Chapter 13. Advances in the Development of HIV Reverse Transcriptase Inhibitors

Abstract

Approximately 13 million people worldwide have been infected with human immunodeficiency virus (HIV). The delineation of the lifecycle of HIV has shown that the virus requires the catalytic activity of many unique enzymes, thereby providing attractive targets for therapeutic intervention. Researchers have most actively targeted the inhibition of the enzymes reverse transcriptase (RT) and protease. RT is a heterodimeric enzyme comprised of two polypeptides of 51-kDa and 66-kDa. These peptides have an identical N-terminus and the smaller p51 peptide is derived, from the larger p66 peptide, via proteolytic cleavage. The multi-purpose enzyme has three distinct catalytic functions, such as, an RNA-dependent DNA polymerase activity, an RNAse H activity that degrades the RNA template to make way for the final function, a DNA-dependent DNA polymerase activity. HIV infection is a chronic process that involves high rates of viral replication and employs the highly error prone enzyme HIV R. Three-dimensional structural studies of HIV-1 RT have provided an enhanced understanding of the structure–function relationships and aid in future drug design. Resistance to azidothymidine (AZT) contributes to the loss of efficacy of AZT during the timecourse of treatment and such AZT resistant HIV-1 is virulent enough to contribute to the disease progression. The differential anti-viral activity of the enantiorners of FTC happens, because of the differences in cellular metabolism, not inherent differences in the RT inhibitory activity.