Study of Pioglitazone in Sporadic Inclusion Body Myositis

Inclusion Criteria: * Age ≥ 50 years * Diagnosis of sporadic inclusion body myositis (sIBM) based on the sIBM Diagnostic Criteria established by the 2010 European Neuromuscular Center. * Must be able to ambulate at least 20 feet, with or without the use of an assistive device. Patients may not use another person, wall, or furniture for support. * Must be able to rise from a chair without support from another person or device. * Premenopausal women must have a negative serum pregnancy test prior to dosing with study medication. * Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Exclusion Criteria: * A history of diabetes mellitus, or prior or concurrent treatment with any diabetes therapy * Use of chronic immunosuppressive therapy including corticosteroids or intravenous immune globulin (IVIG) within the past 6 months. * Use of Vitamin E supplements within the past 3 months * Creatine kinase (CK) \> 15x the upper limit of normal * Any condition other than sIBM that causes significant muscle pain, muscle weakness, muscle atrophy, or joint pain. This includes but is not limited to such neurologic and neuromuscular diseases as polymyositis or dermatomyositis, myasthenia gravis, amyotrophic lateral sclerosis, stroke, multiple sclerosis, epilepsy, muscular dystrophy, fibromyalgia, rheumatoid arthritis, spinal cord injury or degenerative disease of the spine. Osteoarthritis is not exclusionary unless it limits the patient's ability to comply with study tasks. Patients with a history of a hip or vertebral fracture within the past year or surgical hip or knee replacement within the past six months will be excluded. * Patients receiving any medications or substances that are inhibitors or inducers of CYP2C8 are ineligible. These medications include but are not limited to Gemfibrozil, Rifampin, and warfarin. * Pregnant women * History of cancer less than five years prior, other than local basal or squamous cell cancer. * Patient has any medical condition or laboratory finding during screening, which, in the investigator's opinion may interfere with participation, confound the results, or pose any additional risk to the patient.