Momelotinib in Combination With Hypomethylating Agent for Chronic Phase Myelodysplastic Syndromes/Myeloproliferative Overlap Neoplasms and Chronic Neutrophilic Leukemia

This is an open-label study of MMB-HMA in MDS/MPN and CNL that will enroll up to 18 patients. Momelotinib will be administered using modified 3+3 dose escalation design followed by expansion. The first three patients will be treated at 150mg daily and if DLT criteria are not met, the remaining patients will be treated at 200mg daily to a total of 18 evaluable patients (all in combination with azacitidine). If DLTs are met within the dose escalation phase (first three patients), then the patients will be treated at 150mg daily (in combination with azacitidine) Key Eligibility Criteria: 1. Patients with a WHO diagnosis of chronic myelomonocytic leukemia (CMML), MDS/MPN-not otherwise specified (MDS/MPN-NOS), MDS/MPN with neutrophilia (MDS/MPN-N), CNL. 2. Age greater than or equal to 18 years 3. Blood counts with platelets greater than 25,000/microL, ANC greater than or equal to 0.75 x 10\^9/L (without transfusion or growth factor support) 4. Baseline splenomegaly with greater than or equal to 5 cm below costal margin or greater than or equal to 450 cm3 on imaging (ultrasound, CT or MRI)