Mepolizumab helped COPD patients whose eosinophils were high at any point — not only persistently

Design

Pooled post hoc analysis of 3 phase 3 RCTs (METREX, METREO, MATINEE)

Population

Patients with COPD receiving mepolizumab 100 mg or placebo

Primary outcome

Annualised moderate or severe exacerbation rate by eosinophil pattern

Effect

BEC ≥300 at any time: 21% reduction; variable BEC 22–36%; persistently <150: no benefit

This analysis pooled three phase 3, placebo-controlled trials of mepolizumab 100 mg in COPD (METREX, METREO and MATINEE), which recorded eosinophil counts in the year before randomisation, at screening and at baseline.

Moderate or severe exacerbations fell by 21% in patients with a count of 300 cells/µL or more at any pre-randomisation point, 12–27% with persistently raised counts and 22–36% with variable counts. From 150 cells/µL upward, mepolizumab reduced exacerbations needing emergency care or admission. Patients with persistently low counts (below 150) did not benefit.

Eosinophil counts fluctuate, and clinicians often dismiss a single raised value. This analysis suggests that a high count at any point in the prior year identifies a treatable eosinophilic phenotype. Post hoc subgroups across pooled trials are hypothesis-supporting, not definitive.

• Review all blood eosinophil counts from the past year, not just the latest, when assessing COPD for biologics.
• A count of 300 or more at any point suggests a type 2 phenotype that may respond to anti-IL-5 therapy.
• Patients with persistently low counts (below 150) are unlikely to benefit.
• Eosinophil counts also guide inhaled corticosteroid decisions in COPD.

Why it matters

It stops a variable biomarker from excluding patients who would respond.

Don't overread it

Post hoc subgroup analysis of pooled trials; the effect sizes by pattern are imprecise.

The statistics, in plain English

A 21% reduction in exacerbation rate means about one in five fewer events per year; subgroup ranges like 12–36% reflect small numbers in each group.

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