CHAPEL HILL Hope that one or two anti-AIDS drugs would work as well as a "cocktail" of three drugs in keeping down HIV virus levels among infected patients has disappeared temporarily because a new study shows the three drugs together fight the virus more effectively.
The study, published Thursday (Oct. 29) in the New England Journal of Medicine, indicates the drugs indinavir, zidovudine and lamivudine curbed human immunodeficiency virus (HIV) better than maintenance therapy with indinavir alone or with zidovudine and lamivudine taken simultaneously.
Known as AIDS Clinical Trials Group (ACTG) 343, the study was conducted among an original group of 509 patients -- later reduced to 316 -- at 39 participating institutions across the country.
The University of North Carolina at Chapel Hill School of Medicine enrolled and tested 35 volunteers. UNC-CH was one of four centers that published a study two years ago showing that indinavir, when combined with zidovudine (ZDV) and lamivudine (3TC) both cut AIDS virus levels in patients and boosted levels of CD4 cells, the infection-fighting cells that the virus slowly destroys.
"Our new results are something of a disappointment," said Dr. Joseph Eron, associate professor of medicine and associate director of UNC-CHs AIDS Clinical Trials Unit.
"The idea was that because patients have to take a complicated therapy that is expensive and sometimes has side effects, perhaps we could give the more complex therapy for six months and then reduce it to something simpler and more easily tolerated," Eron said. "At least in these patients, reducing therapy just didnt work."
The researchers, led by Dr. Diane V. Havlir of the University of California at San Diego, found that virus particles that were undetectable in infected patients after triple-drug therapy began to rebound during the less rigorous maintenance treatment. For ethical reasons, the double-blinded study was then halted in January. Patients receiving the one or two-drug regimens were returned to the more effective three-drug combination.
During maintenance therapy, 23 percent of patients receiving indinavir and 23 percent of those taking zidovudine and lamivudine showed increases in the AIDS virus. Only 4 percent of volunteers getting the stronger treatment began showing detectable virus levels. Subjects with more virus when the study began, a greater increase in CD4 cells during treatment or a slower virus clearance rate were at greater risk of losing their ability to suppress the deadly particles.
Indinavir, a protease inhibitor, works by preventing protease enzymes from cutting up proteins needed to form viruses, Eron said. Zidovudine and lamivudine work by blocking the enzyme that copies the genetic blueprints for the virus.
"The next step will be to front-load the therapy by trying more potent medications initially and giving them over a longer period, perhaps a year," he said. "This kind of induction and maintenance therapy is something we do all the time with diseases like tuberculosis."
Besides Eron, others participating at UNC-CH were Drs. Timothy Lane and Jim Horton and nurses David Ragn and Pamela Mently.
The National Institute of Allergy and Infectious Diseases supported the multi-center trial. Merck, Glaxo Wellcome and Bristol-Myers Squibb provided the study medications.
Note: Eron can be reached at (919) 966-2536.