Sanofi has confirmed termination of itepekimab, its IL-33 monoclonal antibody (mAb), in chronic obstructive pulmonary disease (COPD) and chronic rhinosinusitis programmes after mixed Phase III signals. In the AERIFY-1 trial, the every-two-week and every-four-week regimens reduced annualised COPD exacerbation rates by 27% and 21% versus placebo at week 52, but AERIFY-2 showed only 2% and 12% reductions, prompting Sanofi to halt further COPD development. The CEREN-1 and CEREN-2 Phase III studies in chronic rhinosinusitis with nasal polyps will not proceed to final analysis, while a Phase II trial in chronic rhinosinusitis without nasal polyps missed internal efficacy expectations.

Itepekimab was one of only three IL-33/IL-33R-targeted agents to reach Phase III, alongside AstraZeneca's tozorakimab (four COPD Phase III trials completed, filed in June 2026) and Roche's astegolimab (COPD Phase III missed primary endpoint). Sanofi's withdrawal leaves the IL-33 pathway without a late-stage respiratory winner to date and reinforces its strategic concentration on dupilumab and next-wave immunology assets rather than diffuse inflammatory mechanism spreads.