injury

CTCL Diagnosis After Dupixent Use

Start Your Free Review
Free Case Review

Start Your Free Review

Answer 2-3 quick questions to review your potential case.

Researched By
People's Justice Research Team

Verified against court records, regulatory records, and peer-reviewed research.

How we research

Why CTCL Mimics Eczema — And Why That Matters

The clinical tragedy of Dupixent-associated CTCL is that the cancer looks almost identical to the disease being treated. Both atopic dermatitis and early-stage mycosis fungoides present as erythematous, scaly patches on the trunk and extremities. Both cause intense pruritus. Both wax and wane with environmental triggers. A dermatologist monitoring a Dupixent patient may attribute worsening or changing skin lesions to eczema flare rather than malignant transformation — especially when the patient is on a drug marketed as a breakthrough eczema therapy.

Studies from Memorial Sloan Kettering and the University of Pennsylvania Cutaneous Lymphoma Program have documented average diagnostic delays of 3 to 6 years for CTCL in the general population. For Dupixent patients, this delay may be even longer because prescribers have a ready explanation for any skin abnormality. The cost of delay is measured in staging: a patient diagnosed at Stage IA has a near-normal life expectancy, while a patient diagnosed at Stage IIB faces median survival of approximately 5 years.

Key distinguishing features that should prompt biopsy include: lesions that appear in non-typical eczema locations (bathing suit distribution), patches with poikiloderma (mottled red-brown discoloration with atrophy and telangiectasia), plaques that are fixed and do not migrate like eczema patches, and lesions that worsen despite adequate Dupixent dosing and compliance.

The Skin Biopsy: What Pathologists Look For

A skin punch biopsy is the gold standard for CTCL diagnosis. The pathologist examines the specimen for epidermotropism — the presence of atypical lymphocytes migrating into the epidermis without accompanying spongiosis (the intercellular edema typically seen in eczema). The hallmark finding is Pautrier microabscesses: discrete clusters of atypical lymphocytes within the epidermis, surrounded by a clear halo. While Pautrier microabscesses are highly specific for CTCL, they are present in only 25 to 40 percent of confirmed cases, meaning their absence does not rule out the diagnosis.

Immunohistochemistry (IHC) staining adds diagnostic precision. Classic CTCL shows CD3+, CD4+ T-cells with aberrant loss of CD7 and CD26 surface markers. The loss of these normally expressed markers signals malignant transformation. Some pathologists also stain for CD30, which is positive in large-cell transformation and carries prognostic significance. The IHC panel is essential because routine H&E staining alone has poor sensitivity for early CTCL, particularly in patients with concurrent inflammatory conditions like atopic dermatitis.

T-cell receptor (TCR) gene rearrangement analysis by polymerase chain reaction (PCR) provides molecular confirmation of T-cell clonality. A monoclonal T-cell population strongly supports CTCL, while a polyclonal result suggests reactive (non-malignant) inflammation. In litigation, pre-Dupixent biopsies showing polyclonal T-cells compared to post-Dupixent biopsies showing monoclonal T-cells provide powerful causation evidence.

CTCL Staging: From Patch-Stage to Visceral Spread

CTCL staging uses the TNMB system developed by the International Society for Cutaneous Lymphomas (ISCL) and the European Organisation for Research and Treatment of Cancer (EORTC). The T component measures skin involvement: T1 is limited patches or plaques covering less than 10 percent of the body surface area (BSA), T2 involves 10 percent or more BSA, T3 indicates one or more tumors (nodular lesions at least 1 cm in diameter), and T4 denotes erythroderma (confluent erythema covering 80 percent or more of BSA). Lymph node involvement (N0-N3), visceral organ involvement (M0-M1), and blood involvement (B0-B2) complete the staging.

Stage IA (T1N0M0B0) carries a life expectancy comparable to age-matched controls — these patients typically die with CTCL, not from it. Stage IB (T2N0M0B0) has a 5-year survival of approximately 80 percent. The prognosis drops sharply at Stage IIB (T3N0M0B0), with 5-year survival near 40 percent. Stage III (erythrodermic) and Stage IV (nodal or visceral involvement) carry median survival of 2 to 5 years. Every month of diagnostic delay in a Dupixent patient allows potential stage progression that directly affects survival and drives damage calculations in litigation.

