A Study Evaluating Safety and Efficacy of Venetoclax in Combination With Azacitidine Versus Standard of Care After Allogeneic Stem Cell Transplantation (SCT) in Participants With Acute Myeloid Leukemia (AML)

Morphologic Relapse-Free Survival (RFS) (Part 2)

Morphologic relapse from AML was defined as bone marrow blasts of \>= 5% or reappearance of blasts in the peripheral blood not attributable to any other cause (e.g., bone marrow regeneration) in at least 2 peripheral blood samples at least one week apart or development of extramedullary disease after achieving a complete remission (CR) or complete remission with incomplete count recovery (CRi); or the date of death from any cause, whichever comes first as determined by the investigator.

Time frame: Up to approximately 41 months

Composite Relapse-Free Survival (RFS) (Part 2)

Composite RFS was defined as the time from randomization from either morphologic relapse from AML, or non-morphologic relapse from AML, whichever comes first. Non-morphologic relapse from AML was defined as increase in disease burden determined by standard methods with reappearance or acquisition of new findings with or without change in anti-leukemic treatment per investigator decision due to cytogenetic abnormalities or change in molecular marker or measurable residual disease by multiparameter flow with sensitivity to at least 10\^-3; or the date of death from any cause, whichever came first as determined by the investigator.

Time frame: Up to approximately 41 months

Graft-versus-Host Disease (GvHD)-Free, Relapse Free Survival (GRFS) (Part 2)

GRFS was defined as the time from the date of randomization to occurrence of disease relapse or incidence of GvHD or death from any cause.

Time frame: Up to approximately 41 months

Rate of Participants Without Higher Grade of GvHD (Part 2)

Rate of Participants without higher grade of GvHD was defined as the percentage of participants without grade 2 or higher for acute graft-versus-host disease (aGvHD) and moderate/severe for chronic graft-versus-host disease (cGvHD) assessed by investigator at 90 days after randomization.

Time frame: 90 days after randomization

Change From Baseline in Physical Functioning Subscore as Measured by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC-QLQ-C30) (Part 2)

The EORTC QLQ-C30 is a 30-item participant self-report questionnaire composed of both multi-item and single scales. The physical functioning score, reported here, ranged from 0 to 100, with a higher score indicating a better level of functioning. Positive changes from baseline indicate improvement.

Time frame: Baseline, Month 6

Change From Baseline in Patient Reported Outcomes Measurement Information System (PROMIS) Cancer Fatigue Short Form (SF) 7a Score (Part 2)

PROMIS Cancer Fatigue SF is a seven item questionnaire that assesses the impact and experience of fatigue over the past 7 days. All questions employ the following five response options: 1 = Not at all, 2 = A little bit, 3 = Somewhat, 4 = Quite a bit, and 5 = Very much. The total raw score is the sum of the responses to each question and is converted to a T-score. The T-score re-scales the total raw score to a standardized score with a mean of 50 and a standard deviation of 10. T-Scores range from 29.4 to 83.2, with higher scores indicating more fatigue. Negative changes from baseline indicate improvement.

Time frame: Baseline, Month 6

Percentage of Participants With Measurable Residual Disease (MRD) Conversion in Participants With MRD >= 10^-3 at Baseline (Part 2)

MRD conversion rate was defined as the percentage of participants who convert to MRD \< 10\^-3 after initiation of treatment. The population for MRD analysis included participants whose bone marrow was MRD positive (\>=10\^-3, as determined by central flow cytometry) at baseline prior to randomization.

Time frame: Up to approximately 41 months

Time to Deterioration in Global Health Status (GHS)/Quality of Life (QoL) in Adult Participants (Part 2)

Time to deterioration was defined as number of days from randomization to either deterioration of \>= 5 points based on the EORTC QLQ-C30 version 3 or death due to any cause. The GHS/QoL scale includes 2 questions in which participants were asked to rate their overall health and overall quality of life during the past week on a scale from 1 (very poor) to 7 (excellent). The 2 scores were averaged and transformed to a scale from 0 to 100, where a high score represents a high QoL.

Time frame: Up to approximately 41 months

Change From Baseline in European Quality-of-Life-5 Dimensional-5-Level (EQ-5D-5L) Score

The EQ-5D-5L is a generic preference instrument that has been validated in numerous populations and has 5 dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression, each of which are rated on five levels of severity (1: no problems, 2: slight problems, 3: moderate problems, 4: severe problems, 5: extreme problems) with higher scores representing higher symptom burden. A negative change from baseline indicates improvement in health status.

Time frame: Baseline, Month 6