Myeloproliferative Overlap Neoplasms

This research is being done to evaluate effectiveness, safety, and tolerability of a study drug called momelotinib in participants with myelodysplastic/myeloproliferative neoplasms (MDS/MPNs), MDS/MPN-not otherwise specified (MDS/MPN-NOS), MDS/MPN with neutrophilia (MDS/MPN-N), also called as atypical chronic myeloid leukemia, or chronic neutrophilic leukemia. Momelotinib will be added to standard treatment which usually includes a hypomethylating agent like azacitidine. Treatment options for this diagnosis remain limited and investigators need better treatments to help control the disease, improve symptoms, and potentially help more patients become eligible for transplant. Participants for this study will be asked to take some screening tests which will include routine physical examination, blood tests, and imaging scans to determine eligibility for the study. Those who continue to qualify for this study will begin treatment and may be asked to remain on the study drug for up to 24 months, depending upon how they are responding to treatment. After the study drug is completed, patients will have one additional clinic visit to evaluate overall health and response to study drug. The study drug treatment on this study will include taking momelotinib by mouth in combination with azacitidine, which is given by injection for all patients for the first 5 days of each 28-day cycle. The most common side effect that may be related to participation in this study can include (i) infections which can present as fever, chills, cough, breathing problems, diarrhea, vomiting, pain or burning with urination; or (ii) low blood platelet count which can result in bruising or bleeding for longer than usual if the participant hurts themself.