JP Garnier and his team may have difficulty breathing today. The agency mailed Glaxo a ‘not approvable’ letter for its Advair Diskus inhalable med in patients with chronic obstructive pulmonary disease, or COPD, a common lung disorder that makes it hard to breath. Glaxo estimates about 20 million people in the US suffer from some form of the disease.

In a statement issued this morning, Glaxo says the FDA letter raised concerns about proposed dosing levels, and that Glaxo officials plan to meet with the agency to discuss data on side effects connected with Advair, as well as data concerning the existing lower dose 250/50 version.

“We are very surprised and disappointed by this FDA decision particularly given the outcome of the FDA advisory committee meeting earlier this year,” says Katharine Knobil, a Glaxo vp for development. “The advisory committee voted unanimously that Advair 500/50 demonstrated a significant reduction in the risk of exacerbations. We believe in the strength of the data; this application is based on the results of the largest COPD study conducted in more than 6,000 patients over three years. We are committed to working with the FDA to address any questions they have and to pursue a way forward.”

In May, an FDA panel voted unanimously that Advair reduces the risk of the pulmonary disease, but the agency doesn’t have to follow the advise of its advisory committees, although it usually does. Glaxo, already reeling from the controversy over heart attack risk attributed to its Avandia diabetes med, was counting on increased Advair sales. The respiratory drug is a big seller, generating $3.3 billion in revenue last year. The big rival is Merck’s Singulair.