Novel Glycoprotein VI Antagonists as Antithrombotics: Synthesis, Biological Evaluation, and Molecular Modeling Studies on 2,3-Disubstituted Tetrahydropyrido(3,4-b)indoles

The development of small molecule inhibitors targeting GPVI has promising therapeutic role, as they inhibit arterial thrombosis with limited risk of bleeding. Among the compounds showing in vivo antithrombotic activity, the most active compound 6b (ED50 = 28.36 mu mol/kg po in mice) showed improved inhibition for collagen (IC50 = 6.7 mu M), CRP-XL (IC50 = 53.5 mu M), and convuban (CVX) (IC50 = 5.7 /./M) mediated platelet aggregation as compared to losartan (LOS) (collagen, IC50 = 10.4 mu M; CRP-XL, IC50 = 158 /2M; CVX, IC50 = 11 1.4M) than any of its enantiomers S (6c) (collagen, IC50 = 25.3 mu M; CRP-XL, IC50 = 181.4 mu M; CVX, IC50 = 9 mu M) and R (6d) (collagen, IC50 = 126.3 mu M; CRP-XL, IC50 > 500 mu M, IC50 = 86.8 mu M). Compound 6b also inhibited platelet P-selectin expression and thus may diminish atherosclerosis. The molecular interactions of both enantiomers 6c and 6d at the GPVI receptor have been explained through docking studies.