WILMINGTON, DE — AstraZeneca reported statistically significant Phase III results showing that Fasenra (benralizumab) can substantially delay disease worsening for patients with hypereosinophilic syndrome (HES), a rare and potentially life-threatening immune-driven disorder.
According to full data from the NATRON trial, patients treated with Fasenra experienced a 65% reduction in the risk of HES worsening or flare compared with placebo (19.4% vs. 42.4%; HR 0.35). The biologic also demonstrated a noticeable improvement in fatigue symptoms, one of the most debilitating aspects of the condition.
HES is marked by persistently elevated eosinophils—white blood cells that, when overactive, can damage organs and lead to progressive complications. Because symptoms vary widely and can affect multiple systems, diagnosis and treatment remain challenging. Current therapies include steroids, chemotherapy agents, tyrosine kinase inhibitors, and IL-5–targeted monoclonal antibodies.
Princess U. Ogbogu, the trial’s principal investigator and Division Chief of Pediatric Allergy, Immunology, and Rheumatology at University Hospitals Rainbow Babies and Children’s Hospital, said the results point to meaningful clinical benefit. She noted that patients often struggle with fatigue, organ involvement, and significant quality-of-life impacts, and highlighted the potential of benralizumab to reduce flare risk and hematologic relapse while improving fatigue with a monthly dose regimen.
AstraZeneca said the findings reinforce Fasenra’s role in addressing eosinophilic inflammation across complex, difficult-to-treat conditions. Sharon Barr, Executive Vice President of BioPharmaceuticals R&D, said the company is advancing regulatory filings with the goal of expanding treatment options for patients with few viable alternatives.
The trial also met all key secondary endpoints. Fasenra reduced the proportion of patients experiencing flares or withdrawals (22.4% vs. 45.5%), cut the annualized flare rate by 66%, and significantly delayed time to hematologic relapse. Improvements in PROMIS Fatigue scores were seen as early as Week 4 and continued through Week 24.
The safety profile observed in NATRON was consistent with previously known data for Fasenra, which is already approved for severe eosinophilic asthma and eosinophilic granulomatosis with polyangiitis in multiple countries.
AstraZeneca said the results strengthen its long-term strategy in respiratory and immunology, a core growth area for the company.
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