Trial Outcomes & Findings for Study in Pediatrics With HypEREosinophilic Syndrome (SPHERE) (NCT NCT04965636)

Last Updated: 2026-05-04

Results Overview

A HES flare is defined as a HES related clinical manifestation based on a physician-documented change in clinical signs or symptoms (worsening symptoms and/or elevated blood eosinophil level) which resulted in need for either: an increase from the most recent dose in the maintenance Oral Corticosteroid (OCS) dose (prednisone/prednisolone equivalent) by at least 10 mg per day for 5 days or an increase in or addition of any immunosuppressive and/or cytotoxic HES therapy from/to the most recent dose of HES therapy. Data is presented by the number of HES flares (0, 1, 2, 3 ,4 and \>=5) in the participants.

Recruitment status

COMPLETED

Study phase

PHASE3

Target enrollment

16 participants

Primary outcome timeframe

Up to Week 52

Results posted on

2026-05-04

Participant Flow

This was a 52-week, open-label, multicenter study to evaluate the efficacy and safety of mepolizumab subcutaneous (SC) injection in children (aged 6 to 11 years) and adolescent (aged 12 to 17 years) participants with hypereosinophilic syndrome (HES) who were receiving standard of care (SoC) therapy.

A total of 16 participants with HES were enrolled in this study. All participants received active treatment with mepolizumab SC injection every 4 weeks over a treatment period of 52 weeks. The initial dose was dependent on age and weight. During the study, the dose was to be adjusted once the participants reached a bodyweight of 40 kg or the age of 12 years.

Participant milestones

Participant milestones
Measure	Mepolizumab 100 mg SC Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.
Overall Study STARTED	10	4	1	1
Overall Study COMPLETED	9	4	1	1
Overall Study NOT COMPLETED	1	0	0	0

Reasons for withdrawal

Reasons for withdrawal
Measure	Mepolizumab 100 mg SC Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.
Overall Study Withdrawal by Subject	1	0	0	0

Baseline Characteristics

Study in Pediatrics With HypEREosinophilic Syndrome (SPHERE)

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Total n=16 Participants Total of all reporting groups
Age, Customized 6 to 11 Years	10 Participants n=54 Participants	0 Participants n=60 Participants	1 Participants n=114 Participants	1 Participants n=1 Participants	12 Participants n=9 Participants
Age, Customized 12 to 17 Years	0 Participants n=54 Participants	4 Participants n=60 Participants	0 Participants n=114 Participants	0 Participants n=1 Participants	4 Participants n=9 Participants
Sex: Female, Male Female	3 Participants n=54 Participants	2 Participants n=60 Participants	NA Participants n=114 Participants	NA Participants n=1 Participants	NA Participants n=9 Participants
Sex: Female, Male Male	7 Participants n=54 Participants	2 Participants n=60 Participants	NA Participants n=114 Participants	NA Participants n=1 Participants	NA Participants n=9 Participants
Race/Ethnicity, Customized WHITE	10 Participants n=54 Participants	4 Participants n=60 Participants	1 Participants n=114 Participants	1 Participants n=1 Participants	16 Participants n=9 Participants

PRIMARY outcome

Timeframe: Up to Week 52

Population: The analysis was performed on the Full Analysis Set (FAS) that included all participants who received at least one dose of mepolizumab.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period 0 HES flare	10 Participants	4 Participants	1 Participants	1 Participants
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period 1 HES flare	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period 2 HES flares	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period 3 HES flares	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period 4 HES flares	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Who Experienced HES Flares Over the 52-Week Study Treatment Period >=5 HES flares	0 Participants	0 Participants	0 Participants	0 Participants

SECONDARY outcome

Timeframe: Baseline (Weeks 0-4), Weeks 4-8, Weeks 8-12, Weeks 12-16, Weeks 16-20, Weeks 20-24, Weeks 24-28, Weeks 28-32, Weeks 32-36, Weeks 36-40, Weeks 40-44, Weeks 44-48 and Weeks 48-52

Population: Full Analysis Set. Only those participants who were measured and analyzed (i.e., contributed to data reported in the table) were included in the Overall Number of Participants Analyzed field. 'Number Analyzed' signifies participants evaluable for the specified time points. Data is presented for subpopulation of participants that were taking OCS at Baseline. Zeros reported reflect measured data derived during analysis.

