EmergingLast updated: February 23, 2026

Dupixent (dupilumab) is a monoclonal antibody biologic drug developed by Regeneron Pharmaceuticals and marketed jointly with Sanofi-Aventis and its subsidiary Genzyme Corporation. The FDA first approved Dupixent in March 2017 for adults with moderate-to-severe atopic dermatitis (eczema) who had not responded adequately to topical treatments. Subsequent FDA approvals expanded its use to moderate-to-severe asthma in October 2018, chronic rhinosinusitis with nasal polyps (CRSwNP) in June 2019, eosinophilic esophagitis (EoE) in May 2022, prurigo nodularis in September 2022, and chronic obstructive pulmonary disease (COPD) with an eosinophilic phenotype in September 2024. With more than 37 million prescriptions dispensed globally, Dupixent became one of the best-selling biologic drugs in the world, generating over $13 billion in annual revenue for its manufacturers. The drug works by inhibiting interleukin-4 (IL-4) and interleukin-13 (IL-13) signaling — two cytokines that drive type 2 inflammation. While this mechanism was considered targeted and relatively safe, post-market surveillance and independent research have identified a concerning association between Dupixent use and cutaneous T-cell lymphoma (CTCL). CTCL is a rare cancer in which T-cells become malignant and attack the skin, often presenting initially as rashes or patches that can be mistaken for eczema. The critical concern is that symptoms of CTCL closely mimic the very conditions Dupixent is prescribed to treat, potentially masking the cancer and delaying diagnosis. A peer-reviewed study analyzing 19,612 patients found that Dupixent users faced a 4.5 times higher risk of developing CTCL compared to patients not using the drug. The FDA placed Dupixent on its drug safety watchlist in March 2025 and escalated to a formal investigation in September 2025 after receiving over 300 adverse event reports related to lymphoma and blood cancers. As of February 2026, individual lawsuits are being filed against Regeneron Pharmaceuticals, Sanofi-Aventis, and Genzyme Corporation. Plaintiffs allege that the manufacturers knew or should have known about the cancer risk and failed to adequately warn patients and prescribing physicians. Specific allegations include failure to warn, defective design of the drug's labeling, negligence in post-market surveillance, and fraudulent concealment of safety data. A wrongful death suit was filed in Tennessee in October 2025 on behalf of Chandra Richardson. Additional cases have been filed in Florida (January 2026) and Illinois (December 2025). Legal experts anticipate that the Judicial Panel on Multidistrict Litigation will consolidate federal cases into an MDL within the next 12 months.

Case Timeline

Litigation Timeline

February 2026

JPML Consolidates Federal Dupixent Cases into MDL No. 3180

In February 2026, the Judicial Panel on Multidistrict Litigation (JPML) granted a motion to consolidate all federal Dupixent lawsuits alleging cancer injuries into a single multidistrict litigation, designated MDL No. 3180. The consolidation transferred cases from multiple federal districts to a single judge for coordinated pretrial proceedings, including discovery, expert witness challenges (Daubert motions), and bellwether trial selection. The JPML's decision cited the common factual questions across all cases — including the mechanism of IL-4/IL-13 blockade, the adequacy of Regeneron and Sanofi's warnings, and the epidemiological evidence linking dupilumab to CTCL. The MDL assignment signals that federal courts recognize the volume and legitimacy of Dupixent cancer claims. For plaintiffs, MDL consolidation offers several advantages: shared discovery reduces individual litigation costs, coordinated expert challenges prevent duplicative motions, and bellwether trials create settlement benchmarks. For Regeneron and Sanofi, the MDL structure means they face organized, well-resourced plaintiffs' committees rather than scattered individual lawsuits. Attorneys across the country are filing new cases into the MDL, and the early plaintiffs' committee is expected to begin propounding discovery requests targeting Regeneron's internal safety data, FAERS analysis records, and communications with the FDA about the CTCL signal.

litigation

October 2025

Richardson Wrongful Death Lawsuit Filed in Tennessee — First Known Death Claim

The lawsuit that put Dupixent litigation on the map was filed in Tennessee state court in October 2025 on behalf of Chandra Richardson, a woman who allegedly died from complications related to T-cell lymphoma after being treated with Dupixent for atopic dermatitis. The Richardson complaint named Regeneron Pharmaceuticals, Sanofi-Aventis U.S. LLC, and Genzyme Corporation as defendants and alleged failure to warn, defective labeling, negligence in post-market surveillance, and fraudulent concealment of safety data. Tennessee's one-year statute of limitations made early filing essential. The complaint detailed how Richardson's dermatologist attributed her worsening skin symptoms to eczema flares for over a year before a biopsy finally revealed CTCL — by which time the cancer had progressed to an advanced stage. The Richardson case illustrates the core liability theory in Dupixent litigation: the manufacturers knew or should have known that their drug's mechanism of action could promote T-cell malignancies, and they failed to warn physicians about the diagnostic confusion that would inevitably result from prescribing an eczema drug that could cause a cancer mimicking eczema. Additional suits followed in Illinois (December 2025) and Florida (January 2026, Fraioli v. Regeneron).

