The main objective of this study is to evaluate the safety and efficacy of SC blinatumomab in children below 12 years of age.

Inclusion Criteria:

• Age ≥28 days to <12 years at the time of informed consent/assent.

• Lansky Performance Status (LPS) of ≥ 50%.

• For Phase 1b and Phase 2 cohort in participants with R/R B-ALL:

  • Participants with B-ALL relapsed after or refractory to any line of treatment including allogeneic hematopoietic stem cell transplant (HSCT).
  • Greater than or equal to 5% blasts in the bone marrow (BM) is considered as relapse in the BM.

• For Phase 2 cohort in participants with MRD+ B-ALL:

  • Participants with MRD+ B-ALL must have between ≥ 0.1% and < 5% blasts in the BM.

• Prior CD19-directed therapy will be allowed (with demonstrated continued CD19+ expression) if treatment ended >4 weeks prior to start of protocol therapy and no prior central nervous system (CNS) complications.

• Any Philadelphia chromosome-positive (Ph+) participant intolerant or refractory to prior tyrosine kinase inhibitors (TKIs) are eligible.

Exclusion Criteria:

• Active ALL in the CNS.
• History or presence of clinically relevant CNS pathology or event such as epilepsy, childhood seizure, paresis, aphasia, stroke, severe brain injuries, cerebellar disease, organic brain syndrome, psychosis, or severe (≥ grade 3) CNS events including immune effector cell-associated neurologic syndrome (ICANS) from prior CAR-T or other T-cell engager therapies.
• Isolated EM disease.
• Current autoimmune disease or history of autoimmune disease with potential CNS involvement.
• Patients with Down Syndrome are not eligible for this study.
• Active acute or chronic graft versus host disease requiring systemic treatment with immunosuppressive medication.
• Known infection with human immunodeficiency virus (HIV) or chronic infection with hepatitis B virus or hepatitis C virus.
• Presence of an acute or uncontrolled chronic infection, or any other concurrent disease or medical condition that could be worsened by the treatment or interfere with the participant's ability to comply with the study protocol.
• Allogeneic HSCT within 12 weeks before the start of blinatumomab.

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request.

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication (or other new use) have been granted marketing authorization in both the US and Europe, or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors, and if not approved, may be further arbitrated by a Data Sharing Independent Review Panel. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.