This clinical trial is focused on studying a type of blood cancer called B-cell acute lymphoblastic leukemia (B-ALL). The trial is investigating a new treatment called AZD0486, which is a special kind of medicine known as a human IgG4 kappa monoclonal antibody. This medicine is designed to target specific proteins on cancer cells, known as CD3 and CD19. The study will also involve another medication called tocilizumab, which is already used in other treatments.

The purpose of the study is to determine if AZD0486 is safe and effective for people with B-ALL that has either returned after treatment or has not responded to previous treatments. Participants in the study will receive AZD0486 through an infusion, which means the medicine will be given directly into a vein. The study will be conducted in different parts, with each part focusing on different age groups and specific characteristics of the disease. Some participants may receive a placebo, which is a substance with no active medication, to compare the effects of AZD0486.

Throughout the study, participants will be closely monitored to assess how well they tolerate the treatment and to observe any changes in their condition. The study aims to gather information on the safety of AZD0486 and its ability to help control the disease. The trial is expected to continue until the end of 2025, with recruitment starting in 2024. Participants will be involved in regular check-ups and assessments to track their progress and any side effects they may experience.