Cancer Therapy : Preclinical Characterization of Alisertib ( MLN 8237 ) , an Investigational Small-Molecule Inhibitor of Aurora A Kinase Using Novel In Vivo Pharmacodynamic Assays

Purpose: Small-molecule inhibitors of Aurora A (AAK) and B (ABK) kinases, which play important roles in mitosis, are currently being pursued in oncology clinical trials. We developed three novel assays to quantitatively measure biomarkers of AAK inhibition in vivo. Here, we describe preclinical characterization of alisertib (MLN8237), a selective AAK inhibitor, incorporating these novel pharmacodynamic assays. Experimental Design: We investigated the selectivity of alisertib for AAK and ABK and studied the antitumor and antiproliferative activity of alisertib in vitro and in vivo. Novel assays were used to assess chromosome alignment and mitotic spindle bipolarity in human tumor xenografts using immunofluorescent detection of DNA and alpha-tubulin, respectively. In addition, 18F-30-fluoro-30-deoxy-L-thymidine positron emission tomography (FLT-PET) was used to noninvasively measure effects of alisertib on in vivo tumor cell proliferation. Results:Alisertib inhibited AAK over ABKwith a selectivity ofmore than 200-fold in cells and produced a dose-dependent decrease in bipolar and aligned chromosomes in the HCT-116 xenograft model, a phenotype consistent with AAK inhibition. Alisertib inhibited proliferation of human tumor cell lines in vitro and produced tumor growth inhibition in solid tumor xenograft models and regressions in in vivo lymphomamodels. In addition, a dose of alisertib that caused tumor stasis, asmeasured by volume, resulted in a decrease in FLT uptake, suggesting that noninvasive imaging could provide value over traditional measurements of response. Conclusions:Alisertib is a selective andpotent inhibitor of AAK. Thenovelmethods ofmeasuringAurora A pathway inhibition and application of tumor imaging described here may be valuable for clinical evaluation of small-molecule inhibitors. Clin Cancer Res; 17(24); 7614–24. 2011 AACR.