Sanofi's phase 3 study of amlitelimab for atopic dermatitis (eczema) met all primary and key secondary endpoints, including validated skin clearance and severity improvements at 24 weeks135.
Despite statistical success, amlitelimab's efficacy fell below analyst forecasts, with EASI-75 rates (a 75% improvement in eczema severity) between 35.9% and 46%, and 'clear or almost clear' skin (vIGA-AD 0/1) in 21.1% to 26.5% of patients—lower than some expected1.
Analysts had expected EASI-75 rates of 45–50% and IGA 0/1 of 35–40% at 24 weeks based on earlier phase 2 data and peer benchmarks1.
Shares in Sanofi dropped 9–10%, erasing nearly $13 billion from its market value due to investor concerns that amlitelimab may not be strong enough to meaningfully replace revenues from Dupixent (which faces loss of patent exclusivity in 2031)15.
Amlitelimab is an anti-OX40L antibody, representing a potential new mechanism distinct from Dupixent, and can be dosed as infrequently as four times per year13.
Sanofi leadership highlighted that the study enrolled a diverse population, including many previously treated with advanced therapies, emphasizing amlitelimab’s differentiated clinical profile and longer-term promise3.
Sources:
1. https://www.fiercebiotech.com/biotech/rash-selling-sanofi-shares-slump-phase-3-eczema-win-fails-soothe-market-fears
3. https://www.sanofi.com/en/media-room/press-releases/2025/2025-09-04-05-00-00-3144170
5. https://trial.medpath.com/news/12fc3c2ced895667/sanofi-shares-plummet-10-as-amlitelimab-phase-iii-data-falls-short-of-dupixent-expectations