Alternation of antiretroviral drug regimens for HIV infection. Efficacy, safety and tolerability at week 96 of the Swatch Study.

Methods: A total of 161 antiretroviral-naive HIV-1-infected patients were randomized to receive stavudine/didanosine/efavirenz (group A) or zidovudine/lamivudine/ nelfinavir (group B) or to alternate between the two regimens every 3 months starting with regimen A (group C). Antiviral efficacy, adherence, safety and tolerability were analysed every 12 weeks.

Results: After 96 weeks, time to virological failure was significantly delayed in the alternating regimen compared with the standards of care regimens. Virological suppression was seen in 46%, 48% and 58% of patients in groups A, B and C, respectively, in the intention-to-treat analysis and in 75%, 76% and 97% in the on-treatment analysis (A vs C: P=0.014; B vs C: P=0.016; A vs B: P=0.849). At the end of the study, 94% of patients in group A and 92% in groups B and C reported an adherence greater than 95%. Alternating therapy was associated with a similar impact on CD4+ counts in comparison with the standards of care regimens, as well as a lower mitochondrial DNA/nuclear DNA (mtDNA/nDNA) ratio decrease in the mitochondrial substudy performed on 37 patients. The frequency and intensity of adverse events in the alternating group decreased during subsequent cycles.

Conclusion: After 96 weeks, time to virological failure was significantly delayed in the alternating regimen compared with the standards of care regimens. Virological suppression was seen in 46%, 48% and 58% of patients in groups A, B and C, respectively, in the intention-to-treat analysis and in 75%, 76% and 97% in the on-treatment analysis (A vs C: P=0.014; B vs C: P=0.016; A vs B: P=0.849). At the end of the study, 94% of patients in group A and 92% in groups B and C reported an adherence greater than 95%. Alternating therapy was associated with a similar impact on CD4+ counts in comparison with the standards of care regimens, as well as a lower mitochondrial DNA/nuclear DNA (mtDNA/nDNA) ratio decrease in the mitochondrial substudy performed on 37 patients. The frequency and intensity of adverse events in the alternating group decreased during subsequent cycles.