Ravulizumab Versus Placebo in Adult Participants With Dermatomyositis

Key Inclusion Criteria:

• 18 years of age or older at the time of signing the informed consent.

• Body weight ≥ 30 kilograms at the time of Screening.

• Male or female.

• Diagnosis: Meet 2017 American College of Rheumatology/European League AgainstRheumatism classification criteria for definite or probable DM.

• Participants who have an inadequate response or are intolerant to 1 or more DMtreatments, including systemic corticosteroids or immunosuppressive/immunomodulatorytherapies (for example, azathioprine, methotrexate, rituximab, intravenousimmunoglobulin), either in combination or as monotherapy.

• Vaccinated against Neisseria meningitidis within 3 years prior to initiatingravulizumab as per national and local guidelines. Participants must receive thevaccination at least 2 weeks before first study intervention. The sponsor recommendsthat national and local guidelines for prophylactic antibiotics should also befollowed.

• Female participants of childbearing potential and male participants must followspecified contraception guidance as described in the protocol.

Key Exclusion Criteria:

• Participants who have been diagnosed with cancer within the last 3 years need tohave appropriate negative cancer screening as per local standard of care within 6months before Screening (basal or squamous cell skin cancer or carcinoma in situ ofthe cervix needs to have been excised and without evidence of residual disease forat least 3 months before Screening).

• Evidence of active malignant disease or malignancies diagnosed within the previous 3years including hematological malignancies and solid tumors.

• Participants with other forms of myositis.

• As per investigator discretion, participants with significant muscle damage (forexample, severe muscle atrophy, end stage muscle disease, MRI with severe atrophy orfibrofatty replacement)

• History of Neisseria meningitidis infection.

• Human immunodeficiency virus (HIV) infection (evidenced by HIV Type 1 or Type 2antibody titer).

• Active systemic bacterial, viral, or fungal infection within 14 days prior toravulizumab administration.

• Presence of fever ≥ 38°Celsius (100.4°Fahrenheit) within 7 days prior to study drugadministration on Day 1.

• History of hypersensitivity to murine proteins or to 1 of the excipients ofravulizumab.

• Pregnant, breastfeeding, or intending to conceive during the course of the study.

• Inability or unwillingness to adhere to the protocol requirements.