FDA Approves First Ever Biologic for Hypereosinophilic Syndrome

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Mepolizumab will be used to treat both adult and pediatric patients with HES for at least 6 months without an identifiable non-hematologic secondary cause.

The US Food and Drug Administration (FDA) has approved mepolizumab (Nucala) as the only biologic treatment for hypereosinophilic syndrome (HES).

The approval, awarded to GlaxoSmithKline, is earmarked for the treatment of adult and pediatric patients at least 12 years old with HES for at least 6 months without an identifiable non-hematologic secondary cause.

“HES is a complex, life-threatening condition that impacts nearly 5,000 patients in the US. Today’s approval gives these patients access to a biologic treatment for the first time and demonstrates our commitment to maximizing Nucala’s impact on eosinophil-driven diseases,” Hal Barron, MD, Chief Scientific Officer and President R&D, GSK, said in a statement.

The FDA approval comes following a priority review of data from a clinical development program including positive results from a recent phase 3 study that showed 50% fewer patients experienced a HES flare following treatment with mepolizumab compared to placebo, when added to standard of care treatment over the 32-week study period (28% vs. 56%; P = 0.002).

Currently, mepolizumab is used as an add-on maintenance therapy for severe eosinophilic asthma and the treatment of eosinophilic granulomatosis with polyangiitis (EGPA). It is also being examined for the treatment of several other eosinophil-driven diseases.

Patients suffering from HES often have a persistent and marked overproduction of eosinophils. By reducing the overproduction of these white blood cells to normal levels, treatment can help patients with eosinophil-driven diseases including HES.

“HES can take many years to diagnose and most patients go through a long and frustrating journey that continues even after the diagnosis is confirmed as treatment roadmaps are often unclear and limited,” Mary Jo Strobel, Executive Director, American Partnership for Eosinophilic Disorders (APFED), said in a statement. “APFED welcomes this approval of Nucala for HES as it gives our community hope.”