AstraZeneca’s benralizumab (Fasenra), previously approved to treat a severe form of asthma, significantly improved the health of people with hypereosinophilic syndromes (HES) in whom other treatments proved ineffective or intolerable.
HES is caused by high levels of eosinophils in the blood, tissues, or both. Symptoms can affect the heart, lungs, skin, gastrointestinal tract, central nervous system, and other organ systems. Most existing therapies use drugs that are not specifically approved for the syndromes, have significant side effects, and whose effectiveness can decrease over time.
Results from a phase 2 clinical trial by scientists at the National Institute of Allergy and Infectious Diseases (NIAID) were recently published in the New England Journal of Medicine. The study, NCT02130882, is only the second randomized, placebo-controlled trial testing the effectiveness of a drug specifically for treating HES.
Benralizumab consists of an antibody that binds to the IL-5 receptor protein, found on the surface of eosinophils. Scientists believe that once the binding occurs, natural killer cells destroy the eosinophils.
The trial enrolled 20 people with severe forms of HES with a minimum of 1,000 eosinophils/µL of blood, whose condition had been stable on other HES therapies for at least one month prior. Participants were randomly assigned to either 30 mg benralizumab or placebo solution once every four weeks, while continuing their current HES therapy. In the second phase all participants received 30 mg benralizumab once every four weeks.
After at least 12 weeks of benralizumab during the first phase, second, or both, 17 of 19 participants had undetectable levels of eosinophils in the blood and a reduction in symptoms, with few or no side effects. These responses lasted through the end of the third phase in 74% of participants, 64% of whom were able to taper off other HES therapies during the third phase.
Also, eosinophils were undetectable in the bone marrow of nine of 10 participants in the treatment group in the first phase, and in the tissue of all eight participants whose tissue was tested at the end of the second phase.
The investigators say a larger, placebo-controlled trial of benralizumab for treating HES is needed to confirm these results.
Source: National Institute of Allergy and Infectious Diseases, April 3, 2019