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
• Subjects who are not willing to receive red blood cell (RBC) transfusions to treat low hemoglobin levels
• Inadequate liver function at screening as demonstrated by the following:
• Direct bilirubin ≥ 2.0 × the upper limit of laboratory normal (ULN). (NOTE: direct bilirubin will only be determined if total bilirubin is ≥ 2.0 × ULN)
• alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 2.5 × ULN
• Inadequate renal function at screening as demonstrated by creatinine clearance < 50 mL/min or glomerular filtration rate < 50 mL/min/1.73 m^2