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The Body Covers: The 39th Annual Meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy
Session 93.I: Late-Breaker Slide Session II

September 27, 1999

One of the most anticipated drugs in development is ABT 378. The results of these two studies provide the information that has led to this enthusiasm. ABT 378 is a protease inhibitor, and a small dose of ritonavir (100 mg twice a day) is added into the capsules that contain the 378 as well -- this is done because the blood levels of 378 are markedly increased by the ritonavir. The high blood levels allows the drug to be given twice a day, and also provides a concentration of drug that is high enough so that not only are the "wild type" HIV strains sensitive to the agent, but PI resistant HIV strains are also sensitive to this drug. Here, the results of two studies are presented. One is using ABT 378 in combination with d4T and 3TC in antiviral naïve persons starting this as their first combination. Second is using ABT 378 in combination with nevirapine and nucleosides for those who have resistance to their first PI.

In the naïve study, the results of this combination are impressive. One hundred people were given this combination, which did compare slightly different doses of both the 378 and the ritonavir. Regardless of which dose was given, 95% achieved a viral load below 400 copies at week 36. Most of these had a viral load below 50 copies as well. In the PI experienced study, those who had a viral rebound on any of the available PI's were eligible, as long as they had never taken a nonnucleoside, and had a viral load between 1000 and 100,000. All were given 378/r, in combination with nevirapine and two nucleosides, one of which had to be a new one for this person. No matter which PI the person took previously, this new combination was very effective, with 78% having a viral load below 400 copies at week 36 (50 copy data were not available yet). The combinations using 378/r are very well tolerated by most. The major side effect noted is looser stools, but this has led only 1% of persons to stop the drug.

The future role of 378/r is still a flexible one, as these results show. The data in both naïve and PI experienced participants suggests a high level of effectiveness, and a high degree of tolerability. It is a relatively easy drug to take, as it is only three capsules twice a day with some amount of food. Ongoing studies will further clarify the role of this drug, but it is now available in some countries in an expanded access study, where those who have a CD4 count below 50 cells may be able to use it in a combination. Like t-20, it represents hope for those who are struggling with HIV that is resistant to the available drugs, as it represents a possible new "swing at the ball."

Abstract: ABT 378/Ritonavir Suppresses HIV RNA to <400 Copies in 95% of Treatment Naïve Patients and in 78% of PI-Experienced Patients at 36 Weeks
Authored by: J. Eron, M. King, Y. Xu, et al.

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