Important note: Information in this article was accurate in 2008. The state of the art may have changed since the publication date.

Reuters NewMedia - October 1, 2008
Gene Emery

At least 42 percent of patients in Europe, North America and Australia who took maraviroc once or twice a day on top of standard drug cocktails had blood virus counts below levels that cause visible damage to the immune system.

Only 18 percent of patients who got a placebo plus a standard HIV drug combination got their viral levels that low over the 48 weeks that have been studied so far.

In all, 1,049 volunteers who were resistant to three of the six classes of HIV drugs were involved in the two Pfizer-sponsored studies, reported in the New England Journal of Medicine.

Industry analysts have said maraviroc could be worth $500 million to Pfizer by 2011. Marketed as Celsentri in Europe and Selzentry in the United States, it was approved a year ago based on 24-week results from the two studies.

Maraviroc stops the virus from getting into the immune cells it affects by blocking a doorway called the CCR5 co-receptor. It was given with other HIV drugs that target the ability of the virus to replicate.

The volunteers, all with advanced human immunodeficiency virus infections, were screened to be sure they carried a strain of the virus that uses CCR5. More than half of infected people do.

The researchers said maraviroc did not produce any unusual side effects and, although the drug carries a warning about possible liver problems, "our study simply didn't see liver toxicity, so that's reassuring," said Dr. Roy Gulick of the Weill Cornell Medical Center in New York, who led the study.

In a telephone interview, Gulick said the liver warning was "based on a single case, and that patient had a lot of complicating factors, so there are other possible reasons why they ran into liver trouble."

An estimated 33 million people worldwide are infected with HIV. There is no cure and no vaccine, although a drug cocktail can help control infection and keep people healthy.

But the virus mutates constantly and usually becomes resistant to the drugs after a while, meaning patients must switch to different cocktails. AIDS experts say they need constant new additions to the list of 20 or so existing HIV drugs.

Maraviroc belongs to a new class of these drugs, called HIV entry inhibitors or CCR5 receptor antagonists.

Gulick said results from the 96-week mark are now being analyzed and may be presented at a scientific meeting in November.

(Editing by Maggie Fox and John O'Callaghan)

On the Net: http://content.nejm.org

Reference: Maraviroc for Previously Treated Patients with R5 HIV-1 Infection. N Engl J Med. 2008 Oct 2;359(14):1429-41

081001
RE081004

Copyright © 2008 - Reuters, Ltd. All rights reserved. Republication or redistribution of Reuters content is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon.   Contact Reuters.

AEGiS is a 501(c)3, not-for-profit, tax-exempt, educational corporation. AEGiS is made possible through unrestricted funding from Boehringer Ingelheim, Bridgestone/Firestone Charitable Trust, Bristol-Myers Squibb Company, Elton John AIDS Foundation, the National Library of Medicine, Roche and Trimeris, and donations from users like you. Always watch for outdated information. This article first appeared in 2008. This material is designed to support, not replace, the relationship that exists between you and your doctor.

AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.

Copyright ©1980, 2008. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content. .