(Adds details, background, analyst comment, paragraphs 4-13)
By Toni Clarke
March 19 (Reuters) - GlaxoSmithKline Plc's drug to treat chronic breathing problems is safe and effective enough for adults with asthma to use but not adolescents, an advisory panel to the U.S. Food and Drug Administration concluded on Thursday.
The panel voted 16-4 that Breo Ellipta should be approved for once daily treatment of asthma in adults 18 years and older. It voted 19-1 that the data did not support approval for use in children aged 12 to 17.
The FDA is not obliged to follow the advice of its advisory panels but typically does so. Glaxo licensed the product from Theravance Inc in 2002.
The drug consists of a corticosteroid, which reduces inflammation, and a long-acting beta-agonist, or LABA, called vilanterol, which is designed to open the airways.
The LABA class of drugs has been linked in the past with asthma-related deaths, though there were no asthma-related deaths in studies of Breo Ellipta reviewed by the FDA.
Timothy Anderson, an analyst at Sanford Bernstein, said in a research report that children represent about 10 percent of the eligible population for the drug. Even so, the company's inability to market it for children "will have certain commercial implications," he added.
Anderson said insurance companies will need to include more than one LABA/corticosteorid on their formulary to meet the needs of the total asthma population, when most would prefer just one agent.
In addition, he said, competitors will be quick to rally behind a "one drug meets all" approach. He predicts $750 million in Breo sales in 2020.
The panel vote came after the U.S. market closed. Anderson said he expects Theravance stock to fall Friday morning to between $13-$15 a share from $17.97 on Thursday.
The panel recommended that a large safety trial be conducted similar to others being conducted for drugs in the same class, including Glaxo's Advair, AstraZeneca's Symbicort and Merck & Co's Dulera and Foradil, in both adolescents and adults.
Breo Ellipta is an inhaled treatment that has already been approved to treat chronic obstructive pulmonary disease, or COPD, a condition that includes emphysema, chronic bronchitis, or both.
Darrell Baker, head of Glaxo's global respiratory franchise, said the company's aim is to work with the FDA and "answer any outstanding questions to enable them to make a fully informed decision."
The FDA is expected to rule on whether to approve the drug by April 30, 2015.
(Reporting by Toni Clarke in Washington; Editing by Sandra Maler, Peter Cooney and David Gregorio)