15th International HIV Drug Resistance Workshop 13-17 June 2006, Sitges, Spain

THE PATHWAY LEADING TO TMC114 RESISTANCE IS DIFFERENT FOR TMC114 COMPARED WITH OTHER PROTEASE INHIBITORS

Antivir Ther. 2006, 11:S24 (abstract no. 19)

S De Meyer, H Azijn, E Fransen, I De Baere, M Van Ginderen, B Maes and M-P de Béthune
Tibotec BVBA, Mechelen, Belgium

BACKGROUND: TMC-114 (darunavir), a novel HIV protease inhibitor (PI), is active against wild-type (WT) and PI-resistant HIV-1. In-vitro selection experiments from WT HIV-1 were conducted in order to characterize the pathway leading to resistance to TMC-114.

METHODS: HIV-1-infected MT4 cells were exposed to increasing concentrations of TMC-114 and other PIs, to select for viruses able to replicate at high PI concentrations. Phenotypes and genotypes of selected HIV populations were determined by the Antivirogram® and virco®TYPE assays, respectively. Site-directed mutants (SDM) were constructed using the Medigenomix™ proprietary technology.

RESULTS: Data already presented has shown that 75 passages (260 days) of HIV-1/IIIB in the presence of increasing concentrations of up to 200nM TMC-114 resulted in virus populations with the protease mutations R41T and K70E. These viruses showed resistance to TMC-114 (fold change in EC₅₀ [FC] ~10), but replicated poorly. Moreover, SDM strains with these two mutations were not resistant to TMC-114. The study has now been extended to 327 passages (1,155 days), and selected viruses have shown TMC-114 FC >10. Virus populations did not grow at TMC-114 concentrations exceeding 350nM. The H69Q and V77I mutations also accumulated in the protease. Eight mutations in the gag gene, both inside and outside the cleavage sites, were also observed. Recombinant viruses encompassing the protease and reverse transcriptase of the selected viruses remained susceptible to TMC-114 (FC<1). Recombinant viruses encompassing gag and protease of the selected viruses had TMC-114 FC values between 1 and 10 (further SDM strains with the mutations in the gag gene are currently being constructed). Experiments conducted with other WT HIV-1 strains produced comparable results. In contrast, experiments conducted with other PIs resulted in a more rapid selection of virus populations able to grow at high micromolar PI concentrations; these viruses contained typical PI resistance-associated mutations.

CONCLUSIONS: Selection of TMC-114-resistant HIV-1 from WT strains is slower and more difficult than for other PIs. Characterization of the selected viruses showed that resistance to TMC-114 occurs through a different pathway compared with other PIs.

2006-06-13
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