Inclusion Criteria:

• Patients with Chronic Idiopathic Myelofibrosis (CIMF) requiring therapy, including those 1) previously treated by CIMF-directed therapy and relapsed, intolerant, or refractory to therapy; or 2) if newly diagnosed then with intermediate or high risk according to Lille scoring system (adverse prognostic factors are: Hb < 10 g/dl, WBC < 4 or > 30 x 10^9/L; risk group: 0 = low, 1 = intermediate, 2 = high), or with symptomatic spleen that is >/= 10cm below costal margin. However, patients with asymptomatic intermediate risk disease are not eligible.
• JAK2 mutation positive test
• Age of at least 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2
• Adequate liver and renal function: total bilirubin </=2.0 mg/dL, alanine aminotransferase (ALT or SGPT) </=2.0 x institutional upper limit of normal (ULN), and creatinine </=2.0 mg/dl
• Patients must be at least 2 weeks from prior chemotherapy, biological therapy, radiation therapy, major surgery, or other investigational anticancer therapy that is considered MF-directed, and have recovered from prior toxicities to Grade 0-1. Concurrent therapy with supportive care medications (hydroxyurea, anagrelide) is allowed during the study.
• All men of reproductive potential and women of child-bearing potential (WOCBP) must agree to practice effective contraception (iud, birth control pill, latex condoms, diaphragm) during the entire study period and for one month after the study ends, unless documentation of infertility exists. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. WOCBP are women who are not menopausal for 12 months or no previous surgical sterilization."
• Ability to understand and willingness to sign the informed consent form
• Not willing to undergo, not a candidate for, or not having a donor for, a bone marrow transplant

Exclusion Criteria:

• Pregnant or nursing women, due to the unknown effects of therapy on the developing fetus or newborn infant.
• Patients diagnosed with another malignancy - unless following curative intent therapy the patient has been disease free for at least 3 years. Patients with early stage squamous cell carcinoma of the skin, basal cell carcinoma of the skin, or cervical intraepithelial neoplasia (CIN) are eligible for this study
• Any condition, including serious medical condition, laboratory abnormality, or psychiatric illness, which places the subject at unacceptable risk as judged by the Principal Investigator, if he/she was to participate in the study
• Known positive for Human immunodeficiency virus (HIV) or infectious hepatitis, type A, B or C
• Presence of any gastrointestinal condition or concomitant medication use (e.g. coumadin) that would render a patient at high risk for gastrointestinal bleeding as judged by treating physician
• History of any upper or lower gastrointestinal bleeding in the 6 months prior to enrollment
• Elevated international normalized ratio (INR) or Partial thromboplastin time (PTT)