Medical News

Clinical Data Show Pfizer's Antiretroviral Maraviroc Reduces HIV Viral Loads Among Treatment-Naive People, Company Says

July 26, 2007

Pfizer's antiretroviral drug maraviroc can reduce HIV viral loads among people who have never taken antiretrovirals, the company announced on Wednesday, AFX/ reports (AFX/, 7/25). The company made the announcement at a session during the 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention in Sydney, Australia (Pfizer release, 7/25).

Maraviroc works by blocking a protein, called CCR5, on human immune system cells that HIV uses as a portal to enter and infect the cell. Pfizer also has proposed using the drug to treat people with advanced HIV or AIDS who have not responded to other medications. The company plans to offer the drug with a test developed by Monogram Biosciences that determines if people are likely to respond to the treatment. Pfizer has proposed selling maraviroc under the brand name Celsentri (Kaiser Daily HIV/AIDS Report, 7/23).

Clinical Trial Details
Pfizer conducted a 48-week trial comparing the efficacy of maraviroc as an initial therapy with Merck's antiretroviral efavirenz. Participants in the trial never had undergone antiretroviral treatment and showed no signs of resistance to any of the drugs used in the study (AFX/, 7/25). Researchers found that the rates of viral load suppression among people taking maraviroc compared with efavirenz were 70.6% versus 73.1% for less than 400 virus copies per milliliter of blood and 65.3% versus 69.3% for less than 50 copies per milliliter of blood. In addition, people taking maraviroc experienced an average increase in CD4+ T cell count during the study period of 170 cells per cubic milliliter of blood, compared with an increase of 144 cells per cubic milliliter of blood among people taking efavirenz (Pfizer release, 7/25).

According to Pfizer, the trial's findings showed that half as many participants taking maraviroc experienced a "category C" AIDS defining event, such as infection or malignancy, compared with those taking efavirenz. The most common side effects of maraviroc were nasopharyngitis and bronchitis, and the side effects associated with efavirenz were dizziness, diarrhea, abnormal dreams and rashes, Pfizer said (AFX/, 7/25).

In addition, the overall incidence of malignancies was lower in patients taking maraviroc than those taking efavirenz. "These data are very exciting," Michael Saag -- professor of medicine and director of the Center for AIDS Research at the University of Alabama-Birmingham, who presented the results -- said. "The CD4 benefit and the tolerability profile observed in patients treated with maraviroc are particularly interesting," he added (Pfizer release, 7/25).

Genetic Test Identifies HIV-Positive Patients With Adverse Reaction to Antiretroviral Drug Abacavir
A new genetic test has proven effective in identifying HIV-positive people who might experience adverse reactions to GlaxoSmithKline's antiretroviral drug abacavir, according to data presented at the IAS conference, the AAP/ reports. One in 20 people who take abacavir has an adverse reaction -- such as severe flu-like illness with ongoing fever, rashes, and gastro-intestinal and respiratory problems -- to the drug during the first three weeks of therapy.

Simon Mallal from the Royal Perth Hospital in Perth, Australia, and colleagues in 2002 discovered that the gene, HLA 5701, was causing the reactions and developed a test to identify it. They enrolled 2,000 HIV-positive people at 265 clinics worldwide to take abacavir. Half of the participants were screened using the test, and those who tested positive for the gene were given an alternative drug. Mallal said there were "literally zero immune reactions in the patients that had the genetic tests."

According to the AAP/, the $30 test is "fast becoming" available across Australia and much of Europe. Mallal said that the test has "really revolutionized the use of abacavir in Australia," adding, "We've already seen a lot more of the drug used because of the confidence that doctors and patients have." He also said that applications could extend beyond antiretrovirals. "We're cautiously optimistic that other drugs in other treatment areas will now follow behind us," Mallal said. David Cooper, director of Australia's National Centre for HIV Epidemiology and Clinical Research and IAS conference co-chair, said the test "gives us a much-needed additional tool to use ... to reduce the potential toxicity" of abacavir (McLean, AAP/, 7/25). served as the official webcaster of the IAS conference. Individuals can find more information about conference webcasts online.

Video of the session in which the two studies were presented is available online.

PRI's "The World" on Wednesday included a discussion with Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases, about progress in combating HIV/AIDS (Schachter, "The World," PRI, 7/25). Audio of the segment is available online.

Back to other news for July 2007

Reprinted with permission from You can view the entire Kaiser Daily HIV/AIDS Report, search the archives, or sign up for email delivery at The Kaiser Daily HIV/AIDS Report is published for, a free service of the Kaiser Family Foundation, by The Advisory Board Company. © 2007 by The Advisory Board Company and Kaiser Family Foundation. All rights reserved.

This article was provided by Henry J. Kaiser Family Foundation. It is a part of the publication Kaiser Daily HIV/AIDS Report. Visit the Kaiser Family Foundation's website to find out more about their activities, publications and services.


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