To collect data on actual-use to assess technical performance and user injections of dupilumab auto-injection device by patients with atopic dermatitis (AD).

Study is conducted in 2 parts: part A and part B.

Part A - Patients with moderate-to-severe AD will be randomized to receive dupilumab (dose 1) by auto-injector (AI) device or prefilled syringe.

Once part A is completely enrolled, part B will randomize patients with moderate-to-severe AD to receive dupilumab (dose 2) by auto-injector (AI) device or prefilled syringe.

Key Inclusion Criteria:

1. Diagnosis of chronic atopic dermatitis for at least 3 years with inadequate response to topical medications within 6 months before screening
2. Willing and able to comply with all clinic visits and study-related procedures
3. Provide signed informed consent

Key Exclusion Criteria:

1. Patient < 30.0 kilograms (Kg) in weight

2. Patient who has previously participated in a dupilumab clinical study

3. Patient who has been treated with the following:

   • An investigational drug within 8 weeks or within 5 half-lives (if known),whichever is longer, before the baseline visit
   • Immunosuppressive/ immunomodulating drugs (e.g., systemic corticosteroids, cyclosporine, mycophenolate-mufti, IFN-γ, Janus kinase inhibitors, azathioprine, methotrexate, etc.) or Phototherapy for AD within 4 weeks before the baseline visit
   • An experimental monoclonal antibody within 5 half-lives or within 6◦months prior to visit 1 if the half-life is unknown
   • Biologic agents within 5 half-lives (if known) or 16 weeks prior to baseline visit, whichever is longer
   • Anti-immunoglobulin E therapy (omalizumab) within 130 days prior to visit 1
   • A live (attenuated) vaccine within 4 weeks before the baseline visit

4. Patient who has initiated treatment with prescription moisturizers or moisturizers containing additives such as ceramide, hyaluronic acid, urea, or filaggrin degradation products during the screening period (patients may continue using stable doses of such moisturizers if initiated before the screening visit)

5. Patient who has skin comorbidities that may interfere with study assessments

6. Patient with a planned or anticipated major surgical procedure during the patient's participation in this study

7. Women of childbearing potential unwilling to use adequate birth control measures during the study

8. Pregnant or breastfeeding women, or women planning to become pregnant or breastfeed during the study

Note: Other protocol defined Inclusion/Exclusion criteria may apply