Sanofi SA's stock (NASDAQ: SNY) experienced a decline following disappointing late-stage trial results for amlitelimab, a potential successor to the popular eczema drug Dupixent. The global COAST 1 phase 3 study revealed that amlitelimab met primary and secondary endpoints, showing significant skin clearance and disease severity improvement compared to a placebo at Week 24 for patients aged 12 and older with moderate-to-severe atopic dermatitis. However, analysts highlighted that amlitelimab, as a second anti-OX40 ligand antibody, did not meet expectations. Amgen Inc.'s (NASDAQ: AMGN) rocatinlimab and amlitelimab in Phase 3 trials also did not perform as well as Dupixent, which showed approximately a 36% enhancement in EASI-75 scores. These outcomes have raised concerns about Sanofi's dermatology franchise sustainability post-patent expiration.