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Objectives: To evaluate the risk of virologic failure conferred by suboptimal adherence to nonnucleoside reverse transcriptase inhibitors (NNRTIs) and minority NNRTI resistance mutations., Design: Pooled analysis of the risk of virologic failure conferred by minority NNRTI resistance mutations and NNRTI adherence from three studies of treatment-naïve individuals initiating an NNRTI-based regimen., Methods: Participants from each study were categorized into both adherence quartiles (Q1-Q4) and four strata: at least 95%, 80-94%, 60-79%, and below 60%. Weighted Cox proportional hazard models were used to estimate the risk of virologic failure., Results: The majority of participants (N = 768) had high measured adherence, but those in the lowest adherence quartile had the highest proportion of participants with virologic failure and the risk of virologic failure increased step-wise with adherence below 95%. Detection of minority NNRTI drug resistance mutations increased the proportion of participants with virologic failure across adherence quartiles (Cochran-Mantel-Haenszel P < 0.001) and adherence strata [Cochran-Mantel-Haenszel P < 0.001; <60% adherence, hazard ratio 1.7 (1.1-2.7), P = 0.02; 60-79% adherence, hazard ratio 1.2 (0.5-3.2), P = 0.67; 80-94% adherence, hazard ratio 2.5 (0.98-6.3), P = 0.06; ≥95% adherence, hazard ratio 3.6 (2.3-5.6), P < 0.001]. On multivariate analysis, the effect of minority variants was also most prominent at higher levels of medication adherence., Conclusions: The presence of minority NNRTI resistance mutations and NNRTI adherence were found to be independent predictors of virologic failure, but also modify each other's effects on virologic failure. In addition to the focus on medication adherence counseling, ultrasensitive HIV-1 drug resistance assays could play a role in optimizing the success rates of first-line antiretroviral therapy.

Objective: To assess the association between adherence to antiretroviral therapy and the presence of class-specific antiretroviral medication resistance., Design: Secondary analysis of prospective clinical trial data., Methods: Participants randomized to the protease inhibitor or nonnucleoside reverse transcriptase inhibitor (NNRTI) strategies of the Community Programs for Clinical Research on AIDS (CPCRA) Flexible Initial Retrovirus Suppressive Therapies (FIRST) Study were included. Adherence was measured by 7-day self-report. Virological failure was defined as an HIV-RNA more than 1000 at or after 4 months. The association between cumulative adherence and the development of class-specific genotypic resistance was assessed by Cox regression analysis., Results: Included were 457 and 446 antiretroviral-naive participants on the protease inhibitor and NNRTI strategies, respectively. The median time to initial virological failure in the protease inhibitor strategy was 1.2 years; 135 (30%) individuals failed with resistance. The median time to initial virological failure in the NNRTI strategy was 3.0 years; 127 (28%) failed with resistance. No association was found between cumulative adherence and protease inhibitor resistance [hazard ratio 1.1, 95% confidence interval (CI) 0.9-1.4 per 10% lower adherence]. However, lower cumulative adherence was associated with an increased risk of NNRTI resistance at initial virological failure (hazard ratio 1.2, 95% CI 1.1-1.3 per 10% lower adherence). In both strategies, lower cumulative adherence was associated with an increased risk of nucleoside reverse transcriptase inhibitor (NRTI) resistance at initial virological failure., Conclusion: Adherence-resistance relationships are class-specific. For NRTIs and NNRTIs, initial virological failure with resistance is more likely at lower levels of cumulative adherence.