A Study of INCB050465 in Combination With Ruxolitinib in Subjects With Myelofibrosis

Inclusion Criteria: * Diagnosis of primary myelofibrosis, post-polycythemia vera myelofibrosis, or post-essential thrombocythemia myelofibrosis * Palpable spleen of \> 10 cm below the left subcostal margin on physical examination at the screening visit OR * Palpable splenomegaly of 5 to 10 cm below left subcostal margin on physical exam AND active symptoms of MF at the screening visit as demonstrated by presence of 1 symptom score ≥ 5 or 2 symptom scores ≥ 3 using the Screening Symptom Form * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 Exclusion Criteria: * Use of experimental drug therapy for myelofibrosis, or any other standard drug (eg, danazol, hydroxyurea, etc) with the exception of ruxolitinib within 6 months of starting study (combination) therapy and/or lack of recovery from all toxicities from previous therapy (except ruxolitinib) to Grade 1 or better * Inability to swallow food or any condition of the upper gastrointestinal tract that precludes administration of oral medications * Unwillingness to be transfused with blood components * Recent history of inadequate bone marrow reserve as demonstrated by the following: * Platelet count \< 50 × 10\^9/L in the 4 weeks before screening or platelet transfusion(s) within 8 weeks before screening * Absolute neutrophil count levels \< 0.5 × 10\^9/L in the 4 weeks before screening * Subjects with peripheral blood blast count of \> 10% at the screening or baseline hematology assessments …