• Planned receipt of highly emetogenic chemotherapy (HEC) or cyclophosphamide 61 g/m2/day (633 mg/kg/day) for cancer treatment or autologous or allogeneic HSCT conditioning
• Plan for inpatient admission from first study drug dose until 24 hours following last study drug dose
• Body weight of at least 12.5 kg
• Age between 2.5 months and under 18 years
• Laboratory tests within one week prior to first chemotherapy or HSCT dose showing: plasma creatinine within 1.5 times the upper limit of normal for age, amylase within age-appropriate limits, plasma conjugated bilirubin 3 3x upper limit of normal for age unless Gilbert's Syndrome, ALT 4 5x upper limit of normal for age
• Baseline ECG within one month prior to study drug administration without clinically significant abnormalities including no pathologic QTc prolongation
• Scheduled, round-the-clock use of ondansetron, granisetron, or palonosetron for antiemetic prophylaxis during chemotherapy or HSCT conditioning
• Negative pregnancy test if female of childbearing potential
• Agreement to use adequate contraception or abstinence if of childbearing potential
• Parent or child able to speak a language in which the modified Pediatric Adverse Event Rating Scale (PAERS) is available
• For optional nausea severity assessment, children must be 4 to 18 years old with English, Spanish, or French speaking parent or guardian

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety