Mepolizumab as Add-on Treatment IN Participants With COPD Characterized by Frequent Exacerbations and Eosinophil Level

This is a multi-center, randomized, placebo-controlled, double-blind, parallel group study designed to confirm the benefits of mepolizumab treatment on moderate or severe exacerbations in chronic obstructive pulmonary disease (COPD) participants given as an add on to their optimized maintenance COPD therapy. The maximum duration of participant participation is approximately 109 weeks, consisting of 2 screening visits (up to 3 weeks), a run-in period (up to 2 weeks), and an intervention period of at least 52 weeks and up to 104 weeks. 800 participants will be randomized in a 1:1 ratio to receive mepolizumab 100 milligrams (mg) or placebo every 4 weeks for at least 13 doses (52 weeks treatment period) up to a maximum of 26 doses (104 weeks treatment period). The number of randomized participants may increase up to approximately 1400.

Inclusion Criteria: * Participant must be at least 40 years of age at Screening Visit 1. * Participants with a peripheral blood eosinophil count of \>=300 cells per microliter (μL) from the hematology sample collected at Screening Visit 0 AND a documented historical blood eosinophil count of \>=150 cells per μL in the 12 months prior to Screening Visit 0 that meets the following: It must have been measured between 12 months and 1 month prior to Screening Visit 0, and it must not have been measured within 14 days of a COPD exacerbation. Participants with no documented historical blood eosinophil count of \>=150 cells per µL must meet this threshold at the Screening Visit 1 assessment. * Participants with a clinically documented history of COPD for at least 1 year in accordance with the definition by the American Thoracic Society or European Respiratory Society. * Participants must present with a measured pre- and post-salbutamol Forced expiratory volume in one second (FEV1)/Forced vital capacity (FVC) ratio of \20% and \=500 microgram (mcg) per day fluticasone propionate dose equivalent plus 2) Long acting beta2-agonist (LABA) and 3) Long acting muscarinic antagonist (LAMA) unless documentation of safety or intolerance issues related to LABA or LAMA. For participants who are not continually maintained on ICS plus LABA plus LAMA for the entire 12 months prior to Visit 1 use of the following is allowed (but not in the 3 months immediately prior to Visit 1); inhaled corticosteroid at a dose \>=500 mcg per day fluticasone propionate dose equivalent plus inhaled LABA or inhaled LAMA and Phosphodiesterase-4-inhibitors, methylxanthines, or scheduled daily use of short acting beta2-agonist (SABA) and/or short acting muscarinic antagonist (SAMA). * Current or former cigarette smokers with a history of cigarette smoking of \>=10 pack-years at Screening (Visit 1) calculated as (number of pack years = \[number of cigarettes per day/20\] multiplied by number of years smoked \[For example, 20 cigarettes per day for 10 years or 10 cigarettes per day for 20 years\]). * Contraceptive use for female participant should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. * A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: She is not a woman of childbearing potential (WOCBP) or she is a WOCBP and using a contraceptive method that is highly effective, with a failure rate of \