October 27, 2008

Fighting the “Superbug”

Two new forms of experimental drugs may battle a dangerous form of evolving infection, according to researchers.

The health condition is called methicillin-resistant Staphylococcus aureus or MRSA.

Doctors want the necessary tools to fight the so-called superbug infection.

MRSA kills an estimated 19,000 people a year in the United States.

The previous treatment, Pfizer Inc's Zyvox, has side effects and MRSA bacteria are already beginning to adapt by what is known as resistance.

Paratek Pharmaceuticals Inc. said its experimental antibiotic cleared MRSA infections in 98 percent of patients treated. That's a favorable number when compared to 93 percent of those treated with Zyvox, known generically as linezolid.

"There were no drug-related serious adverse events," Dr. Michael Scheld of the University of Virginia and the Infectious Diseases Society of American said.

During the treatment, 188 patients got either PTK 0796 or Zyvox intravenously for four days and then in pill form for about a week.

Swiss company Arpida said its intravenous drug iclaprim cured 92.3 percent of patients versus 97 percent of those given Zyvox.

The studies of 991 patients included those infected with both MRSA and other staph infections.

The U.S. Centers for Disease Control and Prevention estimates that 94,000 Americans contract invasive MRSA infections each year and 19,000 die.

"What we really, really need ... is a very potent anti-MRSA drug ... which can be taken orally," Scheld said during a meeting of infectious disease experts.

"Linezolid doesn't fit that bill." Zyvok does not kill bacteria, but only limits their growth, and it can damage nerves and the bone marrow.

"Novel compounds can fill a niche here," Scheld said.

PTK 0796 is the first in a new set of drugs called aminomethylcyclines, which are related to tetracycline.

Paratek president and chief executive officer Thomas Bigger said the company plans to take the drug to phase III trials. This will mark the last needed stage of human testing before seeking U.S. Food and Drug Administration approval.

Other companies claim their drugs may work against MRSA, including Basilea's and Johnson & Johnson's ceftobiprole, made under the brand name Zeftera.

Zeftera, Pfizer's dalbavancin and Theravance Inc's telavancin are awaiting FDA approval.

"Most of these compounds are from classes that we already knew about ... which is disappointing," said Dr. Karen Bush of Johnson & Johnson and Indiana University.

Bacteria evolve most quickly to drugs that are in similar classes to drugs already in use.

"The need is really critical for us to be finding new agents," Bush said. This means drugs that work against less common infections such as Acinetobacter, Pseudomonas, and Klebsiella, she said.

"There is almost nothing in the pipeline now," agreed Scheld. "We as clinicians have nothing that we can obtain to treat these multi-drug resistant organisms for least probably five to 10 years."


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