The US Food and Drug Administration (FDA) has approved GlaxoSmithKline (GSK)’s Nucala (mepolizumab) as a treatment for hypereosinophilic syndrome (HES).

Approval is for adult and paediatric patients aged 12 years and above with HES for six months or more without a detectable non-haematologic secondary cause.

GSK said the FDA approval marks Nucala as the first and only targeted biologic therapy approved for HES patients in the US.

Nucala is a monoclonal antibody designed to prevent IL-5 from attaching to its receptor present on the eosinophils surface, decreasing blood eosinophils to normal levels.

The drug secured first approval in 2015 to treat severe eosinophilic asthma (SEA) as an add-on maintenance therapy for SEA and treatment of eosinophilic granulomatosis with polyangiitis (EGPA).

Last year, the FDA approved Nucala to treat severe eosinophilic asthma in children.

The latest approval comes after GSK’s drug received a priority review for clinical development programme data that demonstrated positive results from a Phase III trial.

In the 32-week trial, 50% lesser patients demonstrated HES flare when treated with Nucala as compared to placebo, given along with the standard of care, the company said.

GSK chief scientific officer and R&D president Hal Barron said: “HES is a complex, life-threatening condition that impacts nearly 5,000 patients in the US.

“Today’s approval gives these patients access to biologic treatment for the first time and demonstrates our commitment to maximising Nucala’s impact on eosinophil-driven diseases.”

In a similar development, the FDA granted approval for Vertex Pharmaceuticals’ Kalydeco (ivacaftor) to treat cystic fibrosis (CF) in children aged four months to less than six months.

Kalydeco becomes the first cystic fibrosis transmembrane conductance regulator (CFTR) modulator that can treat CF patients as early as four months, Vertex said.

The approval comes from findings of a Phase III ARRIVAL trial cohort, which included six children who have one of the G551D, G178R, S549N, S549R, G551S, G1244E, S1251N, S1255P, G1349D or R117H mutations in CFTR gene.