The purpose of this study is to assess the safety and tolerability of repeated subcutaneous (SC) doses of Dupilumab in participants with moderate-to-severe atopic dermatitis (AD).

Inclusion Criteria:

1. Male or female, 18 years or older;
2. Chronic AD diagnosed by the Eichenfield revised criteria of Hannifin and Rajka that had been present for at least 3 years before the screening visit;
3. Eczema Area and Severity Index (EASI) score ≥ 12 at the screening and baseline visits;
4. Investigator's Global Assessment (IGA) score ≥ 3 at the screening and baseline visits;
5. ≥ 10% body surface area (BSA) of AD involvement at the screening and baseline visits;
6. History of inadequate response to a stable (≥ 1 month) regimen of topical corticosteroids or calcineurin inhibitors as treatment for AD within 3 months before the screening visit.

Exclusion Criteria:

1. Positive Hepatitis B surface antigen, and/or positive Hepatitis C antibody at the screening visit;
2. Treatment with an investigational drug within 8 weeks or within 5 half-lives, if known, whichever is longer, before the baseline visit;
3. Treatment with leukotriene inhibitors within 4 weeks before the baseline visit;
4. Treatment with systemic corticosteroids within 4 weeks before the baseline visit;
5. Treatment with topical corticosteroids, tacrolimus, and/or pimecrolimus within 1 week before the baseline visit;
6. Systemic treatment for AD with an immunosuppressive/immunomodulating substance within 4 weeks before the baseline visit;
7. Chronic or acute infection requiring treatment with oral or IV antibiotics, antivirals, or antifungals within 4 weeks before the screening visit or superficial skin infections within 1 week before the screening visit;
8. Known history of human immunodeficiency virus (HIV) infection;
9. History of clinical parasite infection, other than treated trichomoniasis;
10. History of malignancy within 5 years before the baseline visit, with the following exceptions: participants with a history of completely treated carcinoma in-situ of cervix, and non-metastatic squamous or basal cell carcinoma of the skin were allowed;
11. Any medical or psychiatric condition which, in the opinion of the investigator or the sponsor's medical monitor, would place the participant at risk, interfere with participation in the study, or interfere with the interpretation of study results;
12. Pregnant or breast-feeding women;
13. Unwilling to use adequate birth control, if of reproductive potential and sexually active.