UPDATE 2-U.S. FDA says Glaxo failed to report Avandia data

(Recasts; adds details on studies; updates shares)

By Lisa Richwine

WASHINGTON, April 8 (Reuters) - GlaxoSmithKline Plc (GSK.L: Quote, Profile, Research) (GSK.N: Quote, Profile, Research) failed to report all of the required post-approval data on its diabetes drug Avandia to U.S. regulators, the Food and Drug Administration said in a warning to the company released on Tuesday.

A strong warning about heart attack risk was added to the drug in November, and Glaxo said the FDA had received all the information before that decision was made.

In a letter to GlaxoSmithKline Chief Executive Jean-Pierre Garnier, the FDA said an inspection from August through November 2007 found Glaxo did not list multiple post-approval studies as required in various reports dating back to 2001.

"The specific violations in this letter are serious and may be symptomatic of underlying postmarketing safety reporting failures," the FDA said in the letter, which was dated March 25 and posted on the agency's Web site on Tuesday.

GlaxoSmithKline spokeswoman Nancy Pekarek said the omissions were "inadvertent" and the information did not raise any new safety concerns.

Nine studies were not disclosed to the FDA until September 2007, the FDA letter said. The company failed to include 11 others in required annual reports, although the FDA and Glaxo said that information was given to the agency in other ways.

The information included the start and progress of clinical trials and summaries of final data from some trials, the company said.