In a significant development, the manufacturers of Dupixent (dupilumab) — Sanofi and Regeneron Pharmaceuticals — have agreed that the growing number of lawsuits alleging the drug causes T-cell lymphoma should be consolidated into a formal multidistrict litigation (MDL) for coordinated pretrial proceedings.
What Is Dupixent?
Dupixent is a biologic medication approved to treat moderate-to-severe atopic dermatitis (eczema), asthma, chronic rhinosinusitis with nasal polyps, and other inflammatory conditions. It works by blocking interleukin-4 and interleukin-13, key proteins in the immune system's inflammatory response. Since its approval in 2017, Dupixent has become one of the best-selling drugs in the world, generating over $13 billion in annual revenue.
The Cancer Allegations
Plaintiffs allege that Dupixent's mechanism of action — suppressing certain immune pathways — may inadvertently allow T-cell lymphomas to develop or progress unchecked. T-cell lymphoma is a rare but serious cancer of the immune system's T-cells.
The first wave of lawsuits was filed after the FDA updated Dupixent's prescribing label in 2024 to include a warning about cases of T-cell lymphoma reported in patients using the drug. Plaintiffs argue that the manufacturers were aware of this risk before the label update but failed to warn patients and doctors in a timely manner.
Why MDL Consolidation Matters
MDL consolidation means that all federal Dupixent cancer cases will be assigned to a single judge for pretrial proceedings, including discovery, Daubert hearings on expert testimony, and bellwether trial selection. This streamlines the litigation process and ensures consistent rulings on key legal and scientific questions.
The fact that the defendants agreed to consolidation — rather than opposing it, as is common — suggests they may prefer to address the scientific evidence in a single, structured proceeding rather than face individual trials across the country.
Next Steps
The Judicial Panel on Multidistrict Litigation (JPML) will formally establish the MDL and assign it to a federal district court. Early case management orders are expected in mid-2026, with discovery beginning shortly thereafter.