- WASHINGTON - Scientists at drug giant Merck and Co. Inc. said on Thursday
they had redesigned a drug in a way they hope will help make it harder
for bacterial "superbugs'' to develop resistance against.
- Tests in monkeys show it worked against
several strains of drug-resistant bacteria, including those that can evade
last line of defence drugs such as vancomycin.
- Writing in the journal Science, they
said the new drug blocked the mechanism the bacteria use to fight off penicillin
and related drugs.
- Hugh Rosen and colleagues at Merck Research
Laboratories in Rahway, New Jersey have been working on a class of drugs
known as carbapenems, which are related to penicillin. The carbapenems
are strong drugs and hard for the bacteria to evolve resistance to.
- But they often do. Bacteria reproduce
so quickly that they can evolve new forms in just a few years.
- Antibiotics are so widely used "
and misused " that plenty of bacteria have had enough exposure to
them to develop resistance, without actually being killed.
- The new drug, called by its experimental
name L-786,392, targets a bacterial protein known as PBP2a (short for penicillin-binding
protein). It is found in drug-resistant staphylococci and enterococci,
and essentially blocks the chemical doorways that penicillin usually uses
to get into and kill bacteria.
- Rosen's lab has been working for years
to modify the drug so it can get around this protein. But previous attempts
have resulted in a drug that also activates an improper immune response.
- This time they think they have cracked
the problem. The new drug killed the bacteria and did not activate the
immune systems of the monkeys they tested.
- "L-786,392 was well tolerated in
animal safety studies,'' they wrote in a report in Science. They said it
had "significant'' action against staphylococci that have evolved
resistance against methicillin and vancomycin, as well as against vancomycin-resistant
- Human tests are still some way off. But
doctors are anxious for new antibiotics.
- Last year, the Institute of Medicine
noted that 90 percent of all strains of Staphylococcus aureus, the most
common cause of infections, some of them deadly, now resisted penicillin.
- Dr. Jeffery Koplan, director of the Centres
for Disease Control and Prevention (CDC), says 70 percent of bacteria involved
in infections that people get in hospitals are now resistant to at least
- The CDC says 50 million unnecessary prescriptions
are written for antibiotics in the United States every year.