Structural basis for the selective inhibition of activated thrombin-activatable fibrinolysis inhibitor (TAFIa) by a selenium-containing inhibitor with chloro-aminopyridine as a basic group.

Activated thrombin-activatable fibrinolysis inhibitor (TAFIa) is a target molecule for treating thromboembolic disorders. We previously reported that design and synthesis of compound 1 containing a selenol group and chloloaminopyridine. Compound 1 showed high inhibitory activity towards TAFIa, with a high degree of selectivity for TAFIa over carboxypeptidase N (CPN). Here we report investigation of this selectivity. To obtain co-crystal of 1/pp-CPB (a surrogate of TAFIa), we synthesized protected compound 5 as a stabilized precursor of 1. The X-ray crystal structure and docking study indicated that the Cl substituent is accommodated in the pp-CPB specific pocket whereas CPN has no identical pocket. This is important information for the design of drugs targeting TAFIa with high selectivity.