The Phase III data for the drug, which GSK is developing with Theravance, will support the British drugmaker's plans to start global filings to regulators for the combination pill from the end of this year, the firm said in a statement.

GSK is working hard to develop next-generation medicines to become successors to its $8 billion lung drug Advair.

Advair and Pfizer's Spiriva currently dominate the respiratory drug market, but Swiss firm Novartis is also fighting the next generation battle with its experimental combination drug QVA149, which some analysts are already tipping as a potential $5 billion-a-year seller.

GSK's hopes are not only resting on the novel LAMA/LABA combination drug.

It also has high expectations for its "son of Advair" drug, Relovair, also being developed with Theravance, which combines a LABA and an inhaled corticosteroid (ICS).

LAMA/LABA is a combination of two molecules - umeclidinium bromide (UMEC), a long-acting muscarinic antagonist (LAMA) and vilanterol (VI), a long-acting beta2 agonist (LABA), administered by a new dry powder inhaler.

The new Phase III data showed the combination drug produced statistically significant improvements when compared with its individual components alone, and compared to placebo, in two 24-week trial involving around 1,500 patients each.

Two further studies compared LAMA/LABA against Spiriva, known generically as tiotropium, and also found statistically significant positive results for the GSK combination pill.

Savvas Neophytou, an analyst at Panmure Gordon, was unmoved by the fresh data and said he would not be changing his view on GSK stock, which he currently rates as a hold.

"This particular product is a large-scale programme which GSK has been investing in so it was good to see the trials come to successful fruition," he said in a research note. "It has to be said, however, that some of the data is patchy."

GSK said the most common adverse events across all four studies in all treatment arms, including placebo, were headaches, common colds, upper respiratory tract infections, cough, sore throats and back pain.

Darrell Baker of GSK's respiratory portfolio division said LAMA/LABA was an important cornerstone of the firm's broad respiratory portfolio.

"Subject to successful completion of the ongoing studies, we plan to commence global regulatory filings from the end of this year," he said in a statement.

(Editing by Mark Potter)

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