Clinical Decision-Making With PERSIST-2: Optimizing Therapy for Anemic Myelofibrosis Patients With Splenomegaly
Panelists discuss how Janus kinase (JAK) inhibitors like pacritinib offer crucial treatment options for myelofibrosis patients with severe thrombocytopenia (platelet counts <50,000 ), highlighting its advantages in providing significant spleen volume reduction (29% vs 3% in PERSIST-2 trial) while also offering unexpected anemia benefits possibly due to ACVR1 inhibition, with clinicians noting they set realistic expectations about platelet stabilization rather than improvement when counseling patients.
Summary of Pacritinib in Thrombocytopenic Myelofibrosis Patients
PERSIST-2 Trial: Key Findings
- Pivotal data: Led to FDA approval of pacritinib for MF patients with platelets <50,000/μL
- Spleen response: 29% SVR35 rate with pacritinib vs 3% in control arm (approximately 10-fold improvement)
- Comparative benefit: Control arm included patients on ruxolitinib, suggesting superior efficacy of pacritinib in thrombocytopenic patients
Anemia Benefits
- Unexpected finding: Anemia improvement was not initially anticipated but emerged as a significant benefit
- Potential mechanism: Likely related to ACVR1 inhibition, possibly combined with IRAK1 pathway effects
- Clinical observations: Some patients achieve transfusion independence
Clinical Application
- Patient counseling approach:
- Setting realistic expectations about transfusion burden reduction rather than promising complete independence
- Goals include: fewer transfusions, reduced infusion center visits, delayed iron overload
- While platelet count increases may occur, clinicians should set expectations for platelet stabilization rather than improvement
- Key advantage: Ability to deliver effective JAK2 inhibition for spleen and symptom benefits in severely thrombocytopenic patients while maintaining stable platelet counts
The panel emphasized that pacritinib offers a unique therapeutic option for the challenging bicytopenic myelofibrosis patient population (thrombocytopenia plus anemia), addressing a significant unmet need in myelofibrosis management.
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