Chokri Ben Lamine: Pacritinib Is a Key JAK Inhibitor for Cytopenic Myelofibrosis
Chokri Ben Lamine, Assistant Consultant at King Faisal Specialist Hospital and Research Center, shared a post on X:
“Pacritinib (Vonjo): A Key JAK Inhibitor for Cytopenic Myelofibrosis
Credits for sharing: Dr. Omar Albanyan
Pacritinib is uniquely developed for patients with Myelofibrosis and severe thrombocytopenia and/or anemia.
Why Pacritinib Is Different
Key Targets
- JAK2
- IRAK1
- ACVR1
- Minimal JAK1 inhibition (JAK1-sparing)
JAK1-sparing may help reduce myelosuppression while preserving immune signaling.
Benefits in Thrombocytopenic MF
Approved for symptomatic myelofibrosis with platelet counts less than 50 ×10⁹/L
- Effective spleen volume reduction
- Improvement in constitutional symptoms
- No dose reduction required in severe thrombocytopenia
Benefits in Anemic MF
ACVR1 inhibition may:
- Reduce hepcidin levels
- Increase iron availability
- Improve erythropoiesis
- Enhance transfusion independence
In vitro data suggest stronger ACVR1 inhibition compared with Momelotinib, although this does not confirm superior clinical efficacy.
Key Clinical Trials
- PERSIST-2
Demonstrated significant spleen and symptom responses in thrombocytopenic MF. - PACIFICA
Confirmed efficacy and manageable safety in patients with platelet counts <50 ×10⁹/L.
Ideal Patient Profile
- Platelet less than 50 ×10⁹/L
- Concurrent anemia or transfusion dependence
- Massive splenomegaly
- Significant constitutional symptoms
- Unsuitability for Ruxolitinib or Fedratinib because of thrombocytopenia
Common Adverse Events
- Diarrhea (most common; usually early and manageable)
- Nausea
- Anemia
- Thrombocytopenia
- Peripheral edema
Clinical Pearl
Pacritinib is often considered the preferred JAK inhibitor when severe thrombocytopenia and anemia coexist.
MCQ
Which feature most distinguishes Pacritinib from other JAK inhibitors?
- Intravenous administration
- Potent JAK1 inhibition
- Use in platelet counts <50 ×10⁹/L
- Causes profound myelosuppression
Answer: C. Use in platelet counts <50 ×10⁹/L
Key References
- NCCN Guidelines for Myeloproliferative Neoplasms
- Pacritinib (Vonjo) Prescribing Information
- PERSIST-2 Trial Publication
- PACIFICA Trial Update”
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