Two COPD biologic results today report similar-sounding benefits and are not comparable, because they enrolled different diseases.
Dupilumab required blood eosinophils of at least 300 cells per microlitre — the type 2 inflammatory phenotype, a minority of COPD patients. Astegolimab enrolled irrespective of eosinophil count and irrespective of chronic bronchitis. A 38% reduction in one and 15% in the other are not a ranking; they are measurements in different populations, and the smaller effect in the broader group may address far more patients.
The habit generalises to any therapy with a biomarker-defined indication. Before comparing two trials, check whether they enrolled the same patients. In COPD specifically the eosinophil threshold is the question to ask first, because it determines both who the result applies to and how large an effect you should expect — enrichment raises the effect size and narrows the denominator at the same time.
When a trial reports a smaller effect in an unselected population, that is often the more useful result, not the weaker one.
- Check the eosinophil threshold before comparing two COPD biologic trials
- Enrichment inflates effect size and shrinks the eligible population together
- A smaller effect in a broader group can help more patients overall
- Ask what fraction of your own clinic would have met the enrolment criteria
- The same logic applies to any biomarker-selected indication
The statistics, in plain English
Enrichment selects patients more likely to respond, which raises the observed effect size without the drug being more effective in any individual. It is a legitimate way to make a trial feasible, and it means the reported effect applies only within the enrichment criterion. Extrapolating an enriched trial's effect size to an unselected clinic overstates benefit, usually substantially.
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