Eosinophilic COPD Below the Dupilumab Threshold: What 210 Cells Actually Buys
A patient whose eosinophil count sits above the mepolizumab threshold and below the dupilumab one, on evidence that is real for the drug he qualifies for and stronger for the one he does not.
Walter D. spent thirty-four years driving long-haul freight before his lungs, not his back, finally ended the career two winters early. He still keeps a CB radio charged on his nightstand out of habit. His COPD carries the chronic-bronchitis stamp he has had since his forties — a productive cough most mornings, sometimes worse, sometimes just background — and for the past eighteen months he has been on maximal inhaled therapy: a triple combination of inhaled corticosteroid, long-acting beta-agonist, and long-acting muscarinic antagonist. It has not been enough. He is two weeks out from his second hospitalization this year, the same wet cough and breathlessness both times, and the team reviewing his case is looking at his blood eosinophil trend rather than just his spirometry.
His numbers land him in a real gap between two approved thresholds. His blood eosinophil count has run 210/µL across two measurements in the past year — comfortably above the 150 cells/µL mepolizumab requires, and comfortably below the 300 cells/µL GOLD 2026 sets for dupilumab in chronic-bronchitis COPD. That difference is not just a matter of which drug he happens to qualify for. The trial evidence behind each threshold is not symmetric: BOREAS and NOTUS showed dupilumab reducing exacerbations by roughly a third and producing a genuine placebo-corrected FEV1 gain of roughly 80 mL that mepolizumab’s own COPD program never replicated, while the mepolizumab data showed a real but smaller exacerbation benefit with no consistent lung-function or quality-of-life signal. The trial that actually enrolled patients down to his eosinophil range is METREX, which took counts from 150 cells/µL; MATINEE, the larger and more recent of the two, screened at 300 and so does not describe a man at 210 at all. He qualifies for the drug with the thinner data package.
In clinic, two weeks after his second hospitalization this year
He is not eligible for dupilumab today — 210 is real, documented, and twice repeated, well short of the 300 GOLD sets for chronic-bronchitis COPD. What he is eligible for is mepolizumab, and the exacerbation reduction across its COPD program is genuine evidence, not a fallback chosen only because the better-studied drug is out of reach. I would be precise about which trial covers him, though: MATINEE screened at 300 cells/µL, so it is METREX, enrolling from 150, that actually describes him. And MATINEE’s emergency-visit-or-hospitalization result, real as the number looks, fell outside its own formal testing hierarchy once an earlier endpoint failed — I am not going to present it to him as an established endpoint.
I would not call 210 a settled number before we act on it. A single blood eosinophil count is not a fixed biological ceiling — timing relative to a recent exacerbation, recent steroid exposure, even seasonal variation can shift it meaningfully. BOREAS and NOTUS produced an FEV1 gain that mepolizumab’s own COPD trials never reproduced, and if a repeat measurement clears 300, that is a materially stronger evidence base sitting one blood draw away.
I am not arguing his current number is wrong — I am arguing it may not be his real, stable number, and the difference matters enough here to check before committing.
He is two weeks past his second admission this year. Whatever we start, it should start now, not after a repeat draw and a follow-up visit to interpret it. Mepolizumab’s benefit at his actual documented level is real evidence, not a placeholder while we wait for a better number — and if a future eosinophil count does clear 300, nothing about starting mepolizumab today forecloses reconsidering dupilumab later.
Confirming the number is a reasonable question. It is not a reason to leave him on the regimen that has already failed him twice this year while we ask it.
Agreed: start mepolizumab today rather than delay for repeat eosinophil testing, given his exacerbation burden and recent discharge.
Not agreed, and left open rather than resolved: whether a future eosinophil count clearing 300 should trigger an automatic switch to dupilumab, or whether a real, working response to mepolizumab should be left alone regardless of what a later number shows. The pharmacologist and pulmonologist left with different defaults on that question; nothing was decided beyond ordering the repeat count.