The 40% Misdiagnosis Problem

A landmark study published in the Journal of the American Academy of Dermatology found that 41 percent of CTCL patients were initially misdiagnosed with a benign skin condition, most commonly eczema, psoriasis, or contact dermatitis. The average time from symptom onset to correct CTCL diagnosis was 4.4 years. For Dupixent patients, this number is likely worse: their treating physician already has a confirmed diagnosis of atopic dermatitis, creating a cognitive anchor that biases clinical interpretation of new or changing skin findings.

The misdiagnosis problem is compounded by Dupixent's mechanism of action. By suppressing Th2 inflammation, the drug may partially mask the inflammatory component of early CTCL while allowing the malignant clone to expand. Patients may report that their skin 'looks better' even as the underlying lymphoma progresses. Sanofi and Regeneron have never issued a Dear Healthcare Provider letter alerting dermatologists to the specific risk of CTCL misdiagnosis masking in Dupixent patients — an omission that plaintiffs' experts characterize as a failure of post-market safety surveillance.

Pautrier Microabscesses: The Diagnostic Smoking Gun

Pautrier microabscesses are the single most specific histological finding for mycosis fungoides. These are collections of three or more atypical cerebriform lymphocytes within the epidermis, typically in a cluster surrounded by a clear space (the 'halo' artifact). They represent direct evidence of malignant T-cell epidermotropism — the defining feature that separates CTCL from inflammatory dermatoses. When Pautrier microabscesses are identified in a Dupixent patient's biopsy, the diagnosis is essentially confirmed and the defense's 'pre-existing misdiagnosed eczema' argument is significantly weakened.

However, Pautrier microabscesses are present in only a minority of confirmed CTCL cases, particularly at early stages. Their absence does not exclude the diagnosis. Courts have accepted expert testimony that the full diagnostic picture — combining histopathology, immunohistochemistry, TCR gene rearrangement, and clinical presentation — establishes CTCL diagnosis even without Pautrier microabscesses. The key legal question is not whether the pathological finding is present, but whether the totality of evidence supports the diagnosis and temporal causation to Dupixent use.

What a Strong Dupixent CTCL Case Requires

Building a Dupixent CTCL claim requires documentary proof across four domains. First, exposure: pharmacy records, prior authorization documentation, and injection logs confirming the patient received Dupixent for a defined period (typically 6 months or more) before symptom onset. Second, diagnosis: pathology-confirmed CTCL with immunohistochemistry and, ideally, TCR gene rearrangement studies showing clonality. Third, temporal causation: medical records demonstrating that suspicious skin changes emerged or worsened after Dupixent initiation, not before. Fourth, absence of alternative causation: documentation that the patient did not have pre-existing risk factors such as prior radiation therapy, HTLV-1 infection, or known immunodeficiency syndrome.

The strongest cases involve patients who had well-documented, stable eczema for years before starting Dupixent, developed new or morphologically different lesions during treatment, and received a confirmed CTCL diagnosis supported by molecular evidence. Pre-treatment skin biopsies that show only inflammatory infiltrate (no clonality) compared to post-treatment biopsies showing monoclonal T-cells create a before-and-after evidentiary chain that is extremely difficult for the defense to overcome.

Medical Information

Condition Overview

Cutaneous T-cell lymphoma (CTCL) is a group of non-Hodgkin lymphomas that originate in mature T-lymphocytes and primarily manifest in the skin. The two most common subtypes are mycosis fungoides, which progresses through patch, plaque, and tumor stages, and Sezary syndrome, a leukemic variant characterized by erythroderma and circulating malignant T-cells (Sezary cells) in the blood. CTCL accounts for approximately 4 percent of all non-Hodgkin lymphomas, with roughly 3,000 new U.S. diagnoses per year. The disease disproportionately affects adults over age 50, though Dupixent-associated cases have emerged in younger patients whose immune modulation began during treatment for atopic dermatitis.

