Study to Evaluate Changes in CD4 on Replacing TDF With ABC or DDI+TDF With ABC+3TC

• Proportion of patients that increase their number of CD4 lymphocytes with regard to the baseline. [ Time Frame: At 12, 24, 36 and 48 weeks ] [ Designated as safety issue: No ]
  

• To evaluate the proportion of patients with viral load of HIV-1 <50 copies of the combinations studied during the follow-up period. [ Time Frame: At 12, 24, 36 and 48 weeks. ] [ Designated as safety issue: Yes ]
  
• Incidence of new clinical adverse events that appear . [ Time Frame: during 48 weeks of follow-up ] [ Designated as safety issue: Yes ]
  
• Evolution of the clinical adverse events that were already present at the time they were included in the study. [ Time Frame: during the 48 weeks of follow-up ] [ Designated as safety issue: Yes ]
  
• Rate of treatment drop-outs due to the appearance of adverse events [ Time Frame: during the 48 weeks of follow-up ] [ Designated as safety issue: Yes ]
  
• Incidence of new laboratory alterations that appear during the follow-up period (change in renal parameters, changes in lactate levels, modification of pancreatic enzymes, changes in lipid parameters). [ Time Frame: during the follow-up period ] [ Designated as safety issue: Yes ]
  
• Evolution of the laboratory alterations that were already present at the time they were included in the study. [ Time Frame: during the 48 weeks of follow-up ] [ Designated as safety issue: Yes ]
  

Different works have shown a high rate of virological failure among patients on abacavir + lamivudine + tenofovir or ddI + 3TC + tenofovir, thus rendering the use of these combinations actively unadvisable.

Furthermore, recent studies have also shown that ABC+3TC are associated with a significantly higher increase in CD4 than the current treatment standard formed by AZT+3TC. This provides us with grounds to suppose that patients with TDF+ddI may recover their CD4 with ABC+3HT. Similarly, and recently, the existence of pharmacokinetic interactions between tenofovir + abacavir has begun to be questioned.

Finally, the replacement of tenofovir with abacavir or tenofovir + ddI with abacavir + lamivudine does not detract from the potency of HAART, the toxicity profile is different and their behaviour at mitochondrial level is similar.

This study aims to ascertain whether the sole replacement of tenofovir with abacavir once a day improves the immunological response obtained with tenofovir + ddI or whether it is better to perform a double replacement of tenofovir and ddI with abacavir + lamivudine (joint formulation) in a single daily dose to achieve these objectives.