A Study to See How Well Lebrikizumab Works in Adults and Adolescents With Moderate Atopic Dermatitis (Eczema) and High Itch Burden

Inclusion Criteria:

• Have chronic atopic dermatitis (AD) (according to American Academy of DermatologyConsensus Criteria) that has been present for ≥1 year before screening visit.

• Have 10% to 25% body surface area (BSA) of AD involvement at screening and baseline.

• Have pruritus numeric rating scale (NRS) ≥6 at baseline.

• Have an Eczema Area and Severity Index (EASI) score ≥16 at screening and baseline.

• Have an Investigator's Global Assessment (IGA) score ≥3 (on a scale of 0 to 4) atscreening and baseline.

• Based on investigator judgement, have a history of inadequate response to treatmentwith topical medications, or determination that topical treatments are otherwisemedically inadvisable.

• For participants aged 12 to less than 18, have a body weight ≥40 kilograms (kg) atbaseline.

Exclusion Criteria:

• Have an uncontrolled chronic disease that might require multiple intermittent usesof oral corticosteroids at screening (as defined by the investigator).

• Have known liver cirrhosis and/or chronic hepatitis of any etiology.

• History of malignancy, including mycosis fungoides or cutaneous T-cell lymphoma,within 5 years before the screening, except completely treated in situ carcinoma ofthe cervix of completely treated and resolved nonmetastatic squamous or basal cellcarcinoma of the skin with no evidence of recurrence in the past 12 weeks.

• Are diagnosed with active endoparasitic infections or at high risk of theseinfections.

• Have a known or suspected history of immunosuppression, including history ofinvasive opportunistic infections despite infection resolution; or unusuallyfrequent, recurrent, or prolonged infections, per the investigator's judgment.

• Have presence of skin comorbidities that may interfere with study assessments.

• Have a severe concomitant illness(es) that in the investigator's judgment wouldadversely affect the participant's participation in the study.

• Have had any of the following types of infection within 3 months of screening ordevelop any of these infections during screening:

• Serious (requiring hospitalization, and/or intravenous or equivalent oralantibiotic treatment).

• Opportunistic - Note: Herpes zoster is considered active and ongoing until allvesicles are dry and crusted over.

• Chronic (duration of symptoms, signs, and/or treatment of 6 weeks or longer).

• Recurring (including, but not limited to, recurring cellulitis and chronicosteomyelitis).

• Have an active or acute infection requiring treatment with systemic antibiotics,antivirals, antiparasitics, antiprotozoals, or antifungals within 2 weeks before thebaseline visit or superficial skin infections within 1 week before the baselinevisit.

• Have had any prior treatment with a biologic therapy for AD.

• Have had treatment with any of the following agents within 4 weeks prior to thebaseline visit:

• systemic immunosuppressive or immunomodulating drugs (for example, systemiccorticosteroids, cyclosporine, mycophenolate mofetil, interferon-gamma,

• azathioprine, methotrexate, and other immunosuppressants)

• small molecules (for example, Janus kinase inhibitors [topical or systemic]),or

• phototherapy and photochemotherapy for AD.

• Treatment with B-cell-depleting biologics, including rituximab, within 6 monthsprior to baseline.