|Exclusion Criteria:||1) Primary central nervous system tumors|
2) Subjects with currently active malignancy (other than MF) or with a prior history of malignancy with the exception of: (i) adequately treated basal cell carcinoma of the skin, (ii) curatively treated in situ carcinoma of the cervix, (iii) other localized malignancy that has undergone potentially curative therapy with no evidence of disease recurrence equal to or greater than 3 years and that is deemed by the Investigator to be at low risk of recurrence;
3) Any condition requiring chronic use of moderate/high dose steroids (equivalent to equal to or greater than 30mg daily prednisolone). Inhalation or oral steroids for mild pulmonary disease (not leading to exclusion using the defined criteria) are permitted.
4) Any clinically significant acute or chronic medical illness as judged by the treating physician
5) Current or recent (within 3 months of study drug administration) gastrointestinal disease
6) Any gastrointestinal surgery that could impact upon the absorption of study drug as judged by the treating physician
7) Inability to tolerate oral medication as judged by the Investigator
8) Evidence of uncontrolled active infection
9) Failure to recover (to CTCAE V4.0 Grade 0-1) from acute, reversible effects of prior chemotherapy or therapies associated with transplantation
10) Presence of active graft vs. host disease
11) Subjects who have significant cardiac disease or who have a personal or family history of congenital long QT syndrome, or have a baseline equal to or greater than 450 msec QTcF abnormality unless attributable to a pre-existing Bundle Branch Block;
12) Subjects with a history of myocardial infarction or uncontrolled angina equal to or less than 6 months prior to the administration of study medication
13) Symptomatic congestive cardiac failure (New York Heart Association equal to or less than Class 3, an unstable cardiac arrhythmia requiring medication, presence of a significant atrial or ventricular tachyarrhythmia, use of a cardiac pacemaker, complete left bundle branch block, or left ventricular ejection fraction (LVEF) < institutional lower limit of normal as determined by a MUGA or ECHO
14) The MUGA or ECHO must have been performed within 3 months of Cycle 1 Day 1 and be within normal limits
15) Presence of any underlying medical condition that could adversely affect the ability of the subject to comply with study procedures and/or study therapy as judged by the treating physician
16) Uncontrolled or significant inflammatory bowel disease (IBD) or uncontrolled peptic ulcer disease
17) Uncontrolled disseminated intravascular coagulation (DIC)
18) History of significant upper or lower gastrointestinal bleeding equal to or less than 6 months prior to enrollment
19) Splenic irradiation equal to or less than 3 months prior to treatment with study drug
20) Any other sound medical, psychiatric and/or social reason as determined by the Investigator and/or MM.
21) Positive blood screen for hepatitis C antibody, hepatitis B surface antigen, or HIV-1, or HIV-2 antibodies
22) Abnormalities in serum electrolytes (sodium, potassium, calcium, phosphorus and magnesium) that are equal to or more than CTCAE v.4.0 Grade 2 and that are not correctable.
23) Abnormalities in serum electrolytes must be corrected to equal to or less than Grade 1 prior to study treatment
24) History of allergy to a JAK2 inhibitor
25) Prisoners or subjects who are involuntarily incarcerated
26) Subjects who are compulsorily detained for treatment of either a psychiatric or physical (e.g. infectious disease) illness.