GlaxoSmithKline’s experimental monoclonal antibody Bosatria has shown promise in a late-stage trial assessing the drug as a treatment for the rare inflammatory disorder hypereosinophilic syndrome (HES).

Currently, the only treatment for patients with HES - which is potentially fatal and characterised by dangerously high levels of a type of white blood cells called eosinophils, leading to widespread inflammation and organ damage - is with corticosteroids such as prednisone (off-label), and so any new potential treatment for the condition is likely to be very welcome news indeed.

In a Phase III clinical trial of Bosatria (epolizumab), results of which are published in the New England Journal of Medicine, 95% of patients receiving the drug plus steroids were able to keep their eosinophils levels within a normal range, compared to 45% of those taking a ghost pill/steroid regimen.

Reducing steroids
Furthermore, almost half of patients (47%) taking Bosatria were able to cut down on their use of steroids during the 36-week study, while just 5% of the control group reduced their intake, which represents an important potential benefit as long-term use of steroids can lead to unpleasant side effects such as weight gain and high blood pressure.

Given the small treatment population for HES the drug has been granted orphan status in both Europe and the USA, and GSK is hoping to file for approval in this indication on both sides of the Atlantic sometime this year, according to media reports.