 1. Diagnosis of myelofibrosis, either PMF, post-PV or post-ET MF with IPSS score of 2 intermediate risk or 3 high risk plus at least one of the following: Symptomatic spenomegaly 10cm BCM Hemoglobin 10 or red cell transfusion dependent. The presence of a JAK2 V617F mutation is not required for study entry 2. Patients must meet the following laboratory criteria: 