Retrovirus & Opportunistic Infections (cont.)
While much was learned about strategic CD4-guided therapy from the above studies, many patients still decide to stop treatment for a variety of reasons. Another study of treatment interruption in those who never had low CD4 cells and wanted to stop treatment was reported. This study, ACTG 5170 followed these subjects while off treatment. They found that when therapy was discontinued, viral loads went up and CD4 cells went down, but most people remained quite healthy and tolerated the interruption. The primary endpoint of this study was the CD4 count of less than 250 cells/uL or progression to a CDC category B or C diagnosis, or death, or the need to restart therapy. These patients were highly selected to have high CD4 cells in the past and to never have had a high viral load. They were followed over time and found that the majority of them were able to safely stay off therapy or when they reinitiated, they did well. There were some interesting events that occurred related to coronary artery disease in three individuals, the clinical significance and relationship between this study and those events remains unknown.
Results from ACTG 5201 were presented at this meeting, a small open-label study to determine whether patients virologically suppressed on combination therapy can be maintained on a single ritonavir (RTV)-boosted protease inhibitor (PI). The rational for this would be to reduce the pill burden and potentially the toxicities associated with NRTIs. This trial enrolled individuals who were on stable antiretroviral therapy with a viral load persistently less than 50 copies/mL. These individuals were put on two NRTIs with ATV/RTV, and once confirmed to have a viral load less than 50 copies/mL; they stopped the NRTIs and continued ATV/RTV alone. Although there was no control group that remained on combination therapy, 34 individuals were followed on ATV/RTV for 24 weeks with 91 percent maintaining viral suppression, with the lower 90 percent confidence interval being 85 percent, which is as good as or better than what was predicted if combination therapy were continued. Three individuals experienced virologic failure in this study: 2 of whom had undetectable levels of ATV at the time of viral rebound, one of which resuppressed on RTV-boosted ATV alone. There was no PI resistance noted. Although this is a very small study, it may lead to larger controlled trials in the future as it was consistent with previous results published last year looking at maintenance therapy with lopinavir/ritonavir .