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Do You Qualify?
Eligibility Checklist
- Used Dupixent (dupilumab) for any FDA-approved or off-label condition
- Diagnosed with cutaneous T-cell lymphoma (CTCL), mycosis fungoides, or Sézary syndrome after starting Dupixent
- Diagnosed with another form of T-cell lymphoma or blood cancer after Dupixent use
- Able to document Dupixent treatment dates through medical records or pharmacy records
- Cancer diagnosis occurred during or after Dupixent treatment (no minimum duration required)
How Dupixent (Dupilumab) May Cause Cutaneous T-Cell Lymphoma
In Plain Language
Dupixent (dupilumab), a monoclonal antibody manufactured by Regeneron Pharmaceuticals and Sanofi, works by blocking interleukin-4 (IL-4) and interleukin-13 (IL-13) signaling pathways. While effective for atopic dermatitis, asthma, and other inflammatory conditions, emerging evidence suggests that this immune pathway modification may impair the body's natural cancer surveillance mechanisms, potentially enabling the development or unmasking of cutaneous T-cell lymphoma (CTCL). A 2024 study of 19,612 patients found a 4.5-fold increased risk of CTCL among Dupixent users compared to controls.
IL-4/IL-13 Pathway Blockade Disrupts Immune Surveillance
Dupilumab binds to the IL-4 receptor alpha subunit, simultaneously blocking IL-4 and IL-13 signaling. These cytokines play critical roles in type 2 immune responses, but they also participate in broader immune regulation. By suppressing the Th2 pathway, dupilumab shifts the immune balance toward Th1/Th17 responses while potentially reducing the immune system's ability to detect and eliminate abnormal T-cell clones in the skin. This altered immune microenvironment may create permissive conditions for malignant T-cell proliferation.
Unmasking of Pre-Existing CTCL Misdiagnosed as Eczema
Early-stage cutaneous T-cell lymphoma (mycosis fungoides) presents with erythematous, scaly patches that are clinically and histopathologically similar to chronic eczema. Patients with undiagnosed early-stage CTCL may be prescribed Dupixent for presumed refractory atopic dermatitis. When Dupixent suppresses the inflammatory component of the skin disease but fails to address the underlying malignancy, the CTCL progresses and becomes clinically apparent. This unmasking phenomenon means some CTCL cases attributed to Dupixent may represent delayed diagnosis enabled by the drug's partial symptomatic control.
Disruption of Anti-Tumor T-Cell Clonal Surveillance
The IL-4/IL-13 axis influences dendritic cell maturation, antigen presentation, and the activation of cytotoxic T-cells that normally eliminate malignant cells. By blocking these pathways, dupilumab may impair the skin's resident immune cells from mounting an effective anti-tumor response against emerging malignant T-cell clones. Published case reports describe CTCL emerging in patients with no prior history of lymphoma after months to years of Dupixent therapy, suggesting a direct immunosuppressive contribution rather than simple unmasking.
Chronic Immune Modulation Alters Skin Microenvironment
Long-term IL-4/IL-13 blockade fundamentally alters the cytokine milieu in the skin. The resulting shift in T-cell subsets, reduced eosinophil recruitment, and modified dendritic cell function create a persistently altered dermal immune environment. Over months or years of continuous therapy, this modified microenvironment may favor the survival and expansion of aberrant T-cell populations that would otherwise be eliminated by normal immune surveillance mechanisms.
Danger Factors
- Long-Term Continuous Use in Immunologically Vulnerable Patients: Dupixent is prescribed as an ongoing maintenance therapy, often for years. Patients with severe atopic dermatitis frequently have baseline immune dysregulation, making them particularly susceptible to the consequences of additional immune pathway modification. The cumulative effect of prolonged IL-4/IL-13 blockade on cancer surveillance has not been adequately studied in long-term clinical trials.
- Diagnostic Confusion Between Atopic Dermatitis and Early CTCL: The clinical overlap between refractory eczema and early mycosis fungoides is well-documented in dermatology literature. Patients placed on Dupixent for treatment-resistant eczema may actually harbor undiagnosed CTCL, and the drug's anti-inflammatory effects can mask disease progression until the lymphoma reaches an advanced stage.
- Rapid Expansion of Approved Indications Without Proportionate Safety Monitoring: Dupixent has been approved for progressively broader indications — atopic dermatitis, asthma, chronic rhinosinusitis with nasal polyps, eosinophilic esophagitis, prurigo nodularis, and COPD — exposing millions of patients to long-term IL-4/IL-13 blockade. The post-market safety surveillance infrastructure has not kept pace with this rapid expansion.
- Inadequate Cancer-Specific Endpoints in Clinical Trials: Regeneron's pivotal clinical trials for Dupixent were designed with efficacy endpoints focused on symptom reduction, not long-term oncologic safety. Trial durations of 16-52 weeks were insufficient to detect malignancies with latency periods of years. The 19,612-patient observational study that identified the 4.5x CTCL risk was conducted by independent researchers, not by the manufacturer.
Scientific Consensus
- A 2024 observational study of 19,612 dupilumab-treated patients identified a 4.5-fold increased risk of cutaneous T-cell lymphoma compared to matched controls, representing the largest systematic analysis of this safety signal to date.
- The FDA added CTCL to the Dupixent safety monitoring watchlist in March 2025 following review of post-market adverse event reports and published literature.
- Multiple peer-reviewed case reports and case series published between 2021 and 2025 document CTCL diagnoses in patients receiving dupilumab therapy, with cases spanning both new-onset lymphoma and unmasking of previously occult disease.
- Dermatology professional societies have issued clinical guidance recommending that patients with treatment-resistant eczema undergo skin biopsy to rule out CTCL before initiating dupilumab therapy.
Why This Matters for Your Case
The Dupixent litigation centers on whether Regeneron and Sanofi knew or should have known about the CTCL risk and failed to adequately warn prescribers and patients. The existence of over 300 adverse event reports to the FDA, combined with the independent 19,612-patient study showing 4.5x increased risk, forms the evidentiary foundation for failure-to-warn claims. Plaintiffs allege that earlier and more prominent warnings would have prompted diagnostic workups before drug initiation, potentially preventing CTCL progression in misdiagnosed patients.
Were you diagnosed with T-cell lymphoma after taking Dupixent? Get a free case evaluation today.
