Exacerbations are defined as the worsening of asthma which requires use of systemic corticosteroids intravenous (IV) or oral steroid like prednisone, for at least 3 days or a single intramuscular (IM) corticosteroid (CS) dose is required. For maintenance systemic corticosteroids, at least double the existing maintenance dose for at least 3 days was required) and/or hospitalization and/or emergency department (ED) visit. On-Treatment data between first dose date and earliest of Withdrawal date/last dose + 28 days was considered for analysis. Analysis of the number of exacerbations was performed using a negative binomial generalized linear model.

As Treated (AT) Population. AT Population included all participants who received at least one dose of mepolizumab within study 201312.

An AE is any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. Any untoward event resulting in death, life threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, congenital anomaly/birth defect, any other situation according to medical or scientific judgment that may not be immediately life-threatening or result in death or hospitalization but may jeopardize the participant or may require medical or surgical intervention or event associated with liver injury and impaired liver function were categorized as SAE. On-treatment AEs and on-treatment SAEs are the events occurring on/after the first dose of open-label mepolizumab date and before/on last dose+28 days.

AT Population

The ACQ-5 is a five-item questionnaire developed as a measure of participants asthma control. The five questions enquire about the frequency and/or severity of symptoms (nocturnal awakening on waking in the morning, activity limitation, shortness of breath, wheeze). The response options for all these questions consist of a 0 (no impairment/limitation) to 6 (total impairment/ limitation) scale. The overall ACQ score is calculated as the mean of the 5 questions and therefore ranges between 0 (totally controlled) and 6 (severely uncontrolled). Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value.

AT Population. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

FEV1 is defined as the volume of air forcefully expelled from the lungs in 1 second. Pre-bronchodilator FEV1 measurements were taken by spirometry at Baseline and Weeks 24, 48, 72, 96, 120, 144 and 168. Spirometry was performed within 1 hour of the Baseline assessment. Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles). Data between first dose date and earliest of Withdrawal date/last dose + 28 days considered on-treatment.

AT Population

AE is defined as any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a medicinal product. Number of participants withdrawn due to lack of efficacy and adverse events from the study have been presented.

AT Population

AE is defined as any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. SAE is any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, or is a congenital anomaly/birth defect or is medically significant or all events of possible drug induced liver injury with hyperbilirubinemia. Number of participants requiring hospitalization due to an on-treatment serious adverse event including asthma exacerbations are presented. On-treatment SAEs are the events occurring on/after the first dose of mepolizumab date and before/on last dose of mepolizumab + 28 days.

AT Population

AEs were collected from the Baseline visit until the follow-up visit (Week 172). Participants were monitored to evaluate the AEs of systemic and local site reaction. AE is defined as any untoward medical occurrence in a participant or clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. On treatment AEs were defined as events occurring from the first dose until 28 days after the last dose of mepolizumab. Number of participants with AEs including both systemic (i.e. allergic/immunoglobulin (Ig)E-mediated and non-allergic) and local site reactions have been presented.

AT Population

Twelve-lead ECG measurements were recorded after the participant has rested in the supine position for 5 minutes. The ECG was obtained before lung function testing followed by other study procedures. Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles)..

AT Population

Twelve-lead ECG measurements were recorded after the participant has rested in the supine position for 5 minutes. The ECG was obtained before lung function testing followed by other study procedures. Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value. Participants with maximum change from Baseline were summarised at any time post Baseline for the following categories <-60, >=-60 to <-30, >=-30 to <0, >=0 to <30, >=30 to <60 and >=60. QTc intervals shown at any time post Baseline are the maximum seen in each participant over the course of the trial.

AT Population

Vital sign measurements including systolic blood pressure (SBP) and diastolic blood pressure (DBP) were done pre-injection with the participants sitting, having rested in this position for at least 5 minutes before each reading. They were taken before measurement of any clinic lung function tests or ECGs at the specified time point. Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value.

AT Population. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

Vital sign measurements including pulse rate was done pre-injection with the participants sitting, having rested in this position for at least 5 minutes before each reading. They were taken before measurement of any clinic lung function tests or ECGs at the specified time point. Baseline was considered as the latest assessment prior to first dose of mepolizumab in this study. The change from Baseline is defined as the difference between the value of the endpoint at the time point of interest and Baseline value.

AT Population. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

Blood samples were collected for the determination of ADA just prior to administration of mepolizumab. Samples that tested positive for anti-mepolizumab antibodies were further tested for the presence of NAb. The highest value post-Baseline visit are based on each participant's highest post-Baseline titer. NAb assay result was only presented for participants with positive ADA assay. Highest value post-Baseline would be positive for a participant who had both negative and positive post-Baseline results. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

AT Population

Blood samples were collected to assess clinical chemistry laboratory parameters. Number of participants with Potential Clinical Importance values for change from Baseline relative to the reference range at any time post-Baseline are presented. Any time post Baseline = all visits (including scheduled and unscheduled) post-Baseline. Participants are counted in the category that their value changes to (low, normal or high), unless there was no change in their category. If lab value category was unchanged, participants were recorded in the "To Normal or No Change" category. Alanine Aminotransferase=ALT. Only those participants with data available at the specified time points were analyzed (represented by n=X in the category titles).

AT Population

Blood samples were collected to assess hematology laboratory parameters. Number of participants with Potential Clinical Importance values for change from Baseline relative to the reference range at any time post-Baseline are presented. Any time post Baseline = all visits (including scheduled and unscheduled) post-Baseline. Participants are counted in the category that their value changes to (low, normal or high), unless there was no change in their category. If lab value category was unchanged, participants were recorded in the "To Normal or No Change" category.

AT Population