Observational study aimed at evaluating the use of momelotinib in patients with primary or post polycythemia vera (PV) or post essential thrombocythemia myelofibrosis (post-ET MF) in a real-world setting.

This is a multicenter prospective and retrospective observational clinical study in adult patients with primary or post polycythemia vera (PV) or post essential thrombocythemia myelofibrosis (post-ET MF) being treated with momelotinib in a real-world setting. The aim of the study is to evaluate the efficacy of momelotinib in terms of splenic response. All patients are managed according to the clinical practice of the participating Center.

Inclusion Criteria:

1. Patients aged 18 years or older.
2. Patients diagnosed with primary or post-polycythemia vera/post-essential thrombocythemia myelofibrosis start treatment with MMB according to clinical practice from AIFA authorization.
3. Patients with palpable splenomegaly at baseline of momelotinib treatment.
4. Informed consent signed, if applicable.

Exclusion Criteria:

1. Diagnosis of MPN, unclassifiable, myelodysplastic/myeloproliferative neoplasms, myelodysplastic syndromes, essential thrombocythemia, polycythemia vera.
2. Accelerated/blast phase of MF.
3. Patients with platelets <20 x10(9)/L at baseline of MMB treatment.
4. Patients JAK inhibitors-exposed for other diseases apart from MF.

Patients treated for primary myelofibrosis or post polycythemia vera or post essential thrombocythemia at the Italian hemathology units with access to momelotinib. All participating centers belong to the GIMEMA network.