GlaxoSmithKline says it faces a new delay in winning US approval for its top-selling asthma drug Advair as a treatment for "smoker's cough", sending its shares as much as three per cent lower.
Europe's biggest drug maker has received a second so-called "approvable" letter from the US Food and Drug Administration but is still working with the agency to clarify outstanding issues, a process industry analysts said could take around one year.
The stock market has been waiting for Advair to win a green light for chronic obstructive pulmonary disease (COPD), a condition most frequently caused by smoking, since a first approvable letter was received in March.
The company gave no details about the outstanding issues with the FDA but spokeswoman Ms Siobhán Lavelle said a meeting with the agency to discuss Advair was planned for early in next year.
COPD, which kills some 100,000 people in the United States each year and affects about 21.7 million Americans, is a huge potential market.
Advair is, in fact, already being used to treat some patients with the condition, for which there is no cure, with off-label use in COPD estimated to account for up to a quarter of prescriptions.
Formal FDA approval would give further impetus to the drug, which analysts believe has the potential to win about $5 billion in sales by 2006.