WILMINGTON, Del., May 14, 2026
AstraZeneca announced that the U.S. Food and Drug Administration has approved FASENRA® (benralizumab) for the treatment of adult and pediatric patients aged 12 years and older with hypereosinophilic syndrome (HES) without an identifiable non-hematologic secondary cause. The approval expands FASENRA’s growing respiratory and immunology portfolio while providing a new targeted treatment option for patients living with the rare and potentially life-threatening eosinophilic disorder.
The FDA approval was supported by positive results from the Phase III NATRON trial, which demonstrated that treatment with FASENRA significantly delayed the time to first HES flare and reduced the risk of first flare by 65% compared with placebo. Investigators reported a hazard ratio of 0.35 with strong statistical significance, highlighting the biologic therapy’s potential to improve disease management in a patient population with limited targeted treatment options.
Phase III NATRON Trial Demonstrates Strong Clinical Benefit
Hypereosinophilic syndrome is a group of rare disorders characterized by persistently elevated eosinophil levels that can lead to progressive organ and tissue damage over time. Patients often experience debilitating symptoms including fatigue, skin manifestations, chest pain, neurologic complications, abdominal pain, and respiratory issues. If left untreated, HES can become fatal due to irreversible organ injury.
The Phase III NATRON study was a randomized, multicenter, double-blind, placebo-controlled trial evaluating the efficacy and safety of FASENRA 30 mg administered subcutaneously every four weeks. A total of 133 participants were randomized to receive either benralizumab or placebo while continuing stable HES therapy. The primary endpoint focused on time to first HES worsening or flare requiring increased corticosteroids, immunosuppressive therapy, or hospitalization.
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Researchers confirmed that FASENRA successfully met the primary endpoint, significantly reducing flare risk while also evaluating key secondary endpoints including annualized flare rates and changes in fatigue-related quality-of-life scores. The therapy demonstrated clinically meaningful improvements in disease control, reinforcing the importance of eosinophil-targeted biologics in immune-mediated diseases.
Princess U. Ogbogu, principal investigator of the NATRON trial and Division Chief of Pediatric Allergy, Immunology, and Rheumatology at University Hospitals Rainbow Babies and Children’s Hospital, stated that the approval marks an important advancement for HES patients by providing an additional treatment option capable of meaningfully reducing flares while also helping address severe fatigue symptoms.
AstraZeneca Expands Eosinophilic Disease Leadership
FASENRA is already approved in more than 80 countries as an add-on maintenance treatment for severe eosinophilic asthma (SEA) and in more than 70 countries for adults with eosinophilic granulomatosis with polyangiitis (EGPA). The latest FDA approval significantly broadens AstraZeneca’s leadership position in eosinophilic-driven diseases and rare immunologic disorders.
James Teague, Vice President of US Respiratory & Immunology and Vaccine & Immune Therapies at AstraZeneca, stated that the approval builds upon FASENRA’s established foundation in targeting eosinophilic-driven diseases while addressing a substantial unmet medical need in patients experiencing significant disease burden and limited targeted therapies.
The most common adverse reactions reported in the NATRON study included headache, hypersensitivity reactions, and influenza-like illness, with the therapy generally demonstrating a manageable safety profile. AstraZeneca noted that FASENRA should not be used for sudden breathing problems and warned of potential hypersensitivity reactions, including anaphylaxis.
Rare Disease Treatment Landscape Continues to Evolve
The approval underscores increasing industry focus on targeted biologic therapies for rare inflammatory and immunologic disorders. Experts estimate that HES affects between 0.3 and 6.3 individuals per 100,000 people in the United States, although diagnosis remains challenging due to the wide range of symptoms and organ involvement.
AstraZeneca continues investing heavily in respiratory and immunology research, positioning biologic therapies such as FASENRA at the center of its strategy to address chronic immune-mediated diseases through precision-targeted approaches.
Source: AstraZeneca press release
