A randomized comparative trial of continued zidovudine/lamivudine or replacement with tenofovir disoproxil fumarate/emtricitabine in efavirenz-treated HIV-1-infected individuals.

Background: Long-term antiretroviral therapy dramatically reduces HIV-related morbidity and mortality but is also associated with metabolic and morphological changes and requires high levels of adherence.

Methods: A randomized, 48-week, open-label, comparative study of continuation of twice-daily zidovudine/lamivudine or replacement with once-daily tenofovir disoproxil fumarate/emtricitabine in individuals on successful efavirenz-based antiretroviral therapy. Limb fat mass was assessed by dual x-ray absorptiometry in a subset of participants through week 48.

Results: Two hundred thirty-four individuals were randomized and treated (117 each to continue or switch) with 206 subjects completing 48 weeks of study. Five percent subjects in the continue group and 3% subjects in the switch group discontinued due to adverse events. By intent-to-treat, missing = failure analysis, no differences in virological efficacy were observed at any time point (week 48 <50 copies/mL continue 85%, switch 88%). At week 24, switching was associated with significant increases in hemoglobin (mean difference 0.37 g/dL, 95% confidence interval: 0.15 to 0.58 g/dL, P < 0.001) and significant declines in total cholesterol and triglycerides. In the dual x-ray absorptiometry substudy (n = 100), fat was preserved or increased in the switch group but declined in the continue group (mean difference 448 g, 95% confidence interval: 57 to 839 g, P = 0.025). Individuals with longer exposure to zidovudine and lower baseline limb fat experienced less limb fat increase after switching. No differences in renal adverse events were observed between groups.

Conclusions: Switching from zidovudine/lamivudine to tenofovir disoproxil fumarate/emtricitabine in persons on efavirenz therapy maintains virological control, establishes a once-daily regimen, results in improvements in hemoglobin and key lipid parameters, and preserves and restores limb fat relative to continuation of zidovudine/lamivudine.