Mepolizumab is investigative treatment for adults with eosinophilic chronic obstructive pulmonary disease (COPD) being developed by GSK. It works to deplete eosinophils, a type of white blood cell whose production, activation, recruitment, and proliferation at inflammation sites is controlled by interleukin 5 (IL5), an immune system hormone. In excess, eosinophils can cause inflammation in the lungs, ultimately leading to excess sputum production that causes exacerbations (a worsening of respiratory symptoms).
The drug is an antibody (biological drug) of the IL5 hormone and has demonstrated efficacy in people with severe asthma. It is designed to weaken the immune response in the bronchi by reducing the number of eosinophils. About 18 percent of COPD patients have high levels of eosinophils in their airways, and the treatment is under Phase 3 clinical testing in these people.
Under the brand name Nucala, mepolizumab was approved by the U.S. Food & Drug Administration (FDA) in 2015 as an add-on maintenance treatment for severe asthma patients with an eosinophilic phenotype. It is taken every four weeks as a 100-milligram subcutaneous injection.
Mepolizumab and clinical trials for the treatment of COPD
According to the clinicaltrials.gov website three Phase 3 studies were undertaken into mepolizumab as a COPD treatment.
The first study (NCT01463644), which ended in 2015, evaluated mepolizumab’s effects in COPD patients with sputum eosinophilia. In this double blind study, about 18 participants (ages 40–80) were given either mepolizumab (intravenous 750 milligram dose) or a placebo (intravenous 100 ml saline solution) once a month for six months. Its primary measure was the percentage decrease in sputum eosinophils, and a secondary measure looked at the proportion of patients with a major exacerbation. Results showed that mepolizumab reduced sputum and blood eosinophils, but the drug did not improve the secondary measures of lung function and exacerbation rates. A study of the trial’s data, published in the European Respiratory Journal in 2016, suggested that, unlike asthma, eosinophils may not contribute to airway obstruction in COPD.
A second Phase 3 study (NCT02105948) compared mepolizumab (100 milligrams) to placebo (0.9% saline solution), both taken by subcutaneous injection every four weeks. About 837 people with severe COPD exacerbations were followed over a 62-week period (1-2 weeks for initial screening; a 52 week treatment period; an 8-week follow-up period), and were evaluated for frequency of disease flares — moderate or severe — and other exacerbation measures during the trial. The study, which ended in January 2017, does not yet have published results.
A third Phase 3 study (NCT02105961) is evaluating two mepolizumab doses (100 and 300 milligrams, subcutaneous injection) against a placebo. About 660 COPD patients with a baseline blood eosinophil count of at least 150 cells/microliters are enrolled in this 62-week global study, which is expected to end in early 2017. The treatment is being evaluated as an add-on therapy to standard COPD care.
Mepolizumab is taken by subcutaneous injection in the upper arm, thigh or stomach.
The most frequent reported side effects of mepolizumab use include injection site reaction (pain, redness, swelling or itching), headache, back pain, and fatigue.
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