S-227928

The objective of this study is to determine the safety, tolerability, and anti-leukemic activity of S227928 as single agent and in combination with venetoclax, and to determine the recommended Phase 2 dose (RP2D) of this combination. The study will begin as a Phase 1 Dose Escalation study to determine the RP2D and then will transition to a Phase 2 Dose Expansion study to assess the efficacy of the selected RP2D. During the treatment period participants will have study visits every two weeks, with additional visits occurring during the first and second cycle. Approximately 30 days after treatment has ended, an end-of-treatment visit will occur and then participants will be followed for survival every 12 weeks for the next 6 months. Study visits may include a bone marrow aspirate and/or biopsy, blood and urine tests, ECG, vital signs, physical examination, and administration of study treatment.