Alternative Dosing Strategy of Ruxolitinib in Patients With Myelofibrosis

Inclusion Criteria: * Diagnosis of Primary Myelofibrosis (PMF), Post-Polycythemia Vera Myelofibrosis (PPV-MF), or Post-Essential Thrombocythemia Myelofibrosis (PET-MF) as confirmed by bone marrow biopsy. * Must score at least 2 points on the Dynamic International Prognostic Scoring System (DIPSS) scale for prognostic risk factors. * Peripheral blast count \< 5% at both Screening and Baseline hematology assessments. * Must discontinue all drugs used to treat underlying myelofibrosis (MF) disease no later than Day -1 (the day prior to starting ruxolitinib). * Must have hemoglobin value ≥ 6.5 g/dL and be willing to receive blood transfusions. * Platelet count ≥ 100\*10\^9/L. * Must have a palpable spleen. Exclusion Criteria: * Inadequate liver or bone marrow reserves, end stage renal disease on dialysis, clinically significant concurrent infections requiring therapy, or unstable cardiac function. * Invasive malignancies over the previous 5 years (except treated early stage carcinomas of the skin, completely resected intraepithelial carcinoma of the cervix, and completely resected papillary thyroid and follicular thyroid cancers). * Splenic irradiation within 6 months prior to receiving the first dose of study medication. * Life expectancy less than 6 months.