The mean daily OCS (prednisone or equivalent) dose for each 4-week period from Weeks 0-4 to Weeks 48-52 for each participant were calculated as the sum of the daily doses of OCS during each 4-week period divided by the total number of days. The change in the mean daily OCS dose for each 4-week period from Weeks 0-4 to Weeks 48-52 was calculated for each participant as the mean daily OCS dose for Weeks 48-52 minus the mean daily OCS dose for Weeks 0-4. Baseline value was derived as the sum of the daily doses of OCS during first 4 weeks following the initiation of mepolizumab treatment (Weeks 0-4) divided by total number of days. Change from Baseline was calculated as post-Baseline value minus Baseline Value.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=4 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=2 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 4-8	-0.4 Milligrams per day (mg/day) Standard Deviation 0.7	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	0.0 Milligrams per day (mg/day) Standard Deviation NA As there was a single participant, mean value presented is the actual value. Standard deviation could not be calculated for single participant.	0.0 Milligrams per day (mg/day) Standard Deviation NA As there was a single participant, mean value presented is the actual value. Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 8-12	-1.1 Milligrams per day (mg/day) Standard Deviation 1.4	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	0.0 Milligrams per day (mg/day) Standard Deviation NA As there was a single participant, mean value presented is the actual value. Standard deviation could not be calculated for single participant.	0.0 Milligrams per day (mg/day) Standard Deviation NA As there was a single participant, mean value presented is the actual value. Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 12-16	-1.8 Milligrams per day (mg/day) Standard Deviation 1.4	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	0.0 Milligrams per day (mg/day) Standard Deviation NA As there was a single participant, mean value presented is the actual value. Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 16-20	-1.9 Milligrams per day (mg/day) Standard Deviation 1.4	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-1.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 20-24	-1.9 Milligrams per day (mg/day) Standard Deviation 1.4	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	1.9 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 24-28	-2.6 Milligrams per day (mg/day) Standard Deviation 0.7	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-1.9 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 28-32	-2.6 Milligrams per day (mg/day) Standard Deviation 0.7	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-2.2 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 32-36	-2.5 Milligrams per day (mg/day) Standard Deviation 0.9	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-2.6 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 36-40	-2.5 Milligrams per day (mg/day) Standard Deviation 0.9	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	0.8 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 40-44	-2.5 Milligrams per day (mg/day) Standard Deviation 0.9	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-3.9 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 44-48	-2.5 Milligrams per day (mg/day) Standard Deviation 0.9	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-4.3 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.
Change in Mean Daily Oral Corticosteroids (OCS) Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 48-52	-2.5 Milligrams per day (mg/day) Standard Deviation 0.9	0.0 Milligrams per day (mg/day) Standard Deviation 0.0	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.	-5.0 Milligrams per day (mg/day) Standard Deviation NA Standard deviation could not be calculated for single participant.

SECONDARY outcome

Timeframe: Baseline (Weeks 0-4), Weeks 4-8, Weeks 8-12, Weeks 12-16, Weeks 16-20, Weeks 20-24, Weeks 24-28, Weeks 28-32, Weeks 32-36, Weeks 36-40, Weeks 40-44, Weeks 44-48 and Weeks 48-52

The mean daily OCS (prednisone or equivalent) dose for each 4-week period from Weeks 0-4 to Weeks 48-52 for each participant were calculated as the sum of the daily doses of OCS during each period divided by the total number of days. For each 4-week period, a reduction of 50% or more in mean OCS dose was defined as (mean OCS dose at each 4-week period minus mean OCS dose during Weeks 0-4) divided by (mean OCS dose during Weeks 0-4) multiplied by 100 was \<= -50. Baseline value was derived as the sum of the daily doses of OCS during first 4 weeks following the initiation of mepolizumab treatment (Weeks 0-4) divided by total number of days.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=4 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=2 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 4-8	1 Participants	0 Participants	0 Participants	0 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 8-12	2 Participants	0 Participants	0 Participants	0 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 12-16	3 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 16-20	3 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 20-24	3 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 24-28	4 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 28-32	4 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 32-36	3 Participants	0 Participants	1 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 36-40	3 Participants	0 Participants	0 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 40-44	3 Participants	0 Participants	1 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 44-48	3 Participants	0 Participants	1 Participants	1 Participants
Number of Participants With Reduction of >=50 Percentage (%) in Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) for Each 4-week Period From Weeks 0-4 to Weeks 48-52 Weeks 48-52	3 Participants	0 Participants	1 Participants	1 Participants

SECONDARY outcome

Timeframe: Weeks 48-52

The mean daily OCS (prednisone or equivalent) dose for Weeks 48-52 for each participant were calculated as the sum of the daily doses of OCS during this period divided by the total number of days. Number of participants with a mean daily OCS dose (prednisone/prednisolone or equivalent) of \<=7.5 mg during period of Weeks 48-52 in subpopulation of participants that were taking OCS at Baseline has been presented.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=4 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=2 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Number of Participants With a Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) of Less Than or Equal to (<=) 7.5 Milligrams (mg) During Weeks 48-52 in Subpopulation of Participants That Were Taking OCS at Baseline	3 Participants	0 Participants	1 Participants	1 Participants

