Chupp 2017

Methods	Multicentre, placebo‐controlled, double‐blind, parallel‐group study
Participants	551 participants with severe eosinophilic asthma Males (%): mepolizumab 125 (46); placebo, 101 (36) Main inclusion/exclusion criteria: blood eosinophils ≥ 150 cells/μL at screening or ≥ 300 cells/μL in previous 12 months ≥ 2 exacerbations in previous 12 months FEV1 < 80% maintenance treatment with high‐dose ICS for ≥ 12 months; + additional controller for ≥ 3 months; ± maintenance OCS
Interventions	Mepolizumab 100 mg SC every 4 weeks for a period of 24 weeks (total of 6 doses) along with their respective standard care of treatment, versus placebo (0.9% sodium chloride) SC every 4 weeks for a period of 24 weeks (total of 6 doses) along with their respective standard care of treatment
Outcomes	Primary outcomes Mean change from baseline in SGRQ score at week 24 Secondary outcomes Mean change from baseline in clinic pre‐bronchodilator FEV1 at week 24 Percentage of participants achieving a 4‐point or greater reduction from baseline in SGRQ score at week 24 Mean change from baseline in 5‐item ACQ‐5 score at week 24
Notes	Funding: GlaxoSmithKline
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomised using an interactive voice‐response system and a centralised, computer‐generated, permuted‐block design of block size six
Allocation concealment (selection bias)	Low risk	Participants, investigators, other site staff, and the entire study team including those assessing outcomes data were masked to treatment assignment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants and investigators remained masked to treatment assignment during the study.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Participants and investigators remained masked to treatment assignment during the study.
Incomplete outcome data (attrition bias) All outcomes	Low risk	In the treatment arm 5 participants were withdrawn from the study: 2 withdrew consent, 2 experienced an adverse event and 1 was lost to follow‐up. In the placebo arm 14 participants were withdrawn from study: 6 withdrew consent, 2 experienced an adverse event, 2 withdrew due to poor efficacy, 2 were lost to follow‐up and 2 were withdrawn on a physician's decision.
Selective reporting (reporting bias)	Low risk	No indication of reporting bias