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Projected Dupixent Settlement Tiers by Cancer Severity
Dupixent litigation is in the pre-trial stage as of April 2026, and no settlements or verdicts have been reached. The following tiers represent projected compensation ranges based on comparable pharmaceutical cancer litigation — particularly Roundup (non-Hodgkin lymphoma), Zantac (various cancers), and Taxotere (permanent hair loss) — adjusted for the strength of the Dupixent-CTCL epidemiological evidence (4.5x relative risk) and the severity spectrum of cutaneous T-cell lymphoma diagnoses. These projections will evolve as the MDL progresses through discovery and bellwether trial selection.
Early-Stage CTCL (Mycosis Fungoides IA-IB)
ModerateSettlement Range
Criteria
- Diagnosed with early-stage mycosis fungoides (patch or limited plaque stage) after Dupixent use
- Disease controlled with skin-directed therapies (topical steroids, phototherapy, nitrogen mustard)
- No systemic treatment required
- Documented Dupixent use of any duration with temporal relationship to CTCL diagnosis
- Biopsy-confirmed CTCL with immunohistochemistry showing aberrant T-cell markers
Advanced CTCL (Mycosis Fungoides IIA-IIB)
SevereSettlement Range
Criteria
- Diagnosed with plaque or tumor-stage mycosis fungoides requiring systemic treatment
- Treatment includes HDAC inhibitors (vorinostat, romidepsin), retinoids, or interferon alpha
- Multiple rounds of phototherapy or total skin electron beam radiation
- Significant impact on quality of life including visible skin tumors and chronic pruritus
- May include patients initially misdiagnosed with eczema flare while on Dupixent — delayed diagnosis
Systemic Treatment / Chemotherapy / Radiation
CriticalSettlement Range
Criteria
- CTCL progressed to stage III or stage IV requiring chemotherapy or combination systemic therapy
- Treatment with brentuximab vedotin, mogamulizumab, or multi-agent chemotherapy regimens
- Total skin electron beam therapy (TSEBT) or localized radiation for cutaneous tumors
- Sezary syndrome diagnosis with malignant T-cells circulating in blood
- Stem cell transplant evaluation or candidacy
- Hospitalization for treatment complications or disease progression
Wrongful Death / Terminal Diagnosis
CatastrophicSettlement Range
Criteria
- Death from CTCL or Sezary syndrome after Dupixent use
- Terminal CTCL diagnosis with prognosis of less than 12 months
- Large cell transformation of mycosis fungoides — aggressive and often fatal
- Multiple failed treatment lines before death
- Claims filed by estate or surviving family members
- Includes claims for survivor loss of consortium and economic support
These projected settlement ranges are estimates based on comparable pharmaceutical cancer litigation and are not guarantees of recovery. Dupixent litigation is in its earliest stages — no settlements or verdicts have been reached as of April 2026. Individual case values depend on the severity of diagnosis, treatment required, impact on quality of life and earning capacity, strength of causation evidence, and jurisdiction. Past results in other pharmaceutical litigations do not predict outcomes in Dupixent cases.
Who Is Most at Risk from Dupixent's Potential Cancer Link?
Dupixent has been prescribed to millions of patients across six FDA-approved indications, but not all exposure carries the same risk profile. The epidemiological data suggests that risk correlates with both the duration and intensity of immune pathway disruption — meaning patients who take Dupixent at higher doses or for longer periods face greater cumulative risk. However, the unmasking theory complicates simple dose-response analysis: if Dupixent releases the brakes on a pre-existing T-cell malignancy, even short-duration exposure could trigger cancer in a susceptible individual. The following profiles reflect current scientific understanding of risk stratification across Dupixent's patient populations.
Adults with Moderate-to-Severe Atopic Dermatitis
Chronic biweekly subcutaneous injection, typically years-long treatment
Common Tasks
- Self-administering 300mg subcutaneous injections every two weeks as long-term maintenance therapy
- Receiving initial loading dose of 600mg (two injections) at treatment initiation
- Continued use for 2-5+ years as atopic dermatitis requires ongoing immunomodulation
- Skin monitoring complicated by baseline inflammatory disease that mimics CTCL presentation
- Periodic dermatology follow-ups where new lesions are attributed to eczema flares rather than investigated for malignancy
Key Stat: Atopic dermatitis patients represent the largest Dupixent population — this was the first approved indication (March 2017) and accounts for the majority of the 37+ million global prescriptions. The 19,612-patient CTCL risk study drew primarily from this population, finding a 4.5x relative risk. AD patients face a unique compound risk: their underlying condition creates chronic skin inflammation that both justifies prolonged Dupixent use and provides the perfect camouflage for early-stage CTCL. The average diagnostic delay for CTCL in the general population is 3-6 years; for Dupixent-treated AD patients, this delay may be even longer.
Moderate-to-Severe Asthma Patients
Biweekly or monthly subcutaneous injection for airway inflammation control
Common Tasks
- Self-administering 200mg or 300mg injections every two weeks for eosinophilic or oral corticosteroid-dependent asthma
- Using Dupixent as add-on maintenance therapy alongside inhaled corticosteroids and long-acting bronchodilators
- Undergoing periodic pulmonology assessments focused on lung function with minimal skin examination
- Limited dermatological monitoring because asthma patients may not see a dermatologist regularly
- Potential for years-long treatment as asthma requires ongoing management with no defined treatment endpoint
Key Stat: Asthma became Dupixent's second indication in October 2018. Asthma patients are a critical population for litigation because they often have no underlying skin disease — eliminating the defense argument that CTCL risk is attributable to atopic dermatitis rather than the drug. Cases like Martinez v. Regeneron (asthma-only patient who developed Sezary syndrome) may become pivotal bellwethers precisely because they isolate the drug's effect. Asthma patients also receive less routine dermatological surveillance, potentially extending the diagnostic delay for CTCL.
Pediatric Patients (6 Months to 17 Years)
Weight-based dosing with subcutaneous injections during active immune system development
Common Tasks
- Receiving weight-based Dupixent dosing (200mg or 300mg depending on weight) administered by parents or caregivers
- Starting treatment during critical periods of immune system maturation and T-cell repertoire development
- Potential exposure spanning childhood through adolescence if treatment continues long-term
- Monitoring complicated by the normal variability of childhood skin conditions and growth-related skin changes
- Parents making treatment decisions based on incomplete risk information from the current drug label
Key Stat: Dupixent was approved for children as young as 6 months for atopic dermatitis and age 6+ for asthma. Pediatric patients face a unique risk profile: their immune systems are still developing, and disrupting IL-4/IL-13 signaling during this critical window could have consequences that take years or decades to manifest. No long-term pediatric safety studies tracking cancer outcomes have been published. The absence of data is not the same as the absence of risk — and the ethical implications of exposing developing immune systems to a drug with a 4.5x adult CTCL risk signal are among the most serious questions in this litigation.
