Abstract
The JAK1 and JAK2 inhibitor ruxolitinib has approved indications in myelofibrosis, a BCR-AB1-negative myeloproliferative neoplasm associated with progressive bone marrow fibrosis and shortened survival. In Phase III clinical studies, ruxolitinib provided rapid and durable improvement of myelofibrosis-related splenomegaly and symptoms irrespective of mutation status, and was associated with a survival advantage compared with placebo or best available therapy. Because of dose-dependent cytopenias, blood count monitoring and dose titration are important to optimize therapy. Specific precautions apply to the treatment of patients with or at risk of serious infections. Discontinuation of ruxolitinib generally leads to symptom return within 1 week. Ruxolitinib also is approved for treatment of patients with polycythemia vera who have had an inadequate response to or are intolerant of hydroxyurea.