FDA panel: Theravance antibiotic safe, effective

Federal health advisers on Wednesday said an antibiotic developed by Theravance appears safe and effective for fighting "superbug" bacteria, despite potential risks for pregnant women.

A panel of infection experts voted 21 to 5 in favor of the drug's benefits and safety.

The Food and Drug Administration is reviewing Theravance's telavancin, a once-daily injection, for patients with hard-to-treat skin infections caused by drug-resistant bacteria. In recent decades, some varieties of germs, including the widespread staph bacteria, have grown immune to popular antibiotics, making them difficult to treat.

Earlier in the week, a review of telavancin by FDA's internal scientists raised questions about its risks of birth defects, and suggested stern warning labels might be needed if it is approved.

Panelists voted 18 to 5 that there were certain medical situations when the drug's benefits would still outweigh its risks for pregnant women. Three panelists abstained from voting.

"In order to save a life, no one would hesitate to use this drug," said Dr. Barth Reller, a professor at Duke University Medical Center. "I just don't think it should be given to pregnant women unless one has exhausted all other options."

Panelists overwhelmingly voted in favor of requiring the company to establish a plan for managing the drug's pregnancy risks. Such plans sometimes involve educational outreach to doctors and limited distribution plans.

Government regulators are not required to follow the advice of the panelists, though they normally do.

Two large studies conducted by Theravance showed its antibiotic was at least as effective as the strongest antibiotic now on the market, vancomycin. That injectable drug is sold as a generic by various manufacturers.

But FDA reviewers said they were concerned that early-stage testing of the drug in lab rats, rabbits and guinea pigs showed a small number of birth defects, including deformed paws and legs.

Results seen in animal studies do not automatically apply to humans, but they are considered important for establishing drug safety.

"While the evidence of drug-induced limb malformations is weak, the weight of evidence across all three species strongly supports that the findings are drug-related," said FDA scientist Zhou Chen, summarizing the agency's view.

The FDA's maternity experts recommended the drug receive a "black box" warning - the most serious type available - and specify that the drug should not be used in pregnant women.

However, a majority of panelists said the drug should be available in certain life-threatening situations.

"I think if a woman is pregnant and all other therapies have failed then she needs the option to use this," said Mary Alice Smith, a professor at the University of Georgia.

About 95,000 serious infections and 20,000 deaths due to drug-resistant staph bacteria occur in the U.S. each year. While most staph infections cause only mild skin irritation, the more powerful strains can enter the bloodstream, destroy flesh and become lethal.

Since 2005, sales of new antibiotics that target superbugs have grown 20 percent to $1 billion last year, according to industry figures.

The Food and Drug Administration is expected to make a decision on whether to approve telavancin in the next few months.

Theravance plans to file an application early next year to market telavancin for hospital-acquired pneumonia. If the FDA approves that additional use, analysts estimate the drug could reach sales of $300 million per year. Existing drugs on the market include Pfizer's Zyvox and Cubist Pharmaceutical's Cubicin.

Shares of San Francisco-based Theravance fell 1 cent to $6.72 in afternoon trading.

The same FDA panel will review a similar antibiotic from Cambridge, Mass.-based Targanta Therapeutics on Wednesday afternoon.