A Study of Subcutaneous Blinatumomab Administration in Participants with R/R and MRD+ B-ALL

- Ph-IIC, Dose Escalation and Dose Expansion: Aged 18 years or older (or same or greater than legal age within the country if it is older than 18 years). - Ph-IIRa and Ph-IIMa: Aged ≥ 17 years at time of informed consent. - Ph-IIRb and Ph-IIMb: Age ≥ 12 years and < 17 years at time of informed consent. - Ph-IIR, Ph-IIC, Dose escalation, Dose Expansion: Participants with R/R B-precursor ALL. - Relapsed or Refractory B-precursor ALL at any time after first salvage therapy. - Relapsed B-precursor ALL at any time after allogenic hematopoietic stem cell transplant (HSCT). - Ph-IIR, Ph-IIC, Dose escalation, Dose expansion: Greater than or equal to 5% blasts in the Bone Marrow per local assessment. - Ph-IIM: B-precursor ALL and bone marrow blasts (BMB) ≥ 0.01% and < 5% per local assessment. - Ph-IIM: Availability of an appropriate archival BM specimen from initial or relapse diagnosis and the screening BM sample. - Participants aged ≥ 18 years: Eastern Cooperative Oncology Group (ECOG) Performance Status less than or equal to 2. - Participants aged 16 to < 18 years old: Karnofsky Performance Score ≥ 50%. - Participants aged < 16 years old: Lansky Performance Score ≥ 50%. - Any Ph+ participant intolerant or refractory to prior tyrosine kinase inhibitors (TKIs) are eligible. - Ph-IIM: BM function as follows: * Absolute Neutrophil Count (ANC) ≥ 500/μL * Platelet count ≥ 50 000/μL (transfusion permitted) * Hemoglobin level ≥ 9 g/dL (transfusion permitted) The above is a summary, other inclusion criteria details may apply.

- Active ALL in the central nervous system (CNS). Presence of greater than 5 white blood cells per cubic millimeter in cerebrospinal fluid (CSF) with lymphoblasts present and/or clinical signs of CNS leukemia. If CSF leukemia is present subjects will have to receive intrathecal therapy and have documented negative CSF prior to enrolling. - History or presence of clinically relevant CNS pathology (excluding headache) such as epilepsy, childhood or adult seizure, paresis, aphasia, stroke, severe brain injuries, dementia, Parkinson’s disease, cerebellar disease, organic brain syndrome, psychosis or severe (≥ grade 3) CNS events including immune effector cell-associated neurotoxicity syndrome (ICANS) from prior chimeric antigen receptor T-cell (CAR T) or other T cell engager therapies. - Isolated Extramedullary (EM) Disease. - For Ph-IIM only: Current EM disease or presence of circulating leukemia blasts. - Current autoimmune disease or history of autoimmune disease with potential CNS involvement. - Active acute or chronic graft versus host disease requiring systemic treatment with immunosuppressive medication. - Symptoms and/or signs that indicate an acute or uncontrolled chronic infection, any other disease or condition that could be exacerbated by the treatment or would complicate protocol compliance. - Testicular leukemia. - History of malignancy (with certain exceptions) other than ALL within 3 years prior to start of protocol-specified therapy. - Allogeneic HSCT within 12 weeks before the start of protocol-specified therapy. - Cancer chemotherapy within 2 weeks before the start of protocol-specified therapy (with certain exceptions). - Immunotherapy within 4 weeks before start of protocol-specified therapy. - Prior failed cluster of differentiation (CD19) directed therapy such as prior blinatumomab or CD19 CAR T cells will be allowed (with demonstrated continued CD19+ expression), if treatment ended more than 4 weeks prior to start of protocol therapy and no prior CNS complications. - Currently receiving treatment in or less than 30 days or 5 half-lives since ending treatment on another investigational study(ies). - Abnormal screening laboratory parameters. - Female participant: Pregnant or breastfeeding or planning to become pregnant or donate eggs, or expected to breastfeed during treatment and for 96 hours after the last dose of investigational product (SC blinatumomab). The above is a summary, other exclusion criteria details may apply.