In June 2026, the U.S. Judicial Panel on Multidistrict Litigation created MDL No. 3180, In re: Dupixent (Dupilumab) Products Liability Litigation, and centralized federal Dupixent lawsuits in the District of New Jersey.
The MDL includes claims brought by patients who allege they developed cutaneous T-cell lymphoma (CTCL), mycosis fungoides, Sezary syndrome, and related lymphomas after treatment with Dupixent.
The JPML determined that the lawsuits involve common factual questions, including whether Dupixent may be associated with CTCL, what the manufacturers knew about potential lymphoma risks, and whether adequate warnings were provided to physicians and patients.
Centralization allows those issues to be addressed in one federal court rather than through duplicative proceedings across the country.
Unlike a class action lawsuit, each plaintiff in the Dupixent MDL maintains an individual claim and must prove their own damages.
No Dupixent settlements or trials have occurred yet, and the litigation remains in the early stages.
Why Was the Dupixent MDL Created?
The lawsuits share a common allegation that Dupixent may contribute to, reveal, or worsen CTCL in certain patients.
CTCL is a rare form of non-Hodgkin lymphoma that can closely resemble eczema and other inflammatory skin conditions, making diagnosis difficult during the disease’s early stages.
Many plaintiffs allege they were prescribed Dupixent for atopic dermatitis before later receiving a CTCL diagnosis.
Others claim Dupixent may have accelerated disease progression or worsened existing CTCL that had not yet been identified through biopsy or other testing.
The JPML concluded that these overlapping allegations make coordinated discovery more efficient and help avoid inconsistent rulings in federal court.
The lawsuits name Sanofi, Regeneron Pharmaceuticals, and related entities as defendants and allege they failed to adequately warn patients and physicians about emerging lymphoma-related safety concerns.
Scientific Evidence Driving the Litigation
Scientific studies will likely play a central role in the MDL proceedings.
A retrospective cohort study reported that Dupixent users faced a 4.59-times higher risk of CTCL compared to non-users, while other published research has examined dupilumab and lymphoma risk across multiple patient populations.
Researchers continue to evaluate whether the drug’s effects on specific immune system pathways could contribute to disease progression, delayed diagnosis, or other mechanisms, although the available data remains subject to ongoing debate.
What Does the MDL Mean for Dupixent Patients?
Patients who received a cancer diagnosis after taking Dupixent may be eligible to pursue a claim if their medical records support the allegations being investigated in the litigation.
Each person must still file an individual lawsuit and provide evidence supporting their claim, including Dupixent prescription records, pathology reports, biopsy results, and other medical documentation.
The MDL creates a coordinated process for evaluating common scientific evidence while preserving each plaintiff’s individual case.
For patients diagnosed with CTCL, mycosis fungoides, Sézary syndrome, or another related lymphoma after using Dupixent, the MDL represents the central federal proceeding where these allegations will be litigated.
Differences Between an MDL and a Class Action Lawsuit
Although multidistrict litigations (MDLs) and class action lawsuits both involve large numbers of plaintiffs with similar claims, they are handled very differently by the courts.
In a class action, one or several representative plaintiffs pursue claims on behalf of an entire group, and any recovery is generally shared among eligible class members.
In an MDL, each plaintiff maintains an individual lawsuit and must prove their own injuries and damages, even though pretrial proceedings are coordinated before a single federal judge.
Most pharmaceutical and medical product litigations are handled through MDLs because injuries, medical histories, and damages often vary significantly from one plaintiff to another.
Differences between an MDL and a class action include:
- MDLs involve individual lawsuits, while class actions combine claims into a single representative case.
- Plaintiffs in an MDL retain their own medical records, damages, and legal claims.
- Class action settlements are typically divided among class members according to a court-approved formula.
- MDLs coordinate discovery, expert testimony, and pretrial proceedings for efficiency.
- Bellwether trials may be used in an MDL to help evaluate the strengths and weaknesses of claims.
- Plaintiffs generally have greater control over their individual cases in an MDL than in a class action.
