|Exclusion Criteria:||1) Subjects with a life expectancy of less than 6 months.|
2) Subjects in whom MF disease is well controlled with current therapy.
3) Females who are pregnant or are currently breastfeeding.
4) Subjects of childbearing potential who are unwilling to take appropriate precautions (from Screening through Follow-up) to avoid becoming pregnant or fathering a child. • Females of non-childbearing potential are defined as women who (a) are equal to or greater than 55 years of age with history of amenorrhea for 1 year, OR (b) are surgically sterile for at least 3 months. • For females of childbearing potential, or for males, appropriate precautions are those that are at least 99% effective in preventing the occurrence of pregnancy. These methods should be communicated to the subjects and their understanding confirmed
5) Subjects with inadequate bone marrow reserve as demonstrated by: a. Absolute neutrophil count (ANC) that is < 1x 10^9/L at the Screening visit. b. Confirmed platelet count that is < 50 x 10^9/L without the assistance of growth factors, thrombopoietic factors or platelet transfusions at the Screening visit. Subjects must not have received growth factors for at least one month (30 days) prior to receiving the first dose of study drug. c. Subjects with known history of platelet counts < 25,000/µL, in the absence of cytoreductive therapy. d. Subjects who have received platelet transfusion(s) or ANC levels < 500/µL in the month (30 days) prior to Screening.
6) Subjects with platelet count >100 x10^9/L at BOTH the Screening and Baseline visits.
7) Subjects with recent (within 12 months of Screening) major bleed requiring transfusion(s) or resulting in a decrease in hemoglobin by 3 g/dL or more.
8) Subjects with inadequate coagulation parameters as follows: International Normalized Ratio (INR) > 1.5 or PTT > 1.5 x ULN.
9) Subjects with known history of esophageal or gastric varices, or any intracranial bleeding. Subjects with a history of an incidental finding of small varices (<5 mm) may be permitted in the study with sponsor approval.
10) Subjects with inadequate liver or renal function at Screening and Baseline visits as demonstrated by: a. Direct bilirubin equal to or more than 2 X upper limit of laboratory normal (ULN). (NOTE: direct bilirubin will only be determined if total bilirubin is equal to or more than 2.0 x ULN). b. Alanine aminotransferase (ALT) > 2.5x ULN. c. Creatinine > 2.0 mg/dL.
11) Subjects with clinically meaningful, active bacterial, fungal, parasitic or viral infection which require therapy, or who are HIV positive
12) Subjects with acute bacterial infections requiring antibiotic use should delay screening/enrollment until the course of antibiotic therapy has been completed and the event is considered resolved.
13) Subjects who are currently receiving therapy with a moderate or potent CYP 3A4 inhibitor. Subjects may enter Screening phase when therapy with the moderate or potent CYP 3A4 inhibitor is completed, and use of moderate inhibitors during the study will be permitted.
14) Subjects with an invasive malignancy over the previous 2 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.
15) Subjects with recent severe or unstable cardiac disease.
16) Subjects who have had splenic irradiation within 6 months prior to Day 1.
17) Subjects who have previously received treatment with a JAK inhibitor.
18) Subjects being treated concurrently with any prohibited medications
19) Subjects with active alcohol or drug addiction that would interfere with their ability to comply with the study requirements.
20) Subjects with any concurrent condition that, in the investigator's opinion, would jeopardize the safety of the subject or compliance with the protocol.
21) Subjects who are unable to complete the daily symptom diary, which is available in English and Spanish versions.