Anagrelide for Control of Thrombocytosis Due to Myeloproliferative Disorders

Myeloproliferative disorders are characterized by overproduction of one or more blood lineages. The clinical course of the Philadelphia-negative myeloproliferative disorders, particularly essential thrombocythemia and polycythemia vera, are characterized by vascular symptoms and in the long-term, transformation to myelofibrosis and leukemia may occur. Control of myeloproliferation has traditionally been achieved using cytotoxic agents but many of these have a documented ability to increase the risk of leukemia. Anagrelide, initially developed as an antiaggregant, is an attractive alternative to these agents as it appears to be relatively selective in reducing the platelet count and is unlikely to be leukemogenic. This article reviews clinical studies in these patients and discusses the future scope for anagrelide.