* Salford COPD study success follows failure of 2015 trial

* 8.4 pct reduction in exacerbations vs standard care

(Adds comment from GSK executive and analyst)

By Ben Hirschler

LONDON, May 24 (Reuters) - GlaxoSmithKline's GSK.L new inhaled medicine Breo proved significantly better than standard care in a large British study that tested it in everyday use, providing a fillip for the product after the failure of another big trial in 2015.

GSK said on Tuesday the study, which tested Breo in day-to-day practice across the town of Salford, showed it was superior in reducing attacks of serious breathing difficulties in patients with chronic obstructive pulmonary disease (COPD).

There was a statistically significant reduction of 8.4 percent in the rate of moderate or severe exacerbations compared with those receiving usual care, the 2,800-patient study found.

GSK said beating optimal standard care was a tough challenge though Deutsche Bank analyst Richard Parkes said the benefit was "modest and of uncertain value given complexities in the trial design".

The positive result comes after another more traditional clinical trial in September found Breo - marketed as Relvar in Europe - failed to prolong life in patients with COPD, which is sometimes known as smoker's lung.

Britain's largest drugmaker is relying on Breo, which was approved in 2013, to help defend its respiratory drug business as its older blockbuster Advair faces generic competition. U.S. drugmaker Innoviva is GSK's partner for Breo.

Since the study was conducted within Britain's National Health Service, its international relevance is unclear.

"The biggest unknown is how the U.S. will view a study like this that has been undertaken in the UK healthcare setting," said Patrick Vallance, GSK's president of pharmaceuticals R&D.

"I think there will be interest in the U.S. but I can't predict how it will be considered by U.S. prescribers and healthcare systems."

A second, similar lung study is being conducted in Salford in asthma patients, with results expected in 2017.

GSK has spent 80 million pounds ($117 million) in conducting the two "real world" studies, including the cost of training more than 2,000 healthcare professionals in the Salford and south Manchester area.

The company's medicine, which is inhaled through a palm-sized device called Ellipta, consists of a corticosteroid to reduce inflammation and a long-acting beta-agonist to open the airways. Unlike some old medications, it only needs to be taken once a day and patients do not need multiple inhalers.

($1 = 0.6852 pounds)

(Editing by David Clarke) ((ben.hirschler@thomsonreuters.com; +44 20 7542 5082; Reuters Messaging: ben.hirschler.thomsonreuters.com@reuters.net))