Glaxo antibody drug combats rare blood disorder

LONDON (Reuters) - An experimental antibody drug from GlaxoSmithKline Plc has proved effective in tests for treating a rare disorder known as hypereosinophilic syndrome (HES), researchers said on Sunday.

A Phase III study found significantly more patients who were given Bosatria, also known as mepolizumab, were able to maintain control of their disease with a reduced dose of a corticosteroid, compared to those who received placebo.

The results of the study, involving 85 patients, were presented at the annual meeting of the American Academy of Allergy Asthma and Immunology in Philadelphia and published online by the New England Journal of Medicine.

HES is characterized by persistent elevated levels of eosinophils -- a type of white blood cell -- leading to respiratory, cardiac, skin and gastrointestinal problems. It can cause heart failure and death.

Worldwide prevalence of the condition has not been established but it is estimated to affect between 2,000 and 5,000 patients in the United States.

The number of individuals with eosinophilic disorders has been increasing rapidly in recent years, especially in patients with gastrointestinal symptoms.

Corticosteroids are frequently used in the condition but their prolonged use is often associated with serious side effects. Glaxo's drug works by inactivating a messenger protein, called interleukin-5, linked to eosinophils levels in the blood.

Dr Marc Rothenberg, director of allergy and immunology at Cincinnati Children's Hospital Medical Center and the leader of the study, said the new drug offered a promising steroid-sparing treatment strategy.

"We found that mepolizumab enabled study patients to significantly reduce their doses of steroids and, often, even withdraw from steroid use," he said.

Bosatria has been granted orphan drug status by regulatory authorities in the United States and Europe.

(Reporting by Ben Hirschler; editing by Rory Channing)