomarker modulation. Specific knockdown of the targets by small interfering RNA was followed to validate the observed phenotypes. Efficacy was determined in different xenograft models and in a transgenic animal model of breast cancer. Results: PHA-680632 is active on a wide range of cancer cell lines and shows significant tumor growth inhibition in different animal tumor models at well-tolerated doses. The mechanism of action of PHA-680632 is in agreement with inhibition of Aurora kinases. Histone H3 phosphorylation in Ser 10 is mediated by Aurora B kinase, and our kinetic studies on its inhibition by PHA-680632 in vitro and in vivo show that phosphorylation of histone H3 is a good biomarker to follow activity of PHA-680632. Conclusions: PHA-680632 is the first representative of a new class of Aurora inhibitors with a high potential for further development as an anticancer therapeutic. On treatment, different cell lines respond differentially, suggesting the absence of critical cell cycle checkpoints that could be the basis for a favorable therapeutic window.

Mechanism of action of the Aurora kinase inhibitor CCT129202 and in vivo quantification of biological activity

“…We did not find an obvious relationship between the sensitivity of cells in the growth inhibition assay and the protein levels of the Aurora kinases within the cell lines analyzed. Differences in sensitivity might rather be associated with different genetic backgrounds of the cell lines, such as lack of proteins associated with Aurora kinases (28).…”

“…Inhibitors of Aurora kinases kill proliferating cells through apoptosis after accumulation of tetraploid cells generated by the inhibition of cytokinesis and blocking of mitotic histone H3 phosphorylation (25 -27). VX-680 and PHA-680632 inhibit all three Aurora kinases, exhibit antiproliferative activity, and induce tumor regression in animal models (28,29), providing a strong support for developing inhibitors against this target. With respect to biomarkers of drug activity in preclinical studies, Aurora kinase inhibitors have been assessed mainly by measuring histone H3 phosphorylation (27,28).…”

“…VX-680 and PHA-680632 inhibit all three Aurora kinases, exhibit antiproliferative activity, and induce tumor regression in animal models (28,29), providing a strong support for developing inhibitors against this target. With respect to biomarkers of drug activity in preclinical studies, Aurora kinase inhibitors have been assessed mainly by measuring histone H3 phosphorylation (27,28). Noninvasive imaging methods can be very advantageous for cancer drug development (30).…”

“…During the past 3 years, the first generation of Aurora kinase inhibitors, including ZM447439 (25), Hesperadin (26), VX-680 (27; also known as MK-0457), and more recently, PHA-680632 (28) and the specific Aurora A inhibitor MLN8054 (29) have been described. Inhibitors of Aurora kinases kill proliferating cells through apoptosis after accumulation of tetraploid cells generated by the inhibition of cytokinesis and blocking of mitotic histone H3 phosphorylation (25 -27).…”

Modeling the temporal evolution of the spindle assembly checkpoint and role of Aurora B kinase

“…Conversely, severe inhibition of Aurora kinase activity leads to a fatally flawed mitosis (7,(10)(11)(12)(13)(14)(15)(16). Hence, this form of inhibition provides a possible mechanism for selective removal of replicating cells and thus has led to the development of Aurora kinase inhibitors as possible anticancer drugs (13)(14)(15)(16)(17).…”