SELECTION AND CHARACTERIZATION OF HIV STRAINS RESISTANT TO A NOVEL NONNUCLEOSIDE INHIBITOR OF ENTRY AND REVERSE TRANSCRIPTION

Abstract

With the number of HIV infections increasing worldwide, and with significant limitations in existing therapeutic strategies in light of drug toxicity and resistance, as well as the increasing percentage of de novo HIV infections now involving the transmission of drug resistant viruses, it is critically important to continue the development of new HIV chemotherapeutic agents. Antiviral efficacy and cellular toxicity are among the critical characteristics that must be defined when developing a new antiviral agent. In addition, the HIV drug development experience has taught us that the complete analysis of the ability of a compound to select for drug resistant strains of virus and the characterization of the mutations found in the selected resistant strains is of great importance. Viral resistance remains a major obstacle in developing agents for use in humans and presents a significant hurdle to defining appropriate combination therapies which will delay or prevent resistance upon introduction of drug selective pressure. Characterizing the resistance profile of a compound in vitro yields a great deal of information that will be required to help determine if a candidate compound will successfully transition from pre-clinical to clinical development. This project was designed to select and characterize viruses resistant to the novel anti-HIV agent SJ-3366 and to define the mutations in drug resistant strains that allow the resistant virus to replicate in the presence of the compound. The research performed effectively confirmed the dual mechanism of action of SJ-3366, determined the relative ease of selecting resistant strains to the compound, defined the genotypic and phenotypic properties of the resistant strains of virus and quantified the effects of specific and nonspecific mutations in the virus on virus replication and replication fitness. The results of these studies have demonstrated that resistance to SJ-3366 involves the accumulation of mutations in both reverse transcriptase and envelope and that the mutations result in a resistant virus with increased fitness in the absence of compound but decreased replication capacity and with a reduced ability to induce cytopathic effects in infected cells. These results serve to further define the antiviral properties of SJ-3366 and provide a rationale for the continued pre-clinical development of the compound.