Inhibitor discovery against blood coagulation factor Xa and Bacillus anthracis protective antigen

The blood coagulation cascade is an important protective mechanism against blood loss. The serine protease domain of Factor Xa is one of the most effective targets in developing direct anticoagulants for the coagulation disorder since it covers both intrinsic and extrinsic pathways. We have developed a systematic characterization of several building blocks in the development of various FXa inhibitors by enzyme kinetics and inhibition assays. Comparison of the isosteric AMSO and AMPA indicated that placement of an anionic group within the oxyanion hole substantially enhances inhibitory activity. The small hydroxyl group is a more effective substituent for placement in the oxyanion hole region than the somewhat bulkier and highly acidic phosphinic acid group. New azaindole inhibitor did not show better inhibition than BABCH derivatives, but Biarylamine gained a 3 fold increase in selectivity for FXa over trypsin.;Bacillus anthracis, the causative agent for anthrax secretes protective antigen (PA), lethal factor (LF), edema factor (EF) within the host system. Anthrax-toxins (complex PA-LF and complex PA-EF) work synergistically to destroy the host's immune system and alter intercellular signal transduction pathways, ultimately leading to death of the host. We can avoid problems of multiple receptors in the host by targeting non-human protein. Thus the disruption of interaction between PA and anthrax toxin receptor is an attractive drug target by non-covalent, small organic compounds. We utilized NMR to screen anti PA molecules and to get structural information of PA domain 4. We identified 50 compounds binding to PA domain 4. Those compounds were evaluated by cytotoxicity assay and blocking assay (Lethal toxin induced macrophage toxicity) on human MHS cells.