Momelotinib in Transfusion-Dependent Adults With Primary Myelofibrosis (PMF) or Post-polycythemia Vera or Post-essential Thrombocythemia Myelofibrosis (Post-PV/ET MF)

Key Inclusion Criteria: * Diagnosis of PMF or Post PV/ET-MF * Requires myelofibrosis therapy, in the opinion of the investigator * High risk OR intermediate-2 risk defined by dynamic international prognostic scoring system (DIPSS) OR intermediate-1 risk defined by DIPSS and associated with symptomatic splenomegaly and/or hepatomegaly * Transfusion dependent at baseline, defined as ≥ 4 U red blood cell (RBC) transfusion in the 8 weeks prior to first dose of MMB * Acceptable organ function as evidenced by the following: * Platelet Count ≥ 50 x 10\^9/L * Aspartate aminotransferase (AST/SGOT) and alanine aminotransferase (ALT/SGPT) ≤ 3 x upper limit of normal (ULN) or AST or ALT ≤ 5 x ULN if liver is involved by disease process as judged by the investigator * Serum creatinine ≤ 2.0 mg/dL or calculated creatinine clearance of ≥ 60 mL/min * Direct bilirubin ≤ 2.0 x ULN * Life expectancy of \> 24 weeks * Males and females of childbearing potential who engage in heterosexual intercourse must agree to use protocol specified method(s) of contraception * Lactating females must agree to discontinue nursing before MMB administration * Able to understand and willing to sign the informed consent form Key Exclusion Criteria: * Prior splenectomy * Splenic irradiation within 3 months prior to the first dose of MMB * Prior treatment with MMB * Known positive status of human immunodeficiency virus (HIV) * Chronic active or acute viral hepatitis A, B, or C infection (testing required …