• Patients must be ≥ 12 months of age at the time of enrollment in the study.

• Diagnosis: Histological confirmation of neuroblastoma or ganglioneuroblastoma at initial diagnosis. (Bone marrow samples with positive catecholamines are acceptable as confirmation of neuroblastoma) OR histological confirmation of osteosarcoma at diagnosis

• Response to prior therapy:

‣ High-risk neuroblastoma with refractory, relapsed or progressive disease, defined as:

⁃ First or greater relapse of neuroblastoma following completion of aggressive multi- drug frontline therapy.

⁃ First episode of progressive neuroblastoma during aggressive multi-drug frontline therapy.

⁃ Persistent/refractory neuroblastoma as defined by less than a complete response by the revised International Neuroblastoma Response Criteria (INRC) after at least 4 cycles of aggressive multidrug induction chemotherapy on or according to a high-risk neuroblastoma protocol (such as A3973 or ANBL0532).

⁃ Note that this excludes patients initially considered low or intermediate-risk neuroblastoma that progressed to high-risk disease but the patient has not progressed after the diagnosis of high-risk neuroblastoma.

⁃ Relapsed or refractory osteosarcoma that is not responsive to standard treatment

• Disease Status

‣ Patients must have measurable or evaluable disease per revised INRC for subjects with neuroblastoma or measurable or evaluable disease by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 for subjects with Osteosarcoma

⁃ Performance Level:Patients must have a Lansky (≤16 years) or Karnofsky (\>16 years) score of ≥50

• Prior Therapy

‣ Patients must have fully recovered from the acute toxic effects of all prior chemotherapy, immunotherapy, or radiotherapy before study registration.

• Prior dinutuximab therapy is allowed regardless of prior response or progression on dinutuximab

∙ Prior temozolomide therapy is allowed

∙ Prior zoledronate is allowed

∙ Prior dinutuximab/temozolomide/irinotecan chemoimmunotherapy is allowed

∙ Prior T cell therapy is excluded

• Organ Function Requirements:

‣ Hematologic Functions : Absolute Neutrofil count ≥750/uL and platelet count ≥ 75,000/µl, transfusion independent .

⁃ Renal Function: Patients must have adequate renal function defined as age-adjusted serum creatinine ≤1.5 ULN for age.

⁃ Liver Function: Total bilirubin ≤ 1.5 x ULN for age and serum glutamic-pyruvic transaminase (SGPT) (ALT) ≤ 135 U/L (≤ 3x ULN).

⁃ Cardiac Function: Normal ejection fraction (≥ 55%) documented by either echocardiogram or radionuclide multigated acquisition scan (MUGA) evaluation OR Normal fractional shortening (≥ 27%) documented by echocardiogram

⁃ Pulmonary Function: Normal pulmonary function with no evidence of dyspnea at rest, no exercise intolerance.