Abstract 3609: Homology structure-based design, synthesis and biological evaluation of a series of novel Axl and Mer kinase inhibitors

Abstract

Abstract Axl and Mer kinases belong to the TAM family that was first identified as a transforming gene in chronic myeloid leukemia. Its intracellular region has the typical receptor tyrosine kinase (RTK) structure and its extracellular domain is similar to cadherin-type adhesion molecules in that it is composed of fibronectin type II and immunoglobulin (Ig) motifs. Axl binds various growth factors, with vitamin K-dependent protein growth-arrest-specific gene 6 (GAS6) being the best studied. Axl is involved in mesenchymal and neuronal development as well as in cell survival, adhesion and blood vessel function. High levels of Axl are found in various tumors, including malignant glioma and metastatic colon, ovarian and breast cancers, and it plays a role in cancer invasion. Recent development of Axl inhibitors suggested that inhibition of Axl activity may be impact both tumor angiogenesis and tumor growth. We describe here the design, synthesis, molecular modeling, and biological evaluation of a series of small molecule, inhibitors of Axl and Mer kinases. Our initial lead compound was identified via cross-docking experiments utilizing the homology model of Axl kinase and screening of a diverse in-house chemical library. We subsequently carried out structure-activity relationship studies and optimized the lead structure which has 2 to 6.1 μM inhibition activity to 2-fold improvement in the Axl and Mer kinase activities to 730 nM. As a starting point for further optimization, it was considered that the modest of these series could be improved by introducing a spacer at the aryl piperazine moiety and focused on maximizing the in vitro potency, addressing the SAR and molecular properties. We further explored Leu620, hydrophobic, Gly543, Phe547 and DFG motif sites through scaffold hoping lead to the identification of an electron-withdrawing functional groups lead to the compound HCI-2084 and HCI-2091 which exhibited potent Axl kinase inhibition activity of 7 and 12 nM in Axl kinase assay and 30-50 nM is panel of cancer cell lines. These novel series of compounds were synthesized in two-step procedure via a standard cross-coupling reaction or with various substituted aryl amine derivatives under amination conditions. In a subsequent step we employed Buchwald-Hartwig amination reaction to prepare target molecules. Due to the ready synthesis accessibility, we extensively investigated the SAR improving the RO5, solubility and permeability parameters. The details of these results will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3609. doi:10.1158/1538-7445.AM2011-3609