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

Inclusion Criteria: 1. Patients with newly diagnosed B- precursor ALL or B-cell MPAL (single lineage) according to the WHO classification of tumours of haematopoietic and lymphoid tissues (revised 4th edition 2017), with KMT2A-rearrangement. 2. ≤ 365 days of age at the time of diagnosis of ALL. 3. Written informed consent of the parent(s) or other legally authorized guardian of the patient according to local law and regulations. Exclusion criteria for blinatumomab: 1. KMT2A-wildtype patients. 2. Multilineage MPAL 3. T-ALL. 4. Age \> 365 days at the time of diagnosis. 5. Down syndrome. 6. Relapsed ALL. 7. Treatment with systemic corticosteroids (equivalent prednisone \>10 mg/m2/day) for more than one week and/or any chemotherapeutic agent in the 4-week interval prior to diagnosis. Patients who received corticosteroids by aerosol are eligible for the study. If exclusion criteria for blinatumomab are met, the patient should be treated according to the protocol but without blinatumomab.