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.