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- NEW YORK - U.S. drug
maker Merck & Co, which began human trials late last year on an HIV
vaccine, believes no drug maker will complete development of a drug to
prevent infection by the virus that causes AIDS for at least another decade,
a senior company official said.
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- The largest U.S. pharmaceutical company, based in Whitehouse
Station, N.J., has been striving since 1986 to develop an AIDS vaccine,
an effort now led by Dr. Adel Mahmoud, president of Merck vaccines.
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- "This is Year 15 in our effort to develop an HIV
vaccine. I think we have (another) decade ahead of us," Mahmoud told
Reuters in a telephone interview.
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- Merck began human trials late last year of its experimental
vaccine against the HIV virus that causes AIDS. The company has divulged
few details about the Phase I trial, including the number of people being
tested or a description of the vaccine.
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- But Raymond Gilmartin, Merck's chief executive, on Thursday
volunteered one intriguing bit of information.
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- "Our objective is to develop a vaccine that would
be effective against multiple strains of the virus, thereby increasing
the vaccine's global utility," Gilmartin said in a statement.
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- Mahmoud earlier this week told Reuters such a "cross-strain"
vaccine was crucial, because at least eight slightly different variants
of the HIV virus have been identified in different parts of the world.
Four of them account for most of the world's infections.
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- AIDS experts believe a vaccine is the only answer to
the global epidemic of the virus, which is rampaging through sub-Saharan
Africa and Southeast Asia. An estimated 35 million people worldwide are
believed infected, with the vast majority in the developing countries,
where tests for infections and contraceptives are not readily available.
Up to 1 million people are believed infected in the United States.
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- With the advent of anti-HIV drug cocktails, some patients
are being kept alive, but the high cost limits their availability outside
prosperous industrialized countries.
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- The Merck trial is designed to determine the vaccine's
safety and evaluate immune responses in the human volunteers. Creating
a vaccine is a Herculean task because the virus mutates so quickly and
therefore is essentially a moving target. Once in the human body, it invades
and disables immune system cells and can lie dormant for years before symptoms
develop.
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- "We think, unfortunately, there is a likelihood
our vaccine will fail," said Laurence Hirsch, a spokesman for Merck
Research Laboratories. In that event, Hirsch said Merck would have a better
idea "how to proceed later, perhaps with another vaccine or a modification
of this one."
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- Some researchers have expressed hope that a fragment
of the HIV virus that is vital to all strains, a so-called "conserved"
portion, will be identified and that it can be used in a vaccine to confer
universal protection against all strains.
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- Asked whether he saw any indications such an approach
will work, Mahmoud said, "Hopefully it may, but not really at this
point." He declined to specify exactly how Merck planned to simultaneously
confer immunity against the world's major HIV strains, but expressed confidence
that would be accomplished.
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- Mahmoud said the main challenge for Merck and other researchers
was to find which antigens, or pieces of protein in the various HIV strains,
could be built into a vaccine to stimulate a protective immune-system response
in people.
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- Instead of actually injecting people with the HIV proteins,
Mahmoud said they might be injected with snippets of real, or "naked,"
DNA from the virus that code for the specific target protein. Human cells
would take up the DNA and use it as the blueprint for making the desired
antigens.
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- The body's immune cells would then produce antibodies
against the proteins " which would then be present to stave off any
future attack from an actual AIDS virus.
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- President Clinton has set a goal of 2007 for coming up
with an effective vaccine, a goal that some vaccine advocates think remains
possible.
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- "Clinton's goal is achievable if scientific concepts
keep improving and we get lucky. Nobody knows who will produce the vaccine
but we need it fast because there are 15,000 new HIV infections every day"
worldwide, said Victor Zonana, vice president of the International AIDS
Vaccine Initiative.
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- Zonana's organization, based in New York, is itself sponsoring
clinical trials on three HIV vaccines and plans to sponsor three more "
financed in part by contributions from the Gates Foundation.
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- He expressed high hopes for Merck's effort. "When
a company like Merck gets behind a product, it automatically is a top contender
because the company is known for coming up with breakthroughs."
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- Aventis Pasteur Inc., the vaccine unit of German-French
life sciences group Aventis S.A. is another source of hope, Zonana said.
It is developing several HIV vaccines, including one that has completed
Phase II trials.
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