Study Comparing Blinatumomab Alternating With Low-intensity Chemotherapy Versus Standard of Care Chemotherapy for Older Adults With Newly Diagnosed Philadelphia-negative B-cell Precursor Acute Lymphoblastic Leukemia

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.

  * 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% and no clinically significant, uncontrolled, or active cardiovascular disease (eg, myocardial infarction or stroke within 3 months). Consult with medical monitor as needed.

Exclusion Criteria:

* Active central nervous system (CNS) leukemia (i.e., CNS 3 leukemia, confirmed by lumbar puncture) not resolved with IT chemotherapy during screening.
* History of other malignancy within the past 3 years, with the following exceptions:

  * Malignancy treated with curative intent and with no known active disease present for ≥ 3 years before enrollment and felt to be at low risk for recurrence by the treating physician Note: History of other malignancy (eg, multiple myeloma) treated with immunomodulatory drugs (eg, lenalidomide, thalidomide) in the past 3 years is an exclusion.
  * Adequately treated non-melanoma skin cancer or lentigo maligna without evidence of disease
  * Adequately treated cervical carcinoma in situ without evidence of disease
  * Adequately treated breast ductal carcinoma in situ without evidence of disease
  * Prostatic intraepithelial neoplasia without evidence of prostate cancer
  * Adequately treated urothelial papillary noninvasive carcinoma or carcinoma in situ
* Clinically relevant CNS pathology or event such as epilepsy, childhood or adult seizure, paresis, aphasia, stroke, severe brain injuries, dementia, Parkinson's disease, cerebellar disease, organic brain syndrome, or psychiatric conditions that preclude the use of high dose of corticosteroids
* 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 IT chemotherapy or optional pre-phase (debulking) chemotherapy. Radiation to a spot lesion such as chloroma or lytic lesion of bone or vertebrae for pain or vertebral stabilization is allowed.