R&D

About Essential Thrombocythemia

The myeloproliferative disease, essential thrombocythemia (ET, also known as essential thrombocytosis), is a chronic blood disorder characterized by increased numbers of platelets in the blood. These platelets may have abnormal function, which can lead to an increased risk of thrombotic or hemorrhagic complications. Patients with ET may also develop myelofibrosis or acute myeloid leukemia.

The precise cause of ET is not known, though approximately half of patients have mutations in the genes for Janus kinase 2 (JAK2) or, less frequently, myeloproliferative leukemia (MPL). These gene mutations result in stable activation of the JAK-STAT signaling pathway and lead to megakaryocytic hyperplasia and thrombocytosis.

In the United States, there are approximately 7,200 new cases of ET annually. Life expectancy may be normal in the majority of patients with ET in the first decade after diagnosis, but subsequent survival is reduced approximately two-fold compared with the general population. Currently used treatments (such as hydroxyurea, anagrelide or interferon-alpha) can be effective in reducing platelet counts in patients with ET, but do not affect the biology or eliminate the disease. Moreover, clinical resistance or intolerance to these standard agents occurs in a proportion of patients.