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Sanofi faces consolidated Dupixent lawsuits

The federal cases are centralized in MDL 3180. Here is what that means for patients weighing a claim.

ACTIVE LITIGATION — NO SETTLEMENT. MDL 3180 underway · filing deadlines vary by state.

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Claims are brought against Sanofi and Regeneron, the makers of Dupixent — not against your doctor. Conversations are confidential. Some matters may be referred to other lawyers. No settlement has been reached, and most cases are in their earliest stages; every case must be proven on its own facts. Attorney Advertising.

Lawsuits consolidated in MDL 3180 (D.N.J.) allege that Dupixent (dupilumab) is associated with an increased risk of cutaneous T-cell lymphoma (CTCL) and that the manufacturers failed to warn about it. No court has ruled on these allegations, no settlement exists, and the litigation is in its earliest stages. Published studies report a statistical association — which the study authors themselves note does not establish causation — and the FDA has identified a potential safety signal it is still evaluating; Dupixent’s FDA label does not currently warn about lymphoma. Whether any individual has a claim depends on their medical records and the law of their state.

Which Sanofi entities are actually named as defendants?

Corporate families are not single defendants, and captions matter. The operating entity named across the Dupixent actions is Sanofi-Aventis U.S. LLC — docketed variously as “SANOFI-AVENTIS U.S. LLC,” “SANOFI-AVENTIS US, LLC,” and “SANOFI-AVENTIS US LLC.” In its corporate disclosure statement filed with the Judicial Panel on Multidistrict Litigation on March 3, 2026, that entity identified Sanofi US Services Inc. as its corporate parent.

A third Sanofi-family entity, Genzyme Corporation, is named in a subset of the actions; its own disclosure identified Aventis Inc. as its corporate parent. The Boggs action (E.D. Pa. 2:26-cv-00763) is one example, its party record listing Genzyme, Sanofi-Aventis U.S. LLC, and Regeneron together.

Most member cases carry the caption form “[Plaintiff] v. REGENERON PHARMACEUTICALS, INC., ET AL.” A smaller number lead with the Sanofi entity — the Durkin action, filed in the Middle District of Florida on February 4, 2026 and now docketed as D.N.J. 3:26-cv-06582.

What is Sanofi’s role in Dupixent?

Dupixent is a prescription biologic made by Sanofi and Regeneron, FDA-approved since March 2017 and now carrying nine indications including atopic dermatitis, asthma, and COPD (FDA-approved labeling, SPL version 60, revised April 22, 2026). The two companies bring the drug to the U.S. market together; the Sanofi entity named in these cases is the U.S. operating company through which that commercial role runs. The companies announce Dupixent regulatory milestones jointly; see, e.g., the September 28, 2022 approval release (sanofi.com).

One record fact shaped where the litigation sits: the June 4, 2026 transfer order recorded that Sanofi’s principal place of business is in the District of New Jersey. What the company tells prescribers travels in the FDA-approved Dupixent label — and what that document does not say is the center of the theory below.

What do plaintiffs allege against Sanofi?

Plaintiffs allege that they, or their decedents, used Dupixent — commonly prescribed for atopic dermatitis, or eczema — and were later diagnosed with cutaneous T-cell lymphoma, and that the drug caused or accelerated it. In consolidating the cases the Panel identified the common questions: whether the scientific literature shows a causal link; if so, when the defendants should have learned of it; and whether the warnings were adequate. Those are allegations and open questions, not findings. Nothing in the record establishes that Sanofi did anything wrong, and what plaintiffs must eventually prove is exactly what the Panel framed: knowledge, timing, and the adequacy of what was disclosed.

What position has Sanofi taken in the litigation so far?

On March 24, 2026, Sanofi-Aventis U.S. LLC filed a joint response with Regeneron Pharmaceuticals, Inc. and Genzyme Corporation to the plaintiffs’ motion to centralize. Two things about that filing are frequently mischaracterized elsewhere:

• The defendants did not oppose centralization outright. They supported it in a different district — the Southern District of New York, alternatively the Southern or Middle District of Florida — rather than any venue plaintiffs proposed.
• They asked the Panel to limit the MDL to CTCL cases only. Movants agreed to exclude B-cell and Hodgkin’s lymphomas but opposed a CTCL-only cap, pointing to literature on peripheral T-cell lymphoma and anaplastic large cell lymphoma.

The Panel rejected those venue positions and sent the cases to New Jersey. On scope it did neither side a favor: it declined to rule that non-CTCL T-cell lymphoma cases belong in the MDL, noting that no plaintiff before it alleged one, and left expansion to the conditional-transfer process. The defense argument for a CTCL-only MDL remains live. The full document is reproduced on our transfer order page.

Has Sanofi been found liable for anything in this litigation?

No. As of the MDL docket’s last filing on September 15, 2026, the New Jersey record consists of incoming transfer orders, Initial Procedure Order No. 1, notices of appearance, service returns, and administrative entries — no dismissals, no remands, no rulings on scientific evidence, no summary judgment, and no leadership appointments.

The same honesty runs the other direction: plaintiffs have prevailed on nothing on the merits either. Their motion for an expedited Panel hearing was denied on February 27, 2026, and the scope ruling they sought was deferred. Anyone describing this Dupixent lawsuit as a case Sanofi has already lost — or already beaten — is describing something that has not happened. Current posture is tracked on our MDL 3180 page.

What does this mean if you took Dupixent and were later diagnosed with CTCL?

It means the companies that made and marketed the drug are the parties who would have to answer, and that your claim would be evaluated on your own records: pharmacy history showing Dupixent use, the pathology report establishing the diagnosis, and the timeline between them. There is no minimum length of time on the drug, and claims may also be brought through the estate of someone who has died. No attorney-client relationship is created until a written engagement agreement is signed.

This page is about a lawsuit — it is not medical advice, and filing a claim does not require you to stop taking Dupixent. Decisions about your medication belong with you and your doctor.

What else do people ask about Sanofi’s role in these cases?