NOVEL GLUCOSE-CONJUGATED HIGHLY POTENT DUAL THROMBIN AND FACTOR Xa INHIBITORS AS POTENTIAL ANTITHROMBOTICS

Novel O-glucosides of the recently reported potent factor Xa (fXa) inhibitors,[1] which bear 5- chlorothien-2-yl moiety and 1-isopropylpiperidine as the fragments binding the S1 and S4 enzyme pockets, respectively, were synthesized. In particular, β-D-glucose was conjugated through an ether-linked C3-alkyl spacer to the central phenyl ring of the most potent inhibitor, providing a β-D-glucosyl derivative which showed picomolar inhibition potency against human fXa (Ki = 60 pM), nanomolar potency against thrombin (fIIa, Ki = 60 nM) and high selectivity over a panel of other serine proteases, including trypsin and leukocyte elastase, as well as in vitro sub-micromolar anticoagulant activity in the prothrombin time (PT) clotting assay and a statistically significant 1.6-fold prolongation of the basal PT in an ex vivo assay in mice. The crystal structures of human thrombin in complex with two highly potent glucose-based compounds were solved, which provided us with useful information on the binding modes of these inhibitors. While as expected from previous studies[2] the chlorothiophene group binds in the S1 pocket and the N1-isopropylpiperidine group in the S4 region, the sugar moiety binds in a protein region hitherto unexploited by small-molecule direct fIIa inhibitors, which is located near the S4 subsite, where the glucose O2 form strong H-bonds with two basic residues, i.e., Arg221A and Lys224