• Participant must be ≥18 years of age

• Participant must have confirmed diagnosis as follows:

• R/R AML and has not achieved adequate response to, cannot tolerate, or refused all approved therapies known to be active for treatment of their disease OR R/R MDS with over 10% blasts in the bone marrow and has not achieved an adequate response to at least 4 cycles of a hypomethylating agent (HMA)- containing regimen or other treatment known to be active for their disease OR R/R AML or R/R MDS that has relapsed after a hematopoietic stem cell transplant (HSCT)

• Participant must be willing and able to comply with scheduled study visits and treatment plans.

• Participant must be willing to undergo all study procedures unless contraindicated due to medical risk.

• Participant must have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of ≤2

• Participant must have adequate hepatic function

• Participant must have adequate renal function

• Participant must have adequate cardiovascular function

• Participant must have a white blood cell (WBC) count ≤20 × 10⁹/L (with stable hydroxyurea use allowed)

⁃ Participant must meet timing requirements with respect to prior therapy and surgery

⁃ Participant must agree to use effective contraception during the study and for the required post-treatment period: Males: Use condoms (even if vasectomized) during the study and for 90 days post-treatment. Females of childbearing potential: Use a combination of 1 highly effective and 1 effective method of contraception during the study and for 180 days post-treatment.