A Phase II Study of Antithymocyte Globulin (ATG) and Cyclosporine to Treat the Cytopenia of Myelodysplastic Syndrome (MDS)

Participants will be admitted to the NIH Clinical Center for the first 10 to 14 days of treatment and will then continue therapy on an outpatient basis. They will undergo the following tests and procedures:

• Placement of central line-An intravenous (IV) catheter (flexible tube inserted into a vein) is placed in a large vein of the neck, chest or arm. Medicines are delivered through this line and blood samples are drawn from it.
• ATG skin testing- ATG is injected under the skin to check for sensitization to horse serum, from which the drug is derived.
• ATG treatment-Four doses of ATG are given through the IV line on each of 4 consecutive days. Prednisone is taken by mouth beginning the first day of ATG therapy and continuing for a total of 17 days. This drug is given to reduce the side effects of ATG, such as fever, skin rash and chills.
• Cyclosporine treatment- Cyclosporine capsules are taken by mouth twice a day for at least 6 months.

During hospitalization, blood will be drawn daily for blood counts and other tests. Upon the patient's discharge after 10 days, the referring physician will do blood tests weekly during the first month of treatment and then every 2 weeks for the rest of the time the patient is taking cyclosporine. Dosages of this drug may be adjusted depending on the test results. Patients will be evaluated at the NIH Clinical Center at 3-month intervals for the first year, then every 6 months for the next 3 years and then at yearly intervals. A blood sample will be drawn at each visit. Bone marrow biopsies will be done at 6-month intervals for the first 3 years after treatment.

A growing body of laboratory and clinical evidence suggests that the cytopenia of MDS is at least partly a result of cytotoxic T cell activity. Treatments to abrogate T cell activity such as anti-thymocyte globulin alone and cyclosporine alone have demonstrated varying degrees of success in alleviating the cytopenia of MDS. A response to such therapy in MDS is associated with improved survival. Experience with aplastic anemia suggests that the combination of these two agents should be more effective in suppressing cytotoxic T cell activity and alleviating cytopenia. This protocol proposes using the combination of antithymocyte globulin (ATG) and cyclosporine (CSA) to treat the cytopenia of MDS, in an effort to improve the response rate to immunosuppressive therapy in this disease.