AZD0486 as Monotherapy in B-cell Acute Lymphoblastic Leukaemia

Inclusion Criteria: * Age: 12 years and above (Parts A, B, C and D). * Participants with B-cell Acute Lymphoblastic Leukemia with CD19 expression by local lab with: 1. Bone marrow infiltration with \>/= 5% blasts 2. Either relapsed or refractory after a minimum of 2 prior therapies or after 1 prior line of therapy if no SOC available option (Parts A, B, C); or relapsed or refractory to ≥1 prior line of therapy (Part D). 3. Philadelphia positive participants are allowed in all parts of the study, if intolerant or refractory to TKIs. * For participants older than 16 years, Eastern Cooperative Oncology Group (ECOG) Performance Status less than or equal to 2. For Participants 16 years or younger, Lansky score more or equal to 50%. The above is a summary, other inclusion criteria details may apply. Exclusion Criteria: * Active CNS involvement by B-ALL, defined by presence of ALL blasts in CSF (CNS2 and CNS3 criteria), or signs of CNS involvement. * Isolated extramedullary disease relapse. * Testicular leukemia * History or presence of clinically relevant CNS pathology such as epilepsy, seizure, paresis, aphasia, stroke, severe brain injuries, dementia, Parkinson's disease, cerebellar disease, organic brain syndrome, or psychosis; or prior Grade 4 neurotoxicity with CAR-T or TCE therapy. * History of other malignancy (with certain exceptions). * Unresolved AEs \>/= Grade 2, from prior therapies * Prior therapy with ADCs within 3 weeks, TCEs within 4 weeks, CAR T-cell therapy or autologous HSCT within 8 weeks or prior alloSCT within 12 weeks of start of therapy. * GVHD requiring immunosuppressive therapy within 3 weeks prior to AZD0486 treatment. The above is a summary, other exclusion criteria details may apply.