SECONDARY outcome

Timeframe: Weeks 48-52

Population: The analysis was performed on the Full Analysis Set that included all participants who received at least one dose of mepolizumab.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Number of Participants With a Mean Daily OCS Dose (Prednisone/Prednisolone or Equivalent) of <=7.5 mg During Weeks 48-52 in Overall Population	9 Participants	2 Participants	1 Participants	1 Participants

SECONDARY outcome

Timeframe: Baseline (Week 0) and Week 52

The BFI is a self-administered questionnaire developed to assess fatigue severity. The BFI has 9 items. BFI- Item 3 assesses the worst level of fatigue during the past 24 hours. Participants report their worst level of fatigue daily, for the previous 24 hours, using a numerical rating scale ranging from 0 (no fatigue) to 10 (as bad as you can imagine). The weekly average score of BFI item 3 was defined as the mean of the observed daily assessments over the 7-day period. The weekly average score of BFI item 3 ranges from 0 to 10, higher score indicates worst outcome. BFI Item 3 was assessed in the participants with the age group of 12 to 17 years at study entry. Baseline was defined as the mean of the 7 daily assessments of BFI item 3 up to but not including the date of first dose of study treatment. Change from Baseline was calculated as post-Baseline value minus Baseline Value.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=2 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Change From Baseline in Fatigue Severity Based on Weekly Average Score of Brief Fatigue Inventory (BFI) Item 3 (Worst Level of Fatigue During Past 24 Hours) for Week 52 for Participants in the Age Group of 12 to 17 Years	0.1 Scores on a scale Standard Deviation 0.12	—	—	—

SECONDARY outcome

Timeframe: Up to Week 52

Population: The analysis was performed on the Full Analysis Set that included all participants who received at least one dose of mepolizumab.

Serum samples were collected for the determination of anti-mepolizumab antibodies (ADA) using a validated electro-chemiluminescent immunoassay. The assay involved screening, confirmation and titration assays. If serum samples tested positive in the screening assay, they were considered 'potentially positive' and were further analyzed for specificity using the confirmation assay. Samples that confirmed positive in the confirmation assay were reported as 'positive'. Confirmed positive ADA samples were further characterized in the titration assay to quasi-quantitate the amount of ADA in the sample and were also further characterized in the Neutralizing antibody (Nab) assay. A participant was considered positive ADA if they had at least one positive any time post-Baseline ADA result.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Number of Participants With Any Time Post-Baseline Positive Anti-mepolizumab Antibodies (ADA)	0 Participants	0 Participants	0 Participants	0 Participants

SECONDARY outcome

Timeframe: Up to Week 52

Population: Full Analysis Set. NAb data was not collected as there were no positive ADA observed. Therefore, Overall Number of Participants Analyzed (N)=0 for this outcome measure.

Blood samples were collected for the determination of positive neutralizing antibodies. NAb test was to be carried out on samples that were positive in the confirmatory binding antibody assay. A participant was to be considered positive for NAb if they had at least one positive any time post-Baseline neutralizing antibody result.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Baseline (Week 0), Weeks 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48 and 52

Blood samples were collected to measure eosinophil count. Ratio to Baseline is defined as post-dose visit value divided by Baseline value. Baseline was defined as the latest blood eosinophil value measured by the central laboratory prior to the first dose of study treatment.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Ratio to Baseline in Blood Eosinophil Count Week 48	0.067 Ratio Interval 0.026 to 0.171	0.101 Ratio Interval 0.038 to 0.272	0.289 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.050 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 52	0.063 Ratio Interval 0.039 to 0.104	0.075 Ratio Interval 0.023 to 0.239	0.237 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	—
Ratio to Baseline in Blood Eosinophil Count Week 16	0.063 Ratio Interval 0.034 to 0.117	0.075 Ratio Interval 0.035 to 0.164	0.289 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.065 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 20	0.075 Ratio Interval 0.052 to 0.108	0.091 Ratio Interval 0.025 to 0.328	0.263 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.045 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 24	0.069 Ratio Interval 0.042 to 0.113	0.048 Ratio Interval 0.026 to 0.089	0.184 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.030 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 28	0.087 Ratio Interval 0.056 to 0.135	0.113 Ratio Interval 0.051 to 0.251	0.158 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	—
Ratio to Baseline in Blood Eosinophil Count Week 32	0.064 Ratio Interval 0.046 to 0.088	0.057 Ratio Interval 0.029 to 0.113	—	0.131 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 36	0.071 Ratio Interval 0.056 to 0.09	0.048 Ratio Interval 0.021 to 0.11	0.289 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.040 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 40	0.066 Ratio Interval 0.034 to 0.127	0.106 Ratio Interval 0.062 to 0.181	0.289 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.045 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 44	0.071 Ratio Interval 0.041 to 0.122	0.091 Ratio Interval 0.039 to 0.212	0.289 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.045 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 8	0.077 Ratio Interval 0.032 to 0.183	0.108 Ratio Interval 0.033 to 0.351	0.368 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.070 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 12	0.078 Ratio Interval 0.045 to 0.137	0.058 Ratio Interval 0.017 to 0.203	0.421 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.035 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant
Ratio to Baseline in Blood Eosinophil Count Week 4	0.089 Ratio Interval 0.03 to 0.269	0.082 Ratio Interval 0.053 to 0.129	0.342 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant	0.045 Ratio NA indicates 95% Confidence Interval could not be calculated for a single participant

