Safety and Effectiveness of h5G1.1-mAb for Dermatomyositis

This study will evaluate the safety and effectiveness of the experimental drug h5G1.1-mAb in treating patients with dermatomyositis. This disease, which causes skin rash, muscle weakness, and sometimes various other symptoms, may be due to an immune system abnormality. Drugs currently used to treat dermatomyositis, such as prednisone and various anticancer drugs, often have serious side effects and may not work in all patients. h5G1.1-mAb is a genetically engineered antibody that blocks the activity of certain proteins involved in the immune reaction that produces inflammation. Patients age 18 years and older who have had dermatomyositis for at least 6 months and who have not improved with prednisone or other therapies, or who cannot tolerate prednisone or other therapies, may be eligible for this 12-week study. Candidates will have a history and physical examination, including blood and urine tests, throat culture, and muscle strength testing. Participants will be randomly assigned to receive either h5G1.1-mAb or placebo (an inactive substance). The drug or placebo will be given intravenously (through a thin tube inserted into a vein) once a week for five doses and then every other week for two more doses. Participants will undergo the following additional tests at various intervals during the study as follows: 1. Complete physical examination ( visit 9) 2. Blood and urine tests (various intervals) 3. Muscle strength testing, assessment of ability to perform daily tasks, and completion of questionnaire regarding functional abilities (visits 2, 6 and 9) 4. Ultrasound imaging of muscle (during certain muscle exercises) (visits 2, 6 and 9) 5. Electrocardiogram (EKG) (visits 2 and 9) 6. Throat swab (culture) (visit 6) 7. Examination and photography of skin lesions (visits 2 and 9) 8. Skin biopsy - removal of small sample of skin tissue under local anesthetic (visits 2 and 9) 9. Magnetic resonance imaging (MRI) scan of muscles (visits 2 and 9) 10. Possible muscle bio