This study investigates the effects of an investigational medication combined with chemotherapy in infants who have a specific type of leukemia called acute lymphoblastic leukemia (ALL) with a KMT2A gene rearrangement. The purpose of the study is to see if the investigational medication can be safely added to the standard chemotherapy treatment for these young patients.

Participants in this study will receive the investigational medication along with the standard chemotherapy regimen known as Interfant-06. This study aims to evaluate how well infants tolerate this combination treatment. The investigational medication is being tested to see if it can be safely used with the existing treatment plan.

• Who can participate: Infants must be over 36 weeks gestational age and have a recent diagnosis of B lymphoblastic leukemia or acute leukemia of ambiguous lineage, excluding those with Down syndrome or a history of secondary leukemia after prior chemotherapy.
• Study details: Participants will receive a combination of the investigational medication and standard chemotherapy. A placebo is not used in this study.