This is a Phase 1, open-label, 3 + 3 dose escalation and expansion study to determine the safety and preliminary efficacy of voruciclib monotherapy in subjects with relapsed/refractory B cell malignancies or AML after failure of prior standard therapies or voruciclib in combination with venetoclax in subjects with relapsed or refractory AML. Escalation to the next higher dose level will depend on demonstrated safety and tolerability at each dose level.