Abstract 3600: Preclinical pharmacokinetic and biomarker analysis of AMG 900, an orally available small molecule inhibitor of aurora kinases, in human xenograft tumor and surrogate tissues
Authors: Ziegler Beth , Juan Gloria , Chung Grace , Manoukian Raffi , Huang Liyue , Lin Min-Hwa Jasmine , Ma Connie , Zoog Stephen , Geuns-Meyer Stephanie , Kendall Richard , Radinsky Robert , Friberg Greg , Payton Marc , Bush Tammy L. 
Published: February 2011

Background: The aurora family of serine-threonine kinases (Aurora-A, -B, -C) regulate cell-cycle progression in mammalian cells. Aurora kinases A and B are essential for proper chromosome congression, segregation, and cytokinesis during mitosis, whereas aurora kinase C function appears restricted to male meiosis. Aurora kinase B is responsible for the direct phosphorylation of histone H3 on serine-10 (p-histone H3). Aurora kinase A and B expression is elevated in a variety of human cancers and is associated with advanced clinical staging and poor prognosis. With the emergence of aurora kinases as key mitotic regulators and their potential role in tumorigenesis, we developed AMG 900, a novel ATP competitive small molecule inhibitor, that is highly potent and selective for aurora kinases A, B, and C. In vivo, AMG 900 inhibits the growth of multiple human tumor xenografts, including multidrug-resistant models.

Objective: The aim of this study was to establish a pharmacokinetic-pharmacodynamic (PK-PD) relationship for AMG 900 in human tumor xenografts and surrogate tissues.

Results: In nude mice, oral administration of AMG 900 inhibited p-histone H3 in tumors and bone marrow in a concentration- and dose-dependent manner. To further refine the AMG 900 PK-PD relationship, p-histone H3 IC50 values for bone marrow and dissociated COLO 205 tumors from mice were associated with plasma concentrations of 294 and 273 ng/mL, respectively. The duration of target coverage required for anti-tumor efficacy was determined to be &gt; 6 hours per day above the in vivo p-histone H3 IC50 using different dosing schedules. To explore whether skin could be a suitable surrogate tissue for measuring p-histone H3 inhibition, tumor-bearing mice were administered AMG 900 at 3.75, 7.5, and 15 mg/kg for 3 hours. Significant suppression of p-histone H3 in skin was only observed at 15 mg/kg (p &lt; 0.0001), whereas in tumor, a dose-dependent inhibition was achieved at all doses (p &lt; 0.0015). To determine the feasibility of measuring p-histone H3 using fine-needle aspirate (FNA) tumor biopsies, tumor-bearing mice were administered AMG 900 at 15 mg/kg for 3 hours. Treatment with AMG 900 significantly inhibited p-histone H3 (&gt; 99%, p &lt; 0.0001) in COLO 205 tumors, suggesting that FNA biopsies may be a viable approach for assessing AMG 900 PD effects in the clinic.

Conclusion: These studies demonstrate that AMG 900 inhibits p-histone H3 in tumors and surrogate tissues, although tissues such as skin may be less sensitive to assess PD effects. The use of p-histone H3 as a biomarker to determine plasma levels of AMG 900 required to inhibit aurora B activity may be useful in clinical studies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3600.