Abatacept in Juvenile Dermatomyositis

Inclusion Criteria

• Adults with definite or probable JDM and pediatric patients 7 years of age and older with definite or probable JDM.
• Body weight of at least 25 kg (or at least 55 lbs) and age ≥ 7 years of age.
• Patients must reside within the United States or Canada.
• Refractory myositis, as defined by the intolerance to or an inadequate response to corticosteroids plus an adequate regimen of at least one other immunosuppressive agent, including azathioprine, methotrexate, IVIG, mycophenolate mofetil, cyclophosphamide, tacrolimus or cyclosporine A, or a biologic therapy. The definition of intolerance is: side effects that require discontinuation of the medication or an underlying condition that precludes the further use of the medication.
• At least moderately active disease as documented by:
• MD global VAS with a minimum value of 2.5 cm on a 10 cm scale AND
• At least 2 other abnormal core set measures listed below:
• Therapy with prednisone or another glucocorticoid is required, unless there is documented intolerance in the medical record or a medical condition that contraindicates further use of prednisone. The prednisone dose must be stable for at least 4 weeks prior to the screening visit.
• Background therapy with at least 1 non-corticosteroid immunosuppressive agent is required at a stable dose for at least 6 weeks prior to the screening visit unless there is documentation that the patient is intolerant, which is defined as side effects that require discontinuation of the medication(s) or an underlying condition that precludes the further use of the IS medication.
• If an immunosuppressive agent was discontinued prior to the screening visit then there must be a:
• 4 week washout for prednisone or methotrexate
• 8 week washout for any other IS agent
• For discontinuation of biologic therapies, a washout of 5 terminal half lives
• If on hydroxychloroquine or colchicine, the dose should be stable for 6 weeks prior to Visit 1.
• If on statin or fibric acid derivative agents, the dose should be stable for 6 weeks prior to Visit 1.
• Ability of patient or parent to complete self-report questionnaires.
• Men and women of reproductive potential must agree to use a reliable method of birth control during the 24 week duration of the trial described in the reproductive risks section of this protocol (section 4.3). They must also agree to use a reliable method of birth control for 100 days after the last dose of study drug is administered.
• Patients must agree to forgo immunization with a live vaccine during the course of the study or within 3 months after discontinuation.
• Patients must have a letter from the referring rheumatologist or specialist supervising the care of the JDM, agreeing to the patient's participation in the study and to continuing to provide care for the patient, including emergency care during the trial.

Core Set Measures:

• An MMT-8 score that is no greater than 125/150
• Patient/Parent Global VAS with a minimum value of 2.0 cm on a 10cm scale
• CHAQ/HAQ disability index with a minimum value of 0.25
• Elevation of at least one of the muscle enzymes [which includes creatine kinase (CK), aldolase, lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST)] at a minimum level of 1.3 x the upper limit of normal.
• Global extra-muscular disease activity score with a minimum value of 2.0 cm on a 10 cm VAS scale

Exclusion Criteria

• Drug-induced myositis (myositis in patients taking medications known to induce myositis-like syndromes, including, but not limited to, statin agents, fibric acid derivatives, and colchicine).
• Juvenile polymyositis; inclusion body myositis; cancer-associated myositis, defined as the diagnosis of myositis within 2 years of the diagnosis of cancer except basal or squamous cell skin cancer or carcinoma in situ of the cervix if at least 5 years since excision
• Myositis in overlap with another connective tissue d