GlaxoSmithKline starts final-stage tests on severe asthma drug

(REUTERS/Toby Melville)

GlaxoSmithKline has started final-stage testing of an experimental drug for treating severe asthma, Britain's biggest drugmaker said on Monday.

The move to progress the injectable antibody treatment mepolizumab into Phase III trials had been expected after an earlier study showed it nearly halved the number of attacks suffered by patients.

Severe refractory asthma only affects around 4 percent of patients with the disease, so the drug may not become a major seller for GSK but could consolidate the group's strong grip on the market for lung drugs.