Dupixent Injections Caused Peripheral T-Cell Lymphoma (PTCL) Diagnosis: Lawsuit

Former user diagnosed with PTCL claims manufacturers failed to properly study the potential Dupixent cancer risks, despite numerous case studies and other reports linking the eczema treatment to various kinds of T-cell lymphoma.

Regeneron and Sanofi-Aventis face a Dupixent lawsuit brought last week by an Illinois man, who says the side effects of the eczema treatment caused him to develop a rare form of blood cancer.

The complaint (PDF) was filed by Anthony Baum in the U.S. District Court for the Northern District of Illinois on April 2. It claims the two manufacturers marketed and sold a drug that could cause serious and life-altering side effects without adequate warnings to the medical community or patients.

The U.S. Food and Drug Administration (FDA) first approved Dupixent (dupilumab) in 2017 as a treatment for atopic dermatitis and eczema. Its approval was later expanded to include use for asthma, chronic obstructive pulmonary disease (COPD), as well as some inflammatory conditions known to target the respiratory tract and skin. The drug generated $18.3 billion in sales in 2025.

However, studies have recently linked Dupixent side effects to an increased risk of certain forms of T-cell lymphoma, a rare form of cancer that affects the white blood cells, which are a key part of the human immune system and help combat infections. At least two forms of T-cell lymphoma have been associated with Dupixent use, including cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma (PTCL).

Baum’s complaint now joins dozens of similar Dupixent injection lawsuits filed nationwide since these findings came to light, each raising similar allegations that the manufacturers knew about potential cancer risks linked to the drug for years, yet hid these risks from regulators, doctors and patients in order to increase profits at the expense of consumer safety.

Dupixent PTCL Lawsuit

According to the complaint, Baum was prescribed Dupixent in March 2022 after being diagnosed with eczema earlier that year, receiving two injections that month and three more by the end of April.

Shortly after starting treatment, he developed swollen lymph nodes and was diagnosed with peripheral T-cell lymphoma (PTCL) in May 2022, just two months later. His doctor immediately discontinued Dupixent as Baum underwent chemotherapy and a stem cell transplant, which led to additional complications, including graft-versus-host disease that allegedly caused COPD.

The lawsuit states that Baum was not informed of any potential link between Dupixent and his cancer until March 2025, which he claims reflects a broader lack of awareness caused by the manufacturers’ failure to disclose the risks. 

Baum alleges the companies withheld warnings for years despite case reports, epidemiological studies and other scientific evidence linking Dupixent to T-cell lymphoma, and failed to conduct adequate testing or update the drug’s label even after cancer signals emerged.

“Defendants made repeated representations that Dupixent is safe and effective, including references to ‘safety results’ from clinical trials. Defendants made these false and misleading statements even though they knew Dupixent had lymphoproliferative disorder risks that had not been adequately studied with respect to its effect on the development and progression of T-cell lymphoma, including CTCL and PTCL.”

– Anthony Baum et al. v. Regeneron Pharmaceuticals Inc. et al

The lawsuit presents claims for failure to warn, negligence, negligent misrepresentation and breach of warranty. Baum’s wife, Jeanette Baum, is also pursuing loss of consortium claims.

Dupixent Injection Lawsuits

The complaint comes as a group of plaintiffs and the defendants seek to have all Dupixent injection lawsuits consolidated before one federal judge for coordinated pretrial proceedings as part of a multidistrict litigation (MDL).

If the U.S. Judicial Panel on Multidistrict Litigation (JPML) approves the requests, the judge appointed to oversee the case will shepherd the litigation through coordinated discovery and pretrial proceedings, and will likely arrange for a series of early test trials. These “bellwether” trials will allow the parties and court to see how juries respond to evidence and testimony that would be cornerstones for the vast majority of claims.

While the outcomes of bellwether trials are not binding, they can help the parties negotiate a settlement agreement once it becomes clear how juries are likely to decide. However, if no Dupixent cancer settlement has been reached by the end of the bellwether trials, the judge may begin remanding the cases back to their original district courts for individual trial dates.

As the JPML weighs the decision on consolidation, individuals are continuing to file Dupixent cancer lawsuits throughout various federal courts nationwide, seeking compensation for their injuries. 

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