Tozorakimab, an investigational monoclonal antibody developed by AstraZeneca, has shown significant promise in reducing moderate-to-severe chronic obstructive pulmonary disease (COPD) exacerbations. The drug targets interleukin-33 (IL-33) and was tested in two replicate phase 3 trials, OBERON and TITANIA. These trials were specifically designed to assess the efficacy and safety of tozorakimab in patients with symptomatic COPD who remain at high risk of exacerbations despite standard inhaled therapy.
Results from these trials, presented at the European Respiratory Society Congress 2026 and published in The New England Journal of Medicine, demonstrate a consistent reduction in exacerbations across a broad population of COPD patients. The FDA has accepted a biologics license application for tozorakimab under Priority Review, with a decision expected in the first quarter of 2027. This accelerated review process shows the potential impact of tozorakimab on COPD management, a disease affecting millions worldwide.
Consistent Reductions Across Trials
The OBERON and TITANIA trials collectively enrolled 2,306 adults with symptomatic COPD, ensuring a diverse and representative patient population. Participants had experienced at least two moderate or one severe exacerbation in the previous year, despite receiving standard inhaled maintenance therapy for at least three months. This inclusion criterion highlights the unmet need for effective treatments in patients with frequent exacerbations.
Patients received 300 mg of tozorakimab every four weeks via subcutaneous injection or a placebo, in addition to their existing treatment. The primary endpoint focused on the annualized rate of moderate-to-severe exacerbations among former smokers, a subgroup particularly vulnerable to COPD progression. Secondary endpoints included assessments in the overall population of current and former smokers, providing a full view of the drug’s efficacy.
Tozorakimab reduced these exacerbations by 29% in OBERON and 34% in TITANIA compared to placebo. In the combined population of current and former smokers, reductions were 30% and 29%, respectively. These findings are particularly significant given the challenges in COPD drug development, where reproducing positive results across key studies has been historically difficult. The consistency of tozorakimab’s benefits across two large, well-designed trials reinforces its potential as a reliable treatment option.
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The trials also included patients across various stages of lung-function impairment and blood eosinophil levels, further validating the drug’s broad applicability. This inclusivity is key for addressing the heterogeneous nature of COPD and ensuring that a wide range of patients can benefit from the treatment.
Benefits Across Eosinophil Subgroups
Biologic treatments for airway diseases typically focus on patients with raised eosinophil counts or type 2 inflammation. However, tozorakimab demonstrated benefits across prespecified blood eosinophil subgroups, suggesting its potential applicability to a broader COPD population. This is a notable advancement, as many existing biologics are limited to specific patient subsets.
In the pooled analysis, patients with baseline blood eosinophil counts below 150 cells/µL experienced a 23% reduction in moderate-to-severe exacerbations. Reductions increased to 34% for patients with counts of at least 150 cells/µL and 43% for those with counts of at least 300 cells/µL. These results indicate that tozorakimab’s mechanism of action effectively addresses the underlying inflammatory processes in COPD, regardless of eosinophil levels.
Tozorakimab targets both reduced and oxidized forms of IL-33, a cytokine involved in inflammatory and epithelial dysfunction pathways. Reduced IL-33 promotes inflammatory signaling through the ST2 receptor, while oxidized IL-33 contributes to epithelial dysfunction via the RAGE/EGFR pathway. By inhibiting both forms, tozorakimab aims to reduce inflammation and disrupt processes linked to excessive mucus production and impaired epithelial repair. This dual-action approach may explain its efficacy across diverse patient subgroups.
An integrated analysis of the trials also found that tozorakimab reduced mucus plug scores, an emerging measure of COPD disease burden associated with worse clinical outcomes. Mucus plugging is a significant contributor to airway obstruction and exacerbations, and its reduction further highlights the drug’s complex benefits.
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Safety and Regulatory Outlook
Tozorakimab was generally well tolerated, with a safety profile comparable to placebo. The only adverse drug reaction identified was injection-site reactions, which were typically mild and transient. This favorable safety profile is critical for long-term use in chronic conditions like COPD. More detailed data will be key for evaluating serious adverse events, treatment discontinuations, infections, and outcomes across clinically relevant subgroups, ensuring a full understanding of the drug’s safety.
COPD exacerbations can accelerate disease progression, increase hospitalization risks, and lead to cardiopulmonary events. Current management relies heavily on inhaled bronchodilators and corticosteroids, with biologics reserved for specific patients. The 2026 Global Initiative for Chronic Obstructive Lung Disease report emphasizes treatment optimization and exacerbation prevention as key components of COPD management. Tozorakimab’s ability to reduce exacerbations aligns with these goals, potentially improving long-term outcomes for patients.
If approved, tozorakimab would introduce new responsibilities for pharmacists. They would need to review patients’ exacerbation history, inhaler adherence, smoking status, and previous treatment optimization before initiating biologic therapy. Pharmacists would also educate patients on subcutaneous administration, dosing, and potential injection-site reactions. Continued assessment of inhaler use would remain essential, as tozorakimab is designed as an add-on therapy rather than a replacement for existing treatments. This expanded role for pharmacists shows the importance of multidisciplinary care in COPD management.
The consistent phase 3 findings position IL-33 inhibition as a promising strategy for COPD patients vulnerable to exacerbations. The FDA’s review will determine whether tozorakimab becomes a new biologic option across eosinophil-defined COPD populations, potentially transforming the treatment environment for this debilitating disease.
