This summarizes the number of participants who returned to at least 50% of their Baseline blood eosinophil levels after maximum inhibition had been achieved and without any subsequent decrease in blood eosinophil levels. Blood samples were collected at Days 1, 3, 7, 28, 56, 70, 84, 112 and 140.

AUC of mepolizumab was estimated by population modeling techniques using non-linear mixed effect methods for the individual and population pharmacokinetic parameters from the sparse sampling. Individual cumulative plasma of mepolizumab AUC to Day 84 (cumAUC(0-day 84)), is the sum of the AUCs over each dosing interval after each of the three doses administered, for those participants with data up to Day 84. Individual cumulative plasma of mepolizumab AUC to Day 140 (cumAUC(0-day 140) is the sum of the AUCs over each dosing interval after each of the three doses administered plus the AUC post the last dose interval up to Day 140 (i.e. from Day 84 to Day 140). Blood samples for PK analyses were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 hour (h), 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

Maximum plasma concentration was estimated by population modelling techniques using non-linear mixed effect methods for the individual and population pharmacokinetic parameters from the sparse sampling. Blood samples for PK analyses of mepolizumab were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 h, 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

Time to maximum plasma concentration was estimated by population modelling techniques using non-linear mixed effect methods for the individual and population pharmacokinetic parameters from the sparse sampling. Blood samples for PK analyses of mepolizumab were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 h, 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

Terminal half-life (t1/2) was estimated by modelling techniques using non-linear mixed effect methods for the individual and population pharmacokinetic parameters for mepolizumab from the sparse sampling. Blood samples for PK analyses of mepolizumab were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 h, 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

Hematology laboratory parameters included platelet count, red blood cells (RBC) count, white blood cell (WBC) count, hemoglobin, hematocrit, reticulocyte count, mean corpuscle volume (MCV), mean corpuscle hemoglobin (MCH), mean corpuscle hemoglobin concentration (MCHC), neutrophils, segmented neutrophils (SN), total neutrophils (TN), lymphocytes, monocytes, eosinophils and basophils assessed at Baseline, Weeks 4, 8, 12 and 20. Hematology abnormalities outside the normal range (high and low values) at any time post-Baseline are presented.

Vital sign measurements including systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at Baseline (pre-dose Day 1), Day 1 (30 minutes, 1 h, 2 h), Day 28 (pre-dose, 30 minutes, 1 h, 2 h), Day 56 (pre-dose, 30 minutes, 1 h, 2 h), Day 84, Day 112 and follow-up (Day 140).

Vital sign measurements including heart rate (HR) was measured at Baseline (Pre-dose Day 1), Day 1 (30 minutes, 1 h, 2 h), Day 28 (pre-dose, 30 minutes, 1 h, 2 h), Day 56 (pre-dose, 30 minutes, 1 h, 2 h), Day 84, Day 112 and follow-up (Day 140).

Blood samples were collected for the determination of anti-mepolizumab antibodies by antibody detection (AD) and antibody neutralisation (AN) assay. For participants who prematurely withdrew from the study and had been dosed, immunogenicity testing occurred (if possible) at the time of premature withdrawal and at 16 weeks after dosing (or the end of the study, whichever came first). Serum was tested for the presence of anti-mepolizumab antibodies using the currently approved analytical methodology incorporating screening, confirmation and titration steps. Samples confirmed positive for the presence of anti-mepolizumab antibodies in the original assay were tested for the presence of neutralizing antibodies.

The number of participants with normal, abnormal - clinically significant (CS), and abnormal - not clinically significant (NCS) ECG findings, as well as the number of participants with no results (NR), at Screening (SCR) and Day 3 are presented. Findings were determined to be normal, abnormal CS, and NCS by the investigator.

Population modelling techniques using non-linear mixed effect methods were used to estimate individual and population pharmacokinetic parameters from the sparse sampling. Log-transformed individual clearance estimates were analysed using an analysis of variance (ANOVA) model. The absolute bioavailability for each SC dose group and across SC doses will be estimated from the model together with associated 90% confidence intervals. Blood samples for PK analyses were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 h, 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

Maximum plasma concentration was estimated by population modelling techniques using non-linear mixed effect methods for the individual and population pharmacokinetic parameters from the sparse sampling. Log-transformed dose-normalized (DM) Cmax were be analyzed using an analysis of variance (ANOVA) model. The ratio for each SC dose group versus IV and across SC doses versus IV will be estimated from the model together with associated 90% confidence intervals. Blood samples for PK analyses of mepolizumab were collected on dosing days (Days 1, 28 and 56) at pre-dose and 0.5 h, 1 h and 2 h post-dose (time was relative to the end of infusion in the IV cohort) as well as on Days 3, 7, 70, 84, 112 and 140 (follow-up visit).

For additional information about this study please refer to the GSK Clinical Study Register

For additional information about this study please refer to the GSK Clinical Study Register

For additional information about this study please refer to the GSK Clinical Study Register

For additional information about this study please refer to the GSK Clinical Study Register

For additional information about this study please refer to the GSK Clinical Study Register

For additional information about this study please refer to the GSK Clinical Study Register

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 125 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 250 mg administered SC (two injections of the same volume) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.

Participants received mepolizumab 75 mg administered intravenously (IV) once every 4 weeks (for a total of three doses on Day 1, Day 28 and Day 56). Maintenance asthma therapy was continued unchanged throughout the study, unless medically indicated.