Inclusion Criteria:

1. Age must be ≥ 18 months and < 21 years

2. Diagnosis of DIPG or high-grade glioma originating from the brainstem.

3. Lansky (for research participants ≤ 16 years) or Karnofsky (for research participants
> 16 years) performance score ≥ 40 at the time of study enrollment

4. Adequate organ function at the time of study enrollment as follows:

- Bone marrow: ANC ≥ 1,000/μL, platelet count ≥ 100,000/μL (transfusion
independent), hemoglobin concentration ≥ 8g/dL (may be transfused)

- Renal: Serum creatinine concentration < 2x the institutional normal values for
age or GFR > 70ml/min/1.73m2

- Hepatic: Total bilirubin concentration < 1.5x the institutional upper limit of
normal for age; SGPT < 5x the institutional upper limit of normal; albumin ≥ 2
g/dL

5. Electrocardiogram (EKG) with an average QTc interval < 450 msec. If a research
participant has QTc interval ≥ 450 msec on screening EKG, the screening EKG may be
repeated twice (at least 24 hours apart). The average QTc interval from the three
screening EKGs must be < 450 msec in order for the research participant to be
eligible for the study. Research participants with abnormal serum electrolytes and a
QTc interval ≥ 450 msec should have a repeat EKG repeated once the concentration of
serum electrolyte is corrected

6. Female research participants of childbearing age must not be pregnant (confirmed by
serum or urine pregnancy test within 1 week of treatment start) or breast-feeding.

7. Female research participants of childbearing age and male research participants of
child fathering potential must agree to use safe contraceptive methods

Exclusion Criteria:

1. Metastatic disease

2. Use of enzyme-inducing anticonvulsants

3. Research participants who received any other type of anticancer treatment

4. Research participants with uncontrolled infection

5. Research participants with any concomitant significant medical illness that in the
investigator's opinion cannot be adequately controlled with appropriate therapy, or
that would impair the evaluation of side effects related to this treatment, alter
drug metabolism or the tolerance to this treatment

6. QTc interval prolongation with other medications that required discontinuation of
that medication

7. Research participants with any history of cardiac arrhythmias or congenital long QT
syndrome

8. Use of any concomitant medication that may cause QT interval prolongation and/or
induce Torsades de Pointes

9. Hypertension defined as systolic and/or diastolic blood pressure > 95th percentile
for age, height and gender, or blood pressure > 140/90 for research participants ≥ 18
years of age. If hypertension is detected, blood pressure values < 95th in two
separate occasions need to be documented before registration. Body surface ≥ 1.8m2
for research participants enrolled on dosage levels 2, 3, and 4