Researchers are looking for new ways to treat people with relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) that is CD19 positive using a medicine called MK-1045. MK-1045 is an immunotherapy, which is a treatment that helps the immune system fight cancer. This trial will compare MK-1045 to a standard immunotherapy called blinatumomab. The goals of this trial are to learn if more people who receive MK-1045 have no cancer cells in their bone marrow compared to people who receive blinatumomab and if people who receive MK-1045 live longer compared to people who receive blinatumomab.
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
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) or chronic GvHD. NOTE: Participants who have received CNI for GvHD within 4 weeks before the first dose of study intervention are also excluded
History of serious cardiovascular and cerebrovascular diseases.