GlaxoSmithKline faces a U.S. investor lawsuit claiming that Europe’s biggest drugmaker misled shareholders about the safety of diabetes drug Avandia.

Law firm Kaplan Fox & Kilsheimer said in a statement it had filed a class-action lawsuit in the U.S. District Court for the Southern District of New York against Glaxo and certain of its officers alleging the company had made false statements.

The suit claims Glaxo failed adequately to disclose the fact that it had performed a pooled, or meta, analysis that showed Avandia increased the risk of heart attacks.

Glaxo publicly disclosed its meta-analysis only after top U.S. cardiologist Steven Nissen published his own meta-analysis on heart-attack risk last month, which sent shares in the British-based drugmaker tumbling.

Kaplan Fox & Kilsheimer said preliminary results of Glaxo’s analysis were presented to the Food and Drug Administration in September 2005 and that updated results were disclosed to the FDA in August 2006. However, the results were never adequately disclosed to the investing public.

Shares in the group, which have fallen 10% since Nissen published his study in the New England Journal of Medicine showing a 43% increased heart-attack risk with Avandia, were 0.5% lower at 1,315 pence.

Investors are concerned that Glaxo’s sales of Avandia — its second-biggest seller, which brought in 1.6 billion pounds ($3.2 billion) last year — will tumble as a result of the scare.

Sales and prescriptions for the drug have already plunged since May 21, although Glaxo disputes Nissen’s conclusion and argues other data show Avandia to be as safe as rival diabetes medicine Actos.

Industry analysts are also concerned that Glaxo could face product-liability lawsuits from patients, although none has yet emerged.

Kaplan Fox & Kilsheimer said it was suing Glaxo on behalf of all persons or entities that purchased Glaxo securities between October 27 and May 21.

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