Development of Small-molecule Inhibitors of Blood Coagulation Factor XIIa as Novel Anticoagulants

• Applicant: Dr. Dmitrii Kalinin
• Subject Area: Pharmacy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462465631

Thrombosis is a life-threatening pathology that is associated with myocardial infarction and ischemic stroke. The high thrombosis-related mortality rate underlines the need for the development of novel antithrombotic drugs. Currently available anticoagulants prevent blood coagulation by targeting the main enzymes of the common blood coagulation pathway (FIIa and FXa) causing thereby life-threatening hemorrhagic complications. Therefore, anticoagulants with new mechanisms of action are needed to prevent thrombosis without the risk of bleeding. In this respect, blood coagulation factor XIIa (FXIIa) a serine protease initiating the intrinsic coagulation pathway is a new promising target. Recent studies have proved a fundamental role of FXIIa in thrombosis but not in hemostasis suggesting that FXIIa inhibition might lead to an antithrombotic effect without the risk of bleeding. The aim of this project is the development of new potent and selective inhibitors of FXIIa with prominent anticoagulant properties. For this purpose, a rational drug design approach will be used exploiting structural features of the FXIIa active site. Particularly, to improve the inhibitory potency and the selectivity profile of the potential inhibitors, the main 1,2,4-triazol-5-amine scaffold will be extended in the directions of FXIIa substrate binding sites. Thus, to fully address the S2 pocket and also to target S1’ and S3-S4 pockets of the FXIIa active site, series 21, 26, 30, and 34 with enlarged substituents in 3-position of the triazole core will be synthesized. To target unoccupied S2’ pocket of FXIIa, the exocyclic amino moiety of 1,2,4-triazol-5-amine scaffold will be “extended” by appropriate substituents (synthesis of series 37 and 43). Also, to improve inhibitors’ residence time in the active site of FXIIa, series of lactams 46, 47, and 49 will be synthesized. In addition to the conventional syntheses, a microscale parallel synthetic approach will be used to access and screen libraries of new inhibitors. New compounds will be tested in enzyme inhibition assays for their inhibitory activity against FXIIa and other physiologically relevant serine proteases (FIIa, FXa, FXIa, plasmin, plasma kallikrein, and urokinase) and serine hydrolases (acetylcholinesterase, monoacylglycerol lipase, and fatty acid amide hydrolase). The mechanism of FXIIa inhibition by the synthesized compounds will be elucidated using MS analysis of the enzyme-inhibitor complexes. To prove the efficacy of new FXIIa inhibitors, their anticoagulant activity will be tested in vitro in aPTT and PT tests. Finally, the cytotoxicity profile, plasma stability, and important pharmacokinetic parameters of the FXIIa inhibitors will be studied.

• DFG Programme: Research Grants