Phase I Trial of the Selective Inhibitor of Nuclear Export, KPT-330, in Relapsed Childhood ALL and AML

The investigators are trying to determine a safe dose of KPT-330 and will be giving participants different dose levels of the study drug. Three to six participants will receive the starting dose of the drug. If the side effects are not too severe, the next group of participants will take the study drug at a higher dose level. Up to 3 dose levels of the study drug will be tested, but once each participant has been assigned a dose level, the participant will always receive the same dose. The highest dose that people can be given safely is called the maximum tolerated dose (MTD). Once the MTD is determined, up to 10 additional participants will receive that dose to further study the drug. Participants between the age of ≥18 months (540 days) and ≤ 21 years with relapsed (second or subsequent relapse) or refractory ALL or AML will be eligible to enroll. KPT-330 will be administered twice a week on Days 1 and 3 for four weeks (a cycle is 4 weeks). All participants will receive intrathecal chemotherapy on Day 1 of each cycle. Participants with CNS-2 disease will receive additional doses of IT chemo. Pharmacokinetic (PK) samples will be collected during Cycle 1 on Days 1-3 and 15. PK samples will be collected during Cycle 2 on Day 15. Pharmacodynamic (PD) samples will be collected during Cycle 1 on Days 1-3. PD samples will be collected during Cycle 2 on Day 15. Additional optional correlative biology sample will be collected. Participants are monitored closely for adverse events. Participants will have physical exams and blood work more than once a week during all cycles.