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"Shadow of fear over new class of HIV
drugs"
The
Star (www.thestar.com.my)
(20/06/06)
WASHINGTON: The excitement over a novel class of drugs being developed to
fight HIV has been dampened by fears they could pose serious safety risks,
including the possibility they might actually speed the progression of AIDS.
The new class of drugs, called CCR5 receptor antagonists, blocks a secondary
but crucial doorway typically used by the human immunodeficiency virus to
enter cells in the body.
Researchers have known for more than a decade that people who lack a working
version of that doorway, called a receptor, are, at best, highly resistant
to infection by HIV and, at worst, slow to develop AIDS once infected.
From a treatment standpoint, drugs that provide the same benefit would be a
welcome addition to the mix of medicines now used to fight HIV.
More dramatically, the drugs would represent a shift in the fight against
HIV, since they don't target the virus itself, as do the 27 other treatments
already approved by the Food and Drug Administration.
That difference is at the root of much of the concern surrounding the drugs.
The drugs attack a target on human white blood cells that play an important
role in the immune system.
“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.
Even as development continues, there is a growing wariness about the future
of the drugs.
“It's a very exciting class and at the same time, people are approaching it
with some trepidation,'' said Tom Gegeny, executive director of the Centre
for AIDS Information and Advocacy in Houston.
Most worrisome is that the drugs could accelerate a shift from one variant
of HIV to a second, which is most often seen in the sickest AIDS patients.
It is also unclear whether the drug would provide the same protection as
occurs naturally in some people.
Nor do researchers know the long-term health effects of the drugs, since
they tinker with cells that are the sentinels of the body's defences against
infection and disease.
“It is targeting a novel pathway with which we don't have a great deal of
experience,'' said Dr Scott Proestel, an FDA medical officer.
Indeed, a recent study found that the West Nile virus can be more lethal to
people who naturally lack a working CCR5 doorway. Resear-chers warned the
same could be true in patients treated with drugs that block that doorway.
That and other concerns reflect the sea change that the world of HIV has
undergone since 1987, when AZT, the first effective treatment for the virus,
gained FDA approval.
A year later, demonstrators mobbed the FDA to demand the agency speed access
to new therapies to treat HIV, even as the safety of those drugs remained
under study. At the time, HIV infection could be a death sentence; efficacy
trumped safety when it came to drugs capable of fighting the virus.
Now, AIDS can be a manageable condition. Existing drugs aren't perfect, but
they work. That has raised the barrier for drugs under development.
Pharmaceutical companies must show their drugs are both safe and effective
to gain FDA approval.
“It becomes more and more difficult to do something different,'' said John
Moore, a Cornell University AIDS researcher. “The pendulum has gone towards
safety at all costs.'' — AP
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