Interfant-21 Treatment Protocol for Infants Under 1 Year With KMT2A-rearranged ALL or Mixed Phenotype Acute Leukemia

All infants that are eligible for this study and for whom the parents/legal representatives give informed consent will be enrolled in this study. All patients will receive one cycle of blinatumomab on top of the standard treatment backbone after induction therapy. Medium risk patients, that respond well to the 1st cycle will be treated with a 2nd cycle of blinatumomab replacing one chemo course after consolidation therapy. If they do not respond well enough they will be treated according to the current treatment standard. Minimal residual disease will be used to determine the response to blinatumomab. High risk patients will be eligible for allogeneic stem cell transplantation after the first blinatumomab cycle if they are Minimal Residual Disease (MRD) negative (defined as < 0.01%). Also medium risk patients with insufficient MRD response after induction or after the 1st cycle of blinatumomab will be allocated to high risk treatment and will be eligible for allogeneic stem cell transplantation.