GlaxoSmithKline heads to the FDA with its next big respiratory bet

GlaxoSmithKline ($GSK) is racing to be the first on the market with a new approach to treating severe asthma, filing U.S. and European applications for the injectable mepolizumab as it jockeys with Teva ($TEVA) and AstraZeneca ($AZN).

The treatment works by blocking the protein interleukin-5 and thus preventing buildups of white blood cells in the lungs that can exacerbate asthma. GSK is angling to get the drug approved as a treatment for sufferers of severe asthma who aren't getting the relief they need from inhaled therapies.

In Phase III trials, GSK's drug met its primary endpoints of cutting the number of flare-ups for severe asthmatics and reducing patients' need for daily corticosteroids. The company believes those results are enough to get its monthly injection on the market, and a victory would pit mepolizumab against Novartis ($NVS) and Genentech's blockbuster Xolair, which was the first non-inhaled treatment for severe asthma approved.

Meanwhile, Teva has posted similarly positive Phase III results with its IL-5 treatment, dubbed reslizumab, and the Israeli drugmaker plans to file regulatory applications of its own early next year. Just behind is AstraZeneca and its benralizumab, an IL-5 blocker the company believes can bring in peak sales of $2 billion. AstraZeneca's treatment has so far posted mixed results in mid-stage studies and is currently in Phase III for severe asthma.

All three contenders are working to prove their antibodies can improve results in COPD as well, hoping to carve out a new market for injectable respiratory treatments that analysts have said could reach above $7 billion a year.

The race is of particular importance for GSK, whose once-lauded respiratory business has consistently disappointed analysts, with sales slipping another 18% last quarter. Advair, long the drugmaker's cash cow in the field, is finally facing generic competition, and the potential blockbusters expected to usurp it, Breo and Anoro Ellipta, have lagged expectations since winning FDA approvals last year. Citing sluggish sales, GSK is rolling out a company-wide reorganization, looking to carve £1 billion ($1.6 billion) out of its annual budget.

But the company is keeping faith in its respiratory pipeline. Behind mepolizumab, GSK is working with longtime partner Theravance ($THRX) to study a new treatment that pools the active ingredients in Anoro and Breo to create a triple-threat solution for COPD. The two companies are also developing a bifunctional muscarinic antagonist-beta agonist that has shown promise in mid-stage trials.

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