Structure-Based Design of Macrocyclic Factor XIa Inhibitors: Discovery of the Macrocyclic Amide Linker

A novel series of macrocyclic FXIa inhibitors was designed based on our lead acyclic phenyl imidazole chemotype. Our initial macrocycles, which were double-digit nanomolar FXIa inhibitors, were further optimized with assistance from utilization of structure-based drug design and ligand bound X-ray crystal structures. This effort resulted in the discovery of a macrocyclic amide linker which was found to form a key hydrogen bond with the carbonyl of Leu41 in the FXIa active site, resulting in potent FXIa inhibitors. The macrocyclic FXIa series, exemplified by compound 16, had a FXIa K_i = 0.16 nM with potent anticoagulant activity in an in vitro clotting assay (aPTT EC_1.5x = 0.27 μM) and excellent selectivity against the relevant blood coagulation enzymes.