First Biologic Tozorakimab Reduces COPD Exacerbations Across All Eosinophil Levels in Phase 3 Trials

For years, major clinical guidelines have operated on a strict biological dividing line: if a patient with chronic obstructive pulmonary disease (COPD) does not have elevated levels of white blood cells known as eosinophils, biologic drugs will not help them. That consensus, which currently locks millions of patients out of advanced treatments, was directly challenged this week. Results from two phase 3 clinical trials, published in the New England Journal of Medicine, demonstrate that a new monoclonal antibody called tozorakimab significantly reduces severe lung flare-ups regardless of a patient's eosinophil count.[4][6]

The data, presented at the European Respiratory Society Congress in Barcelona, showed that tozorakimab cut the rate of moderate and severe COPD exacerbations by 29% in the OBERON trial and 34% in the TITANIA trial among former smokers. In the overall population of both current and former smokers, exacerbations fell by 30% and 29%, respectively. Crucially, this benefit held even for the subgroup of patients with blood eosinophil counts below 150 cells per microliter—a threshold that typically disqualifies patients from receiving existing biologics. In that low-eosinophil group, the drug delivered a 23% reduction in exacerbations, while those with counts above 300 cells per microliter saw a 43% reduction.[1][2][3][4]

"We are not using those words easily, but I think the data set is really a breakthrough for COPD patients and physicians," said Ruud Dobber, president of AstraZeneca's biopharmaceuticals business unit. By demonstrating efficacy across the entire spectrum of inflammation profiles, the trial results effectively redraw the boundaries of who can receive targeted respiratory therapy. Until now, pulmonologists have had little to offer patients who suffer frequent exacerbations but lack the specific type 2 inflammation biomarker required for other approved biologics.[2][3][6]

The mechanism behind this broad efficacy lies in how the drug interacts with interleukin-33 (IL-33), a signaling protein that triggers inflammation and mucus production in the lungs. Previous attempts to target the IL-33 pathway in COPD have yielded mixed results, often failing to show benefit outside of former smokers. Tozorakimab bypasses this limitation by uniquely binding to and inhibiting both the reduced and oxidized forms of IL-33, shutting down two separate inflammatory cascades simultaneously.[1][3][4][6]

This dual-inhibition approach also appears to address a secondary, critical driver of COPD severity: mucus plugging. An integrated analysis of the two trials revealed that patients receiving the biologic experienced a significant reduction in their mucus plug scores. Because obstructing clumps of mucus are strongly associated with accelerated lung decline and higher mortality, clearing these blockages represents a meaningful structural improvement in airway function rather than just symptom management.[1][3][6]

For patients currently managing COPD, these findings offer a tangible shift in future treatment options, though they do not change immediate daily routines. The trials enrolled 2,306 adults who were already receiving optimized, standard-of-care inhaled maintenance therapy—often triple-inhaler regimens—yet were still suffering from at least one severe or two moderate exacerbations annually. Tozorakimab was administered as a 300-milligram subcutaneous injection once every four weeks on top of their existing inhalers, meaning it is designed as an add-on therapy rather than a replacement for daily bronchodilators.[1][4][5][6]

Safety data from the 52-week trials indicate the drug is generally well tolerated, with injection-site reactions emerging as the only notable adverse effect compared to placebo. While investigators noted a slight imbalance in major adverse cardiovascular events, they attributed this to an unusually low rate of such events in the placebo group rather than a direct risk from the biologic. Still, long-term extension studies will be necessary to fully map the drug's safety profile over multiple years of continuous use.[1][4][6]

The regulatory timeline is already in motion. The U.S. Food and Drug Administration has accepted AstraZeneca's biologics license application under Priority Review, with a decision expected in the first quarter of 2027. If approved, the treatment will likely prompt a rapid update to international COPD management guidelines, finally offering a systemic intervention for the millions of patients whose lung disease is not driven by eosinophilic inflammation.[1][2][3][6]