Abstract 2788: Design, optimization, and biological evaluation of potent irreversible inhibitors of BTK kinase

Abstract

Abstract Bruton's tyrosine kinase (BTK) is a cytoplasmic nonreceptor tyrosine kinase belonging to the Tec family of kinases. Critical for its function, BTK contains a pleckstrin homology (PH) domain and Src homology SH3 and SH2 domains. It signals downstream of the B-cell receptor (BCR) and is centrally involved in B-cell development. Activation of B-cells by various ligands is accompanied by the translocation of BTK to the cell membrane where it binds phosphatidylinositol-3,4,5-trisphosphate through its PH domain. Activation of BTK results in downstream signaling through the PI3K/AKT, PLCγ, NFκB, and other signaling pathways important for B-cell development and function. Recent reports have shown the aberrant expression and function of BTK in some cancers, including B-cell malignancies. We describe here the design, synthesis, molecular modeling, and biological evaluation of a series of small molecule, inhibitors of BTK kinase. Our initial lead compounds were identified via cross-docking experiments utilizing the crystal structure of BTK kinase and screening a previously in-house explored kinase inhibitor scaffold. We subsequently carried out structure-activity relationship studies and optimized the lead structures, which have IC50 activities in the range of 1 to 10μM against BTK. A critical step in the optimization of this chemical series against BTK was to explore the possibility of adding a Michael's acceptor group to react with Cys481 in the ATP-binding pocket of BTK. Optimization efforts yielded the currently best leads, HCI-1684 and HCI-1685, which inhibit BTK with IC50 values of 12 and 45 nM, respectively. Modeling data suggest these compounds irrepressibly bind in the ATP-binding pocket of BTK. HCI-1684, HCI-1685 and other lead compounds were further evaluated in cell-based assays and were demonstrated to inhibit BTK function downstream of BCR activation. This series of BTK inhibitors were shown to decrease phospho-PLCγ1/2 levels and other downstream phosphorylation events in malignant B-cell cell lines, such as Ramos B. Compound optimization and biological evaluation of this chemical series and evaluation in animal pharmacodynamic endpoint studies will be presented. Taken together, these results suggest BTK is a potential therapeutic target in cancer and that HCI-1684 is an exciting agent to potentially treat B-cell malignancies 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 2788. doi:10.1158/1538-7445.AM2011-2788