PHA-739358 is a small-molecule 3-aminopyrazole derivative with strong activity against Aurora kinases and crossreactivities with some receptor tyrosine kinases relevant for cancer. PHA-739358 inhibits all Aurora kinase family members and shows a dominant Aurora B kinase inhibitionrelated cellular phenotype and mechanism of action in cells in vitro and in vivo. p53 status -dependent endoreduplication is observed upon treatment of cells with PHA-739358, and phosphorylation of histone H3 in Ser 10

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.

The results of this study confirmed FNAC as a reliable and useful diagnostic procedure for the evaluation of palpable cutaneous and subcutaneous lesions in small animal practice.

Purpose: This study was conducted to assess the safety, tolerability, pharmacokinetics,