The US has become the first country in the world to approve GlaxoSmithKline’s novel biologic Nucala, as an add-on maintenance therapy for a difficult-to-treat form of asthma.

The US Food and Drug Administration has cleared use of Nucala (mepolizumab) in patients with severe asthma aged 12 years and older whose condition is driven by eosinophilic inflammation, offering patients access to the first and only approved biologic therapy that targets interleukin-5.

IL-5 is the main promoter of eosinophil growth, activation and survival, and provides an essential signal for the movement of eosinophils from the bone marrow into the lung. Over-production of eosinophils causes inflammation in the lungs that can affect the airways, limiting breathing and increasing asthma attacks. Around 60% of patients with severe asthma are thought to have eosinophilic airway inflammation.

Nucala, which will be administered as a 100mg fixed-dose subcutaneous injection every four weeks, is a monoclonal antibody that prevents IL-5 from binding to its receptor on the surface of eosinophils, thus reducing their presence in the bloodstream.

In study MEA115588, mepolizumab 75mg cut the frequency of clinically significant exacerbations of asthma by 47% versus placebo, while the 100mg dose cut the amount by 53%.

“As a clinician, the prospect of a treatment that can specifically target the underlying cause of the disease for patients whose condition is driven by eosinophilic inflammation is exciting,” said Ian Pavord, University of Oxford, a mepolizumab trial investigator.

The drug was backed for European approval by the Committee for Medicinal Products for Human Use in September.