A Clinical Study of Ruxolitinib in Patients With Primary Myelofibrosis (PM), Post-polycythemia Vera (PV) Myelofibrosis, or Post-essential Thrombocythemia (ET) Myelofibrosis

Inclusion Criteria:

1. ≥18 years of age

2. Diagnosis of PMF, PPV-MF, or PET-MF, regardless of JAK2 mutational status. Thediagnostic of PMF will be according to the World Health Organization (WHO) criteria (Thiele et al., 2008) and PPV-MF and PET-MF according to the International WorkingGroup for Myelofibrosis Research and Treatment (IWG-MRT) criteria (Barosi et al., 2008).

3. At least one risk factors provided in the definition of IWG-MRT (Cervantes et al., 2009; classified as intermediate risk-1, intermediate risk-2, or high risk)

4. Patients with intermediate risk-1 (patients who have only one of the IMG-MRT riskfactors indicated above ) must have palpable splenomegaly with a length of ≥5 cm fromthe costal margin to the point of the greatest spleen protrusion.

5. Proportion of blasts in peripheral blood <10%

6. ECOG performance status of 0 to 2

7. The following values for bone marrow function prior to treatment:

8. Absolute neutrophil count ≥1,000/μL, and

9. Platelet count ≥50,000/μL without administration of a growth factor,thrombopoietin, or platelet transfusion

10. Stem cell transplantation is not a treatment option at present because it is notindicated or because there are no suitable donors.

11. All drugs used to treat MF were discontinued at least 28 days before treatmentinitiation.

12. Informed consent form should be signed before any screening procedures is performed

Exclusion Criteria:

1. Hepatic or renal impairment as indicated by the following:

• Direct bilirubin ≥2-fold than the upper limit of normal (ULN)

• Alanine aminotransferase (ALT) >2.5-fold ULN

• Creatinine >2.0 mg/dL

2. Clinically significant infection by bacteria, fungus, mycobacteria, parasite, or virus (screening and enrollment postponed until completion of antibiotic treatment inpatients with an acute bacterial infection that requires antibiotic use)

3. Active hepatitis A, B, or C or HIV infection defined by a positive IgM-HA Ab test [hepatitis A virus antibody (immunoglobulin M [IgM])], HBs Ag test (hepatitis Bsurface antigen), HCV Ab test (hepatitis C virus antibody), or HIV Ab (humanimmunodeficiency virus antibody) at screening.

4. History of malignancy within the previous 3 years, except for early-stage squamouscell carcinoma and basal cell carcinoma.

5. History of serious congenital or acquired hemorrhagic disease

6. Previous platelet count <25,000/μL or absolute neutrophil count <500/μL, except forpatients currently undergoing treatment for a myeloproliferative neoplasm or cytotoxictherapy for any other reason.

7. Splenic irradiation within 12 months before screening

8. Administration of hematopoietic growth factor receptor agonists (erythropoietin,granulocyte colony stimulating factor, romiplostim, eltrombopag) within 14 days beforescreening or 28 days before treatment initiation.

9. Currently receiving another investigational drug, or received another investigationaldrug within 30 days before the start of treatment.

10. History of myocardial infarction or acute coronary syndrome within 6 months beforescreening

11. Poorly controlled or unstable angina at present

12. Rapid or paroxysmal atrial fibrillation at present

13. Active alcohol or drug addiction that could hinder the patient's ability to complywith the study's requirements

14. Pregnant or currently breastfeeding woman

15. Women of childbearing potential or men with reproductive ability who are unwilling totake appropriate contraception measures

16. Patient with any concurrent condition that, in the Investigator's opinion, wouldjeopardize the safety of the patient or compliance with the protocol

17. History of hypersensitivity to the study drug or a drug with a similar chemicalstructure