United Press International - July 28, 2005
Ed Susman

With more than two dozen drugs available to treat patients with HIV infection, in five different classes, the number of possible combination treatments numbers into the hundreds. As a result, doctors, scientists and pharmaceutical companies have been struggling to try to find the magic combination: a regimen that is effective in controlling the infection, has few side effects and is convenient to take.

Doctors considered that a once-daily treatment of tenofovir (Viread), a nucleotide reverse-transcriptase inhibitor, plus emtricitabine (Coviracil), another NRTI, plus efavirenz (Sustiva), a non-NRTI, would work just as well as the current "king of the hill," Combivir -- a pill containing zidovudine and lamivudine, both nucleoside analogs -- that is taken twice a day with Sustiva.

"In fact, this trial was set up to prove the once-daily treatment was not non-equivalent to the Combivir regimen," said Dr. Anton Pozniak, consultant in infectious diseases at Chelsea and Westminster Hospital in London.

"We can say that the emtricitabine-tenofovir regimen is superior to the Combivir regimen," Pozniak told attendees at the 3rd International AIDS Society Conference on HIV Pathogenesis and Treatment.

Pozniak said that not only did the new regimen outperform the Combivir regimen in controlling HIV replication during the 48 week trial, it also was associated with fewer adverse side effects.

"Many doctors have already begun using this new regimen based on the 24-week study results," Dr. Kenneth Mayer, professor of medicine at Brown University Medical School in Providence, R.I., told United Press International. "This update through 48 weeks will probably move more physicians to use this regimen with new patients."

Mayer said the Combivir-Sustiva regimen had been the most widely prescribed even before the early results of Pozniak's trial were announced, but although he expects the results of the trial to continue to influence clinical practice, he noted that no single regimen is used by even 15 percent of patients.

"There are now probably more than 300 different regimens available," Mayer said, "and patients are on them for a variety of reasons. I don't expect that doctors would change the prescription of a stable HIV patient on the basis of this trial."

He said patients recently infected with HIV or patients who discover they have been infected with the disease would be those most likely to be treated with the Viread-Coviracil-Sustiva regimen.

Mayer noted that 40,000 new HIV infections occur each year in the United States and of the 1 million U.S. residents living with HIV/AIDS, as many as 300,000 of them do not realize they have the infection. Often, HIV infection has no recognizable symptoms until a person suffers an AIDS-defining event -- usually an infection that cannot be controlled by the immune system.

In the trial, Pozniak reported, 81 percent of patients on the new regimen were able to reduce viral load in the blood to undetectable levels using the 400 copies/ml assay, compared to 70 percent of patients using the double nucleoside regimen. That difference was statistically significant.

When the HIV-lowering impact was scrutinized using the more rigid 50-copy/ml assay, about 77 percent of the 257 patients taking the Viread-Coviracil regimen had undetectable viral loads, compared with 68 percent of the 254 patients on the Combivir regimen, Pozniak said -- a difference that also reached statistical significance.

Ten patients -- about 4 percent -- on Viread-Coviracil experienced adverse events serious enough to force them to discontinue the trial, compared with 23 patients on Combivir -- or 9 percent.

Pozniak said the newer regimen appears to have less of a deleterious impact on patients' cholesterol and triglyceride levels.

"The results of this study," he said, "will have implications in our practices."

Pozniak said he will continue to follow patients in the trial for at least three years.

Edward Susman covers medical research and health matters for UPI Science News. E-mail: sciencemail@upi.com
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