Overall, 180 additional NNRTI mutations were found to have accumulated over 295 years [1 new/1.6 years; 95% confidence interval (CI) 1.5–1.8]. The rate of accumulation was faster ICG-001 cell line in the first 6 months from VF (1 new/1.1 years), and slower in patients exposed to nevirapine vs. those receiving efavirenz [relative risk (RR) 0.66; 95% CI 0.46–0.95; P=0.03]. There is an initial phase of rapid accumulation of NNRTI mutations close to the time of VF followed by a phase of slower accumulation. We predict that it should take approximately one year of exposure to a virologically failing first-generation NNRTI-based cART regimen to reduce

etravirine activity from fully susceptible to intermediate resistant, and possibly longer in patients kept on a failing nevirapine-containing regimen. Global access to antiretroviral drugs has increased dramatically in recent years [1], and concerns regarding the development of drug resistance remain in both resource-rich and resource-limited settings [2,3]. In resource-limited settings, NNRTIs are a fixed component of first-line combination antiretroviral therapy (cART) [3], but HIV-infected populations typically have little access to virological

monitoring and/or genotypic resistance testing, which is likely to result in the accumulation of NNRTI resistance. An improved access to NNRTI drugs for preventing APO866 price mother-to-child transmission has further complicated this issue. A previous analysis of patients in EuroSIDA focused on the estimation of the rate of accumulation of thymidine analogue mutations (TAMs) in patients kept on zidovudine or stavudine despite

Cytidine deaminase a viral load of >500 HIV-1 RNA copies/mL [4,5]. NNRTI resistance accumulation could compromise the efficacy of second-generation NNRTIs (e.g. etravirine [6]) if they ever become available in these settings. Indeed, etravirine has already been used in some resource-limited settings as a component of second-line regimens in patients who could not tolerate protease inhibitors (PIs) [7]. Data on etravirine resistance in patients already exposed to first-generation NNRTIs show that, among 17 mutations in the reverse transcriptase gene, at least three must be present simultaneously in order to reduce etravirine activity, although just two mutations can greatly decrease susceptibility in some cases [7–9]. In addition, this activity is likely to diminish to zero as NNRTI-associated resistance mutations further accumulate. Our analysis is based on data for patients enrolled in clinics in Europe. However, while there are differences in the prevalence of HIV subtypes, some infections and in access to health care between resource-rich and resource-limited settings, there is otherwise generally little evidence of differences between these settings in the damage caused by HIV or the effect of ART [10–12].