Eflornithine (DFMO) and AMXT 1501 for Neuroblastoma, CNS Tumors, and Sarcomas

Participants must have adequate organ function at the time of enrollment: Hematological: Hematological recovery as defined by ANC ≥750/μL (unsupported- >24 hrs off G-CSF and 7 days off neulasta); Liver: Adequate liver function as defined by AST and ALT <10x upper limit of normal; Cardiac: all participants must have: 1. Normal serum Cardiac Troponin Concentration 2. Normal BNP (B-type natriuretic peptide) Level 3. A QTcF ≤ 470 msec (or EKG with no significant findings) 4. Normal ECHO defined as: i. Shortening fraction of ≥ 27% by echocardiogram, or ii. Ejection fraction of ≥ 50% by echocardiogram or radionuclide angiogram; Renal: Participants must have adequate renal function defined as: 1. For participants < 17 years old: estimated Glomerular Filtration rate (eGFR) as calculated from the Bedside Schwartz equation (in units of mL/min/1.73 m2) or via radioisotope GFR of ≥ 70 mL/min/1.73 m2. The Bedside Schwartz equation is: [(0.413) X (Height in cm)] / SCr 2. For participants ≥17 years old: estimated Glomerular Filtration rate (eGFR) as calculated from the Cockcroft and Gault formula (in units of mL/min/1.73 m2) or via radioisotope GFR of ≥ 70 mL/min/1.73 m2. The Cockcroft and Gault formula is: [(140-age) x (Wt in kg) x (0.85 if female)] / (72 x SCr)