Link Between Dupixent and CTCL Withheld From Users, Medical Community: Lawsuit

Former user claims the drug manufacturers knew about reports of cancer linked to Dupixent side effects as early as 2018, yet failed to provide warnings.

A Pennsylvania man has filed a product liability lawsuit alleging the makers of the atopic dermatitis drug Dupixent chose to hide information about the risk that their treatment may cause various forms of T-cell lymphoma, while continuing to rake in billions from unsuspecting patients.

The complaint (PDF) was brought by William Hinton Jr., and his wife, Labarbara, in the U.S. District Court for the Eastern District of Pennsylvania on March 25. Hinton claims Dupixent’s manufacturers, Regeneron Pharmaceuticals Inc. and Sanofi-Aventis U.S. LLC, failed to warn the medical community and patients about the potential cancer risks, indicating that the drug makers should be held liable for his own T-cell lymphoma diagnosis.

Approved for sale in the U.S. in 2017, Dupixent (dupilumab) is a widely used medication approved to treat atopic dermatitis, eczema, asthma, chronic obstructive pulmonary disease (COPD) and other inflammatory conditions, particularly those affecting the respiratory system and skin.

Hinton’s lawsuit identifies Dupixent as a “flagship” product for both Regeneron and Sanofi-Aventis, generating $18.3 billion in sales in 2025. Since its release, and widespread marketing as a safe and effective treatment, sales have increased rapidly. In 2024, sales were $14.1 billion, while the year before the drug brought in $11.6 billion in sales, marking a nearly 18% annual increase over the period.

However, questions about Dupixent side effects and safety began after studies linked the drug to an increased risk of T-cell lymphoma, a rare form of cancer that affects white blood cells, a key part of the body’s immune system. In particular, Dupixent has been linked to two rare forms of the blood cancer, cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma (PTCL).

Like dozens of similar lawsuits over the link between Dupixent and CTCL filed nationwide, Hinton’s complaint alleges that the manufacturers knew about these risks, yet failed to report them to drug regulators, the medical community and patients.

Dupixent Side Effects Lawsuit

The complaint indicates that Hinton received multiple Dupixent injections from April 2025 until October 2025, which were meant to treat his severe asthma and COPD. However, he soon noticed that a preexisting small rash began to worsen, and the development of new rashes occurred while he was on the treatment.

Despite not previously being diagnosed with lymphoma of any kind, doctors told Hinton he had CTCL in late October 2025.

According to the lawsuit, Regeneron and Sanofi-Aventis knew about Dupixent cancer risks long before his injections began.

“Defendants have not informed the FDA of all of the newly-acquired, mounting evidence that use of Dupixent results in the development, accelerated progression and/or exacerbation of T-cell lymphoma, including CTCL. Defendants had such newly acquired information at least as early as 2018 upon receipt of multiple adverse event reports of CTCL development and/or rapid progression with use of Dupixent.”

– William Hinton Jr. et al v. Regeneron Pharmaceuticals Inc. et al

Hinton indicates he has suffered permanent injuries, undergone severe pain, disability, mental anguish, and will require medical treatment and monitoring for the rest of his life. He presents a claim of negligence and seeks both compensatory and punitive damages.

Dupixent Cancer Litigation

Whether Hinton’s lawsuit stays in the Eastern District of Pennsylvania remains to be seen. In February, a group of plaintiffs filed a motion with the U.S. Judicial Panel on Multidistrict Litigation (JPML), requesting to consolidate all federal Dupixent CTCL lawsuits before one judge in the Northern District of Georgia for coordinated pretrial proceedings.

Regeneron and Sanofi-Aventis have indicated they support a Dupixent lawsuit MDL, or multidistrict litigation. However, the manufacturers have requested it be located in the Southern District of New York, near their respective headquarters.

If the panel approves consolidation, the cases will be placed under one U.S. District Judge for the duration of coordinated discovery and pretrial proceedings. It is then likely that the judge will order the parties to prepare a small group of cases for early “bellwether” test trials, meant to see how juries respond to evidence and testimony that would be core to virtually every case.

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