Therapy with at least three anti-HIV drugs — one of which being a protease inhibitor — has been the standard of care in North America over the past four years. Such drug combinations often have complicated dosing schedules and food and meal restrictions, and require PHAs to take many pills several times daily. In addition to potential drug interactions with the use of protease inhibitors and non-nucleoside analogues, or non-nukes, there's the risk of developing diabetes, cardiovascular illness and liver damage with certain combinations. In an effort to create simpler, more tolerable combinations, drug companies and doctors are testing different regimens. One combination that appears to be attractive contains the following three drugs:
AZT, 3TC (Epivir) and abacavir (ABC, Ziagen)
These three drugs are all marketed by Glaxo SmithKline and are being squeezed into one pill and sold as Trizivir. Until Trizivir becomes more widely available (it is not yet approved in Canada), some doctors are prescribing Combivir (a combination of AZT and 3TC) together with ABC. Before the availability of Trizivir, doctors in the U.S. conducted a study of AZT, 3TC and ABC. Subjects who entered this study had relatively low viral loads — averaging about 1,300 copies — and no previous exposure to protease inhibitors. The researchers found that after one year, triple nuke therapy was able to push viral load below the 50 copy mark in 56% of subjects.
Researchers enrolled 87 subjects (16% female, 84% male) for this study. No subjects had symptoms of AIDS at the time the study began and most subjects had more than five months' exposure to nukes (AZT, d4T, 3TC, ddI), but none were using AZT. At the start of the study subjects had the following profile:
Researchers monitored subjects for up to one year after they entered the study.
Significant reductions in viral load occurred in as little as two weeks after subjects started taking triple nuke therapy. Previous use of AZT or 3TC did not significantly decrease the ability of AZT, 3TC and ABC to reduce viral load. After one year, the proportion of subjects who had viral loads below the following levels were as follows:
Despite the use of triple nuke therapy, 15 subjects had viral loads that could not be successfully suppressed. On average, these 15 subjects entered the study with relatively higher viral loads (15,000 copies) compared to other subjects in whom viral loads remained suppressed (800 copies).
One year after starting triple nuke therapy, subjects' CD4+ counts increased on average by 66 more cells.
Study subjects developed the following side effects in the proportions shown:
In other studies, a small proportion of people experienced a hypersensitivity reaction to ABC, symptoms of which can include the following:
The hypersensitivity reaction occurred in only three subjects in the current study; all three stopped taking ABC after developing the reaction.
Triple nuke therapy did not raise the level of sugar, cholesterol or triglycerides in the blood during the study.
The results from this study suggest that triple nuke therapy with AZT, 3TC and ABC can reduce viral load below the 50 copy mark in about 56% of people with HIV. People in this study had never used a protease inhibitor, did not have AIDS and had relatively low viral loads. Results may be less promising in people with higher viral loads and AIDS and in those who have used protease inhibitors.
REFERENCES:
1. Henry K, Wallace RJ, Bellman PC, et al. Twice-daily triple nucleoside intensification treatment with lamivudine-zidovudine plus abacavir sustains suppression of human immunodeficiency virus type 1: results of the TARGET study. Journal of Infectious Diseases 2001;183:571-578.
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Copyright © 2001 - TreatmentUpdate. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Editor, The Canadian AIDS Treatment Information Exchange, 555 Richmond St. West, Suite 505, Box 1104, Toronto, ON, M5V 3B1 • Phone: 416-203-7122 • Toll Free: 1-800-263-1638 • Fax: 416-203-8284 http://www.catie.ca.
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