UPDATE 1-U.S. delays OK to broaden use of Wyeth antibiotic

(New throughout; adds NEW YORK dateline)

NEW YORK, May 29 (Reuters) - U.S. health regulators have declined to immediately approve Wyeth's (WYE.N) antibiotic Tygacil for treating pneumonia outside hospitals or nursing homes as they seek more data on severe cases, the drugmaker said on Thursday.

In issuing its "approvable letter," the U.S. Food and Drug Administration also requested information about potential liver toxicity with Tygacil. Wyeth said it recently provided the information to the FDA, but the agency said in the letter it has not yet reviewed the data.

Approvable letters generally mean the FDA is willing to approve an application once the company satisfies certain conditions.

Meanwhile, Wyeth said the FDA is giving "fast track" status to the company's new form of its blockbuster Prevnar vaccine for preventing childhood infections with pneumococcal bacteria. The new version would protect against 13 strains of the bacteria, compared with seven for the current version.

With its fast-track status, Wyeth can submit data from clinical trials on a rolling basis as information becomes available rather than waiting until pivotal studies are completed. Wyeth plans to complete its U.S. filing for pediatric use of the new Prevnar vaccine in the first quarter of 2009.

Prevnar is currently Wyeth's second-biggest product, with sales of about $2.5 billion last year, and the company hopes its improved formulation will ensure continued strong sales gains.

Tygacil, which had about $138 million in sales last year and is administered intravenously, won U.S. approval in 2005 for treating adults with complicated intra-abdominal infections and complicated skin and skin-structure infections.

In this case, Wyeth is seeking to expand Tygacil's approval to treat a condition known formally as community-acquired pneumonia. According to Wyeth, although pneumonia is not a reportable illness, it appears that up to 5.6 million cases of community-acquired pneumonia occur annually.

"We believe the data from our current clinical development program support Tygacil as a potential therapeutic option for patients with (community-acquired pneumonia)," Gary Stiles, chief medical officer for Wyeth Pharmaceuticals, said in a statement.

Tygacil is a member of a family of antibiotics called glycylcyclines, which are effective against a number of bacteria that have developed resistance to other antibiotics.

Wyeth shares rose 45 cents, or 1 percent, to $44.60 on the New York Stock Exchange. (Reporting by Lewis Krauskopf and Ransdell Pierson; editing by Jeffrey Benkoe)