The primary objective of the study is to assess the long-term safety of dupilumab in pediatric participants with AD.

The secondary objectives of the study are:

• To assess the long-term efficacy of dupilumab in pediatric participants with AD
• To assess the trough concentrations of functional dupilumab in serum and the immunogenicity in pediatric participants with AD after re-treatment with dupilumab

Optional Pre-filled Pen (PFP) Sub-Study in pediatric patients ≥2 to <12 years of age with AD

Co-Primary Objectives are:

• To evaluate the pharmacokinetic (PK) of dupilumab PFPs
• To evaluate the safety of dupilumab PFPs

Secondary Objective is:

- To evaluate the immunogenicity of dupilumab PFPs

Key Inclusion Criteria:

• Participated in a prior dupilumab study in pediatric participants with AD and adequately completed the visits and assessments required for both the treatment and follow-up periods, as defined in the prior study protocol
• PFP Sub-Study Only:
• Age ≥2 to <12 years at time of screening
• Body weight ≥5 kg and <60 kg at time of screening
• Must have received the same dupilumab dose regimen to be used in the PFP sub-study during the previous 12 weeks in the main OLE study using the prefilled syringe, as defined in the protocol

Key Exclusion Criteria:

• Participants who, during their participation in a prior dupilumab study developed an adverse event (AE) or serious adverse event (SAE) deemed related to study drug which could indicate that continued treatment with study drug may present an unreasonable risk for the patient
• Participants, who during the participation in a prior Dupilumab study, developed an AE that was deemed related to study drug and led to study treatment discontinuation, which in the opinion of the investigator or medical monitor could indicate that continued treatment with study drug may present an unreasonable risk for the patient
• Treatment with an investigational drug, other than dupilumab, within 8 weeks or within 5 half-lives (if known), whichever is longer, before the baseline visit
• Having used immunosuppressive/immunomodulating drugs within 4 weeks before the baseline visit
• Treatment with a live (attenuated) vaccine within 4 weeks before the baseline visit
• Diagnosed active endoparasitic infections or at high risk of these infections
• Severe concomitant illness(es) that, in the investigator's judgment, would adversely affect the participant's participation in the study
• PFP Sub-study Only:
• Poor compliance as defined by having missed 1 or more of the planned last 3 injections in the main OLE study prior to entering the sub-study
• Switched dupilumab doses within the past 12 weeks
• Meet criteria for temporary/permanent discontinuation of study drug at time of screening into PFP sub-study, as defined in the protocol.

Note: Other protocol defined Inclusion / Exclusion criteria may apply