Pacritinib After Ruxolitinib: Five-Case Saudi Series Reports Higher Blood Counts and Smaller Spleens

Five patients with advanced myelofibrosis in Saudi Arabia who had already been treated with the JAK inhibitor ruxolitinib were switched to pacritinib, and at their last available assessment all five showed numerically higher platelet counts and haemoglobin levels than at baseline, according to a case series from clinicians at King Abdulaziz Medical City in Riyadh and Jeddah, King Fahad Medical City, and King Saud Bin Abdulaziz University for Health Sciences.

The case series, published in Frontiers in Medicine in the hematology section, describes four patients with primary myelofibrosis and one with post-polycythaemia vera myelofibrosis. Every patient had prior exposure to ruxolitinib, which had been discontinued either because of disease progression or because of adverse events. At the moment pacritinib was started, the cohort carried clinically advanced disease features: three patients had severe thrombocytopenia, three had anaemia, all five had clinically significant splenomegaly, and two had marked leukocytosis.

Pacritinib was initiated at 200 mg orally twice daily in all five cases. One patient required a dose reduction to 100 mg twice daily after a marked decline in white blood cell count, with the absolute neutrophil count falling to 1.2 × 10⁹ per litre.

At the last available assessment, platelet counts and haemoglobin levels were numerically higher than baseline in all five patients, and palpable spleen length had decreased from baseline in every patient with available follow-up spleen assessment. In one patient who had been transfusion-dependent, the requirement for red blood cell transfusions fell from approximately twice weekly before pacritinib initiation to once every two weeks during follow-up.

The safety profile in the series was generally manageable. One patient had no documented adverse events at all. Among the remaining four patients, documented non-haematologic adverse events were grade 1 to 2 in severity and included fatigue, nausea with abdominal pain, and mild diarrhoea. The haematologic event that prompted intervention was the marked leukocyte decline that led to the dose reduction described above.

The authors are explicit that these observations are descriptive and do not establish treatment efficacy. With only five patients, the changes in blood counts and spleen size cannot be attributed to pacritinib with the confidence of a controlled trial. The series is best read as an early signal from routine clinical practice rather than a demonstration of benefit.

Even so, the report carries practical weight for the region. Treatment selection in myelofibrosis with cytopenic features remains challenging, particularly after prior ruxolitinib exposure. Pacritinib was developed specifically for patients with myelofibrosis and thrombocytopenia, yet regional real-world data on its use have remained limited. Documenting how pacritinib was initiated and continued in such patients in Saudi Arabian centres, with mostly grade 1 to 2 non-haematologic toxicity, provides local clinicians with a reference point drawn from their own practice setting.

The authors call for prospective regional studies with standardised response assessment, systematic safety collection and longer follow-up to determine whether the patterns seen in these five patients hold up under controlled observation. Until such studies are available, the series stands as a real-world snapshot of pacritinib use after ruxolitinib exposure in Saudi Arabia, describing a heavily pretreated cohort in whom blood counts trended upward, spleens shrank on palpation, and one transfusion-dependent patient’s transfusion interval roughly doubled.

For patients and families affected by myelofibrosis, the findings underscore both the promise and the limits of early real-world evidence: a drug designed for exactly this difficult population was associated with favourable trends in a small Saudi cohort, but definitive answers about efficacy will require the larger, prospective studies the authors now advocate.

Subject of Research: Real-world use of pacritinib after prior ruxolitinib exposure in five myelofibrosis patients in Saudi Arabia

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

Article References: Yahya, A., Motabi, I., Aljohani, M., Alghamdi, K. A., Rajkhan, W. A., Alsaeed, A. S., & Warsi, A. (2026). Case Report: Real-world experience with pacritinib after prior ruxolitinib exposure in myelofibrosis in Saudi Arabia: a report of five cases. Frontiers in Medicine, 13, Article 1950128. https://doi.org/10.3389/fmed.2026.1950128

Image Credits: AI Generated

DOI: 10.3389/fmed.2026.1950128

Keywords: myelofibrosis, pacritinib, ruxolitinib, JAK inhibitors, thrombocytopenia, case series, Saudi Arabia, hematology, splenomegaly, anaemia, real-world evidence, Case