About The Study

This study aimed to determine whether a 12-week structured treatment interruption (STI) before a switch to a salvage HAART regimen is beneficial. The study compared the percentage of participants from each study group (the STI group and the immediate switch [IS] group) whose viral load dropped below 50 copies/ml after the start of salvage therapy and remained at this level for at least three months.

Study Approach

This was a randomized, open-label, multicentre trial with a target enrollment of 196. At the time participants entered the study, they were experiencing virologic failure (i.e., they had a viral load greater than 1,000 copies/ml) on a HAART regimen and required a switch in antiretroviral therapy. As well, based on their treatment history, participants had at least two new antiretrovirals available that could be included in their salvage regimen of three to five drugs. Resistance testing helped determine the drugs included in each participant’s salvage regimen; all regimens were established before participants were randomly assigned to the two study groups. One study group switched immediately to the salvage regimen, while the other stopped taking antiretrovirals for 12 weeks before switching. Participants were followed for 60 weeks after randomization. The trial was closed early by the Safety and Efficacy Review Committee (SERC) because of slow enrolment.


The study enrolled 147 participants from January 2001 to September 2004. The study results include data from 134 participants who all had at least one post-baseline (i.e., after study entry) viral load recorded and who were randomized before January 1, 2004. Men made up 87% of the study population. The median baseline CD4 count was 343/mm3 and the median viral load was 3.9 log. Seventy-one participants had received a protease inhibitor (PI) or non-nucleoside reverse transcriptase inhibitor (NNRTI) before starting the study, and 63 had received both. Participants’ characteristics at the time they entered the study were similar for the two groups.


The percentage of participants whose viral load dropped below 50 copies/ml and remained at this level for at least three months was 69% in the IS group and 55% in the STI group. The difference between these percentages is not statistically significant. During the 60 weeks of follow-up, there were two non-HIV-related deaths (one in each group), four AIDS-defining events in the STI group (Pneumocystis pneumonia at week seven, lymphoma at week 57, two episodes of esphageal Candida in one participant at weeks 28 and 43) and seven HIV-associated infections (five episodes of zoster in three STI and two IS participants, and two episodes of oral thrush in STI participants).


In this clinical trial, a 12-week STI before the start of a salvage HAART regimen did not prove more beneficial than an immediate switch to a salvage regimen. There was no statistically significant difference in the percentage of participants from the two study groups whose viral load remained less than 50 copies/ml for three months. At 60 weeks, there was a statistically lower rise in CD4 cell counts in the STI group, but similar viral load reductions in the two groups.

Note: These results were taken from an abstract presented at the 12th Conference on Retroviruses and Opportunistic Infections (CROI) in Boston, Massachusetts, February 22-25, 2005.