Inclusion Criteria

Inclusion criteria:

- Diagnosis of primary or post-polycythemia vera or post-essential thrombocythemia
myelofibrosis (Post-ET MF) according to the 2008 World Health Organization (WHO)
criteria

- Myelofibrosis classified as high-risk or intermediate-risk level 2, as defined by
International Working Group - Myelofibrosis Research and Treatment (IWG-MRT)

- Enlarged spleen, palpable at least 5 cm below costal margin

- At least 18 years of age.

- Eastern Collaborative Oncology Group (ECOG) performance status (PS) of 0, 1, or 2 at
study entry.

- Adequate organ function

- Absence of active malignancy other than MF, except adequately treated basal cell
carcinoma and squamous cell carcinoma of the skin, cervical carcinoma in situ or
other malignancies that have been stable and off therapy for 5 years.

- Written informed consent to participate.

- Willing to comply with scheduled visits, treatment plans, laboratory assessments, and
other study-related procedures.

Exclusion criteria:

- Splenectomy.

- Any chemotherapy (eg, hydroxyurea), immunomodulatory drug therapy (eg, thalidomide,
interferon-alpha), immunosuppressive therapy, corticosteroids >10 mg/day prednisone
or equivalent, or growth factor treatment (eg, erythropoietin), hormones (eg,
androgens, danazol) within 14 days prior to initiation of study drug; darbepoetin use
within 28 days prior to initiation of study drug.

- Major surgery therapy within 28 days or radiation within 6 months prior to initiation
of study drug.

- Concomitant treatment with or use of pharmaceutical or herbal agents known to be at
least moderate inhibitors or inducers Cytochrome P450 3A4 (CYP3A4), unless approved
by the sponsor.

- Active acute infection requiring antibiotics.

- Uncontrolled congestive heart failure (New York Heart Association Classification 3 or
4), angina, myocardial infarction, cerebrovascular accident, coronary/peripheral
artery bypass graft surgery, transient ischemic attack, or pulmonary embolism within
3 months prior to initiation of study drug.

- Participation in any study of an investigational agent (drug, biologic, device)
within 30 days, unless during nontreatment phase.

- Prior treatment with a Janus kinase 2 (JAK 2) Inhibitor,

- Contraindications for undergoing Magnetic resonance imaging (MRI) (eg. metal
implants).

- Pregnant or lactating female.

- Women of childbearing potential, unless using effective contraception while on study
drug.

- Men who partner with a woman of childbearing potential, unless they agree to use
effective contraception while on study drug.

- Known human immunodeficiency virus or acquired immunodeficiency syndrome-related
illness.

- Clinically active hepatitis B or C.

- Any severe acute or chronic medical, neurological, or psychiatric condition or
laboratory abnormality that may increase the risk associated with study participation
or study drug administration, may interfere with the informed consent process and/or
with compliance with the requirements of the study, or may interfere with
interpretation of study results and, in the Investigator's opinion, would make the
patient inappropriate for entry into this study.

- Unable to swallow capsules

- Presence of any gastric or other disorder that would inhibit absorption of oral
medication.

The above information is not intended to contain all considerations relevant to a
patient's potential participation in a clinical trial.