Abatacept to Treat Steroid Refractory Chronic Graft Versus Host Disease (cGVHD)

The participant is invited to take part in this study because they have chronic Graft versus Host Disease (cGVHD) that is not responding to standard treatment with steroids. This research study is a way of gaining new knowledge about the treatment of patients with cGVHD. This research study is evaluating a drug called abatacept. Abatacept is a drug that alters and suppresses the immune system. Abatacept is approved by the Food and Drug Administration (FDA) for the treatment of moderate to severe active rheumatoid arthritis in adults and of severe juvenile idiopathic arthritis (JIA) in patients who have failed prior therapy with disease-modifying anti-rheumatic drugs (DMARDs). These are autoimmune conditions, ie caused by an overactive immune system that attacks normal tissues and organs. It is currently being tested in a variety of other autoimmune conditions. In this case it is considered experimental. cGVHD is caused by the donor cells attacking various organs of the recipient. The investigators try to minimize this immune attack by using corticosteroids such as prednisone. In severe cases prednisone is not sufficient and other immunosuppressive medications are used in addition in order to more efficiently control cGVHD and to limit the dose and consequently the multiple side-effects of corticosteroids. This study is being done to determine if the use of abatacept is safe in patients with cGVHD and if it can facilitate a better control of cGVHD. During this study the participants will be evaluated for side effects from the treatment with abatacept, and for response of the cGVHD to the treatment. There will be two groups of participants in the study. The first group will be treated at a relatively low dose of abatacept. If this is found to be safe then the second group will be treated at a higher dose. Three to four tablespoons of blood will be drawn at every 2 week visit in order to determine your blood counts, kidney and liver function. Some of the blood will