Personalized JAK Inhibitor Selection in Myelofibrosis: Clinical Characteristics, Molecular Profiles, and Treatment Sequencing

Summary of JAK Inhibitor Selection and Transplant Considerations in Myelofibrosis

JAK Inhibitor Landscape

• All 4 JAK inhibitors (ruxolitinib, fedratinib, pacritinib, momelotinib) are approved in a line-agnostic fashion
• Specific approval nuances exist:
• Pacritinib: Approved for patients with platelets <50,000/μL
• Momelotinib: Approved for intermediate/high-risk myelofibrosis with anemia (EU label specifies hemoglobin <10 g/dL)
• Important safety considerations include drug interactions and unique concerns (eg, fedratinib’s black box warning for Wernicke encephalopathy)

Treatment Selection Factors

1. Molecular testing is now standard of care:

• Next-generation sequencing panels (typically 50+ genes) help guide risk stratification
• Integration with clinical factors through tools like MIPS is essential
• Results provide both prognostic and transplant selection guidance

1. Cytopenia vs proliferative phenotype influences JAK inhibitor selection:

• Low platelets: Pacritinib may be preferred
• Anemia: JAK inhibitors with ACVR1 inhibition (momelotinib, pacritinib) may be preferred
• Thrombocytosis: Ruxolitinib may help control elevated platelets

1. Symptom control considerations:

• All JAK inhibitors provide constitutional symptom relief
• Ruxolitinib noted as particularly effective for symptom management
• Symptom relief typically occurs quickly after initiating therapy
• Spleen response varies between agents

Transplant Evaluation and Timing

• Transplant decisions remain challenging due to:
• Survival benefit curves crossing only years after transplant
• Significant upfront morbidity
• General approach to transplant consideration:
• Most patients under age 60 should at least consult with transplant team
• Higher-risk myelofibrosis patients with low comorbidity burden are optimal candidates
• Initial human leukocyte antigen typing and donor availability assessment is low risk
• Patient fitness, age, and motivation are important considerations
• Transplant remains the only curative option

The panel emphasized the importance of standardized risk assessment incorporating molecular data and the need to weigh patient-specific factors when selecting between JAK inhibitors.