Dupixent CTCL Lawsuits: The Next Emerging Mass Tort

A new pharmaceutical mass tort is taking shape. Plaintiffs have moved to centralize lawsuits alleging that the blockbuster eczema and asthma drug Dupixent (dupilumab) causes cutaneous T-cell lymphoma (CTCL) into a proposed federal MDL-3180, In re: Dupixent Products Liability Litigation, according to King Law's 2026 case tracking. The cases rest on observational research finding roughly a 3x to 4.5x higher CTCL risk among dupilumab patients, as summarized by SSKB Law.

The litigation follows a regulatory warning sign. The FDA notified manufacturer Regeneron on January 15, 2025 of a newly identified safety signal, and its fourth-quarter 2024 FAERS report listed CTCL as a potential serious risk, stating the agency was "evaluating the need for regulatory action," a representative complaint states. For firms evaluating intake, the early stage of this docket makes case-vetting—and the medical records behind it—the central task.

The Science Behind the Claims

Dupixent, marketed by Sanofi and Regeneron, treats chronic inflammatory conditions including eczema, asthma, and COPD. A series of observational studies has raised concern about a link to CTCL, a rare non-Hodgkin lymphoma that primarily affects the skin. A 2024 JAMA Dermatology analysis found roughly a 3x higher risk, a 2024 TriNetX database study found about 3.5x, and a 2025 study reported up to a 4.5x increased risk, SSKB Law reported.

The most striking figure comes from global pharmacovigilance data. An analysis of the World Health Organization's VigiBase found a statistically significant odds ratio of 11.11 (95% confidence interval 6.77–18.23) for CTCL reports with dupilumab—meaning patients were more than ten times as likely to report CTCL as an adverse event compared with other biologics, according to a representative complaint.

Two Competing Theories

A central question divides the litigation: does Dupixent cause CTCL, or does it unmask or accelerate a pre-existing, undiagnosed cancer? Because CTCL can resemble eczema, patients and physicians may attribute worsening symptoms to a flare-up while the lymphoma advances—delaying diagnosis. Plaintiffs' complaints advance both theories, while defendants are expected to argue the cancers predated treatment. Either way, the answer turns on a precise diagnostic and exposure timeline.

The FDA has not recalled Dupixent, and the agency's stance remains that it is evaluating whether regulatory action is warranted, King Law reported. That open posture is part of why the litigation is still in its early innings.

Will the JPML Centralize It?

Whether the proposed MDL-3180 is created will hinge on the same factors that have governed the panel's recent decisions. The JPML has favored dockets with a clearly defined injury and a recognizable, bounded set of defendants, while refusing broader, open-ended theories, as Lawsuit Intelligencer's 2026 mass tort analysis detailed.

Dupixent fits the favored profile: a single drug, two named manufacturers, and a specific cancer diagnosis. That makes centralization plausible—but until the panel rules, firms are operating in the pre-MDL window where intake decisions are made one case at a time.

Why Vetting Depends on Records

In an emerging tort, the firms that succeed are the ones that screen claims rigorously before signing them. Dupixent CTCL cases require a specific evidentiary foundation:

• Dermatology records documenting the original atopic dermatitis or eczema diagnosis and treatment course
• Biopsy and pathology reports confirming CTCL or mycosis fungoides
• Oncology and hematology records establishing staging and treatment
• Pharmacy and prescribing records pinpointing when dupilumab was started and stopped
• Longitudinal notes that distinguish a misdiagnosed flare from cancer progression

The diagnostic timeline is everything. Confirming exposure dates against the point of CTCL diagnosis is what separates a qualifying claim from one defendants will defeat on causation. Comprehensive retrieval and analysis—offered by services including LlamaLab—lets firms assemble that timeline quickly and identify the specialist records that prove it.

What Firms Should Watch

The Bottom Line

Dupixent CTCL litigation has the hallmarks of the next significant pharmaceutical mass tort: a mounting body of observational research, an FDA safety signal, and a motion to centralize before the JPML. But it remains early, and the "cause versus unmask" dispute means causation will be hard-fought.

For firms considering intake, the discipline is in the vetting. Biopsy-confirmed diagnoses and precise exposure timelines—drawn from complete dermatology, oncology, and pharmacy records—will determine which cases are worth pursuing if and when MDL-3180 is formed.

This article is for informational purposes only and does not constitute legal or medical advice. Sources: King Law, SSKB Law, Lawsuit Information Center, Durkin complaint (King Law), Harding Mazzotti, Lawsuit Intelligencer.