Safety and Efficacy of BAF312 in Dermatomyositis

Key Inclusion Criteria: Written informed consent must be obtained before any assessment is performed. * Patients who have been defined as "definite" or "probable" based on the criteria of Bohan and Peter (Bohan and Peter 1975) for dermatomyositis at least 3 months before screening * Patients must have active disease as defined by muscle weakness * Patients may be on a stable dose of corticosteroid (up/equal to 20 mg once daily prednisone equivalent) * Patients currently treated with oral or subcutaneous MTX must have been a stable dose of no more/equal to than 25 mg per week * Patients currently treated with Azathioprine must have been a stable maintenance dose of no more/equal to 3 mg/kg/day * Negative cancer screening conducted in the 12 months prior to screening visit Key Exclusion Criteria * Dermatomyositis patients having overlap myositis or any other type of myositis including paraneoplastic myositis, drug-induced myopathy, necrotizing myositis * Preexisting severe cardiac or pulmonary conditions, malignancy of any organ system or significant eye diseases. * Uncontrolled diabetes mellitus or diabetes complicated with organ involvement. * Pregnant or nursing (lactating) women