As Teva wins US approval for GSK Advair copy, main fight yet to come

* Teva's Advair copy not substitutable and only for asthma

* Substitutable generics could be approved in March and May

By Ben Hirschler

LONDON, Jan 30 (Reuters) - Israel's Teva Pharmaceutical Industries has won U.S. approval to market a copy of GlaxoSmithKline (Other OTC: GLAXF - news) 's best-selling Advair inhaler, although the real battle is still to come.

Teva's version of GSK's blockbuster medicine, called AirDuo RespiClick, is not directly substitutable for Advair and is only approved for asthma, while Advair is also widely used for chronic obstructive pulmonary disease (COPD).

Teva said on Monday it would launch AirDuo later this year. It has not said how much its product will cost.

AirDuo provides patients with the same two drugs as Advair, fluticasone propionate and salmeterol, but it delivers a lower dose of salmeterol. It also uses Teva's Respiclick inhaler rather than a copy of GSK's device.

Producing cut-price copies of Advair is a major opportunity for generics companies at a time when fewer blockbuster medicines are losing patent protection.

For GSK, it is a challenge since Advair has sold more than $1 billion annually since 2001. Global Advair sales were $5.6 billion in 2015, with half that generated in the United States, although sales are now shrinking.

Teva's product promises to grab some of this business in asthma but the bigger threat will come from fully substitutable generic copies of Advair, which are still pending approval.

The U.S. Food and Drug Administration is due to decide whether to approve the first of these, from Mylan (Hamburg: 27249935.HM - news) , by March 28. A rival version from Hikma and Vectura is close behind, with an approval date of May 10.

GSK said that as Teva's product was not substitutable for or equivalent to Advair it did not "pose the same competitive dynamics as market entry of generic products in the U.S. would."

Advair is already available generically in Europe, but demand for copies is expected to take off more swiftly in the United States, where managers of prescription plans can quickly drive conversion to such cheaper products.

Investors are watching closely to see how GSK's Advair sales will fare in the face of new competitors. One big unknown is the scale of discounts that will be offered by generic companies. (Reporting by Ben Hirschler; Editing by Susan Fenton)