A pooled analysis of BOREAS and NOTUS examined 1,874 patients aged 40 to 85 with COPD, moderate-to-severe airflow limitation and screening blood eosinophils of at least 300 cells per microlitre, randomised to dupilumab 300 mg or placebo for 52 weeks.
Emergency department visits and hospital admissions of any duration fell by 38% (rate ratio 0.62, interval 0.43 to 0.90). Time to a first such event was delayed, with the risk reduced by 45% (hazard ratio 0.55, interval 0.38 to 0.78). Systemic corticosteroid use fell by 42% in patients having severe exacerbations (0.58) and by 28% in those having moderate ones (0.72).
The corticosteroid finding is the one that compounds. Cumulative systemic steroid exposure in COPD drives diabetes, osteoporosis, cataract and adrenal suppression, and it accrues silently across years of exacerbations. A biologic that reduces exacerbations reduces steroid courses, and that second-order benefit rarely appears in a primary endpoint. Here it was measured directly.
The constraint remains the eosinophil threshold: this is evidence for the type 2 phenotype and says nothing about anyone below 300 cells per microlitre.
- Requires blood eosinophils of at least 300 cells per microlitre at screening
- Emergency visits and admissions are patient-relevant, not surrogate, endpoints
- Steroid-sparing effect is measured directly rather than inferred
- Post-hoc pooled analysis of two trials, not a prespecified primary endpoint
- Says nothing about the non-eosinophilic majority of COPD patients
The statistics, in plain English
The interval on the emergency-visit rate ratio, 0.43 to 0.90, is wide because these are relatively uncommon events — a 38% central estimate is compatible with anything from 10% to 57%. The direction is secure, the magnitude is not. Reductions in steroid use follow arithmetically from fewer exacerbations, so they are not an independent finding so much as a quantification of the same one in units that matter.
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