litigation

2024

Peer-Reviewed Study Links Dupixent to 4.5x CTCL Risk — 19,612-Patient Analysis

The scientific inflection point in the Dupixent story arrived when researchers published a peer-reviewed analysis of 19,612 patients examining the association between dupilumab use and cutaneous T-cell lymphoma. The findings were stark: Dupixent users faced a 4.5 times higher risk of developing CTCL compared to matched controls who did not use the drug. The study controlled for confounding variables including age, sex, baseline atopic dermatitis severity, and prior immunosuppressive therapy. A 4.5x relative risk is well above the threshold that epidemiologists and courts consider meaningful — for context, the relative risk of lung cancer from smoking is approximately 15-30x, and asbestos-mesothelioma relative risk is approximately 5-7x. The Dupixent-CTCL association is in the range that supports both clinical concern and legal causation. The researchers proposed a biologically plausible mechanism: dupilumab's blockade of IL-4 and IL-13 shifts the immune system away from type 2 responses, potentially dismantling an immune surveillance mechanism that had been keeping pre-malignant T-cell clones in check. In other words, the drug may not cause CTCL de novo — it may release the brakes on a cancer that the immune system had been suppressing. This mechanism also explains the diagnostic confusion: patients develop cancer in the very skin that Dupixent was treating, and the cancer looks like the disease that prompted the prescription.

scientific

2018–2024

Dupixent Indication Expansions — Asthma, CRSwNP, EoE, COPD, and Pediatric Use

Between 2018 and 2024, the FDA approved Dupixent for a cascade of new indications, each one expanding the drug's patient population dramatically. Moderate-to-severe asthma came in October 2018. Chronic rhinosinusitis with nasal polyps (CRSwNP) followed in June 2019. Eosinophilic esophagitis (EoE) was added in May 2022, prurigo nodularis in September 2022, and COPD with eosinophilic phenotype in September 2024. Simultaneously, age restrictions were lowered: Dupixent was approved for children as young as six months old for eczema and for children aged six and older for asthma. Each expansion was accompanied by aggressive direct-to-consumer advertising and physician education campaigns, but none of the supplemental approval trials were designed or powered to detect cancer signals. By 2024, global prescriptions exceeded 37 million and Dupixent had become the highest-revenue biologic drug outside of oncology. The sheer scale of exposure — millions of patients taking a drug that modifies fundamental immune signaling pathways — meant that even a modest increase in cancer risk would translate to thousands of affected individuals. The expansion into pediatric populations is particularly concerning: children prescribed Dupixent for eczema or asthma face decades of potential exposure during a period of active immune system development.

regulatory

March 28, 2017

FDA Approves Dupixent for Moderate-to-Severe Atopic Dermatitis

The FDA granted approval for dupilumab (brand name Dupixent) as the first biologic treatment for moderate-to-severe atopic dermatitis in adults who had not responded adequately to topical therapies. Regeneron Pharmaceuticals developed the drug and partnered with Sanofi for commercialization. The approval was based on three pivotal clinical trials — SOLO 1, SOLO 2, and CHRONOS — involving more than 2,100 patients. In those trials, roughly 40 percent of patients achieved clear or almost-clear skin after 16 weeks, compared to about 10 percent on placebo. The clinical trial program, however, was not designed to detect rare cancers. The trials enrolled relatively small populations, followed patients for relatively short durations, and excluded patients with significant comorbidities — all factors that would make it difficult to identify a cancer signal that might take years to manifest. What the trials did show was a modest increase in conjunctivitis and injection-site reactions, side effects that dominated the safety conversation and drew attention away from any potential oncologic risk. Regeneron and Sanofi priced Dupixent at approximately $37,000 per year — setting the stage for what would become a $13 billion annual revenue juggernaut.

regulatory

Case Results

Notable Verdicts & Settlements

Verdict

N/A

Richardson v. Regeneron Pharmaceuticals et al. (Tennessee State Court)

The first known Dupixent wrongful death lawsuit, filed in Tennessee state court on behalf of Chandra Richardson. Richardson was prescribed Dupixent for moderate-to-severe atopic dermatitis and allegedly developed cutaneous T-cell lymphoma that went undiagnosed for over a year because her dermatologist attributed worsening skin symptoms to eczema treatment resistance. By the time CTCL was confirmed by biopsy, the cancer had progressed to an advanced stage. Richardson died from complications of T-cell lymphoma. Her estate alleges failure to warn, defective labeling, negligent post-market surveillance, and fraudulent concealment against Regeneron Pharmaceuticals, Sanofi-Aventis U.S. LLC, and Genzyme Corporation. The case is pending.

2025-10-15Tennessee State Court

Verdict

N/A

Fraioli v. Regeneron Pharmaceuticals et al. (S.D. Florida)

Giovanni Fraioli filed one of the first federal Dupixent lawsuits in the Southern District of Florida in January 2026. Fraioli alleges that he developed cutaneous T-cell lymphoma after using Dupixent as prescribed for atopic dermatitis. The complaint names Regeneron Pharmaceuticals, Sanofi-Aventis U.S. LLC, and Genzyme Corporation and alleges failure to warn, strict products liability, negligence, and fraudulent concealment. The case was transferred to MDL No. 3180 following the JPML's consolidation order in February 2026. Fraioli's case is among the earliest-filed federal claims and is positioned for potential bellwether consideration.

2026-01-10Southern District of Florida

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