Case Report: Real-world experience with pacritinib after prior ruxolitinib exposure in myelofibrosis in Saudi Arabia: a report of five cases

Abstract

Background Treatment selection in myelofibrosis with cytopenic features remains challenging, particularly after prior ruxolitinib exposure. Pacritinib has been developed for patients with myelofibrosis and thrombocytopenia; however, real-world regional data remain limited. This case series describes pacritinib use in five patients with previously treated myelofibrosis in Saudi Arabia. Case presentation Four patients had primary myelofibrosis, and one had post-polycythaemia vera myelofibrosis. All patients had prior ruxolitinib exposure, which had been discontinued because of disease progression or adverse events. At pacritinib initiation, the cohort showed clinically advanced disease features, including severe thrombocytopenia in three patients, anaemia in three patients, clinically significant splenomegaly in all patients, and marked leukocytosis in two patients. Pacritinib was initiated at 200 mg orally twice daily in all cases; one patient required dose reduction to 100 mg twice daily after a marked decline in white blood cell count, with an absolute neutrophil count of 1.2 × 10⁹/L. At the last available assessment, platelet counts and haemoglobin levels were numerically higher than baseline in all five patients, and palpable spleen length decreased from baseline in all patients with available follow-up spleen assessment. In one transfusion-dependent patient, red blood cell transfusion requirement decreased from approximately twice weekly before pacritinib initiation to once every 2 weeks during follow-up. One patient had no documented adverse events. Among the remaining four patients, documented non-haematologic adverse events were grade 1–2 and included fatigue, nausea with abdominal pain, and mild diarrhoea; one patient also had a marked leukocyte decline that prompted dose reduction. Conclusion This case series describes pacritinib use after prior ruxolitinib exposure in selected patients with myelofibrosis, including patients with severe thrombocytopenia and concomitant anaemia. The observed changes in haematologic parameters and palpable spleen size are descriptive and do not establish treatment efficacy. Prospective regional studies with standardised response assessment, systematic safety collection, and longer follow-up are needed.

The authors' abstract, as published at the source. Frontiers in Medicine, 2026 · DOI ↗