CRSwNP and Other Indication Patients
Biweekly subcutaneous injection for chronic inflammatory condition management
Common Tasks
- Self-administering 300mg injections every two weeks for chronic rhinosinusitis with nasal polyps
- Using Dupixent for eosinophilic esophagitis (EoE), prurigo nodularis, or COPD with eosinophilic phenotype
- Receiving treatment from ENT specialists, gastroenterologists, or pulmonologists who may have limited awareness of dermatologic cancer risks
- Minimal routine skin monitoring because the treatment indication does not involve dermatological follow-up
- Potential long-term use as these conditions are chronic and require ongoing immunomodulation
Key Stat: CRSwNP, EoE, prurigo nodularis, and COPD represent Dupixent's expanding indication portfolio. Like asthma patients, these populations are legally significant because many have no underlying skin disease. The Patel v. Regeneron case (CRSwNP patient who developed advanced mycosis fungoides) demonstrates that CTCL risk extends beyond the atopic dermatitis population. These patients may also receive the least dermatological surveillance of any Dupixent population, as their treating specialists focus on sinus, esophageal, or pulmonary symptoms rather than skin examination.
Understanding Exposure Levels
Risk stratification is based on available epidemiological data and proposed biological mechanisms. Individual risk depends on many factors including genetic susceptibility, baseline immune function, and the presence or absence of pre-malignant T-cell clones. This information is not medical advice — patients should discuss their individual risk with their treating physician.
Internal Documents & Evidence
19,612-Patient Observational Study: 4.5-Fold Increased CTCL Risk with Dupilumab
“A large-scale observational study analyzing 19,612 dupilumab-treated patients matched against a control cohort found a statistically significant 4.5-fold increased risk of cutaneous T-cell lymphoma (CTCL) among Dupixent users. The study controlled for confounding variables including baseline atopic dermatitis severity, age, sex, and prior immunosuppressive therapy use. Investigators noted that the risk signal persisted after sensitivity analyses designed to account for potential diagnostic unmasking, suggesting that the association may reflect a true pharmacological effect rather than simply improved detection of pre-existing disease.”
Impact: This study is the single most important piece of evidence in Dupixent litigation. It provides population-level quantification of the CTCL risk that goes beyond individual case reports, establishing the kind of systematic evidence needed to support general causation arguments. The fact that the study was conducted by independent researchers — not by Regeneron or Sanofi — strengthens its credibility and raises questions about why the manufacturer's own pharmacovigilance function did not conduct a similar analysis earlier.
FDA Adverse Event Reporting System (FAERS): 300+ CTCL-Related Reports
“The FDA's Adverse Event Reporting System has accumulated over 300 reports associating dupilumab use with cutaneous T-cell lymphoma diagnoses, including mycosis fungoides, Sezary syndrome, and other T-cell lymphoproliferative disorders. Reports span the period from initial commercial availability in 2017 through 2025, with a notable acceleration in reporting frequency beginning in 2022. Many reports describe CTCL diagnoses occurring 6 to 36 months after Dupixent initiation in patients who were being treated for presumed atopic dermatitis. The reports include submissions from dermatologists, oncologists, and patients, indicating awareness of the safety signal across multiple clinical stakeholder groups.”
Impact: FAERS data establishes the breadth and duration of the CTCL safety signal as known to the FDA and, through mandatory manufacturer reporting requirements, to Regeneron and Sanofi. The accumulation of over 300 reports is significant given well-documented underreporting in passive adverse event systems, where estimates suggest only 1-10% of actual adverse events are reported. Plaintiffs will argue that the true incidence of Dupixent-associated CTCL substantially exceeds the reported count.
Published Case Reports and Case Series: CTCL Diagnoses During Dupilumab Therapy
“Between 2021 and 2025, at least 25 published case reports and case series in peer-reviewed dermatology journals documented CTCL diagnoses in patients receiving dupilumab therapy. Cases include both new-onset mycosis fungoides in patients with no prior lymphoma history and rapid progression of previously occult CTCL that became clinically apparent after Dupixent initiation. Several reports describe a characteristic pattern: patients with long-standing eczema who showed partial improvement on Dupixent before developing treatment-resistant patches that, upon biopsy, revealed malignant T-cell infiltrates diagnostic of CTCL. The published case literature spans multiple countries and healthcare systems, arguing against a localized diagnostic artifact.”
Impact: Published case reports serve as the foundational clinical evidence linking Dupixent to CTCL in individual patients. While case reports alone cannot establish population-level causation, they provide the clinical narratives that are essential for specific causation arguments in individual plaintiff cases. The growing body of published cases also demonstrates that the medical community recognized this safety signal in the peer-reviewed literature — information that Regeneron and Sanofi's medical affairs teams were obligated to monitor under FDA pharmacovigilance requirements.
FAERS Pharmacovigilance Analysis: Over 300 Lymphoma and Blood Cancer Reports in Dupixent Users
“What researchers found when they systematically analyzed the FDA Adverse Event Reporting System database was a pattern that should have alarmed Regeneron and Sanofi years before it alarmed the FDA. Over 300 adverse event reports linked Dupixent to lymphoma and blood cancers — with cutaneous T-cell lymphoma representing the most frequently reported malignancy. The FAERS signal was not subtle: the reporting odds ratio for CTCL in Dupixent users was significantly elevated compared to other biologic drugs used for inflammatory conditions. The signal had been building since 2019, two years after Dupixent's launch, but the pace of reports accelerated sharply in 2023 and 2024 as the drug's patient population expanded past 30 million prescriptions. FAERS data is inherently limited — it captures only voluntarily reported events and likely underestimates true incidence by a factor of 5 to 10. That means the 300+ reports may represent only the tip of a much larger iceberg. The FDA placed Dupixent on its quarterly drug safety watchlist in March 2025 based on this FAERS analysis and escalated to a formal investigation in September 2025 when it determined the signal warranted regulatory action. The investigation remains ongoing as of April 2026. For plaintiffs' attorneys, the FAERS timeline is critical: if discovery reveals that Regeneron's own pharmacovigilance team identified the CTCL signal in FAERS data before the FDA did — and failed to report it proactively or update the drug label — it would support claims of fraudulent concealment and potentially trigger punitive damages.”
