RecruitingPhase 1Drug trialVenetoclax Basket Trial for High Risk Hematologic MalignanciesThis trial is evaluating the safety and tolerability of venetoclax with chemotherapy in pediatric and young adult patients with hematologic malignancies, including myelodysplastic syndrome (MDS), acute myeloid leukemia derived from myelodysplastic syndrome (MDS/AML), and acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL). The names of the study drugs involved in this study are below. Please note this is a list for the study as a whole, participants will receive drugs according to disease cohort. * Venetoclax * Azacitidine * Cytarabine * Methotrexate * Hydrocortisone * Leucovorin * Dexamethasone * Vincristine * Doxorubicin * Dexrazoxane * Calaspargase pegol * Hydrocortisone