 Male or female individuals, aged 18 years or older who have been diagnosed with Myelofibrosis either Primary Myelofibrosis PMF or Post-Polycythemia Vera Myelofibrosis PPV-MF or Post-Essential Thrombocythemia Myelofibrosis PET-MF, were observed to have palpable splenomegaly, were not candidates for stem cell transplantation, and had 2 or more risk factors, thereby placing them in an intermediate-2 or high-risk prognostic group may enroll. Subjects were permitted to have received any or no prior therapy for MF. This is an open label, randomized study comparing the efficacy and safety of INCB018424 tablets versus best-available therapy, as selected by the investigator. The purpose is to compare the efficacy, safety and tolerability of INCB018424 given twice daily to the best-available therapy, in subjects with primary myelofibrosis PMF, post polycythemia vera myelofibrosis PPV-MF or post essential thrombocythemia myelofibrosis PET-MF. 