PAT-1251 in Treating Patients With Primary Myelofibrosis, Post-Polycythemia Vera Myelofibrosis, or Post-Essential Thrombocytosis Myelofibrosis

PRIMARY OBJECTIVES: I. To determine the efficacy of LOXL2 inhibitor PAT-1251 (PAT-1251) as therapy for primary myelofibrosis (PMF), post-polycythemia vera (PV) myelofibrosis (MF), and post-essential thrombocytosis (ET) MF. II. To determine the objective response of PAT-1251 treatment which is defined as CR (complete remission) + PR (partial remission) + CI (clinical improvement) after three and six cycles of treatment. SECONDARY OBJECTIVES: I. To determine the safety of PAT-1251 as therapy for PMF, post-PV MF and post-ET MF. II. To determine time to response and response duration. III. To assess changes in symptom burden as assessed by Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF TSS). EXPLORATORY OBJECTIVES: I. To explore changes in bone marrow reticulin fibrosis, collagen, osteosclerosis (grading). II. To determine the percent target engagement based on a plasma target engagement assay after treatment with PAT-1251. OUTLINE: Patients receive LOXL2 inhibitor PAT-1251 orally (PO) twice daily (BID) on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up at 30 days.