In the UK, ruxolitinib, a JAK 1 and 2 inhibitor, is currently licensed for the treatment of disease-related splenomegaly or symptoms in adult patients with primary myelofibrosis, post polycythaemia vera myelofibrosis or post essential thrombocythaemia myelofibrosis. In January 2015, it was granted an EU positive opinion for a licence extension for treatment of adults with polycythaemia vera who are resistant to or intolerant of hydroxyurea.