AstraZeneca (LSE/STO/NYSE: AZN) reported that tozorakimab, its anti-IL-33 monoclonal antibody, met the primary endpoint in both the OBERON and TITANIA Phase III trials, reducing the annualized rate of moderate-to-severe exacerbations in patients with COPD compared with placebo — making tozorakimab the first IL-33-targeting biologic to deliver confirmatory Phase III data in this disease.
The OBERON and TITANIA trials are replicate, double-blind, placebo-controlled studies that together randomized 2,306 adults with symptomatic COPD and a history of at least two moderate or one severe exacerbation in the prior year. Patients received tozorakimab 300mg or placebo subcutaneously every four weeks for 52 weeks, on top of inhaled maintenance therapy. Enrollment was unrestricted by blood eosinophil count, smoking status, or lung function severity.
The primary endpoint — annualized rate of moderate-to-severe exacerbations among former smokers — was met with statistical significance in both trials. A key secondary endpoint measuring the same rate in the overall population, which included both former and current smokers, was also met. AstraZeneca has not yet disclosed specific rate reductions or hazard ratios, stating that full results will be presented at an upcoming medical meeting. Tozorakimab was described as generally well tolerated with a favorable safety profile; no specific adverse event data were released.
The absence of quantitative efficacy data limits any assessment of clinical magnitude. Whether the exacerbation reductions observed with tozorakimab match, exceed, or fall short of those seen with dupilumab or mepolizumab — the two biologics already approved for COPD — cannot be determined until detailed results are available.
What IL-33 blockade means for COPD exacerbations treatment
Tozorakimab binds IL-33, an epithelial-derived alarmin released upon tissue damage from viral infection, cigarette smoke, or other insults. AstraZeneca describes the molecule as uniquely inhibiting signaling through both the reduced form of IL-33 (which signals via the ST2 receptor, driving type 2 inflammation) and the oxidized form (which signals via the RAGE/EGFR complex, contributing to mucus dysfunction and epithelial pathology). This dual mechanism positions tozorakimab upstream of the pathways targeted by existing COPD biologics, which act on more distal cytokines.
Dupilumab (Dupixent), approved by the US FDA in September 2024 for COPD with an eosinophilic phenotype (blood eosinophils ≥300 cells/µL), blocks IL-4 and IL-13 signaling. Mepolizumab (Nucala), approved in May 2025 for COPD patients with eosinophils ≥150 cells/µL, depletes eosinophils via IL-5 blockade. Both are restricted to eosinophil-defined subpopulations. Roflumilast (Daliresp), an oral PDE4 inhibitor approved in 2011, is limited to the chronic bronchitis phenotype and carries tolerability issues including gastrointestinal and psychiatric side effects.
The central question for tozorakimab is whether IL-33 blockade can deliver clinically meaningful benefit across a broader COPD population than these existing options. The OBERON and TITANIA trials enrolled patients regardless of eosinophil count — a design choice that, if supported by subgroup analyses, could position tozorakimab as the first biologic for non-eosinophilic frequent exacerbators, a population currently without any approved biologic therapy.
Tozorakimab Phase III results in context of the competitive landscape
The only other anti-IL-33 antibody in late-stage COPD development is itepekimab, from Sanofi and Regeneron, which has completed Phase IIb studies but has not yet entered Phase III for COPD. Cross-trial comparisons are limited by differences in trial design, patient populations, and endpoint definitions, and no head-to-head data exist between any of these agents.