Experimental antibiotics help against 'superbug'

By Maggie Fox, Health and Science Editor

WASHINGTON, Oct 26 (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 (PFE.N) 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 (ARPN.S) 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 BSLN.VX and Johnson & Johnson's (JNJ.N) ceftobiprole, made under the brand name Zeftera.