Inclusion Criteria:  - Age ≥ 55 years at the time of informed consent. OR  Age 40 to < 55 years of age if at least 1 of the following comorbidities at the time of informed consent:  history of grades 3 and 4 pancreatitis diabetes mellitus with end-organ damage severe liver disease such as cirrhosis stage 2 with portal hypertension or history of esophageal variceal bleeding and aspartate transaminase (AST)/alanine aminotransferase (ALT) > 10 x upper limit of normal (ULN) (liver cirrhosis must be confirmed by biopsy) body mass index (BMI) ≥ 40 combined with relevant comorbidities such as metabolic syndrome  Any further combination of documented severe comorbidities that the investigator judges to be incompatible with administering an intensive pediatric based, adult adapted standard chemotherapy regimen but still compatible with the suggested protocol for older participants in both the experimental and the SOC arm. The participant history will be reviewed by the medical monitor during screening to determine enrollment acceptability based on a standard list with types of comorbidities allowed. A medical advisory board is available to the investigators for questions/advice and includes experts in the field of adult leukemia with experience with the use of blinatumomab, the global development lead for blinatumomab and the medical monitor of the study.  Participants with newly diagnosed Philadelphia (Ph)-negative B-cell precursor acute lymphoblastic leukemia (ALL) Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2, higher ECOG score allowed if due to underlying leukemia All participants must have adequate organ function as defined below: renal: estimated glomerular filtration rate based on MDRD calculation ≥ 50 mL/min/1.73 m^2 liver function: total bilirubin ≤ 2x upper limit of normal (ULN; unless Gilbert's Disease or if liver involvement with leukemia); exception for participants 40 to < 55 years of age if they have a comorbidity listed above: severe liver disease such as cirrhosis stage 2 with portal hypertension or history of esophageal variceal bleeding and AST/ALT > 10 x ULN (liver cirrhosis must be confirmed by biopsy) cardiac: left ventricular ejection fraction (LVEF) ≥ 50%  Exclusion Criteria:  Active central nervous system (CNS) leukemia not resolved with IT chemotherapy during screening. Clinically relevant CNS pathology requiring treatment (eg, unstable epilepsy). Current autoimmune disease or history of autoimmune disease with potential CNS involvement Known infection with human immunodeficiency virus (HIV) Known infection with chronic or active infection with hepatitis B (eg, hepatitis b surface [HBs] antigen reactive or quantifiable hepatitis b virus [HBV] viral load) or hepatitis C virus (HCV) (eg, HCV RNA [qualitative] is detected).  Active hepatitis B and C based on the following results:  positive for hepatitis B surface antigen (HepBsAg) (indicative of chronic hepatitis B or recent acute hepatitis B) negative HepBsAg and positive for hepatitis B core antibody: negative HBV DNA by PCR result is necessary to enroll.  positive Hepatitis C virus antibody (HepCAb): negative hepatitis C virus RNA by PCR result is necessary to enroll.  Participant with symptoms and/or clinical signs and/or radiographic and/or sonographic signs that indicate an acute or uncontrolled chronic infection. Cancer chemotherapy for this newly diagnosed B cell ALL before the start of protocol-required therapy with the exception of intrathecal chemotherapy or pre-phase chemotherapy. Radiation to a spot lesion such as chloroma or lytic lesion of bone or vertebrae for pain or vertebral stabilization is allowed.