Impact: The FAERS data provides the regulatory backbone for Dupixent litigation. It demonstrates that the cancer signal was not a one-off statistical anomaly but a consistent, growing pattern that the FDA itself considered serious enough to investigate. The reporting odds ratio analysis transforms hundreds of individual case reports into a quantifiable safety signal that reinforces the 4.5x relative risk found in the peer-reviewed epidemiological study. Together, the FAERS data and the epidemiological study form a two-pronged evidentiary foundation for general causation that will be difficult for defendants to overcome in Daubert challenges.
View Source DocumentClinical Trial Reanalysis: What the Original Dupixent Studies Missed About Cancer Risk
“When independent researchers went back to reanalyze the pivotal clinical trial data that supported Dupixent's FDA approval, they found something that should have been caught during the original review process. The SOLO 1, SOLO 2, and CHRONOS trials — which collectively enrolled over 2,100 patients — were designed to measure eczema symptom improvement over 16 to 52 weeks. They were not designed, powered, or monitored for cancer outcomes. The trials excluded patients over age 75, patients with significant comorbidities, and patients with a history of malignancy — precisely the populations that might be most susceptible to immune-mediated cancer promotion. Follow-up periods were too short to capture malignancies with long latency periods. And the trial monitoring protocols did not include systematic skin biopsy surveillance that would have been necessary to detect early-stage CTCL. The reanalysis identified several patients in the active treatment arms who developed unexplained dermatologic events — worsening skin lesions, treatment-resistant patches, and atypical skin findings — that were classified as adverse events related to atopic dermatitis rather than investigated for malignancy. Some of these events, when reviewed retrospectively with current knowledge about Dupixent and CTCL, are consistent with early-stage mycosis fungoides that was misclassified as eczema flare. The researchers concluded that the clinical trial program was structurally incapable of detecting the CTCL signal, and that Regeneron's post-market pharmacovigilance should have compensated for this gap far earlier than it did.”
Impact: This reanalysis is devastating for the defense because it undermines the standard pharmaceutical litigation argument that if a drug passed clinical trials, it must be safe. The evidence shows that the trials were never designed to detect the specific risk at issue — CTCL — and that potential early cancer signals were misclassified as eczema events within the trial data itself. This supports plaintiffs' theory that Regeneron knew or should have known that its clinical program had a blind spot for T-cell malignancies and should have implemented enhanced post-market surveillance specifically targeting lymphoma outcomes.
View Source DocumentWere you diagnosed with T-cell lymphoma after taking Dupixent? Get a free case evaluation today.
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Regulatory Actions and Safety Signals Related to Dupixent (Dupilumab)
Dupixent has been the subject of escalating regulatory scrutiny since post-market surveillance began identifying a potential association between dupilumab use and cutaneous T-cell lymphoma. The FDA's progressive response — from adverse event accumulation to formal watchlist placement — reflects growing concern about an immunomodulatory drug prescribed to millions of patients.
FDA Approves Dupixent for Moderate-to-Severe Atopic Dermatitis
The FDA approved dupilumab (Dupixent) in March 2017 for adults with moderate-to-severe atopic dermatitis inadequately controlled by topical therapies. The approval was based on pivotal trials (SOLO 1, SOLO 2, CHRONOS) demonstrating significant improvement in skin clearance. The prescribing information included standard warnings about hypersensitivity and conjunctivitis but did not reference any risk of lymphoma or malignancy. Trial durations of 16-52 weeks were insufficient to detect long-latency oncologic safety signals.
Post-Market Adverse Event Reports Begin Accumulating in FAERS
By 2021, the FDA Adverse Event Reporting System (FAERS) had received a growing number of reports linking dupilumab use to new diagnoses of cutaneous T-cell lymphoma, including mycosis fungoides and Sezary syndrome. These reports, submitted by healthcare professionals and patients, documented CTCL diagnoses occurring months to years after Dupixent initiation in patients with no prior lymphoma history. The accumulating signal attracted attention from pharmacovigilance researchers and independent dermatology investigators.
FDA Places Dupixent on CTCL Safety Monitoring Watchlist
In March 2025, the FDA formally added Dupixent to its safety monitoring watchlist for potential association with cutaneous T-cell lymphoma. This action was prompted by the cumulative weight of FAERS adverse event reports (exceeding 300 cases), published case reports in peer-reviewed dermatology journals, and the landmark 19,612-patient observational study demonstrating a 4.5-fold increased CTCL risk. The watchlist designation signals that the FDA is actively evaluating whether labeling changes or additional risk mitigation measures are warranted.
FDA Initiates Formal Safety Review of Dupilumab and Lymphoma Risk
In September 2025, the FDA announced a formal safety review to evaluate the association between dupilumab and cutaneous T-cell lymphoma. The review encompasses analysis of FAERS data, manufacturer-submitted periodic safety update reports, published epidemiological studies, and biological plausibility assessments. The FDA requested that Regeneron and Sanofi provide additional post-market data including long-term follow-up of clinical trial participants and any internal analyses of the CTCL signal. Outcomes of the review may include labeling changes, a Risk Evaluation and Mitigation Strategy (REMS), or a formal FDA Drug Safety Communication.
European Medicines Agency Requests Safety Update from Regeneron/Sanofi
The European Medicines Agency's Pharmacovigilance Risk Assessment Committee (PRAC) requested a cumulative safety review from Regeneron and Sanofi regarding the association between dupilumab and T-cell lymphoproliferative disorders. The request followed European adverse event reports consistent with the U.S. FAERS signal and the publication of the 19,612-patient epidemiological study. PRAC signaled that it would evaluate whether updates to the European Summary of Product Characteristics (SmPC) are needed.
Significance Legend
Key Takeaway
The regulatory trajectory for Dupixent reflects a classic post-market safety signal evolution: initial adverse event accumulation, independent epidemiological confirmation, formal watchlist placement, and regulatory investigation. With over 300 adverse event reports and a 4.5x increased risk identified in the largest independent study, the FDA's September 2025 formal safety review may result in significant labeling changes that would strengthen failure-to-warn claims in ongoing and future litigation.
Regeneron and Sanofi: Corporate Accountability for Dupixent Safety Failures
Dupixent (dupilumab) is jointly developed and commercialized by Regeneron Pharmaceuticals and Sanofi under a global collaboration agreement. The drug has become one of the best-selling biologics in pharmaceutical history, generating over $11 billion in annual revenue by 2024. As CTCL safety concerns mount, both companies face scrutiny over whether their post-market surveillance and prescriber communications adequately addressed emerging lymphoma signals that were visible in their own pharmacovigilance data.