The malignancy arises when skin-homing T-cells undergo clonal expansion and acquire oncogenic mutations while evading immune surveillance. Under normal conditions, the immune system identifies and destroys aberrant T-cells. Dupixent (dupilumab) blocks interleukin-4 and interleukin-13 signaling — cytokines that regulate the Th2 immune response. Emerging research suggests this IL-4/IL-13 blockade may shift the immune balance toward Th1 dominance, potentially allowing pre-malignant T-cell clones to proliferate unchecked. This mechanism is the biological basis for the growing number of CTCL diagnoses in Dupixent patients.

Causation

How This Injury Occurs

The causation theory linking Dupixent to CTCL centers on immune dysregulation. Dupilumab blocks the IL-4 receptor alpha subunit, suppressing Th2-mediated inflammation. While this reduces eczema symptoms, it may simultaneously remove a Th2-mediated tumor surveillance mechanism that keeps pre-existing T-cell clones in check. Published case reports in the Journal of the American Academy of Dermatology, JAMA Dermatology, and Blood have documented CTCL emergence within 6 to 36 months of Dupixent initiation. The FDA's FAERS database contains a statistically significant disproportionality signal for dupilumab-associated lymphoma. Sanofi and Regeneron were aware of lymphoma signals during clinical trials but elected not to include a specific CTCL warning on the Dupixent label.

Defense experts will argue that CTCL can be misdiagnosed as atopic dermatitis before Dupixent use — meaning the lymphoma was already present and merely unmasked by treatment. Plaintiffs counter this with temporal evidence: many patients had well-controlled eczema for years, began Dupixent, and developed new or dramatically different lesions inconsistent with their historical dermatitis pattern. Molecular testing showing T-cell receptor gene rearrangement clonality in post-Dupixent biopsies — absent in pre-treatment biopsies — provides the strongest causation evidence.

Diagnosis

Diagnostic Criteria

CTCL diagnosis requires: (1) Skin biopsy with histopathological examination showing atypical lymphocytic infiltrate with epidermotropism; (2) Immunohistochemistry panel demonstrating CD4+/CD7- or CD4+/CD26- T-cell phenotype; (3) T-cell receptor (TCR) gene rearrangement studies showing clonal T-cell population; (4) Staging workup including complete blood count with Sezary cell quantification, LDH, flow cytometry of peripheral blood, CT or PET-CT imaging for lymphadenopathy/organ involvement; (5) Classification by TNMB staging system (Tumor, Node, Metastasis, Blood) from Stage IA through Stage IVB.
Documentation

Records You May Need

Records Checklist

  • Complete dermatology records from at least 2 years prior to Dupixent initiation
  • All skin biopsy pathology reports (pre- and post-Dupixent)
  • Dupixent prescription records including start date, dosing, and duration
  • Immunohistochemistry panel results (CD3, CD4, CD7, CD8, CD26, CD30)
  • T-cell receptor gene rearrangement study results
  • Flow cytometry reports from peripheral blood
  • CT or PET-CT imaging reports
  • Oncology consultation notes and staging determination
  • Pharmacy records confirming Dupixent dispensing history
  • Insurance prior authorization records for Dupixent
FAQ

Frequently Asked Questions

Can Dupixent cause cancer?

The short answer is yes — and the science behind it is alarming. A peer-reviewed study of 19,612 patients found that Dupixent users face a 4.5 times higher risk of developing cutaneous T-cell lymphoma (CTCL) compared to people who never took the drug. To put that in perspective, a 4.5x relative risk is in the same ballpark as the asbestos-mesothelioma association that drove one of the largest mass tort litigations in American history. The proposed biological mechanism is straightforward and troubling. Dupixent blocks two signaling molecules — IL-4 and IL-13 — that are part of the type 2 immune response. Blocking these signals is what makes the drug effective against eczema and asthma. But those same signals appear to play a role in immune surveillance against T-cell malignancies. By suppressing them, Dupixent may release the brakes on pre-malignant T-cell clones that the immune system had been keeping in check. The result: a cancer that literally disguises itself as the disease the drug is supposed to treat. The FDA placed Dupixent on its safety watchlist in March 2025 and escalated to a formal investigation in September 2025 after receiving more than 300 adverse event reports related to lymphoma and blood cancers. As of April 2026, the investigation is ongoing. Regeneron and Sanofi have not added a specific CTCL warning to the Dupixent label.

