HIV Digest	HIV Digest Archive

A new class of experimental HIV drugs, CCR5 receptor antagonists, is raising safety concerns. Designed to block a secondary but crucial doorway through which HIV enters cells in the body, the drugs would represent a shift in the fight against HIV, since they do not target the virus itself as do 27 other Food and Drug Administration-approved treatments.

That the drugs attack a target on human white blood cells is the source of much of the concern about them. "HIV profoundly affects the immune system. We are adding another layer of complexity by using a drug that also affects the immune system," said Veronica Miller, director of the Forum for Collaborative HIV Research based at George Washington University.

View our poll archive

Some worry the drugs could accelerate a shift from one variant of HIV to a second, a kind often seen in the sickest patients. It is also unclear whether the drugs would afford the same protection as occurs naturally in some people.

"It's a very exciting class and at the same time, people are approaching it with some trepidation," noted Tom Gegeny, executive director of the Center for AIDS Information and Advocacy in Houston.

Researchers do not know the long-term effects of the drugs, although some have been linked to liver problems and cancer.

GlaxoSmithKline, one of three major pharmaceutical companies developing the drugs, said in October it had halted trials of aplaviroc after patients showed signs of liver damage. Schering- Plough Corp. scrapped trials of its drug in January after smaller doses did not work as expected. In March, the company reported that a small number of patients had developed lymphomas. Pfizer Inc. reported a single case of liver problems in its trials, but said it appeared unrelated to the drug, maraviroc. Pfizer may file for FDA approval later this year, putting it at the forefront of the CCR5 drug competition.

Editor's Note: from the Associated Press