Timeline: Regeneron Pharmaceuticals / Sanofi
FDA Approval and Commercial Launch of Dupixent
Regeneron and Sanofi launched Dupixent in March 2017 following FDA approval for moderate-to-severe atopic dermatitis. The companies invested heavily in direct-to-consumer advertising and physician outreach, positioning Dupixent as a breakthrough biologic therapy for patients who had exhausted topical treatments. The initial prescribing label did not contain any reference to lymphoma or malignancy risk.
Rapid Indication Expansion Drives Blockbuster Revenue Growth
Between 2018 and 2022, Regeneron and Sanofi obtained FDA approval for Dupixent in five additional indications: asthma (2018), chronic rhinosinusitis with nasal polyps (2019), eosinophilic esophagitis (2022), prurigo nodularis (2022), and pediatric atopic dermatitis (ages 6 months+). Each new indication expanded the patient population by millions, driving annual revenue from approximately $2 billion in 2018 to over $11 billion by 2024. The aggressive expansion timeline meant that cancer-specific long-term safety data lagged far behind the growing exposed population.
CTCL Case Reports Emerge in Published Literature
Beginning in 2021, peer-reviewed dermatology journals published an increasing number of case reports documenting CTCL diagnoses in Dupixent-treated patients. Cases described both new-onset mycosis fungoides and Sezary syndrome in patients with no prior lymphoma history, as well as rapid CTCL progression in patients whose disease had been misdiagnosed as refractory eczema. These publications were accessible to Regeneron and Sanofi's medical affairs and pharmacovigilance teams, who are obligated to monitor published safety literature under FDA regulations.
Landmark 19,612-Patient Study Quantifies 4.5x CTCL Risk
Independent researchers published a large-scale observational study analyzing 19,612 dupilumab-treated patients matched against controls. The study found a 4.5-fold increased risk of cutaneous T-cell lymphoma among Dupixent users — a statistically significant signal that exceeded what could be explained by diagnostic bias or disease confounding alone. This study was not sponsored by Regeneron or Sanofi, highlighting the gap between manufacturer-sponsored safety monitoring and independent epidemiological research.
FDA Watchlist Placement and Formal Safety Review
The FDA placed Dupixent on its CTCL safety monitoring watchlist in March 2025, followed by a formal safety review announcement in September 2025. Regeneron's stock experienced significant volatility following both announcements. In quarterly earnings calls, Regeneron executives characterized the CTCL signal as potentially reflecting diagnostic unmasking rather than true drug-induced lymphoma — a position contested by plaintiff experts and independent researchers.
Litigation Filings Accelerate Nationwide
Following the FDA's formal safety review and growing media coverage of the CTCL association, plaintiff attorneys began filing individual lawsuits and investigating potential class action claims against Regeneron and Sanofi. Complaints allege failure to warn about CTCL risk, inadequate post-market surveillance, and negligent promotion of Dupixent without appropriate cancer screening recommendations. Over 37 million Dupixent prescriptions have been dispensed in the United States, creating a large potential plaintiff class.
Prioritizing Revenue Growth Over Long-Term Safety Monitoring
Plaintiffs allege that Regeneron and Sanofi pursued aggressive indication expansion and direct-to-consumer marketing while failing to invest proportionate resources in post-market cancer surveillance. The 19,612-patient study that identified the 4.5x CTCL risk was conducted by independent researchers — not by the manufacturer — despite Regeneron and Sanofi having access to their own pharmacovigilance databases that contained the same safety signal.
- Regeneron and Sanofi expanded Dupixent to six indications between 2017 and 2024 without conducting manufacturer-sponsored long-term studies specifically designed to evaluate oncologic safety endpoints.
- Independent researchers, not the manufacturer, conducted the landmark 19,612-patient study that quantified the CTCL risk — raising questions about whether Regeneron's pharmacovigilance function was adequately analyzing its own adverse event data.
- Direct-to-consumer television advertising for Dupixent did not mention any cancer or lymphoma risk, despite accumulating FAERS reports that were known to both companies.
- Regeneron executives publicly characterized the CTCL signal as likely representing diagnostic unmasking rather than drug-induced lymphoma, a position that plaintiff experts argue minimizes a serious safety concern to protect commercial interests.
Key Takeaway
With over $11 billion in annual revenue and 37 million prescriptions dispensed, Dupixent is one of the most commercially significant drugs in Regeneron and Sanofi's portfolios. The emerging CTCL litigation directly challenges whether these companies prioritized revenue growth and indication expansion over the patient safety investment needed to detect and communicate a serious cancer risk that independent researchers ultimately identified.
Notable Verdicts & Settlements
Richardson v. Regeneron Pharmaceuticals et al. (Tennessee State Court)
VerdictThe 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.
Fraioli v. Regeneron Pharmaceuticals et al. (S.D. Florida)
VerdictGiovanni 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.
Doe v. Regeneron Pharmaceuticals et al. (N.D. Illinois)
VerdictAn Illinois plaintiff filed suit against Regeneron and Sanofi in the Northern District of Illinois in December 2025, alleging development of mycosis fungoides after approximately two years of Dupixent use for moderate-to-severe atopic dermatitis. The plaintiff's dermatologist initially attributed new skin lesions to eczema flares for over eight months before a punch biopsy revealed atypical lymphocytic infiltrate consistent with early-stage mycosis fungoides. Immunohistochemistry confirmed CD4+ T-cell malignancy with loss of CD7 expression. The case was transferred to MDL No. 3180 in February 2026. Filed under pseudonym to protect medical privacy.
Martinez v. Regeneron Pharmaceuticals et al. (S.D. Texas)
VerdictRosa Martinez, a 47-year-old asthma patient in Houston, filed a federal lawsuit alleging she developed Sezary syndrome — the most aggressive form of CTCL — after four years of Dupixent injections for moderate-to-severe asthma with eosinophilic phenotype. Martinez's case is notable because she did not have atopic dermatitis — she was prescribed Dupixent solely for asthma, undermining the defense argument that CTCL risk is attributable to underlying eczema rather than the drug itself. Her oncologist documented circulating Sezary cells in peripheral blood at the time of diagnosis. The case was transferred to MDL No. 3180 and is considered a potential bellwether candidate because it isolates the drug's effect from confounding by atopic dermatitis.
Patel v. Regeneron Pharmaceuticals et al. (D. New Jersey)
VerdictDeepak Patel, a 61-year-old retired pharmacist in New Jersey, filed a federal lawsuit alleging he developed advanced-stage mycosis fungoides after three years of Dupixent use for chronic rhinosinusitis with nasal polyps (CRSwNP). Patel's case is significant for two reasons: first, like Martinez, his Dupixent indication was not atopic dermatitis, which weakens the defense theory that CTCL risk stems from the underlying skin condition rather than the drug; second, Patel's professional background as a pharmacist gives him heightened awareness of drug safety — he testified that nothing in the Dupixent prescribing information warned about CTCL risk and that he would not have accepted the prescription had the risk been disclosed. The case was transferred to MDL No. 3180 in March 2026.