What is cutaneous T-cell lymphoma, and why is it connected to Dupixent?

Cutaneous T-cell lymphoma is a cancer of the immune system that begins in the skin. Specifically, T-lymphocytes — white blood cells that are supposed to protect you from infections and abnormal cells — become malignant and accumulate in the skin, forming patches, plaques, and eventually tumors. The most common subtype is mycosis fungoides, which can remain indolent for years or progress to Sezary syndrome, an aggressive form where cancer cells circulate through the bloodstream. The connection to Dupixent lies in the drug's mechanism of action. Dupixent works by blocking IL-4 and IL-13 — two signaling molecules that drive type 2 inflammation. But these molecules also appear to play a role in keeping abnormal T-cells under control. When Dupixent shuts down that pathway, it may allow pre-existing T-cell clones with malignant potential to proliferate unchecked. Researchers describe this as an 'unmasking' effect — the cancer was there, but the immune system was holding it back. Dupixent may remove that restraint. The most dangerous aspect of this connection is diagnostic mimicry. Early CTCL looks almost identical to eczema — red, scaly patches on the skin. For a patient taking Dupixent for eczema, new skin lesions are almost always attributed to eczema flares rather than cancer. This can delay diagnosis by months or years, allowing the cancer to progress to stages where treatment options narrow and survival rates drop sharply.

Who qualifies to file a Dupixent lawsuit?

If you took Dupixent for any condition — atopic dermatitis, asthma, chronic sinusitis, COPD, or any other indication — and were subsequently diagnosed with cutaneous T-cell lymphoma (including mycosis fungoides or Sezary syndrome), you may have a valid claim. There is no minimum duration of Dupixent use required. Some reported cases involve patients who developed CTCL after relatively short treatment periods, which is consistent with the unmasking theory: if Dupixent releases the brakes on a pre-existing malignancy, the cancer can manifest quickly. Family members of people who died from CTCL or T-cell lymphoma after Dupixent use may be eligible to file wrongful death claims. You do not need to have stopped taking Dupixent — active patients with a CTCL diagnosis can file while still receiving treatment for their cancer. The key requirements are documentation of Dupixent use (pharmacy records, insurance claims, or medical records), a confirmed CTCL or T-cell lymphoma diagnosis (pathology report with biopsy confirmation), and filing within your state's statute of limitations. A free consultation with a mass tort attorney can determine whether your specific circumstances support a claim. Consultations are confidential, and most Dupixent attorneys work on contingency — fee terms vary by attorney.

What is the current status of Dupixent lawsuits in 2026?

As of April 2026, all federal Dupixent lawsuits alleging cancer injuries have been consolidated into Multidistrict Litigation No. 3180 by the Judicial Panel on Multidistrict Litigation. The MDL is in its earliest procedural stages — the court has appointed a plaintiffs' steering committee, and initial case management orders are being issued. Discovery has not yet begun in earnest, but attorneys expect the first round of document requests to target Regeneron's internal safety data, communications with the FDA, and pharmacovigilance records. No settlements have been reached and no cases have gone to trial. The litigation follows a well-established pattern for pharmaceutical MDLs: after discovery is substantially complete, the court will select bellwether cases for trial. Bellwether verdicts — typically the first three to five cases tried — establish the litigation's settlement value and create pressure for global resolution. This process typically takes two to four years from MDL formation, meaning bellwether trials could begin in 2028 or 2029. Separately, the FDA's formal investigation into Dupixent's cancer risk remains ongoing. Any regulatory action — particularly a boxed warning or label change requiring specific CTCL risk disclosure — would significantly strengthen plaintiffs' cases and could accelerate settlement discussions.

How much could a Dupixent lawsuit be worth?

