Sanofi’s eczema drug hits targets but disappoints investors

Sanofi’s amlitelimab met primary and secondary endpoints in a phase 3 eczema trial, but underdelivered on efficacy, triggering a sharp drop in share price.

Why it matters: Amlitelimab was seen as a potential $5B blockbuster and a crucial proof point for Sanofi’s R&D pipeline. Falling short of expectations risks both revenue projections and investor confidence.

Backstory: Analysts expected 45–50% EASI-75 (patients achieving 75% improvement in eczema severity) response rates; Sanofi delivered 35.9–46%. Its IGA0/1 (patients with clear or almost clear skin) scores also lagged. Though statistically significant, these results aligned with analysts’ “bear case,” driving Sanofi stock down 9% in Paris and over 7% on the Nasdaq.

Big picture: The atopic dermatitis market is becoming crowded with high-efficacy biologics. Amlitelimab’s novel mechanism (anti-OX40L) and 12-week dosing offer convenience, but its “middle of the pack” efficacy limits its ability to challenge leaders like Dupixent, a drug Sanofi has developed with Regeneron.

What’s next: Sanofi needed a win after recent R&D setbacks—including failures in COPD, asthma, and psoriasis. Sanofi has four more phase 3 amlitelimab trials underway, with data expected through 2026.