DEVELOPMENT OF PSEUDOPEPTIDE INHIBITORS OF HIV-1 ASPARTIC PROTEASE - ANALYSIS AND TUNING OF THE SUBSITE SPECIFICITY

HIV-1 aspartic protease (PR) is a promising target for acquired immuno deficiency syndrome (AIDS) therapy and the development of PR inhibitor s can be accelerated by computer-aided design methods. We describe an approach for the design of new inhibitors, based on the modification o f a known reference inhibitor, and the calculation of relative binding energies, taking into account contributions from all species in the b inding equilibrium (inhibitor PR and inhibitor/PR complex), as well as their solvation. This allows for a rational selection of new structur es that are likely to have increased inhibition potency. We have analy zed reduced amide bond hexapeptides (Ac-P-3-P-2-P-1-Psi[CH2-NH]-P-1'-P -2-P-3'-NH2), based on the structure of the known inhibitor MVT-101. A maximum gain in binding energy (approximate to -55 kcal/mol) is obser ved when Phe or Tyr are present in positions P-1 and P-1', Glu in posi tion P-2' and aromatic residues (Phe, Trp or Tyr) in positions P-3 and P-3', while, in general, the presence of positively charged residues is destabilizing. This specificity is explained in terms of the intera ction of individual inhibitor residues with proximal and distal PR res idues. The validity of this computational approach has been confirmed by solid-phase synthesis of several of the designed pseudopeptides, fo llowed by in vitro enzyme inhibition assaying. The best candidate stru ctures show IC50 values in the low nanomolar range.