(Adds FDA reviewer comments on cardiovascular safety)
WASHINGTON, Sept 6 (Reuters) - An experimental drug to treat chronic obstructive pulmonary disease made by GlaxoSmithKline Plc and Theravance Inc appears to work, but the safety data is not entirely conclusive, reviewers for the U.S. Food and Drug Administration said.
They posted their opinion on the FDA's website on Friday, days before a meeting next Tuesday of an outside panel of medical experts, who will discuss the drug and recommend whether the agency should approve it. The FDA is not required to follow the advice of its expert panels but typically does so.
The FDA's reviewers said that while the safety database submitted by GSK is fairly large, it is "not entirely conclusive, particularly in regards to cardiovascular safety."
The total number of major heart-related problems were fairly low, the reviewers said, and the overall cardiovascular safety profile was unremarkable, but imbalances were found when subsets of data were examined, particularly in non-fatal heart attacks.
"Whether these imbalances and discrepancies constitute a safety signal when taken in the context of the complete development program will be a topic for further discussion," the reviewers said.
The drug, Anoro, is an inhaled combination of vilanterol, a long-acting beta-agonist that is designed to open the airways, and umeclidinium, a long-acting muscarinic receptor antagonist, which works to improve lung function.
Analysts expect the drug to win FDA approval, and generate sales of more than $2 billion a year according to the average estimate of six analysts polled by Thomson Reuters. A decision is expected by Dec. 18.
Chronic obstructive pulmonary disease, or COPD, is the third-leading cause of death in the United States, according to federal data. It is a condition often associated with smoking that can include emphysema, chronic bronchitis, or both.
In May, the FDA approved another drug for COPD made by the two companies called Breo. Breo is an inhaled combination of vilanterol and the corticosteroid fluticasone furoate, which reduces inflammation. That drug is expected to generate $1.9 billion by 2018.
Theravance plans to split into two publicly traded companies, separating the respiratory drugs it is developing with Glaxo from its other operations.
After the split, the company holding the respiratory drugs will be called Royalty Management Co. The second company, to be called Theravance Biopharma, will focus on developing drugs for rare diseases.
The move has fueled speculation that Glaxo, which owns 27 percent of Theravance, may eventually buy Theravance's most lucrative products. (Reporting by Toni Clarke in Washington; Editing by Gerald E. McCormick and Grant McCool)