RecruitingDrug trialPhase I/II Clinical Trial of Axatilimab, a CSF1R Monoclonal Antibody, in Combination With Ruxolitinib as Therapy for Patients With Myelofibrosis (MF) and Chronic Myelomonocytic Leukemia (CMML)* To find the recommended dose of axatilimab given alone and in combination with ruxolitinib in patients with MF and CMML. * To learn if axatilimab given in combination with ruxolitinib can help to control MF and CMML.