This study aims to evaluate real-world effectiveness of pacritinib through a site-based retrospective chart review of medical records of adult patients with myelofibrosis treated with pacritinib in routine clinical settings with platelet count ≥50 x 10^9/L at the time of treatment initiation. Treatment effectiveness will be based on spleen size and symptom burden, hematological parameters, progression to leukemia, survival, pacritinib treatment patterns, patient demographic and clinical characteristics, and allogenic-hematopoietic stem cell transplant (allo-HSCT)-related outcomes. Data will be collected from medical charts of patients with pacritinib initiation between 01 June 2022 and 31 December 2025 with an end of study observation on 30 June 2026.