French drugmaker Sanofi SA (NASDAQ: SNY ) stock fell sharply Thursday after late-stage trial results for amlitelimab, its potential successor to blockbuster eczema drug Dupixent, failed to match investor expectations, raising fresh doubts about the company's ability to sustain its dermatology franchise once patent protections expire. Results from the global COAST 1 phase 3 study showed that amlitelimab met all primary and key secondary endpoints, demonstrating statistically significant and clinically meaningful skin clearance and disease severity compared to placebo at Week 24 in patients aged 12 years and older with moderate-to- severe atopic dermatitis. Amlitelimab was well-tolerated, with no new safety concerns identified in this study.