Dupixent CTCL
OpenFILINGCausation
Plaintiffs allege dupilumab's mechanism of action — blocking IL-4 and IL-13 signaling — disrupts immune surveillance against malignant T-cell clones, allowing cutaneous T-cell lymphoma to develop or progress. Case reports published in JAMA Dermatology, the Journal of the American Academy of Dermatology, and other peer-reviewed journals document CTCL diagnosis following dupilumab initiation. A key concern is diagnostic confusion: CTCL can mimic atopic dermatitis clinically, and dupilumab may mask early CTCL symptoms while the malignancy progresses. Plaintiffs argue Regeneron and Sanofi failed to warn about the CTCL risk and failed to recommend skin biopsy monitoring for patients with refractory eczema on dupilumab.
Defendants
| Entity | Role | Note |
|---|---|---|
| Regeneron Pharmaceuticals | Co-Developer/Manufacturer | Developed and manufactures dupilumab — primary defendant |
| Sanofi S.A. | Co-Developer/Marketer | Co-developed and co-markets Dupixent with Regeneron globally |
Litigation Timeline
Intelligence Signals
Buethe MG, Sy T, Eichenfield LF. Pediatric dermatology. 2026 May 31.
Lyu W et al.. Cancer medicine. 2026 May.
Xiao Y et al.. The Journal of allergy and clinical immunology. 2026 May 18.
Status: TERMINATED. Phase: PHASE2. Conditions: Atopic Dermatitis. Sponsor: Regeneron Pharmaceuticals. Interventions: REGN3500, Dupilumab, REGN3500 + Dupilumab Combo
Status: RECRUITING. Phase: N/A. Conditions: Chronic Spontaneous Urticaria (CSU), Hidradenitis Suppurativa (HS), Psoriasis (PsO). Sponsor: Leiden University Medical Center
Calvão J et al.. The Journal of allergy and clinical immunology. 2026 Apr 10.
Planella-Fontanillas N et al.. Clinical and experimental dermatology. 2026 Apr 11.
The Food and Drug Administration (FDA or the Agency) has determined the regulatory review period for DUPIXENT and is publishing this notice of that determination as required by law. FDA has made the determination because of the submission of an application to the Director of the U.S. Patent and Trademark Office (USPTO), Department of Commerce, for the extension of a patent which claims that human biological product.
The Food and Drug Administration (FDA) announces a forthcoming public advisory committee meeting of the Pediatric Advisory Committee (PAC). The general function of the Committee is to provide advice and recommendations to FDA on pediatric regulatory issues. The meeting will be open to the public. FDA is establishing a docket for public comment on this document.
Farah M, Zarabian N, Friedman A. Journal of drugs in dermatology : JDD. 2025 Nov 1.
Talasila S et al.. International journal of dermatology. 2026 Jan 23.
Kridin K et al.. Frontiers in medicine. 2025.
Amatore F et al.. Journal of the European Academy of Dermatology and Venereology : JEADV. 2026 Mar 12.
Baghdasarian S, Al-Saedi O, Cuomo RE. JAAD international. 2026 Apr.
Key Facts
- Status
- active
Geographic Exposure
Eligibility Criteria
- ✓Prescribed Dupixent (dupilumab) for atopic dermatitis, asthma, or other approved indication
- ✓Diagnosed with cutaneous T-cell lymphoma (CTCL), mycosis fungoides, or Sezary syndrome
- ✓CTCL diagnosis occurred during or after dupilumab use
- ✓No prior history of CTCL or lymphoma before starting Dupixent