By Esha Dey and Bill Berkrot
WASHINGTON/NEW YORK (Reuters) - U.S. health regulators have ordered drugmakers to conduct clinical trials involving a total of 53,000 patients to test the safety of a controversial class of inhaled asthma drugs that are already on the market.
The trials are being required to demonstrate the safety of medicines known as long-acting beta-agonists (LABAs) when used in combination with inhaled steroids, another class of asthma drugs, the U.S. Food and Drug Administration said on Friday.
LABAs to be studied are AstraZeneca's Symbicort, GlaxoSmithKline's Advair Diskus, Merck & Co's Dulera, and Novartis AG's Foradil.
LABAs have long been under FDA scrutiny as they can increase the risk of severely worsening asthma symptoms that can lead to hospitalizations and death.
The drugs work by relaxing the muscles of the airways to help people breathe easier and are also used to treat the serious lung condition, chronic obstructive pulmonary disease
The FDA expects to receive results in 2017 for the studies that will begin later this year.
In four of the trials sought by the FDA, each of the LABAs plus a corticosteroid will be compared with the steroid alone in patients 12 years of age and older. Those studies are expected to include a total of 46,800 patients.
Some of these drugs. such as Advair and Symbicort, are combination drugs that include a LABA with a corticosteroid.
The agency has also asked for a trial of 6,200 younger patients, aged 4 to 11, using Glaxo's Advair Diskus.
The huge size of the studies signals that FDA wants to be completely sure about the safety profile of these drugs as they are used so widely, Morningstar analyst Damien Conover said.
Such a large study population might pose some financial challenges for the drugmakers, he said.
"Glaxo is complying with the FDA request to implement the Phase 4 study," Glaxo spokeswoman Lisa Behrens said of the post-marketing trial.
AstraZeneca said it was finalizing study protocol with the agency and supports efforts to address any questions regarding use of its drug.
Novartis said it was reviewing the post-marketing requirements issued by the FDA, while Merck said it would have a comment shortly.
The FDA last June issued warnings on LABAs, saying they should never be used on their own to treat asthma and called on drugmakers to conduct further studies to better understand the safety of LABAs when used with inhaled steroids.
The agency posted the study requirements on its website at http://www.fda.gov/Drugs/DrugSafety/ucm251512.htm .
(Reporting by Esha Dey in Washington and Bill Berkrot in New York; Editing by Tim Dobbyn)