Pyrazinyl-Substituted Aminoazoles as Covalent Inhibitors of Thrombin: Synthesis, Structure, and Anticoagulant Properties

This study presents a novel series
of N-acylated
1,2,4-triazol-5-amines and 1H-pyrazol-5-amines, featuring
a pyrazin-2-yl moiety, developed as covalent inhibitors of thrombin.
These compounds demonstrated potent inhibitory activity, with derivatives 13a and 13b achieving IC50 values
as low as 0.7 and 0.8 nM, respectively. Mass-shift assays confirmed
that these inhibitors covalently bind to the catalytic Ser195 of thrombin,
leading to temporary inhibition of its activity through specific acylation.
The anticoagulant efficacy of these compounds was validated in plasma
coagulation assays, with selected derivatives extending coagulation
times in both an activated partial thromboplastin time (aPTT) and
prothrombin time (PT) test. Thrombin generation assays further demonstrated
that compounds of this series effectively reduced thrombin generation
without substantially prolonging clotting times, suggesting a lower
risk of bleeding. Selected compounds also strongly inhibited cancer
cell- and thrombin-induced platelet aggregation. These results indicate
that acylated aminoazoles hold a promise as new anticoagulants.