ABSTRACT
OBJECTIVES: To evaluate the effects of sex and initial antiretroviral regimen on decay of HIV-RNA and virologic outcome. METHODS: We conducted a viral dynamics substudy of A5142, a trial comparing lopinavir (LPV)/ritonavir with efavirenz (LPV/EFV) versus LPV and two nucleoside reverse transcriptase inhibitor (NRTI) (LPV) versus EFV and two NRTI (EFV) in antiretroviral (ARV)-naive individuals. HIV-RNA was measured at days 2, 10, and 14 in the substudy and at weeks 1, 4, and 8 in A5142 participants. Two-phase viral decay was estimated in the substudy with biexponential mixed-effects modeling and compared using Wilcoxon tests. Week 1 HIV-RNA change was assessed as a predictor of virologic failure (HIV-RNA above 50 or 200â copies/ml) at weeks 24-96 using logistic regression. RESULTS: Sixty-eight individuals were enrolled in the substudy (median HIV-RNA 4.9 log(10) âcopies/ml). Median rates of phase 1 viral decay by treatment were 0.61(EFV/LPV), 0.53(LPV), and 0.63(EFV) per day. Phase 1 decay was significantly faster for EFV than LPV (Pâ=â0.023); other comparisons were not significant (Pâ>â0.11). Viral decay did not differ by sex (Pâ=â0.10). Week 1 HIV-RNA change, calculated in 571 participants of A5142, was greater for the EFV (median -1.47 log(10) âcopies/ml) than either the LPV/EFV or LPV groups (-1.21 and -1.16 log(10â) copies/ml, respectively; Pâ<â0.001). Week 1 HIV-RNA change was associated with virologic failure above 50 âcopies/âml at weeks 24 and 48 (Pâ<â0.018), but not above 200â copies/ml at these time points or for any value at week 96. CONCLUSION: Phase 1 decay was faster for EFV than LPV or LPV/EFV. Week 1 HIV-RNA change predicted virologic outcome up to week 48, but not at week 96.