Study: NCT04029688

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Idasanutlin
Description: Idasanutlin will be administered as an oral medication once daily on Days 1-5 of a 28-day cycle.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Idasanutlin
Description: Idasanutlin will be administered as an oral medication once daily on Days 1-5 of a 28-day cycle.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Idasanutlin
Description: Idasanutlin will be administered as an oral medication once daily on Days 1-5 of a 28-day cycle.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Venetoclax
Description: Venetoclax will be administered orally at the adult dose equivalent (adjusted by body weight) of 400 milligrams (mg) in participants with neuroblastoma and the adult dose equivalent of 600 mg in participants with leukemia.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Venetoclax
Description: Venetoclax will be administered orally at the adult dose equivalent (adjusted by body weight) of 400 milligrams (mg) in participants with neuroblastoma and the adult dose equivalent of 600 mg in participants with leukemia.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Venetoclax
Description: Venetoclax will be administered orally at the adult dose equivalent (adjusted by body weight) of 400 milligrams (mg) in participants with neuroblastoma and the adult dose equivalent of 600 mg in participants with leukemia.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Cyclophosphamide
Description: Cyclophosphamide will be administered once daily on Days 1-5 of each 28-day cycle at 250 milligrams per meter squared of body surface area (mg/m\^2) as an intravenous (IV) infusion.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Topotecan
Description: Topotecan will be administered once daily on Days 1-5 of each 28-day cycle at 0.75 mg/m\^2 as an IV infusion.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Fludarabine
Description: Fludarabine will be administered once daily on Days 1-5 of each 28-day treatment cycle at 30 mg/m\^2 as an IV infusion.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Cytarabine
Description: Cytarabine will be administered once daily on Days 1-5 of each 28-day treatment cycle at 2000 mg/m\^2 as an IV infusion.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Intrathecal Chemotherapy
Description: All participants with leukemia, irrespective of arm, will receive intrathecal chemotherapy on Day 1 of each 28-day treatment cycle. Intrathecal chemotherapy will consist of either single-agent cytarabine or methotrexate, or a combination of methotrexate, cytarabine, and hydrocortisone, at appropriate age-based dosing as specified in the protocol.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Intrathecal Chemotherapy
Description: All participants with leukemia, irrespective of arm, will receive intrathecal chemotherapy on Day 1 of each 28-day treatment cycle. Intrathecal chemotherapy will consist of either single-agent cytarabine or methotrexate, or a combination of methotrexate, cytarabine, and hydrocortisone, at appropriate age-based dosing as specified in the protocol.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Intrathecal Chemotherapy
Description: All participants with leukemia, irrespective of arm, will receive intrathecal chemotherapy on Day 1 of each 28-day treatment cycle. Intrathecal chemotherapy will consist of either single-agent cytarabine or methotrexate, or a combination of methotrexate, cytarabine, and hydrocortisone, at appropriate age-based dosing as specified in the protocol.