Genzyme Ireland Ltd.

To evaluate the efficacy of amlitelimab in regrowth of hair in adult subjects with alopecia areata (AA) who have lost 50% or more of their hair compared to placebo. To evaluate the efficacy of amlitelimab in improving signs, symptoms, and quality of life in adult subjects with AA who have lost 50% or more of their hair compared to placebo; To assess the safety and tolerability of amlitelimab treatment in AA subjects; To characterize the PK profile of amlitelimab SC-administered in AA subjects; To characterize the immunogenicity of amlitelimab SC-administered in AA subjects.

Primary: To demonstrate the efficacy of amlitelimab monotherapy compared to placebo in subjects 12 years and older with moderate to severe atopic dermatitis (AD). Secondary: To evaluate the efficacy of amlitelimab monotherapy compared to placebo in subjects 12 years and older with moderate to severe AD. To evaluate the safety of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD. To characterize the pharmacokinetics (PK) of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD. To characterize the immunogenicity of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD.

To demonstrate the efficacy of amlitelimab monotherapy compared with placebo in subjects 12 years and older with moderate to severe atopic dermatitis (AD); to evaluate the efficacy of amlitelimab monotherapy compared with placebo in subjects 12 years and older with moderate to severe AD; to evaluate the safety of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD; to characterize the pharmacokinetics (PK) of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD; to characterize the immunogenicity of amlitelimab monotherapy in subjects 12 years and older with moderate to severe AD.