HIV entry
inhibitors raise concerns among researchers

Although HIV entry inhibitors--experimental drugs that aim to prevent HIV from attaching to and infecting immune system cells--are being touted as the next major step forward in HIV treatment, some researchers are beginning to worry that the drugs may pose safety risks, the Associated Press reports.

Most of the drugs in development work to jam a key receptor on the surface of immune system cells, called CCR5, that HIV attaches to. Previous research has showed that people who naturally have non-working CCR5 cell receptors are somewhat resistant to HIV infection and, if they do become infected, are unlikely to experience HIV disease progression to the point of developing AIDS.

But clinical trials of some of the experimental entry inhibitors have been called off when study participants began experiencing severe drug-related side effects, including liver damage and certain cancers. Worse yet, some researchers worry that by jamming the CCR5 receptors on immune system cells, HIV will be forced to adapt to use another cell receptor, called CXCR4. Studies have shown that HIV strains that have mutated to primarily use CXCR4 receptors are much more virulent than CCR5 strains and progress much more quickly to AIDS diagnosis and disease complications.

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

"The clinical development of this class has, in a word, been challenging," Cornell University AIDS researcher Roy Gulick told the news agency. (The Advocate)