GlaxoSmithKline bags an FDA OK for its asthma drug with eyes on a respiratory turnaround

GlaxoSmithKline ($GSK) won FDA approval for an antibody designed to treat severe asthma, leading a pack of drugmakers at work on similar therapies as it seeks to bolster its respiratory business.

The treatment, mepolizumab, works by blocking the protein interleukin-5 to prevent buildups of white blood cells in the lungs that can exacerbate asthma. The FDA's approval covers severe asthmatics 12 and over, a wider indication than previously recommended by a group of agency advisers that voted in favor of the drug only for adults.

The antibody, to be marketed as Nucala, is injected under the skin every four weeks to relieve symptoms of severe asthma for patients who aren't properly served by inhaled therapies, a population GSK estimates at about 400,000 in the U.S.

With the approval, GSK takes the lead among a group of drugmakers developing IL-5 antibodies for severe asthma. AstraZeneca ($AZN) is in Phase III with the similar benralizumab, and Teva ($TEVA) has said it's on track to file the IL-5-blocking reslizumab this year. 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.

Nucala's stateside success is particularly key for GSK, whose banner respiratory franchise has come under investor scrutiny over the past year. Advair, long the drugmaker's cash cow in COPD, is facing generic competition, and the potential blockbusters expected to usurp it, Breo and Anoro Ellipta, have underperformed analyst expectations since winning FDA approvals in 2013. The recent approvals for competing treatments from Boehringer Ingelheim and Novartis ($NVS) have only further complicated matters.

Touting its pipeline to investors earlier this week, GSK has promised to submit up to 20 new drugs for approval by 2020, highlighting its work in immuno-oncology, HIV and rare diseases as it combats suggestions that it break up its business.

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