Discovery of novel P2 substituted 4-biaryl proline inhibitors of hepatitis C virus NS3 serine protease.

Inhibitors of hepatitis C virus NS3 serine protease often incorporate a large P2 moiety to interact with the surface of the enzyme while shielding part of the catalytic triad. This feature is important in many inhibitors in order to have the necessary potency needed for efficacy. In this Letter we explore some new P2 motifs to further exploit this region of the enzyme. In a continuing effort to replace the often found 4-hydroxyproline P2 core found in the majority of inhibitors for this target, various directly attached aryl derivatives were evaluated. Of these, the 2,4-disubstituted thiazole core proved to be the most interesting. SAR around this motif has lead to compounds with Ki's in the high picomolar range and provided cellular potencies in the single digit nM range.

Nucleotide competing reverse transcriptase inhibitors: discovery of a series of non-basic benzofurano[3,2-d]pyrimidin-2-one derived inhibitors.

A HTS screen led to the identification of a benzofurano[3,2-d]pyrimidin-2-one core structure which upon further optimization resulted in 1 as a potent HIV-1 nucleotide competing reverse transcriptase inhibitor (NcRTI). Investigation of the SAR at N-1 allowed significant improvements in potency and when combined with the incorporation of heterocycles at C-8 resulted in potent analogues not requiring a basic amine to achieve antiviral activity. Additional modifications at N-1 resulted in 33 which demonstrated excellent antiviral potency and improved physicochemical properties.

Structural and biochemical studies of inhibitor binding to human cytomegalovirus protease.

Herpesvirus protease is required for the life cycle of the virus and is an attractive target for the design and development of new anti-herpes agents. The protease belongs to a new class of serine proteases, with a novel backbone fold and a unique Ser-His-His catalytic triad. Here we report the crystal structures of human cytomegalovirus protease in complex with two peptidomimetic inhibitors. The structures reveal a new hydrogen-bonding interaction between the main chain carbonyl of the P(5) residue and the main chain amide of amino acid 137 of the protease, which is important for the binding affinity of the inhibitor. Conformational flexibility was observed in the S(3) pocket of the enzyme, and this is supported by our characterization of several mutants in this pocket. One of the structures is at 2.5 A resolution, allowing us for the first time to locate ordered solvent molecules in the inhibitor complex. The presence of two solvent molecules in the active site may have implications for the design of new inhibitors against this enzyme. Favorable and stereospecific interactions have been established in the S(1)' pocket for one of these inhibitors.