SECONDARY outcome

Timeframe: Pre-dose at Weeks 4 and 24; Week 52

Blood samples were collected at the indicated time points for pharmacokinetic analysis of Mepolizumab.

Outcome measures

Outcome measures
Measure	Mepolizumab 100 mg SC n=10 Participants Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 Participants Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 Participants A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.
Plasma Concentrations of Mepolizumab Week 4, Pre-dose	12350.99 Nanograms per milliliter (ng/mL) Interval 10298.38 to 14812.72	16498.72 Nanograms per milliliter (ng/mL) Interval 12004.15 to 22676.14	22993.84 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant	31998.66 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant
Plasma Concentrations of Mepolizumab Week 24, Pre-dose	23186.66 Nanograms per milliliter (ng/mL) Interval 19969.73 to 26921.81	24067.17 Nanograms per milliliter (ng/mL) Interval 14519.85 to 39892.22	36129.28 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant	23697.43 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant
Plasma Concentrations of Mepolizumab Week 52	26870.67 Nanograms per milliliter (ng/mL) Interval 23028.56 to 31353.8	22613.09 Nanograms per milliliter (ng/mL) Interval 12211.2 to 41875.64	57853.69 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant	18695.75 Nanograms per milliliter (ng/mL) NA indicates 95% Confidence Interval could not be calculated for a single participant

Adverse Events

Mepolizumab 100 mg SC

Serious events: 0 serious events

Other events: 9 other events

Deaths: 0 deaths

Mepolizumab 300 mg SC

Serious events: 0 serious events

Other events: 1 other events

Deaths: 0 deaths

Mepolizumab 200/100 mg SC

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Mepolizumab 200/300 mg SC

Serious events: 1 serious events

Other events: 1 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	Mepolizumab 100 mg SC n=10 participants at risk Participants in the age group of 6 to 11 years with body weight less than (\<) 40 kilogram (kg) received Mepolizumab 100 milligram (mg) subcutaneous (SC) injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 300 mg SC n=4 participants at risk Participants in the age group of 12 to 17 years received Mepolizumab 300 mg SC injection every 4 weeks over a treatment period of 52 weeks.	Mepolizumab 200/100 mg SC n=1 participants at risk A participant in the age group of 6 to 11 years with body weight greater than or equal to (\>=) 40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was reduced to 100 mg SC injection every 4 weeks as body weight of the participant reduced to less than (\<) 40 kg over a treatment period of 52 weeks.	Mepolizumab 200/300 mg SC n=1 participants at risk A participant in the age group of 6 to 11 years with body weight \>=40 kg received mepolizumab 200 mg SC injections every 4 weeks. During the conduct of the study, the mepolizumab dose was increased to 300 mg SC injection every 4 weeks as age of the participant increased to the age group of 12 to 17 years over a treatment period of 52 weeks.
Respiratory, thoracic and mediastinal disorders Bronchospasm	0.00% 0/10 • All-cause mortality, serious adverse events (SAEs) and non-serious adverse events (non-SAEs) were collected up to week 60 (follow up period) Full Analysis Set included all participants who received at least one dose of mepolizumab.	0.00% 0/4 • All-cause mortality, serious adverse events (SAEs) and non-serious adverse events (non-SAEs) were collected up to week 60 (follow up period) Full Analysis Set included all participants who received at least one dose of mepolizumab.	0.00% 0/1 • All-cause mortality, serious adverse events (SAEs) and non-serious adverse events (non-SAEs) were collected up to week 60 (follow up period) Full Analysis Set included all participants who received at least one dose of mepolizumab.	100.0% 1/1 • Number of events 2 • All-cause mortality, serious adverse events (SAEs) and non-serious adverse events (non-SAEs) were collected up to week 60 (follow up period) Full Analysis Set included all participants who received at least one dose of mepolizumab.

Other adverse events

Additional Information

GSK Response Center

GlaxoSmithKline

Phone: 866-435-7343

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee GSK agreements may vary with individual investigators, but will not prohibit any investigator from publishing. GSK supports the publication of results from all centers of a multi-center trial but requests that reports based on single site data not precede the primary publication of the entire clinical trial.
Publication restrictions are in place

Restriction type: OTHER