 This study consists of three portions: The first portion- Phase 1, or dose-escalation portion, that will evaluate the safety and pharmacokinetic profile of venetoclax in combination with low-dose cytarabine LDC, define the maximum tolerated dose MTD, and generate data to support a recommended Phase 2 dose RPTD in treatment-naïve subjects with Acute Myelogenous Leukemia AML. Second portion, initial Phase 2 that will evaluate if the RPTD has sufficient efficacy and acceptable toxicity to warrant further development of the combination therapy. Subsequently, Phase 2 Cohort C, will evaluate the overall response rate ORR for subjects allowed additional supportive medications strong CYP3A inhibitors if medically indicated. 