Dual inhibition of HCV and HIV by ring-expanded nucleosides containing the 5:7-fused imidazo[4,5-e][1,3]diazepine ring system. In vitro results and implications

Examples of ring-expanded nucleosides (RENs), represented by general structures 1 and 2, exhibited dual anti-HCV and anti-HIV activities in both cell culture systems and the respective target enzyme assays, including HCV NTPase/helicase and human RNA helicase DDX3. Since HCV is a leading co-infection in late stage HIV AIDS patients, often leading to liver cirrhosis and death, the observed dual inhibition of HCV and HIV by the target nucleoside analogues has potentially beneficial implications in treating HIV patients infected with HCV.

Peptidomimetic therapeutic agents targeting the protease enzyme of the human immunodeficiency virus and hepatitis C virus

During the past two decades, great strides have been made in the design of peptidomimetic drugs for the treatment of viral infections, despite the stigma of poor drug-like properties, low oral absorption, and high clearance associated with such compounds. This Account summarizes the progress made toward overcoming such liabilities and highlights the drug discovery efforts that have focused specifically on human immunodeficiency virus (HIV) and hepatitis C virus (HCV) protease inhibitors. The arsenal against the incurable disease AIDS, which is caused by HIV infection, includes peptidomimetic compounds that target the virally encoded aspartic protease enzyme. This enzyme is essential to the production of mature HIV particles and plays a key role in maintaining infectivity. However, because of the rapid genomic evolution of viruses, an inevitable consequence in the treatment of all viral infections is the emergence of resistance to the drugs. Therefore, the incomplete suppression of HIV in treatment-experienced AIDS patients will continue to drive the search for more effective therapeutic agents that exhibit efficacy against the mutants raised by the earlier generation of protease inhibitors. Currently, a number of substrate-based peptidomimetic agents that target the virally encoded HCV NS3/4A protease are in clinical development. Mechanistically, these inhibitors can be generally divided into activated carbonyls that are transition-state mimics or compounds that tap into the feedback mode of enzyme-product inhibition. In the HCV field, there is justified optimism that a number of these compounds will soon reach commercialization as therapeutic agents for the treatment of HCV infections. Structural research has guided the successful design of both HIV and HCV protease inhibitors. X-ray crystallography, NMR, and computational studies have provided valuable insight in to the free-state preorganization of peptidomimetic ligands and their enzyme-bound conformation. Researchers have designed a variety of novel bioisosteric replacements of amino acids and short peptides that contain all of the required pharmacophore moieties and play a key role in inducing conformational changes to the overall molecule. The knowledge gained from these studies will undoubtedly guide the future design of therapeutic agents and further contribute to the success of this field.