To Assess the Safety and Tolerability of INCB000928 in Participants With Myelodysplastic Syndromes or Multiple Myeloma

Inclusion Criteria

• Agreement to avoid pregnancy or fathering children.
• Participants who are transfusion-dependent or present with symptomatic anemia For MDS participants:
• Ineligible to receive or have not responded to available therapies for anemia such as ESAs or lenalidomide.
• Not requiring cytoreductive therapy other than hydroxyurea.
• BM and peripheral blood myeloblast count < 10%.
• Histologically confirmed diagnosis of the MDS, CMML and unclassifiable MDS/MPN overlap syndromes. For MM participants:
• Histologically confirmed diagnosis of MM.
• After failure of available standard treatments such as alkylating agents, glucocorticoids, immunomodulatory drugs (lenalidomide,pomalidomide, or thalidomide), proteasome inhibitors (bortezomib or carfilzomib), and daratumumab.

Exclusion Criteria

• Any prior allogeneic stem cell transplantation or a candidate for such transplantation.
• Any major surgery within 28 days before the first dose of study drug.
• Any prior chemotherapy, immunomodulatory drug therapy, immunosuppressive therapy, biological therapy, endocrine therapy, targeted therapy, or antibody or hypomethylating agent to treat the participant's disease within 5 half-lives or 28 days (whichever is shorter) before the first dose of study drug.
• Undergoing treatment with another investigational medication or having been treated with an investigational medication within 28 days before the first dose of study drug. -Undergoing treatment with ESAs, granulocyte colony-stimulating factor or granulocyte/macrophage colony-stimulating factor, romiplostin, or eltrombopag at any time within 28 days before the first dose of study drug.
• Undergoing treatment with a strong or potent inhibitor or inducer of CYP3A4/5 within 28 days or 5 half-lives (whichever is longer) before the first dose of study drug or expected to receive such treatment during the study.
• History of clinically significant or uncontrolled cardiac disease.
• History or presence of an abnormal ECG that, in the investigator's opinion, is clinically Meaningful.
• Presence of chronic or current active infectious disease requiring systemic antibiotic, antifungal, or antiviral treatment.
• Diagnosis of chronic liver disease.