A Study Evaluating the Safety, Tolerability, Pharmacokinetics and Preliminary Activity of Idasanutlin in Combination With Either Chemotherapy or Venetoclax in Treatment of Pediatric and Young Adult Participants With Relapsed/Refractory Acute Leukemias or Solid Tumors

This is a Phase I/II, multicenter, open-label, multi-arm study designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary efficacy of idasanutlin, administered as a single agent or in combination with chemotherapy or venetoclax, in pediatric and young adult participants with acute leukemias or solid tumors. This study is divided into three parts: Part 1 will begin with dose escalation of idasanutlin as a single agent in pediatric participants with relapsed or refractory solid tumors to identify the maximum tolerated dose (MTD)/maximum administered dose (MAD) and to characterize dose-limiting toxicities (DLTs). Following MTD/MAD identification, three separate safety run-in cohorts in neuroblastoma, acute myeloid leukemia (AML), and acute lymphoblastic leukemia (ALL) will be conducted to identify the recommended Phase 2 dose (RP2D) of idasanutlin in each combination, with chemotherapy or venetoclax. Part 2 will evaluate the safety and early efficacy of idasanutlin in combination with chemotherapy or venetoclax in newly enrolled pediatric and young adult participants in neuroblastoma, AML,and ALL cohorts at idasanutlin RP2D. Part 3 will potentially be conducted as an additional expansion phase of the idasanutlin combination cohorts in neuroblastoma, AML, or ALL for further response and safety assessment.