Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 1, and they are poorly tolerated, highlighting the unmet medical need for new therapeutics. The HCV-encoded NS3 protease is essential for viral replication and has long been considered an attractive target for therapeutic intervention in HCV-infected patients. Here we identify a class of specific and potent NS3 protease inhibitors and report the evaluation of BILN 2061, a small molecule inhibitor biologically available through oral ingestion and the first of its class in human trials. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor. Our results further illustrate the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.

An assay recapitulating the 3′ processing activity of HIV-1 integrase (IN) was used to screen the Boehringer Ingelheim compound collection. Hit-to-lead and lead optimization beginning with compound 1 established the importance of the C3 and C4 substituent to antiviral potency against viruses with different aa124/ aa125 variants of IN. The importance of the C7 position on the serum shifted potency was established. Introduction of a quinoline substituent at the C4 position provided a balance of potency and metabolic stability. Combination of these findings ultimately led to the discovery of compound 26 (BI 224436), the first NCINI to advance into a phase Ia clinical trial.

The pharmaceutical industry has recognized that many drug-like molecules can self-aggregate in aqueous media and have physicochemical properties that skew experimental results and decisions. Herein, we introduce the use of a simple NMR strategy for detecting the formation of aggregates using dilution experiments that can be performed on equipment prevalent in most synthetic chemistry departments. We show that (1)H NMR resonances are sensitive to large molecular-size entities and to smaller multimers and mixtures of species. Practical details are provided for sample preparation and for determining the concentrations of single molecule, aggregate entities, and precipitate. The critical concentrations above which aggregation begins can be found and were corroborated by comparisons with light scattering techniques. Disaggregation can also be monitored using detergents. This NMR assay should serve as a practical and readily available tool for medicinal chemists to better characterize how their compounds behave in aqueous media and influence drug design decisions.

Human cytomegalovirus (hCMV), a herpesvirus, infects up to 70% of the general population in the United States and can cause morbidity and mortality in immunosuppressed individuals (organ-transplant recipients and AIDS patients) and congenitally infected newborns. hCMV protease is essential for the production of mature infectious virions, as it performs proteolytic processing near the carboxy terminus (M-site) of the viral assembly protein precursor. hCMV protease is a serine protease, although it has little homology to other clans of serine proteases. Here we report the crystal structure of hCMV protease at 2.0 angstroms resolution, and show that it possesses a new polypeptide backbone fold. Ser 132 and His 63 are found in close proximity in the active site, confirming earlier biochemical and mutagenesis studies. The structure suggests that the third member of the triad is probably His 157. A dimer of the protease with an extensive interface is found in the crystal structure. This structure information will help in the design and optimization of inhibitors against herpesvirus proteases.

CommunicationsPotent and selective macrocyclic inhibitors of the hepatitis C virus NS3 serine protease based on the conformation of a enzyme-bound substratelike hexapeptide demonstrate many of the desirable properties of a druglike archetype, which could lead to an antiviral agent for the treatment of hepatitis C in man. For more details see the following communication by Tsantrizos et al.