The trial, which evaluated the efficacy of two dose regimens of mepolizumab, also met its primary endpoint of reduction in the frequency of exacerbations.
Throughout the trial, patients remained on their current asthma maintenance therapy and were randomized to receive either mepolizumab 75mg intravenous (IV), 100mg subcutaneous (SC), or placebo every four weeks.
For the primary end point, both mepolizumab treatment arms demonstrated significant reductions in the frequency of clinically significant exacerbations of asthma compared to placebo.
The company said that the adverse events reported in the trial were similar across all treatment groups.
The most common reported adverse events were nasopharyngitis, headache, upper respiratory tract infection and asthma.
GSK head of Respiratory Therapy Area Unit, R&D Dave Allen said the company is happy to have generated further positive data on mepolizumab, consistent with the findings from its earlier exacerbation study.
"We now have two studies showing a reduction in exacerbations in a specific group of patients with a severe form of asthma who continue to exacerbate despite treatment with high doses of their current maintenance therapies," Allen said.
"For GSK it is exciting that this is the first non-inhaled treatment for severe asthma and we will be progressing towards global filings at the end of the year."
Separately, a second Phase III trial designed to assess the use of mepolizumab 100mg SC, every four weeks in comparison to placebo in reducing daily oral corticosteroid use while maintaining asthma control also met its primary endpoint.
Image: GlaxoSmithKline headquaters in Brentford, London, England. Photo: courtesy of Maxwell Hamilton