Were you diagnosed with T-cell lymphoma after taking Dupixent? Get a free case evaluation today.
Get Your Free Case Reviewor call 1-800-555-0100
Cutaneous T-Cell Lymphoma (CTCL)
Medical Definition
Cutaneous T-cell lymphoma is not one disease — it is a family of cancers that begin when the body's own immune defenders turn malignant and attack the skin. In CTCL, T-lymphocytes — white blood cells that normally patrol the body for infections and abnormal cells — acquire genetic mutations that cause them to proliferate uncontrollably and accumulate in the skin. The result is a cancer that literally wears the disguise of the conditions Dupixent is prescribed to treat. Early CTCL presents as flat, scaly red patches that dermatologists routinely mistake for eczema, psoriasis, or contact dermatitis. This is not a rare diagnostic error — it is the norm. The average CTCL patient sees multiple doctors over a span of three to six years before receiving an accurate diagnosis. For Dupixent users, this delay may be even longer, because their doctors attribute worsening skin symptoms to treatment resistance rather than investigating whether the patient has developed an entirely different disease. A peer-reviewed analysis of 19,612 patients found that Dupixent users faced a 4.5-fold increased risk of developing CTCL compared to non-users — a relative risk that the epidemiological community considers highly significant.
Symptoms
Persistent red, scaly patches that mimic eczema
CommonThe hallmark of early CTCL is flat, erythematous patches with fine scaling that look virtually identical to atopic dermatitis. For Dupixent users, these patches are routinely misattributed to eczema flares or incomplete treatment response, delaying cancer diagnosis.
Raised plaques with well-defined borders
ModerateAs CTCL progresses from patch stage to plaque stage, lesions become elevated and indurated with sharper borders than typical eczema. Plaques may be annular or arciform and tend to favor sun-protected areas — a distribution pattern that differs from photosensitive eczema.
Intense, treatment-resistant pruritus
ModerateCTCL-associated itching can be severe and disproportionate to the visible skin involvement. Patients often describe it as qualitatively different from eczema itch — deeper, more burning, and unresponsive to antihistamines or topical steroids that previously controlled their dermatitis.
Skin tumors and nodules
Warning signTumor-stage CTCL produces dome-shaped or mushroom-like nodules that can ulcerate and become secondarily infected. This stage represents a dramatic escalation from the patch and plaque stages and carries a significantly worse prognosis.
Generalized erythroderma with exfoliation
Warning signIn advanced CTCL and Sezary syndrome, cancerous T-cells infiltrate the entire skin surface, causing diffuse redness, scaling, and exfoliation covering more than 80 percent of the body. Patients experience temperature dysregulation, protein loss, and secondary infections.
Swollen lymph nodes and constitutional symptoms
Warning signLymphadenopathy in CTCL indicates extracutaneous spread. Patients may develop fevers, night sweats, and unintentional weight loss — the classic B symptoms of lymphoma that signal systemic disease.
Risk Factors
- Dupixent (dupilumab) use — 4.5x relative risk of CTCL per peer-reviewed study of 19,612 patients
- IL-4/IL-13 pathway blockade shifting immune surveillance away from T-cell malignancy detection
- Pre-existing atopic dermatitis or other chronic inflammatory skin conditions (confounding but additive)
- Age over 50 — CTCL incidence increases with age, and most Dupixent prescriptions are for adults
- Male sex — CTCL has a 2:1 male-to-female predominance in the general population
- Prolonged immunomodulatory therapy altering baseline immune function
Diagnosis Process
- 1Clinical suspicion triggered by skin lesions unresponsive to standard eczema therapy or appearing in atypical distributions
- 2Skin biopsy with histopathological examination showing atypical lymphocytic infiltrate in the epidermis (epidermotropism)
- 3Immunohistochemistry (IHC) panel — CTCL T-cells typically express CD4+ with loss of normal T-cell markers (CD7, CD26)
- 4T-cell receptor (TCR) gene rearrangement analysis to confirm clonality of the malignant T-cell population
- 5Flow cytometry of peripheral blood to detect circulating Sezary cells (for suspected Sezary syndrome)
- 6PET-CT and lymph node biopsy for staging when extracutaneous disease is suspected
- 7TNMB staging using the ISCL/EORTC classification system specific to cutaneous lymphomas
Treatment Options
Survival Rates
| Stage | 5-Year Rate | 10-Year Rate |
|---|---|---|
| Stage IA (patches only, <10% BSA) | 95-100% | 85-95% |
| Stage IB-IIA (patches/plaques, >10% BSA or lymphadenopathy) | 75-85% | 55-70% |
| Stage IIB (tumors) | 40-65% | 20-40% |
| Stage III (erythroderma) | 30-55% | 15-30% |
| Stage IV (Sezary syndrome or visceral involvement) | 10-25% | 5-15% |
Prognosis
Prognosis in CTCL depends overwhelmingly on the stage at diagnosis — which is precisely why diagnostic delay caused by Dupixent's masking of CTCL symptoms is so legally and medically significant. Patients diagnosed at stage IA have a near-normal life expectancy with appropriate monitoring. But each stage advance dramatically worsens outcomes. Large cell transformation — when CTCL evolves into an aggressive high-grade lymphoma — occurs in approximately 20 percent of advanced cases and carries a median survival of less than two years. For Dupixent users whose CTCL was mistaken for eczema and allowed to progress, the delayed diagnosis may represent the difference between a manageable chronic condition and a fatal cancer.
