A Phase 1/2a Dose Escalation Study of FF-10501-01 in Patients with Relapsed or Refractory Hematological Malignancies to determine the safety and tolerability. A total of 6 cohorts will be enrolled in Phase 1 to establish the MTD. A total of 20 subjects with MDS/CMML treated at the RP2D are planned, including MDS/CMML subjects treated at the RP2D in Phase 1.