Fludarabine is a chemotherapy drug used in the treatment of hematological malignancies (cancers of blood cells such as leukemias and lymphomas). It is a purine analog, which interferes with DNA synthesis. Fludarabine is highly effective in the treatment of chronic lymphocytic leukemia, producing higher response rates than alkylating agents such as chlorambucil alone. Fludarabine is used in various combinations with cyclophosphamide, mitoxantrone, dexamethasone and rituximab in the treatment of indolent non-Hodgkins lymphomas. As part of the FLAG regimen, fludarabine is used together with cytarabine and granulocyte colony-stimulating factor in the treatment of acute myeloid leukaemia. Because of its immunosuppressive effects, fludarabine is also used in some conditioning regimens prior to allogeneic stem cell transplant.