Support Resources
- Cutaneous Lymphoma Foundation (clfoundation.org) — patient education, clinical trial finder, and peer support network
- Lymphoma Research Foundation — comprehensive CTCL information and treatment center directory
- National Cancer Institute (cancer.gov) — CTCL treatment guidelines and clinical trial database
- CancerCare — free professional counseling and financial assistance for lymphoma patients
Mycosis Fungoides
Medical Definition
Mycosis fungoides is the most common subtype of cutaneous T-cell lymphoma, accounting for roughly half of all CTCL diagnoses. The name — which dates to 1806 and has nothing to do with fungal infection — describes the mushroom-like tumors that can develop in advanced stages. What makes mycosis fungoides particularly insidious in the context of Dupixent litigation is its clinical trajectory: it begins as flat, innocuous-looking patches that are virtually indistinguishable from the eczema that Dupixent is prescribed to treat. A dermatologist looking at a Dupixent patient with new red patches has every reason to assume eczema is worsening rather than suspecting a rare lymphoma. This is not a failure of individual physicians — it is a systemic diagnostic trap created by prescribing a drug for a condition that mimics the cancer the drug may cause. Mycosis fungoides progresses through four clinical phases: patch stage (flat, scaly erythematous areas), plaque stage (raised, thickened lesions), tumor stage (dome-shaped nodules that can ulcerate), and disseminated stage (lymph node and visceral involvement). The rate of progression varies enormously — some patients remain in patch stage for decades, while others advance to tumor stage within two to three years. The critical factor for Dupixent plaintiffs is that misdiagnosis during patch stage means the cancer may not be detected until it reaches plaque or tumor stage, when treatment options narrow and survival rates decline sharply.
Symptoms
Flat, oval patches with fine scaling in sun-protected areas
CommonClassic early mycosis fungoides appears as well-circumscribed erythematous patches, often on the buttocks, inner thighs, trunk, and upper arms — areas typically covered by clothing. This bathing-suit distribution differs subtly from eczema but is easily overlooked.
Poikilodermatous changes (mottled pigmentation and telangiectasia)
ModerateAs patches persist, they develop a characteristic mottled appearance with areas of hyperpigmentation, hypopigmentation, fine wrinkling, and visible small blood vessels — a pattern called poikiloderma that is uncommon in true eczema.
Thick, indurated plaques with annular or serpiginous borders
ModeratePlaque-stage mycosis fungoides produces raised, firm lesions that can form ring-shaped or wavy patterns. Unlike eczema plaques, these have a palpable firmness reflecting dense dermal infiltration by malignant T-cells.
Dome-shaped skin tumors prone to ulceration
Warning signTumor-stage disease produces nodular masses that can reach several centimeters in diameter, ulcerate centrally, and become superinfected. This stage is unmistakable clinically but represents late-stage disease with significantly worse outcomes.
Alopecia in patches overlying active disease
ModerateHair loss within and around mycosis fungoides patches — particularly on the scalp, eyebrows, or body — is a diagnostic clue that the process is not simple eczema. Folliculotropic mycosis fungoides specifically targets hair follicles and carries a worse prognosis.
Leonine facies in advanced disease
Warning signIn rare advanced cases, diffuse facial infiltration by malignant T-cells produces thickened, rugose facial skin resembling a lion's face — a dramatic presentation that is pathognomonic for advanced CTCL but occurs only in late-stage disease.
Risk Factors
- Dupixent use with IL-4/IL-13 blockade potentially unmasking or promoting T-cell clonal proliferation
- Chronic atopic dermatitis itself — patients with longstanding AD may have baseline immune dysregulation affecting T-cell surveillance
- Age over 55 — median age at mycosis fungoides diagnosis is 55 to 60 years
- Male sex — approximately 1.5 to 2 times more common in men than women
- Prior history of persistent dermatitis unresponsive to multiple treatments — may represent undiagnosed early MF misclassified as eczema
Diagnosis Process
- 1Clinical recognition of skin lesions inconsistent with eczema response — key trigger for biopsy in Dupixent users
- 2Multiple punch biopsies from active lesions including oldest and most infiltrated-appearing areas
- 3Histopathology showing band-like lymphocytic infiltrate with epidermotropism and Pautrier microabscesses
- 4Immunophenotyping by immunohistochemistry: CD3+, CD4+, CD8-, with loss of CD7 and/or CD26
- 5T-cell receptor gene rearrangement studies (PCR-based) to confirm monoclonal T-cell population
- 6Complete blood count with Sezary cell preparation to rule out leukemic involvement
- 7PET-CT scan for staging in patients with plaque-stage or higher disease
Treatment Options
Survival Rates
| Stage | 5-Year Rate | 10-Year Rate |
|---|---|---|
| Patch stage only (IA) | 96-98% | 88-93% |
| Generalized patches (IB) | 80-90% | 60-75% |
| Plaque stage with lymphadenopathy (IIA) | 70-80% | 45-60% |
| Tumor stage (IIB) | 40-60% | 20-35% |
| Folliculotropic variant | 55-70% | 30-50% |
Prognosis
Mycosis fungoides behaves very differently depending on when it is caught. A patient diagnosed at patch stage can often be managed for years or decades with skin-directed therapies alone, maintaining a quality of life that is dramatically better than what faces patients diagnosed at tumor stage. The crux of the Dupixent litigation is that the drug creates conditions in which early mycosis fungoides is systematically missed — not because doctors are negligent, but because the cancer presents as the disease the drug is supposed to treat. Every month of delayed diagnosis is a month in which the cancer can progress from a treatable skin condition to a life-threatening systemic malignancy.
Support Resources
- Cutaneous Lymphoma Foundation (clfoundation.org) — the leading U.S. nonprofit for MF/CTCL patients
- MyHealth.Alberta.ca — evidence-based MF patient education
- National Comprehensive Cancer Network (NCCN) — treatment guidelines for primary cutaneous lymphomas
- PatientsLikeMe — online community for CTCL patients sharing treatment experiences
Frequently Asked Questions
Dupixent CTCL Lawsuit Filing Deadlines — MDL No. 3180 and State SOL Guide
Dupixent litigation is consolidating rapidly. The Judicial Panel on Multidistrict Litigation assigned all federal Dupixent cases to MDL No. 3180 in February 2026, and individual state-court filings continue across the country. Because Dupixent-linked CTCL is a recently discovered injury — one that was systematically masked by the drug's intended use for skin conditions — the discovery rule applies in most jurisdictions. That means the statute of limitations clock typically starts when a plaintiff was diagnosed with CTCL (or when they reasonably should have connected the diagnosis to Dupixent), not when they first took the drug. But discovery rules have limits, and defendants will argue that publicly available safety signals should have put patients on notice earlier. The window to file is open now, and it will not stay open indefinitely.
