Study of Venetoclax in Combination With Chemotherapy in Pediatric Patients With Refractory or Relapsed Acute Myeloid Leukemia or Acute Leukemia of Ambiguous Lineage

The purpose of this study is to test the safety and determine the best dose of venetoclax and cytarabine when given with or without idarubicin in treating pediatric patients with acute myeloid leukemia (AML) that did not respond to treatment (refractory) or has come back after treatment (relapsed). PRIMARY OBJECTIVE: Determine a tolerable combination of venetoclax plus chemotherapy in pediatric patients with relapsed or refractory AML or acute leukemia of ambiguous lineage. The primary endpoints are the recommended phase 2 doses (RP2D) of venetoclax plus cytarabine and venetoclax plus cytarabine and idarubicin. SECONDARY OBJECTIVE: Estimate the overall response rate to the combination of venetoclax and chemotherapy in pediatric patients with relapsed or refractor AML or acute leukemia of ambiguous lineage. The secondary endpoints are the rates of complete remission (CR) and complete remission with incomplete count recovery (CRi) for patients treated at the RP2D.