AstraZeneca reported that its experimental drug tozorakimab became the first biologic to significantly reduce “mucus plugs” in chronic obstructive pulmonary disease (COPD), according to data presented at the European Respiratory Society (ERS) 2026 congress.

What COPD is, and why mucus plugs matter

COPD is a progressive lung disease — a leading cause of death worldwide, driven largely by smoking and air pollution — in which the airways become inflamed and obstructed, making it steadily harder to breathe. One under-appreciated culprit is the mucus plug: thick mucus that physically clogs the small airways, segment by segment, blocking airflow. These plugs are increasingly recognized as a marker of faster disease progression and more frequent exacerbations — the flare-ups that land patients in hospital and accelerate decline. Yet no biologic drug had been shown to clear them.

The finding

AstraZeneca said tozorakimab achieved “a significant reduction in the number of lung segments with mucus plugs in a broad population” — the first time a biologic has demonstrated this specific effect. Because mucus plugging is tied to worse outcomes, reducing it could, in principle, slow the disease and cut exacerbations, though that link would need to be borne out in the full data.

How the drug works

Tozorakimab is an IL-33 inhibitor. IL-33 is what immunologists call an “alarmin” — an early-warning molecule released by damaged airway cells that kicks off a cascade of inflammation. By blocking IL-33 near the top of that cascade, the drug aims to calm airway inflammation upstream, rather than mopping up its downstream effects. COPD has historically had far fewer targeted biologic options than asthma, so a new mechanism that also happens to tackle mucus obstruction is notable for the field.

The important caveat

This is a conference readout, and several specifics — the trial name, phase, enrollment size and other endpoints such as exacerbation rates and lung-function changes — were part of analyst commentary rather than fully detailed in public. Conference headlines can outpace the complete, peer-reviewed picture. The mucus-plug result is genuinely differentiating and encouraging, but its ultimate value depends on whether it translates into fewer flare-ups and better breathing in the full dataset. Not medical advice.