The Body Covers: The 42nd Interscience Conference on Antimicrobial Agents and Chemotherapy
Atazanavir (ATV) QD and Efavirenz (EFV) QD With Fixed-Dose ZDV+3TC
September 28, 2002
To be eligible for this study, patients had to have a viral load greater than 2000, and a CD4 count greater than 100. This study was conducted in 91 sites in several continents. After full enrollment, there were 404 people enrolled, with about one third women, and two thirds non-Caucasian. The baseline viral load was about 4.9 log, and CD4 count about 280. Thirteen percent of patients had either hepatitis B or C. About 7 percent dropped out of the study before one year on either arm for adverse events, while about 20 percent withdrew in total.
In terms of viral suppression, there were similar results in the two arms. In the intent-to-treat analysis, about 70 percent on atazanavir and 64 percent on efavirenz achieved a viral load of less than 400 copies. When using the 50 copy assay, 37 percent on efavirenz and 32 percent on atazanavir met this degree of suppression. In an on-treatment analysis, there were about 82 percent less than 400 copies on both arms, and about 50 percent less than 50. In various subset analyses presented, it was noted that there were similar degrees of suppression for those with baseline viral loads above 5 log. In addition, a time-to-failure analysis showed similar outcomes overall in the two arms. In terms of side effects, about 33 percent had an elevated bilirubin on the atazanavir arm, but only 5 percent had evidence of jaundice, and only 1 percent needed to stop study participation due to this side effect. Of importance, there were no changes to lipid measurements including total cholesterol and HDL/LDL fractions, and there was no change in the blood sugar and insulin levels.
These results increase our understanding of this new PI. There was much good news here about this agent, as it is clear that it is very active and has a safety advantage over several of the other agents in the class. It is also a simple drug to take, as it is only two capsules once a day. It was also stated that this is the first "non-boosted" PI that has shown comparable efficacy to one of the best agents we have, efavirenz.
The one concern raised is how to understand the lower than expected suppression rates in both arms, especially with regard to the percent below 50 copies. Dr. Squires mentioned a few factors did exist, including the use of a newer generation viral load assay that is more sensitive than prior tests used in most other studies. Further analysis will be done to help us understand that particular observation.
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