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5th International Workshop on HIV Drug Resistance & Treatment Strategies4-8 June 2001, Scottsdale, Arizona |
OBJECTIVES: Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are highly selective inhibitors of HIV-1 that have shown potential in protease inhibitorsparing antiretroviral regimens. Their use is limited, however, by the rapid emergence of NNRTI (cross-) resistance. Recently we have described two molecules, TMC120 (R147681) and TMC125 (R165335) with potent activity against wild-type and NNRTI-resistant HIV-1 strains. We wished to compare the rates of resistance emergence between these compounds and the first generation NNRTIs nevirapine and efavirenz.
METHODS: In vitro selection experiments were conducted using high multiplicity of infection (MOI) to maximize the genetic diversity of the virus population. CD4+ cell cultures, infected at high MOI (≥1 CCID50/cell) with wild-type HIV-1 in the presence of various concentrations of the inhibitors (40, 200, 1000 and 5000 times the EC50), were monitored twice a week for virus replication. Emerging virus was collected for pheno- and genotyping. Cultures without evidence of virus replication were further sub-cultivated in the presence of the same concentration of inhibitor for a total duration of 30 days (10 passages).
RESULTS: Resistance to nevirapine emerged within 3–6 days, at all tested concentrations. Breakthrough virus harboured the typical Y181C mutation. The same experiments with efavirenz resulted in the selection of the G190E variant at all tested concentrations (up to 5 μM) within 3–7 days. TMC120 selected for the Y181C + Y188L variant after 10 days at 200 nM and, in one case, for the G190E mutant after 10 days at 1 μM. In other cases, no virus replication could be observed within 30 days in the presence of 1 μ M TMC120. At 200 nM, TMC125 selected for the L100I + Y181C variant after 21 days. No sign of virus breakthrough could be observed at 1 μM within 30 days.
CONCLUSION: In this experimental setting, characterized by high genetic diversity of the virus population, HIV-1 resistant to first generation NNRTIs (nevirapine and efavirenz) was selected very rapidly. Emerging resistant viruses harboured only one mutation. In contrast, emergence of HIV-1 resistant to TMC120 or TMC125 was delayed or did not occur, and usually required the presence of two mutations. Similar experiments with NNRTI-resistant strains are ongoing.
PRESENTING AUTHOR: M-P de Béthune
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