Ruxolitinib (INCB018424) in Subjects With Primary Myelofibrosis, Post Essential Thrombocythemia-myelofibrosis and Post Polycythemia Vera-myelofibrosis

Inclusion Criteria:

- Diagnosed with PMF, PPV-MF or PET-MF as confirmed by bone marrow biopsy

- Discontinuation of all drugs used to treat underlying MF disease at least 7 days prior
to baseline visit

- INR < 1.5 or PTT value < 1.5 x upper limit of normal (ULN) at study entry

- Hemoglobin level at least 6.5 g/dL at Screening visit

- Willingness to be transfused to treat low hemoglobin levels

Exclusion Criteria:

- Females who are pregnant, unable to comply with birth control use to avoid becoming
pregnant or breastfeeding

- Males who cannot comply with birth control use to avoid fathering a child

- Platelet count < 50 x10^9/L or absolute neutrophil count (ANC) < 1 x10^9/L at the
Screening visit

- Inadequate liver or renal function; Intracranial bleeds or invasive malignancy over
the previous 2 years - international normalized ratio (INR) laboratory values cannot
be > 1.5 x upper limit of normal at study entry.