It is too early to provide specific settlement projections for Dupixent cases because no settlements or verdicts have been reached. But we can look at comparable pharmaceutical cancer litigations to understand the range of possibilities. In the Roundup litigation, individual settlements for non-Hodgkin lymphoma ranged from approximately $100,000 to over $2 million depending on cancer severity and treatment burden. Bayer ultimately paid over $10 billion to resolve approximately 100,000 claims. For Dupixent, case values will likely be stratified by the severity of the CTCL diagnosis. Early-stage mycosis fungoides managed with skin-directed therapies may fall in the $75,000 to $200,000 range. Advanced CTCL requiring chemotherapy, radiation, or targeted biologic therapy could be valued at $200,000 to $1 million. Wrongful death cases and terminal diagnoses — particularly Sezary syndrome and large cell transformation — could exceed $2 million. One factor that may favor Dupixent plaintiffs is the strength of the epidemiological evidence. A 4.5x relative risk is considered highly significant in both medical research and legal causation standards. The Daubert challenge to plaintiffs' expert testimony — often the most contentious phase of pharmaceutical MDLs — may be less of an obstacle than in litigations with weaker statistical associations.

Did Regeneron and Sanofi know about the cancer risk?

This is the central question in Dupixent litigation — and the answer will emerge from discovery as the MDL progresses. What we know publicly is this: adverse event reports linking Dupixent to lymphoma and blood cancers had been accumulating in the FDA Adverse Event Reporting System (FAERS) for years before the formal investigation. The scientific literature on IL-4/IL-13 pathway disruption and immune surveillance against T-cell malignancies was available to Regeneron's and Sanofi's research scientists at the time of approval and throughout the post-market period. Plaintiffs allege that the manufacturers engaged in inadequate pharmacovigilance — that they failed to investigate the cancer signal with the urgency that the data warranted, and that they failed to update the drug's label to warn specifically about CTCL risk. The current Dupixent label mentions the possibility of malignancies in general terms, but does not specifically warn about cutaneous T-cell lymphoma or the diagnostic confusion that arises from prescribing an eczema drug that can cause a cancer mimicking eczema. If discovery reveals internal documents showing that Regeneron or Sanofi were aware of the CTCL signal and chose not to act — or that they deliberately framed CTCL reports as eczema treatment failures in their pharmacovigilance databases — it could dramatically increase both liability and damages, including potential punitive damages.

Can I file a Dupixent lawsuit if I am still taking the drug?

Yes — you do not need to stop taking Dupixent to file a lawsuit. If you have been diagnosed with CTCL or another T-cell lymphoma while using or after using Dupixent, your legal claim exists regardless of whether you continue the medication. The decision to stop or continue Dupixent is a medical decision that should be made with your treating physician, not your attorney. Some patients with severe atopic dermatitis or asthma have no adequate alternative treatments, and stopping Dupixent could cause significant health deterioration. That said, if you have a confirmed CTCL diagnosis, your oncologist will almost certainly recommend discontinuing Dupixent — continuing a drug that may be promoting T-cell malignancy while simultaneously undergoing cancer treatment is medically counterproductive. The important thing is to make this decision in consultation with your medical team, not based on legal strategy.

How is a Dupixent MDL different from a class action?

The distinction matters because it directly affects how much you can recover. In a class action, all members share a single settlement pot — often resulting in relatively small per-person payments. In a multidistrict litigation (MDL), each plaintiff maintains their own individual case with their own specific facts, damages, and potential recovery. The MDL structure simply consolidates the pretrial process — discovery, expert challenges, and procedural motions — before a single judge for efficiency. In MDL No. 3180, your case is uniquely yours. A patient diagnosed with early-stage mycosis fungoides managed with topical therapy will have a different case value than a patient who underwent chemotherapy for Sezary syndrome or whose family filed a wrongful death claim. The MDL process allows the court to handle common legal issues efficiently while preserving each plaintiff's right to individual assessment and compensation based on their specific circumstances. After bellwether trials establish settlement benchmarks, most MDLs move toward global resolution — a structured settlement program in which individual case values are assigned based on severity tiers, treatment burden, and other case-specific factors. Plaintiffs who are unsatisfied with their assigned value retain the right to opt out and pursue individual trial.

What evidence do I need to file a Dupixent lawsuit?

