The Discovery of Novel Potent <i>trans</i>-3,4-Disubstituted Pyrrolidine Inhibitors of the Human Aspartic Protease Renin from in Silico Three-Dimensional (3D) Pharmacophore Searches

The small-molecule <i>trans</i>-3,4-disubstituted pyrrolidine <b>6</b> was identified from in silico three-dimensional (3D) pharmacophore searches based on known X-ray structures of renin–inhibitor complexes and demonstrated to be a weakly active inhibitor of the human enzyme. The unexpected binding mode of the more potent enantiomer (3<i>S</i>,4<i>S</i>)-<b>6a</b> in an extended conformation spanning the nonprime and S1′ pockets of the recombinant human (rh)-renin active site was elucidated by X-ray crystallography. Initial structure–activity relationship work focused on modifications of the hydrophobic diphenylamine portion positioned in S1 and extending toward the S2 pocket. Replacement with an optimized P3–P1 pharmacophore interacting to the nonsubstrate S3^sp cavity eventually resulted in significantly improved in vitro potency and selectivity. The prototype analogue (3<i>S</i>,4<i>S</i>)-<b>12a</b> of this new class of direct renin inhibitors exerted blood pressure lowering effects in a hypertensive double-transgenic rat model after oral administration