This study investigates the safety and early effects of an investigational medication in people with certain types of blood cancers, specifically chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia (AML). CMML is a type of cancer that affects blood-forming cells in the bone marrow, while AML is a cancer of the blood and bone marrow with excess immature white blood cells. The study is being conducted to see how well the investigational medication works in people whose cancer has not responded to other treatments.

Participants in the study will receive the investigational medication as an intravenous (IV) infusion every 21 days. The study is divided into two parts: first, testing different doses to find a safe level, and then expanding to more participants at the chosen dose. The study will monitor participants closely to ensure their safety and to collect data on how their cancer responds to the treatment.

• Who can participate: Adults with refractory or resistant CMML or relapsed/refractory monocytic or monocytic-predominant AML can participate. They must have an ECOG Performance Status of 2 or less and agree to use contraception during the study and for 90 days after.
• Study details: Participants will receive the investigational medication through an IV infusion every 21 days. Their health and response to the treatment will be monitored.