PDGFR Inhibitor Crenolanib in Children/Young Adults With Diffuse Intrinsic Pontine Glioma or Recurrent High-Grade Glioma

Inclusion Criteria: * Age must be ≥ 18 months and \< or equal to 21 years * Body surface Area (BSA) ≥ 0.55 m\^2 * Lansky (for research participants ≤ 16 years) or Karnofsky (for research participants \> 16 years) performance score ≥ 40 at the time of study enrollment * Adequate organ function at the time of study enrollment as follows: * Bone marrow: Absolute neutrophil count (ANC) ≥ 1,000/μL, platelet count ≥ 75,000/μL (transfusion independent), hemoglobin concentration ≥ 8g/dL (may be transfused) * Renal: Normal serum creatinine concentration based on age as shown below or glomerular filtration rate (GFR) \> 70 ml/min/1.73m\^2 * Age (years): \< or equal to 5 and the maximum serum creatinine (mg/dL) is 0.8; * 5 \< age \< or equal to 10 and the maximum serum creatinine (mg/dL) is 1.0; * 10\< age \< or equal to 15 and the maximum serum creatinine (mg/dL) is 1.2; * \>15 and the maximum serum creatinine (mg/dL) is 1.5; * Hepatic: Total bilirubin concentration \< or equal to 1.5 times the institutional upper limit of normal for age; SGPT \< or equal to 3 times the institutional upper limit of normal * Pancreatic: Serum amylase \< or equal to 3 times the institutional upper limit of normal for age; lipase \< or equal to 3 times the institutional upper limit of normal * Female research participants of childbearing age must not be pregnant as confirmed by a serum or urine pregnancy test within 1 week of start of treatment. Participants must not be breast-f…