Scientists say they have high hopes for a drug that could one
day provide a new form of treatment for HIV-AIDS. A compound, which interferes
with an elusive protein used by the HIV virus to infect human cells, has worked
extremely well in monkeys. If the drug proves effective in human trials,
scientists say, it could bolster (加强) the effectiveness of two existing AIDS
drugs, particularly in fighting drug-resistant strains of the virus.
Researchers at the pharmaceutical (制药的) company Merck are very excited
about an experimental drug, which has worked as well in monkeys infected with a
primate version of the virus as any of the existing, anti-AIDS drugs.
It works by blocking one of three proteins, or enzymes, the HIV virus uses
to gain entrance into and infect human immune system cells.
Inhibitor drugs have been developed to block two of the proteins, to slow
progression of the disease after infection. They have become standard therapy as
a "cocktail" for people infected with HIV Those enzymes are
reverse transcriptase (转录酶) and protease (蛋白酶). The first converts the virus’
genetic material into that of its host cells. The second chops up the resulting
larger proteins into smaller pieces, producing smaller viral particles that
infect new cells. The third prong of cellular attack is a
protein called integrase (整合酶), which experts say has been harder to block. Once
HIV fools host cells by changing its genetic information so it can enter them.
integrase acts like a cut and paste operation in a word processor, deleting on
immune cell’s genetic material and replacing it with its own. An
integrase inhibitor would give doctors a third line of attack against HIV
infection, according to virologist Daria Hazuda of the division of Virus and
Cell Biology at Merck. "This would offer a third class of
anti-retroviral medications that can be combined with reverse transcriptase
inhibitors and pretense inhibitors. And since it is a new mechanism of action,
these compounds are active against multi-drug resistant variants. So variants
that are resistant to all current therapies have been selected in HIV-patients,"
she said. Current anti-AIDS drugs eventually become resistant to
therapy, or stop working, because the virus changes its shape.
While researchers are encouraged by the success with the compound’s
effectiveness in monkey trials, developing a drug that is equally effective in
humans can be difficult. Steven Young is executive director of
the Department of Medicinal Chemistry at Merck. He says, if scientists find a
compound that is equally effective in people, the company would ask U.S.
regulators to speed approval of the drug. "Yeah, I really think
that’s what we’re hoping for." he said. "I mean. we need to get data that show
it has robust anti-viral effects in people. And if we’re able to get that data.
I think we would petition for fast track status." Dr. Young says
an integrase inhibitor has the potential to prevent drug resistance.
"To ensure our best chances of preventing resistance, we would give this
as part of a cocktail therapy," he added. "And I think it’s really our plan that
we would test this with reverse transcriptase inhibitors and pretense
inhibitors, as well." What has become standard cocktail therapy