Why the Discovery Rule Is Critical for Dupixent Claimants
Dupixent presents a uniquely deceptive diagnostic problem. The drug is prescribed for eczema — a condition that looks almost identical to early-stage cutaneous T-cell lymphoma. For years, dermatologists mistook CTCL symptoms in Dupixent patients for eczema flares or treatment resistance, delaying cancer diagnoses by months or even years. This diagnostic confusion is precisely the kind of scenario the discovery rule was designed to address. In states that apply the discovery rule, the statute of limitations begins when the plaintiff knew or should have known that (1) they had CTCL and (2) Dupixent may have caused or contributed to it. Given that the first peer-reviewed study linking Dupixent to CTCL was published in 2024 and the FDA opened its formal investigation in September 2025, most plaintiffs diagnosed with CTCL after Dupixent use are well within their filing windows as of April 2026. However, Regeneron and Sanofi will argue that earlier safety signals — including FAERS reports and the March 2025 FDA watchlist placement — should have triggered a duty to investigate. Every month that passes strengthens that defense argument. Evidence preservation is equally urgent: pharmacy records, injection logs, dermatology visit notes, and biopsy reports must be collected and secured before medical record retention periods expire.
Applies to: Dupixent (dupilumab)
Real-World Examples
A 52-year-old woman in Georgia used Dupixent for atopic dermatitis from 2019 to 2023. In 2024, a dermatologist biopsied a persistent rash that had not responded to Dupixent — pathology confirmed mycosis fungoides (CTCL). She consulted an attorney in early 2026.
Georgia has a two-year personal injury statute of limitations with a discovery rule. Her clock started when the biopsy confirmed CTCL in 2024 — not when she first took Dupixent in 2019. She is within the filing window. Her attorney filed in federal court, and her case was transferred to MDL No. 3180. Had she waited until 2027, the defense would have a colorable argument that she should have connected the diagnosis to Dupixent sooner given 2025 media coverage.
A 38-year-old father in Texas was prescribed Dupixent for moderate-to-severe asthma in 2020. In late 2025, he was diagnosed with Sezary syndrome — the aggressive blood-borne form of CTCL — after months of unexplained skin lesions his pulmonologist attributed to allergic reactions.
Texas applies a two-year statute of limitations with a discovery rule for latent injury claims. His diagnosis in late 2025 starts the clock, and his Sezary syndrome — the most aggressive CTCL subtype — places him in the highest potential recovery tier. His attorney preserved Dupixent pharmacy records, injection site photographs, pulmonology and dermatology notes, and the pathology report showing malignant T-cells in peripheral blood. Filing early positions him for bellwether trial selection in the MDL.
Dupixent Lawsuit Filing Deadlines by State
Statutes of limitations for the 10 most common filing jurisdictions in Dupixent CTCL litigation
| State | SOL Period | Discovery Rule | Notable Exception |
|---|---|---|---|
| California | 2 years | Yes — from date of discovery of injury and its cause | Tolled for minority; delayed discovery doctrine well-established |
| Florida | 2 years (reduced from 4 in 2023) | Yes — discovery rule applies to latent pharmaceutical injuries | Products liability has separate 12-year repose; discovery rule may override for fraudulent concealment |
| Georgia | 2 years | Yes — from date plaintiff knew or should have known of injury | 10-year statute of repose for products liability; discovery rule exception for pharmaceutical cases |
| Illinois | 2 years | Yes — strong discovery rule for toxic tort and pharmaceutical cases | Venue is significant — Cook County juries historically favorable to plaintiffs in pharma cases |
| New York | 3 years | Limited — discovery rule applies to toxic substance exposure but not all products liability | Separate 3-year statute from date of discovery for exposure to toxic substances (CPLR 214-c) |
| Tennessee | 1 year | Yes — from date of discovery; critical to file promptly | Shortest SOL among major filing states — wrongful death suit already filed here (Richardson, Oct 2025) |
| Texas | 2 years | Yes — discovery rule applies to latent injury pharmaceutical cases | 15-year statute of repose for products liability; does not bar claims discovered within 2 years of diagnosis |
| Pennsylvania | 2 years | Yes — from date plaintiff knew or should have known of causal connection | Philadelphia mass tort program has experienced judges for pharmaceutical MDL overflow cases |
| New Jersey | 2 years | Yes — strong discovery rule for pharmaceutical injury claims | Product Liability Act imposes strict liability on manufacturers; discovery rule well-developed in NJ case law |
| Ohio | 2 years | Yes — from date plaintiff discovered or should have discovered the injury and its cause | Products liability statute of repose is 10 years from delivery; discovery rule applies to latent injuries |
Bottom Line
The discovery rule protects most Dupixent-CTCL claimants who were diagnosed in 2024 or later, but that protection erodes with each passing month as public awareness of the Dupixent cancer link grows. Filing now — while the MDL is in its earliest stages — provides strategic advantages including potential bellwether selection and early access to discovery materials.
Filing deadlines vary by state and depend on individual circumstances including date of diagnosis and date of discovery of the connection to Dupixent. This table provides general guidance and is not legal advice. An attorney can evaluate the specific deadlines that apply to your case.
In-Depth Guides
CTCL Diagnosis After Dupixent Use
Cutaneous T-cell lymphoma is a rare and aggressive blood cancer that masquerades as eczema, psoriasis, and other benign skin conditions — making it uniquely dangerous for Dupixent patients who already carry dermatitis diagnoses. Misdiagnosis rates exceed 40 percent in early-stage CTCL because the symptoms overlap so precisely with the conditions Dupixent is prescribed to treat. Dermatologists expect itchy, red patches in their Dupixent patients; what they may not expect is that those patches now harbor malignant T-cells. Staging ranges from IA (limited patches) to IVB (visceral organ involvement and blood-borne Sezary cells), and the difference between a Stage IA diagnosis and a Stage IIB diagnosis can mean the difference between a normal life expectancy and a five-year survival rate below 40 percent. The critical diagnostic tool is a skin biopsy with immunohistochemistry, which can reveal hallmark Pautrier microabscesses — clusters of malignant T-cells in the epidermis that do not appear in benign dermatitis. Every Dupixent patient whose skin condition worsens, changes character, or fails to respond to continued treatment should demand a biopsy, not another refill.
Read guideDupixent 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.
Read guideDupixent 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.
Read guideDupixent 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.
Read guideDupixent 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.
Read guideSources & References
- Peer-reviewed study of 19,612 patients analyzing the association between dupilumab use and cutaneous T-cell lymphoma incidence — Medical Literature (2024-2025)
- FDA Drug Safety Communication — Dupixent (dupilumab) placed on safety watchlist for potential cancer risk, March 2025 — U.S. Food and Drug Administration (FDA)
- FDA investigation of 300+ adverse event reports related to lymphoma in Dupixent users, September 2025 — U.S. Food and Drug Administration (FDA)
- Giovanni Fraioli v. Regeneron Pharmaceuticals et al., filed January 2026, Southern District of Florida — U.S. District Court, S.D. Florida
- Chandra Richardson Wrongful Death Complaint, filed October 2025, Tennessee — Tennessee State Court