AstraZeneca's Tozorakimab Succeeds in Two Phase 3 COPD Trials Where Rivals Failed, Validating IL-33 as a Drug Target
Tozorakimab becomes the first IL-33-targeting biologic to show statistically significant reductions in COPD exacerbations across two confirmatory Phase 3 trials, after competitors Sanofi and Roche stumbled in the same drug class.
Overview
AstraZeneca announced on March 27 that its experimental monoclonal antibody tozorakimab met the primary endpoint in both the OBERON and TITANIA Phase 3 clinical trials, reducing the annualized rate of moderate-to-severe chronic obstructive pulmonary disease (COPD) exacerbations compared with placebo. The result makes tozorakimab the first drug targeting interleukin-33 (IL-33) to deliver confirmatory evidence across two replicate late-stage studies, according to the company’s SEC filing. AstraZeneca’s stock rose more than 3 percent on the news, as reported by CNBC, with analysts noting the result was a surprise given that competitors had failed in the same drug class.
What We Know
The twin trials randomized a combined 2,306 patients with symptomatic COPD who had experienced two or more moderate exacerbations, or at least one severe exacerbation, in the prior 12 months. Participants received either tozorakimab 300 mg or placebo once every four weeks for 52 weeks, on top of standard-of-care inhaled therapy, according to the SEC filing.
Critically, enrollment was not restricted by blood eosinophil count or smoking status. The drug met its primary endpoint in the prespecified population of former smokers, and also achieved a key secondary endpoint in the overall population that included current smokers and patients across all levels of lung function severity, per the SEC filing. AstraZeneca described the reductions as “statistically significant and highly clinically meaningful,” though specific effect sizes have not yet been disclosed. The company said tozorakimab was generally well tolerated with a favorable safety profile.
Tozorakimab is a potential first-in-class monoclonal antibody that inhibits both the reduced and oxidized forms of IL-33. Sharon Barr, AstraZeneca’s executive vice president of BioPharmaceuticals R&D, called the results “a major scientific advancement in COPD” in the company’s SEC filing.
The drug had already received Fast Track designation from the U.S. FDA for COPD in December 2024, according to the SEC filing. Two additional Phase 3 trials in the LUNA program, PROSPERO (1,713 patients) and MIRANDA (1,454 patients, dosed every two weeks), are expected to report results in the first half of 2026.
Competitive Landscape
The IL-33 pathway has been a graveyard for drug developers. Roche’s astegolimab failed its Phase 3 COPD study, and Sanofi and Regeneron reported mixed results for itepekimab, with one hit and one miss in their Phase 3 program, as reported by Fierce Biotech. Those setbacks had led many investors to write off IL-33 as a viable drug target in COPD.
AstraZeneca’s differentiation may lie in tozorakimab’s dual mechanism. Unlike competitors that block only the ST2 signaling pathway, tozorakimab also inhibits signaling through the RAGE and EGFR pathways, which are implicated in mucus overproduction and epithelial remodeling, two processes that drive COPD progression independently of eosinophilic inflammation.
The existing biologic landscape in COPD is narrow. GSK’s Nucala (mepolizumab) and Sanofi/Regeneron’s Dupixent (dupilumab) are approved but only for patients with elevated eosinophils, a subset of the broader COPD population. Tozorakimab’s broad enrollment criteria suggest it could address a wider patient base.
What We Don’t Know
AstraZeneca has not disclosed specific effect sizes, hazard ratios, or absolute exacerbation rate data from either trial. Detailed results are expected to be presented at an upcoming medical meeting. Without these numbers, it is difficult to gauge how tozorakimab compares in magnitude to existing treatments or to assess its clinical significance beyond the top-line characterization.
It also remains unclear how pricing will be set relative to existing COPD biologics. Analysts estimate peak sales between $3 billion and $5 billion annually, but commercial uptake will depend on how broadly payers approve the drug given the absence of a biomarker-based restriction.
The PROSPERO and MIRANDA trials, testing different dosing frequencies, have yet to report. Their results will be important in determining the optimal regimen and whether the drug’s benefit extends to additional patient subgroups.
Analysis
COPD affects nearly 400 million people worldwide and is the fourth-leading cause of death globally. Despite this burden, the disease has been historically underserved by biologic therapies, with most patients relying on combinations of inhaled bronchodilators and corticosteroids that do not address the underlying inflammatory pathways.
Tozorakimab’s success is significant not only for AstraZeneca but for the broader field of respiratory medicine. By validating IL-33 as a target in COPD, the data reopen a drug class that had been largely abandoned. If the remaining Phase 3 trials confirm these results, and if the detailed efficacy data prove robust, AstraZeneca could have a substantial first-mover advantage in an area where competitors have spent years and billions of dollars without reaching the finish line.