A Clinical Trial of MK-1045 in People With B-cell Acute Lymphoblastic Leukemia (MK-1045-005)

Inclusion Criteria: * Has a confirmed diagnosis of relapsed/refractory (R/R) B-precursor acute lymphoblastic leukemia (ALL) with 5% or more lymphoblasts in the bone marrow. * Has CD19+ disease, confirmed by local flow cytometry and/or immunohistochemistry testing at the time of enrollment. * Has Philadelphia-negative disease, confirmed by testing, at the time of enrollment. * Participants who have AEs due to previous anticancer therapies must have recovered to Grade ≤1 or baseline. * Human immunodeficiency virus (HIV)-infected participants must have well controlled HIV on antiretroviral therapy (ART). Exclusion Criteria: * Has Burkitt's leukemia. * History or presence of clinically relevant central nervous system (CNS) diseases such as epilepsy, hemorrhagic/ischemic stroke, severe brain injuries, dementia, Parkinson's disease, cerebellar disease, organic brain syndrome, and psychosis. * Has active acute graft versus host disease (GvHD), Grade 2 to 4 according to the Glucksberg criteria or active chronic GvHD requiring systemic treatment. * History of serious cardiovascular and cerebrovascular diseases. * HIV-infection with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease. * Received prior treatment with blinatumomab within 12 weeks for Part 1 and 24 weeks for Part 2 before the first dose of study intervention (individuals known to be refractory or intolerant to blinatumomab are to be excluded). * Diagnosis of immunodeficiency or is receiving chronic sy…