Structure-activity relationships for macrocyclic peptidomimetic inhibitors of HIV-1 protease.

A rational approach to developing inhibitors of proteolytic enzymes is the systematic modification of their peptide substrates to proteolytically stable, low molecular weight, nonpeptidic inhibitors. Replacing the scissile amide bond with a noncleavable transition state isostere usually gives potent protease inhibitors, but the remaining hydrolysable amide bonds render the inhibitors unstable to peptidases generally. Attempts to replace them with retention of inhibitor potency has proved difficult(1,2) due to the unpredictable cooperative influences of such variations on the conformations of both neighbouring inhibitor groups and enzyme residues. We recently described a method(3) for regioselectively fixing the conformation of inhibitor components and now show effects on activity of varying both the 'free' and 'fixed' components.