Trial antibiotics help against "superbug"

WASHINGTON Sun Oct 26, 2008 6:51pm EDT

MRSA (Methicillin resistant Staphylococcus Aureus) bacteria strain is seen in a petri dish containing a special jelly for bacterial culture in a microbiological laboratory in Berlin, March 1, 2008. REUTERS/Fabrizio Bensch

MRSA (Methicillin resistant Staphylococcus Aureus) bacteria strain is seen in a petri dish containing a special jelly for bacterial culture in a microbiological laboratory in Berlin, March 1, 2008.

Credit: Reuters/Fabrizio Bensch

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WASHINGTON (Reuters) - Two experimental antibiotics appear to work safely against an increasingly common and dangerous form of infection called methicillin-resistant Staphylococcus aureus or MRSA, researchers said on Sunday.

Doctors are clamoring for drugs that can fight the so-called superbug infection, which kills an estimated 19,000 people a year in the United States alone.

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

Privately owned Paratek Pharmaceuticals Inc. said its experimental antibiotic cleared MRSA infections in 98 percent of patients treated, 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 told a news conference.

The 188 patients got either PTK 0796 or Zyvox intravenously for four days and then as a pill 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 MRSA but also other staph infections.

The U.S. Centers for Disease Control and Prevention estimates that 94,000 Americans get serious, 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 told the news conference at 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.

FILLING A NICHE

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

PTK 0796 is the first in a new class 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, the last stage of human testing before seeking U.S. Food and Drug Administration approval.

Several other companies also presented studies at the conference showing their new 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 have had FDA approval delayed.

"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 quickly evolve resistance and adapt 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 multidrug-resistant organisms for least probably five to 10 years."

Rapid diagnostic tests would help, said Bush, as they would help identify patients with these infections in time to get them into clinical trials to test any new drugs. Currently many patients never learn what caused their infections.

(Editing by Cynthia Osterman)

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