GlaxoSmithKline PLC (GSK.LN) Thursday said Germany's Federal Patents Court revoked its patent for key product Advair, handing a victory to generic drug makers Mylan dura GmbH, Hexal AG, Neolab Ltd., and IVAX International B.V. and highlighting the worldwide generic threat to Glaxo's blockbuster lung treatment.

The ruling relates to the combination of Advair's active ingredients salmeterol and fluticasone propionate.

Glaxo, the U.K.'s biggest drug maker, said the Munich-based court's decision relates solely to the German combination patent for Viani, Advair's German brand name, and is not binding in any other jurisdiction.

The decision is the conclusion to a hearing that was conducted in February.

"This is not the end, and we will be considering whether to appeal to a higher court," a spokeswoman at Glaxo said.

Glaxo also owns a number of other patents in Germany relevant to Advair, including the Diskus dry powder inhaler and HFA aerosol formulation patents which expire in 2011 and 2012 respectively. The company in a statement noted there are significant technical hurdles and complexities associated with the introduction of inhaled respiratory products.

The trial is part of a complex legal struggle between Glaxo and a group of generic drugmakers which hope to sell copies of the two-in-one inhaler for asthma and chronic obstructive pulmonary disease, or "smoker's lung". Teva bought Ivax in 2006 for $7.4 billion. Hexal is part of Novartis' Sandoz generics unit.

Advair last year had sales of $7.8 billion, representing 18% of the company's total turnover. Analysts predict Advair's sales could reach $9.5 billion in 2011.

Shares in Glaxo at 0950 GMT were down 0.8% or 9 pence at 1,169 pence but up 10% from year-ago levels.

Company Web site: www.gsk.com

-By Sten Stovall, Dow Jones Newswires; +44 207 842 9292; sten.stovall@dowjones.com