A Study of Sonrotoclax (BGB-11417) in Children With Relapsed or Refractory Acute Myeloid Leukemia and B-cell Acute Lymphoblastic Leukemia

Key Inclusion Criteria Participants must meet all of the following criteria to be eligible for participation: 1. Have a performance status of Lansky ≥50 for participants ≤16 years of age or Karnofsky ≥50 for participants \>16 years of age. 2. Have adequate renal function, defined as an estimated or measured glomerular filtration rate (GFR) ≥60 mL/min. 3. Have adequate hepatic function, defined as: * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \<2.5 × the institutional upper limit of normal (ULN) * Total bilirubin ≤1.5 × the institutional ULN. 4. Have minimum cardiac function as defined in the study protocol. Acute Myeloid Leukemia (AML)-Specific Inclusion Criteria 1. Have a histologically confirmed diagnosis of acute myeloid leukemia (AML) that is relapsed or refractory (R/R) after ≥2 prior lines of systemic therapy. 2. Have ≥5% blasts in a bone marrow aspirate or biopsy sample, as assessed by morphology. Participants with extramedullary, non-central nervous system (CNS) disease are eligible. B-Cell Precursor Acute Lymphoblastic Leukemia (ALL)-Specific Inclusion Criteria 1. Have a histologically confirmed diagnosis of B-cell precursor acute lymphoblastic leukemia (ALL) that is R/R after ≥2 prior lines of systemic therapy, including at least 1 line of blinatumomab-based therapy. 2. Have ≥5% blasts in a bone marrow aspirate or biopsy sample, as assessed by morphology. 3. Have leukemic blasts expressing cluster of differentiation 22 (CD22) on the cell surface, as assessed by flow cytometry of a bone marrow aspirate. Key Exclusion Criteria Participants will be excluded from participation if any of the following apply: 1. Have central nervous system (CNS) 2 or CNS 3 disease at screening. 2. Have toxicity from prior anticancer therapy that has not recovered to ≤Grade 1, as defined by the applicable toxicity grading criteria. 3. Have a history of prior allogeneic stem cell transplantation \<90 days from enrollment or if if ≥ 90 days from enrollment, with active graft-versus-host disease (GVHD), or requiring immunosuppressive drugs for treatment of GVHD, or have taken calcineurin inhibitors within 4 weeks prior to consent. AML-Specific Exclusion Criteria 1. Have a diagnosis of acute promyelocytic leukemia (APL) or juvenile myelomonocytic leukemia (JMML). 2. Have AML with fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD), as determined by local assessment. ALL-Specific Exclusion Criteria 1. Have Philadelphia chromosome-positive (Ph+) ALL with a breakpoint cluster region::Abelson murine leukemia viral oncogene homolog 1 (BCR::ABL1) fusion. 2. Have received prior therapy with a B-cell lymphoma 2 (BCL-2) inhibitor. Note: Other eligibility criteria may apply.