Adding Dasatinib Or Venetoclax To Improve Responses In Children With Newly Diagnosed T-Cell Acute Lymphoblastic Leukemia (ALL) Or Lymphoma (T-LLY) Or Mixed Phenotype Acute Leukemia (MPAL)

Patients will be identified in the first 3 days of therapy during their treatment on INITIALL.

Treatment will consist of 3 main phases: Induction, Early Post Induction \[including Consolidation, High-Dose Methotrexate, Intensification, Interim 1, Reinduction 1, Interim 2, and Reinduction 2\], and Maintenance.

Induction:

* Remission Induction includes 3 days of therapy on the INITIALL classification protocol as well as the remainder of a total of 4 weeks of induction treatment on this trial. Treatment includes a total of 28 days of dexamethasone, 4 weekly doses of vincristine, 3 doses of daunorubicin, 1 dose of Calaspargase pegol, 6 doses of Intrathecal triple therapy (IT MHA), and one of 3 additional drugs. Patients with T-ALL without near-ETP or ETP phenotype (hereafter referred to simply as T-ALL) will receive 25 days of dasatinib. Patients with ETP or near-ETP ALL as well as those with MPAL will receive 14 days of venetoclax. Patients with T-LLy will receive bortezomib. Patients will have a week without chemotherapy at the end of Induction, although patients with Induction failure (MRD ≥5% disease) will proceed directly to consolidation.

Early Post Induction:

* Consolidation will be given following completion of Remission Induction Therapy. Patients will receive 2 cycles of BFM-1b therapy (a single dose of cyclophosphamide at the start of week 1, 4 daily doses of cytarabine in two consecutive weeks, and 2 weeks of mercaptopurine) separated by a week of nelarabine. Patients will have a week without chemotherapy at the end of Consolidation. * High-dose Methotrexate will be given for 4 cycles to all patients. Patients will also receive an intrathecal chemotherapy treatment with each of the 2-week cycles and will take oral mercaptopurine continuously if tolerated. * Intensification will be given to patients with T-ALL or ETP/ near-ETP. This therapy includes a week of nelarabine, one week of combination cyclophosphamide and cytarabine, and 1 week of rest without chemotherapy. * Interim Therapy 1 includes 6 weeks of oral mercaptopurine, 2 weeks (5 days of each week) of dexamethasone, and two doses (weeks 1 and 4) of daunorubicin, vincristine, and calaspargase pegol. * Reinduction Therapy 1 will consist of 3 weekly doses of vincristine, 1 dose of daunorubicin and calaspargase pegol at the start of the first week, and dexamethasone for 7 days in the first and third weeks. Patients will also receive the same additional agent received during induction based on immunophenotype. * Interim Therapy 2 includes 6 weeks of oral mercaptopurine, two doses (weeks 1 and 4) of daunorubicin, vincristine, and calaspargase pegol. * Reinduction Therapy 2 will consist of 3 weekly doses of vincristine, 1 dose of daunorubicin and calaspargase pegol at the start of the first week, and dexamethasone for 7 days in the first and third weeks. Patients will also receive the same additional agent received during induction based on immunophenotype.