The evidence you need falls into two categories: proof of Dupixent use and proof of cancer diagnosis. For Dupixent use, the strongest evidence includes pharmacy dispensing records showing when you filled your prescriptions, insurance claims showing Dupixent charges, medical records with prescribing notes, and injection logs from your doctor's office or specialty pharmacy. Even partial records are useful — your attorney can subpoena pharmacy records and insurance claim histories to fill gaps. For your cancer diagnosis, the essential document is your pathology report from the skin biopsy that confirmed CTCL or mycosis fungoides. The report should include the histopathological findings, immunohistochemistry results (CD3+, CD4+, loss of CD7/CD26), and ideally T-cell receptor gene rearrangement results confirming clonality. Your oncology treatment records — including staging workups, PET scans, chemotherapy regimens, and radiation plans — document the severity and treatment burden that drive your case value. You do not need to have all of this documentation organized before consulting an attorney. Most mass tort firms have medical record retrieval teams that gather and organize evidence as part of case preparation. The most important step is to preserve what you have — do not discard Dupixent packaging, pharmacy receipts, or medical records.

My doctor says my CTCL is not related to Dupixent. Can I still file?

Yes — and this is more common than you might think. Many treating physicians are not yet aware of the epidemiological data linking Dupixent to CTCL, or they may be reluctant to attribute a rare cancer to a widely prescribed medication. Your doctor's clinical opinion is important for your medical care, but it is not determinative of your legal claim. In mass tort litigation, causation is established through expert testimony from epidemiologists, toxicologists, and oncologists who analyze population-level data and biological mechanisms. The 4.5x relative risk from the 19,612-patient study provides strong statistical support for general causation — the question of whether Dupixent can cause CTCL in the population. Specific causation — whether Dupixent caused your particular CTCL — is then established through expert analysis of your medical records, treatment timeline, and the absence of alternative explanations. An expert who reviews your chart and finds that you had no CTCL risk factors before Dupixent use, developed CTCL during or after treatment, and had a clinical presentation consistent with drug-induced T-cell lymphoma can provide a compelling specific causation opinion regardless of what your treating physician believes.

Should I stop taking Dupixent if I am worried about cancer?

This is a medical decision, not a legal one — and it should be made in consultation with your prescribing physician. Abruptly stopping Dupixent can cause severe rebound flares of atopic dermatitis or worsening of asthma that may require emergency treatment. Your doctor can evaluate your individual risk factors, discuss the emerging safety data, and consider whether alternative treatments are appropriate for your situation. What we do recommend is vigilance. If you are currently taking Dupixent, discuss the CTCL risk with your dermatologist and ask about a monitoring protocol. Any new or changing skin lesions — particularly patches that look different from your usual eczema, lesions in unusual locations like the buttocks or trunk, or skin changes that do not respond to standard eczema treatments — should prompt a biopsy rather than an assumption that it is just another flare. Early detection of CTCL, if it develops, dramatically improves outcomes. If you are diagnosed with CTCL, your oncologist will almost certainly recommend stopping Dupixent immediately. At that point, the medical and legal decisions align: you need cancer treatment, and continuing a drug suspected of promoting that cancer serves no purpose.

How long will the Dupixent lawsuit take to resolve?

Pharmaceutical MDLs are not quick — and anyone promising a fast resolution is not being honest. Based on the typical trajectory of comparable pharmaceutical cancer MDLs, the Dupixent litigation will likely follow this general timeline: 2026 to 2027 for discovery and expert development; 2027 to 2028 for Daubert challenges (where the court decides whether plaintiffs' and defendants' expert witnesses may testify); and 2028 to 2029 for bellwether trials — the first cases to go to trial. If bellwether verdicts favor plaintiffs, global settlement negotiations typically follow within 12 to 18 months. The realistic expectation for most plaintiffs is a resolution timeline of three to five years from the date of MDL formation — meaning 2029 to 2031 for the bulk of cases. Some cases may resolve sooner if early bellwether results are strongly in plaintiffs' favor and the defendants choose to negotiate rather than face repeated trial losses. The Roundup litigation, for comparison, produced its first plaintiff verdict in 2018 and Bayer announced a $10 billion settlement framework in 2020 — a two-year bellwether-to-settlement cycle. Early filing matters because cases filed early are most likely to be considered for bellwether selection, and bellwether plaintiffs often receive the highest individual recoveries. Filing early also ensures that your evidence is preserved, your medical records are secured, and your case is well-developed by the time settlement discussions begin.
Related Topics

