Trial to Evaluate the Efficacy and Safety of Abatacept in Combination With Standard Therapy Compared to Standard Therapy Alone in Improving Disease Activity in Adults With Active Idiopathic Inflammatory Myopathy

For more information regarding Bristol-Myers Squibb Clinical Trial participation, please visit www.BMSStudyConnect.com

Inclusion Criteria:

• Diagnosis of IIM based on the Bohan and Peter classification criteria:

  i) Subjects with dermatomyositis (DM) must also have a confirmed myositis-associated rash (Gottron's papules or a heliotrope rash preferably confirmed by skin biopsy) or a prior muscle biopsy diagnostic for IIM or a positive test for at least one identified myositis-associated autoantibody; ii) Subjects with IIM other than DM (PM, autoimmune necrotizing myopathy, myositis associated with other autoimmune connective diseases (overlap myositis), or juvenile myositis with age ≥ 18 years) must also have a prior muscle biopsy diagnostic for IIM or a positive test for at least one identified myositis-associated autoantibody

• Demonstrable muscle weakness measured by the MMT-8 of ≤ 135 units and any 3 of the following: i) MMT-8 ≤ 125 units; ii) Physician's global assessment (PGA) visual analog scale (VAS) ≥2 cm; iii) Subject's global assessment (SGA) VAS ≥2 cm; iv) HAQ-DI ≥ 0.5; v) One or more muscle enzyme (CK, aldolase, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), ALT) ≥ 1.3 times upper limit of normal (ULN); vi) MDAAT Extramuscular Global Activity VAS ≥2 cm
• Demonstration of currently active IIM will be determined by an adjudication committee unless the subject has any one of the following: i) an active myositis-associated rash (Gottron's papules or heliotrope rash), or ii) a recent (within 1 month prior to signing informed consent) biopsy, magnetic resonance imaging (MRI), or electromyogram (EMG) demonstrating active disease, or iii) an elevated CK > 5 times the upper limit of normal
• Active disease despite prior treatment with corticosteroids, immunosuppressants, or biologics as determined by the investigator
• The subject must be on background standard treatment for IIM. The standard treatments that are allowed as background treatment for IIM includes: i) Corticosteroids alone, or ii) One of the following immunosuppressants: methotrexate, azathioprine, mycophenolate mofetil, tacrolimus, or cyclosporine (combinations of these treatments are not allowed), or iii) A combination of corticosteroids and one of the above immunosuppressants. The subject must have been on the same medication(s) for IIM for 12 weeks prior to randomization and the dose must have been stable for 4 weeks prior to randomization.

Exclusion Criteria:

• Subjects with Inclusion Body Myositis (IBM), or myositis other than IIM, eg, drug-induced myositis and PM associated with HIV
• Subjects treated with penicillamine or zidovudine in the past 3 months
• Subjects treated with rituximab in the past year or any other biologic treatment or Intravenous Immunoglobulin (IVIG) in the past 6 months.
• Subjects with uncontrolled or rapidly progressive interstitial lung disease
• Subjects with severe muscle damage (Myositis Damage Index > 7/10), permanent weakness due to a non-IIM cause, or myositis with cardiac involvement
• Subjects at risk for tuberculosis
• Subjects with recent acute infection requiring antibiotics
• Subjects with history of chronic or recurrent bacterial, viral or systemic fungal infections
• Subjects who have a present malignancy or have had a previous malignancy within the last 5 years prior to screening (except for a documented history of cured non-metastatic squamous or basal cell skin carcinoma or cervical carcinoma in situ).

Other protocol defined inclusion/exclusion criteria could apply