Dupixent Cutaneous T-Cell Lymphoma Warning Label Update Being Evaluated by FDA

FDA indicates it is monitoring reports of Cutaneous T-Cell Lymphoma (CTCL) from Dupixent, and evaluating whether regulatory action is needed, including potential updates to the drug’s warning label.

Dupixent (dupilumab), a blockbuster drug that has revolutionized treatment for eczema and other inflammatory diseases, is now being reviewed by federal drug regulators to determine whether additional warnings may be needed about the risk of triggering cutaneous T-cell lymphoma (CTCL), a rare and aggressive blood cancer often mistaken for eczema in its earliest stages.

The investigation marks a pivotal moment for one of the fastest-growing biologics in the world, raising urgent questions about whether patients and doctors have been adequately warned about the potential Dupixent CTCL side effects.

In March 2025, the U.S. Food and Drug Administration (FDA) placed Dupixent on its quarterly FAERS “Potential Signals” list, citing CTCL and confirming it is “evaluating the need for regulatory action,” which comes after at least 300 adverse event reports involving lymphoma diagnoses submitted by patients and healthcare providers.

That rare designation signals a formal safety review that could carry major consequences for Sanofi and Regeneron, as federal regulators weigh whether stronger warnings or labeling changes are needed.

Alongside the FDA’s investigation, a growing body of medical evidence continues to surface supporting a link between Dupixent and lymphoma side effects. In a study published in the Journal of the American Academy of Dermatology, researchers found a four-fold increase in CTCL diagnoses among Dupixent users, and case reports describing how the drug’s anti-inflammatory effects may mask the cancer in its early stages.

As medical evidence about the drugs link to CTCL mounts, and FDA adverse event reports continue to flag cancer cases, Dupixent lawsuits are now being investigated by attorneys nationwide over Sanofi and Regeneron failure to warn about the potential risks, including claims Dupixent’s aggressive marketing as a long-term eczema therapy may have delayed critical cancer diagnoses by suppressing visible symptoms.

What the FDA Dupixent Investigation Means

While lawsuit investigations over the manufacturers’ potential failure to warn begin to take shape, the FDA’s probe provides the clearest indication yet that regulators are scrutinizing whether Dupixent’s safety profile has been underestimated.

When a drug lands on the agency’s quarterly “Potential Signals” list, it sets off a detailed, months-long process that can result in new black box warnings, public safety communications, or requirements for additional clinical studies.

The FDA’s review began when adverse event reports from patients and physicians were flagged in the agency’s FAERS database. While a listing on the quarterly signal report does not confirm a causal relationship, it indicates the agency has found enough reports to warrant a deeper look. The first step is cleaning and verifying the data, removing duplicates and analyzing timelines of when patients developed CTCL after starting Dupixent.

From there, regulators expand the scope to published studies and medical literature. In the case of Dupixent, several dermatology journals have documented patients who developed CTCL after treatment, while other researchers argue the drug may only unmask cancers that were already present but mistaken for eczema. Sorting through these competing interpretations is at the heart of the FDA’s process.

The agency also relies on its Sentinel program, which draws from millions of health records to track real-world drug use. Sentinel analyses allow reviewers to compare Dupixent patients against those on other eczema treatments, providing a broader population-level perspective that FAERS alone cannot capture.

Behind the scenes, Sanofi and Regeneron have likely been asked to supply additional safety data. This can include pooled analyses of clinical trials, postmarketing surveillance and any internal findings related to CTCL.

If regulators determine that Dupixent carries a measurable cancer risk, the agency has the authority to mandate changes to the drug’s label, require stronger warnings, or issue a public safety communication to doctors and patients.

FDA Reports of Dupixent Lymphoma Side Effects

The FDA’s decision to formally investigate Dupixent stemmed from a steady accumulation of adverse event reports submitted by doctors, patients and manufacturers around the world. These reports, which are collected in the FDA’s Adverse Event Reporting System (FAERS), provide the raw material regulators use to determine whether a drug’s risks may be greater than previously recognized.

Among the cases reviewed in recent months was a 58-year-old woman in the United States who developed cutaneous T-cell lymphoma after years of being treated with Dupixent for eczema. Her case was flagged as “serious” and submitted directly to Sanofi Aventis before being expedited to the FDA in August 2025.

In South Korea, a consumer report described a middle-aged man who developed lymphadenopathy and worsening skin lesions while on Dupixent for atopic dermatitis, with doctors later identifying CTCL as a diagnosis. Another Korean woman’s report detailed nearly identical concerns, atopic dermatitis treatment followed by skin lesions that ultimately led to a CTCL finding.

However, not all reports involved straightforward eczema cases. In one complex U.S. submission, a 71-year-old man using Dupixent alongside multiple other medications for asthma developed a pulmonary mass and was later diagnosed with both asthma complications and T-cell lymphoma. His case required hospitalization.

In another report, a 25-year-old woman developed CTCL after a report initially noted a Dupixent dosing error, underscoring how safety signals can surface even in cases with confounding factors.

The diversity of these cases, spanning young adults in their twenties to elderly patients in their seventies, across multiple countries, is part of what elevated the FDA’s concern. While spontaneous reports cannot by themselves prove causation, the clustering of CTCL diagnoses, often following months or years of Dupixent therapy, presents a signal that regulators could not ignore.

In total, more than 300 reports involving lymphoma diagnoses have now been logged, creating the backbone of the FDA’s current safety review.

Dupixent T-Cell Lymphoma Lawsuits

What happens next could shape both the medical and legal landscape. If the FDA strengthens warnings, it would likely bolster claims lawyers are preparing to file in courts nationwide, providing plaintiffs with evidence that cancer risks were flagged at the highest level of oversight.

If regulators instead conclude the cases reflect unmasking of pre-existing disease rather than direct causation, potential claims could still move forward on the grounds that patients and doctors were not adequately warned about the risk of misdiagnosis and the danger of delayed cancer detection.

Law firms are now investigating Dupixent cancer lawsuits for individuals who were prescribed the drug for any of its approved uses and later diagnosed with cutaneous T-cell lymphoma (CTCL) or another T-cell lymphoma subtype.

To receive a free consultation to determine if you or a loved one may be eligible to file a Dupixent lawsuit, submit information for review by a lawyer.