A Study to Evaluate Safety and Efficacy of Empasiprubart in Adults With Dermatomyositis

Inclusion criteria

• Is at least 18 years of age and the local legal age of consent for clinical studies when signing the Informed Consent Form
• Is capable of providing signed informed consent and complying with protocol requirements
• Agrees to use contraceptive measures consistent with local regulations and women of child-bearing potential must have a negative serum pregnancy test at screening and a negative urine pregnancy test before receiving the study drug
• Has a clinical diagnosis of dermatomyositis or juvenile dermatomyositis. The diagnosis date for juvenile dermatomyositis should be ≤5 years before screening
• Has active muscle disease associated with classic dermatomyositis or juvenile dermatomyositis at screening and before the first study drug adminisitration and at least 1 of the following: elevated levels of creatine kinase, aldolase, lactate dehydrogenase, aspartate aminotransaminase or alanine aminotransferase at screening; or electromyography ≤18 weeks before the first study drug administration; or an MRI depicting active muscle inflammation ≤18 weeks before the first study drug administration; or muscle biopsy demonstrating signs of active inflammation ≤18 weeks before the first study drug administration
• Has at least mild skin disease at screening
• Complies with the permitted background dermatomyositis treatment requirements at screening
• Has had immunization with the first meningococcal, pneumococcal, and the single Haemophilus influenza type B vaccine ≥14 days before the first study drug administration

Exclusion criteria

• Known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of dermatomyositis or puts the participant at undue risk
• Naïve to standard dermatomyositis treatment according to local recommendations
• History of malignancy unless considered cured by adequate treatment with no evidence of recurrence for ≥3 years before the first study drug administration. Adequately treated participants with the following cancers can be included at any time: Basal cell or squamous cell skin cancer; Carcinoma in situ of the cervix; Carcinoma in situ of the breast; Incidental histological findings of prostate cancer
• Clinically significant active infection that is not sufficiently resolved before the first study drug administration in the investigator's opinion
• Positive serum test at screening for active infection with any of the following: Hepatitis B virus, Hepatitis C virus, HIV
• Clinically significant disease, recent major surgery, or intention to have major surgery during the study; or any other medical condition that, in the investigator's opinion, would confound the results of the study or put the participant at undue risk
• Current participation in another interventional clinical study
• Known hypersensitivity to the study drug or any of its excipients
• History (within 12 months before screening) of or current alcohol, drug, or medication abuse, as assessed by the investigator
• Pregnant or lactating state or intending to become pregnant during the study
• Previous participation in an empasiprubart clinical study with at least 1 dose of study drug received
• Known complement component deficiency as assessed by the investigator
• Change in dermatomyositis physical therapy or exercise program from ≤4 weeks before screening
• Inflammatory or non-inflammatory myopathies other than dermatomyositis, such as drug-induced or endocrine-induced myositis, infective myositis, polymyositis, immune-mediated necrotizing myopathy, inclusion body myositis, overlap myositis, metabolic myopathies, or muscle dystrophies
• Paraneoplastic dermatomyositis secondary to malignancy
• Glucocorticoid-induced myopathy
• Severe muscle damage
• Extensive or severe calcinosis
• Interstitial lung disease with at least 1 of the following: forced vital capacity (FVC) ≤60%; supplemental oxygen therapy; rapidly progressing uncontrolled interstitial lung disease; moderate or severe interstitial lung disease