Pfizer's Antiretroviral Maraviroc Reduces HIV Viral Loads

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HIV Viral Loads

Pfizer'santiretroviral drug maraviroc can reduce HIV viral loads among peoplewho have never taken antiretrovirals, the company announced onWednesday, AFX/CNNMoney.com reports (AFX/CNNMoney.com, 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).

Maravirocworks by blocking a protein, called CCR5, on human immune system cellsthat HIV uses as a portal to enter and infect the cell. Pfizer also hasproposed using the drug to treat people with advanced HIV or AIDS whohave not responded to other medications. The company plans to offer thedrug with a test developed by Monogram Biosciencesthat 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'santiretroviral efavirenz. Participants in the trial never had undergoneantiretroviral treatment and showed no signs of resistance to any ofthe drugs used in the study (AFX/CNNMoney.com, 7/25). Researchers foundthat the rates of viral load suppression among people taking maraviroccompared with efavirenz were 70.6% versus 73.1% for less than 400 viruscopies per milliliter of blood and 65.3% versus 69.3% for less than 50copies per milliliter of blood. In addition, people taking maravirocexperienced an average increase in CD4+ T cell count during the studyperiod of 170 cells per cubic milliliter of blood, compared with anincrease of 144 cells per cubic milliliter of blood among people takingefavirenz (Pfizer release, 7/25).

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According to Pfizer, thetrial's findings showed that half as many participants taking maravirocexperienced a "category C" AIDS defining event, such as infection ormalignancy, compared with those taking efavirenz. The most common sideeffects of maraviroc were nasopharyngitis and bronchitis, and the sideeffects associated with efavirenz were dizziness, diarrhea, abnormaldreams and rashes, Pfizer said (AFX/CNNMoney.com, 7/25).

Inaddition, the overall incidence of malignancies was lower in patientstaking maraviroc than those taking efavirenz. "These data are veryexciting," Michael Saag -- professor of medicine and director of the Center for AIDS Researchat the University of Alabama-Birmingham, who presented the results --said. "The CD4 benefit and the tolerability profile observed inpatients 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/News.comreports. One in 20 people who take abacavir has an adverse reaction --such as severe flu-like illness with ongoing fever, rashes, andgastro-intestinal and respiratory problems -- to the drug during thefirst 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 testto identify it. They enrolled 2,000 HIV-positive people at 265 clinicsworldwide to take abacavir. Half of the participants were screenedusing the test, and those who tested positive for the gene were givenan alternative drug. Mallal said there were "literally zero immunereactions in the patients that had the genetic tests."

Accordingto the AAP/News.com, the $30 test is "fast becoming" available acrossAustralia and much of Europe. Mallal said that the test has "reallyrevolutionized the use of abacavir in Australia," adding, "We'vealready seen a lot more of the drug used because of the confidence thatdoctors and patients have." He also said that applications could extendbeyond antiretrovirals. "We're cautiously optimistic that other drugsin other treatment areas will now follow behind us," Mallal said. DavidCooper, director of Australia's National Centre for HIV Epidemiology and Clinical Researchand IAS conference co-chair, said the test "gives us a much-neededadditional tool to use ... to reduce the potential toxicity" ofabacavir (McLean, AAP/News.com, 7/25).
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Reprinted with permission fromkaisernetwork.org.You can view the entire KaiserDaily HIV/AIDS Report, search the archives, and signup for email delivery at kaisernetwork.org/email. The Kaiser Daily HIV/AIDS Report is published forkaisernetwork.org,a free service of The Henry J. Kaiser Family Foundation.

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