Related Pages

Dupixent Eye Problems and Ocular Side Effects

Conjunctivitis is the most common adverse event associated with Dupixent, occurring in approximately 30 percent of atopic dermatitis patients in clinical trials — a rate ten times higher than placebo. But conjunctivitis is just the visible surface of a broader ocular toxicity profile that includes blepharitis, keratitis, dry eye syndrome, limbal stem cell deficiency, and in rare but devastating cases, corneal perforation requiring emergency surgical intervention. These eye problems often develop within the first three months of treatment and can persist even after Dupixent is discontinued. Sanofi and Regeneron have acknowledged conjunctivitis on the Dupixent label but have minimized the severity spectrum, leading patients and prescribers to underestimate the risk of serious, vision-threatening complications. For patients who have suffered permanent vision impairment, corneal scarring, or required corneal transplantation due to Dupixent-related ocular injury, the manufacturer's characterization of these events as manageable side effects is contradicted by their clinical experience.

dupixent-eye-problemsconjunctivitiskeratitis
Learn more

Dupixent MDL Status and Litigation Update

The Judicial Panel on Multidistrict Litigation (JPML) is considering a petition to consolidate all federal Dupixent CTCL lawsuits into a single MDL for coordinated pretrial proceedings. As of early 2026, over 250 individual lawsuits have been filed across multiple federal districts, with plaintiffs proposing consolidation in the Northern District of Georgia (Atlanta) and defendants advocating for the Southern District of New York. MDL No. 3180 would centralize discovery, expert qualification (Daubert) proceedings, and bellwether trial selection under a single transferee judge. For individual plaintiffs, MDL consolidation means coordinated case management and potential leverage from shared discovery, but it also means potential delays as the court works through lead case selection and common issues. The venue decision — Atlanta versus New York versus other candidates — will shape the litigation's procedural landscape, judicial temperament, jury pool demographics, and ultimately the pressure on Sanofi and Regeneron to negotiate a global settlement.

dupixent-mdlmdl-3180jpml
Learn more

Dupixent Pediatric Use and CTCL Risk in Children

Sanofi and Regeneron have aggressively expanded Dupixent's pediatric indications, securing FDA approval for atopic dermatitis in children as young as 6 months old in 2022, following earlier approvals for ages 6 to 11 in 2020 and adolescents aged 12 to 17 in 2019. This expansion exposed millions of children with developing immune systems to a biologic drug that blocks IL-4 and IL-13 — cytokines critical to immune maturation, T-cell differentiation, and tumor surveillance. While CTCL is rare in children overall, the long-term consequences of sustained immune modulation during critical developmental windows are unknown because Sanofi's pediatric trials were not designed to detect rare cancers and follow-up periods were insufficient to capture latent malignancies. Pediatric Dupixent claims carry unique urgency: children have longer remaining lifespans over which to develop delayed-onset lymphoma, the immune insult occurs during a period of rapid lymphocyte development, and parents made treatment decisions based on safety assurances that did not account for the emerging CTCL signal. The duty to warn is heightened for pediatric drugs because parents — not the patient — make the consent decision, and they deserve complete risk information to exercise informed judgment.

dupixent-pediatricdupixent-childrenpediatric-atopic-dermatitis
Learn more

Dupixent Wrongful Death Claims

When cutaneous T-cell lymphoma caused by Dupixent progresses to advanced stages and the patient dies, surviving family members may pursue wrongful death and survival action claims against Sanofi and Regeneron. Richardson v. Sanofi, filed in October 2025 in the Western District of Tennessee, was one of the first named Dupixent CTCL lawsuits and involved allegations of fatal lymphoma progression. Wrongful death claims compensate the decedent's family for loss of companionship, financial support, and funeral expenses, while survival actions compensate the decedent's estate for the pain, suffering, and medical costs the patient endured before death. These are legally distinct claims with different standing requirements, damage calculations, and statutes of limitations. State law controls who may bring a wrongful death claim — in some states, only a surviving spouse or children have standing, while in others, parents, siblings, or domestic partners may also qualify. The interplay between wrongful death statutes and product liability discovery rules creates filing deadline complexities that can extinguish viable claims if not handled promptly.

wrongful-deathdupixent-deathctcl-fatal
Learn more
Parent Case

Dupixent Lawsuit Lawsuit

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.

View full case overview