Sanofi drops eczema drug from $1.1B Kymab deal

Why it matters: Amlitelimab was the principal asset behind Sanofi’s $1.1 billion acquisition of Cambridge, UK-based Kymab in 2021 and had once been viewed as a potential successor to its blockbuster eczema drug Dupixent.

• The decision represents a costly setback for Sanofi’s efforts to build its next generation of immunology products as new CEO Belén Garijo reviews the company’s R&D pipeline.

Zoom in: Sanofi said the total efficacy and safety evidence generated for amlitelimab did not support further development in moderate-to-severe atopic dermatitis.

• The company acknowledged that patients in the Phase 3 ESTUARY extension study maintained their clinical responses without relapsing. But it concluded that the anti-OX40 ligand antibody would not provide a meaningful improvement over the current standard of care.
• Sanofi will wind down the ongoing atopic dermatitis studies and said the decision will not change its financial guidance for 2026.

Backstory: Sanofi acquired Kymab in April 2021 for $1.1 billion upfront, with up to $350 million in additional milestones. The company accounted for the transaction as an asset acquisition because amlitelimab – then known as KY1005 – represented most of Kymab’s value.

• Expectations began to unravel in September 2025. Although the first Phase 3 study met its primary endpoints, the efficacy results fell below investor expectations and appeared weaker than those achieved by Dupixent and other competing therapies.
• The picture became more complicated in January. The Phase 3 SHORE study met its primary and key secondary endpoints, but COAST 2 failed to meet the co-primary endpoints required in Europe, even as Sanofi continued to promise global regulatory submissions.

How it works: Amlitelimab blocks OX40 ligand, an immune regulator involved in activating inflammatory T cells. Sanofi had hoped the mechanism could control inflammation without broadly suppressing or depleting T cells.

What’s next: Amlitelimab is not necessarily dead. A 229-patient Phase 2 study in adults with nonresponsive celiac disease remains active, with the primary completion scheduled for August 2026, but atopic dermatitis was the asset’s most advanced and commercially important indication. Its discontinuation leaves Sanofi with little to show so far for the largest upfront payment made in the Kymab acquisition.