SUBJECT ELIGIBILITY

        All clinical and laboratory data required for determining eligibility must be available in
        the subject's medical/research record which will serve as the source document.

        Because of the nature of iC9.GD2.CAR.IL-15 T cell product preparation, subjects will be
        assessed for initial study enrollment eligibility (prior to cell procurement) and then will
        have to meet criteria prior to starting lymphodepletion and prior to T cell infusion.

        Note: During the period between cell procurement and lymphodepletion, subjects are allowed
        to receive additional standard of care chemotherapy (bridging chemotherapy) to stabilize
        their disease if the treating physician feels it is in the subject's best interests.
        Subjects may receive bridging chemotherapy and/or retinoic acid and/or radiation therapy as
        deemed necessary by treating physician during period from cell procurement until start of
        lymphodepleting chemotherapy.

        3.1 Inclusion Criteria for the Study: 3.1.1 Written HIPAA authorization signed by legal
        guardian. 3.1.2 Adequate performance status as defined by Lansky or Karnofsky performance
        status of ≥ 60 (Lansky for <16 years of age).

        3.1.3 Life expectancy ≥12 weeks. 3.1.4 Histological confirmation of neuroblastoma or
        ganglioneuroblastoma at initial diagnosis. Bone marrow samples are acceptable as
        confirmation of neuroblastoma.

        OR

        Confirmation of osteosarcoma at diagnosis 3.1.5 High risk neuroblastoma with
        persistent/refractory or relapsed 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 INRC) at the conclusion of at least 4 cycles of aggressive multidrug
             induction chemotherapy on or according to a high-risk neuroblastoma protocol (such as
             A3973 or ANBL0532).

          -  Patients must be diagnosed with high risk neuroblastoma at initial diagnosis or if
             non-high risk at time of initial diagnosis must have had evidence of metastatic
             progression when >18 months of age. (See Section 12.8for COG and INRG definitions if
             needed) OR relapsed or refractory osteosarcoma that is not responsive to standard
             treatment.

        3.1.6 Measurable or evaluable disease per Revised International Neuroblastoma Response
        Criteria (See Section 12.5) for subjects with neuroblastoma OR measurable disease by RECIST
        v1.1 criteria (See Section 12.12) for subjects with osteosarcoma.

        3.1.7 Adequate central nervous system function as defined by: • No known CNS disease

          -  No seizure disorder requiring antiepileptic drug therapy 3.1.8 Adequate cardiac
             function as defined by:

          -  Shortening fraction of ≥27% by echocardiogram 3.1.9 Adequate pulmonary function as
             defined by:

          -  No chronic oxygen requirement and room air pulse oximetry >94%. 3.1.10 Females of
             childbearing potential must have a negative serum pregnancy test within 72 hours prior
             to cell procurement. NOTE: Premenarchal females do not require pregnancy testing.

        3.1.11 Females of childbearing potential must be willing to abstain from heterosexual
        activity or to use 2 forms of effective methods of contraception from the time of informed
        consent until 3 months after treatment discontinuation. The two contraception methods can
        be comprised of two barrier methods, or a barrier method plus a hormonal method or an
        intrauterine device that meets <1% failure rate for protection from pregnancy in the
        product label.

        3.1.12 Male subjects with female partners must have had a prior vasectomy, be willing to
        abstain from heterosexual activity or agree to use an adequate method of contraception
        (i.e., double barrier method: condom plus spermicidal agent) starting with the first dose
        of study therapy through 3 months after the last dose of study therapy.

        3.1.13 As determined by the enrolling physician, subject is willing and able to comply with
        study procedures.

        3.2 Exclusion Criteria for the Study Subjects meeting any of the following exclusion
        criteria will not be able to participate in this study (procurement, lymphodepletion and
        cell infusion).

        3.2.1 Pregnant or breastfeeding (NOTE: breast milk cannot be stored for future use while
        the mother is being treated on study).

        3.2.2 Has a known additional malignancy that is active and/or progressive requiring
        treatment.

        3.2.3 History of hypersensitivity reactions to murine protein-containing products.

        3.2.4 History of hypersensitivity to cyclophosphamide or fludarabine. 3.2.5 Systemic
        steroid use except as below:

          -  Physiologic replacement for adrenal insufficiency is allowed at doses of
             hydrocortisone 6-12 mg/m^2/day or equivalent.

          -  Inhaled steroids are allowed.

          -  Other than the above, systemic steroids must be stopped >14 days prior to procurement,
             but may be resumed after procurement if needed as per treating physician. Systemic
             steroids must be stopped 48 hours prior to lymphodepletion and not used after infusion
             unless clinically required.

        3.2.6 Uncontrolled infection requiring systemic therapy. 3.2.7 Subjects are required to be
        negative for HIV antibody or HIV viral load, negative for HTLV1 and 2 antibody or PCR
        negative for HTLV1 and 2, negative for Hepatitis B surface antigen, or negative for HCV
        antibody or HCV viral load. Tests can be pending at the time of cell procurement; only
        those samples confirming lack of active infection will be used to generate transduced
        cells.

        3.3 Eligibility criteria to be met prior to procurement 3.3.1 Written informed consent to
        undergo cell procurement signed by legal guardian must be obtained prior to procurement.
        Written assent required as applicable for age <15 years old.

        3.3.2 Age greater than 18 months and less than 18 years at the time of consent. 3.3.3
        Imaging and bone marrow study results from within 90 days prior to procurement to assess
        presence of active disease. Bone marrow studies are only relevant for neuroblastoma
        subjects.

        3.3.4 Subjects who have received murine antibodies must have documentation of absence of
        human anti-mouse antibodies (HAMA). Test can be pending at the time of cell procurement;
        only those patients with confirmed absence of HAMA will have cells generated.

        3.3.5 Adequate organ function as defined in the table below; all labs to be obtained within
        7 days of procurement

        System Laboratory Value Hematological* Hemoglobin ≥ 9.0 g/dL Absolute Neutrophil Count
        (ANC) ≥ 0.8 x 10^9/L Platelets (transfusion independent) ≥ 50 x 10^9/L Renal Age Maximum
        Serum Creatinine (mg/dL) Male Female

        1 to <2 years ≤0.6 ≤0.6 2 to <6 years ≤0.8 ≤0.8 6 to <10 years ≤1 ≤1 10 to <13 years ≤1.2
        ≤1.2 13 to <16 years ≤1.5 ≤1.4

        ≥16 years ≤1.7 ≤1.4

        Hepatic Total Bilirubin ≤ 1.5 × upper limit of normal (ULN) for age Alanine
        aminotransferase (ALT) ≤ 500 U/L Coagulation International Normalized Ratio (INR) ≤ 2 × ULN

          -  Subjects with known bone marrow involvement are eligible even if they have not met the
             above Hematological eligibility criteria. However, those subjects must be able to be
             supported with transfusions to prevent life-threatening bleeding as per investigator
             discretion. NB: Bone marrow involvement is only relevant to neuroblastoma subjects.

        3.3.1 Females of childbearing potential must have a negative serum pregnancy test within 72
        hours prior to cell procurement. NOTE: Premenarchal females do not require pregnancy
        testing.

        3.4 Eligibility criteria to be met prior to lymphodepletion

        3.4.1 Written informed consent to enroll in the iC9.GD2.CAR.IL-15 cell therapy trial signed
        by legal guardian must be obtained prior to starting lymphodepletion. Written assent
        required as applicable for age <15 years old.

        3.4.2 Subjects must have imaging and bone marrow study (bone marrow only applicable for
        neuroblastoma subjects) results within 14 days prior to lymphodepletion (used as baseline
        measure for documentation of progression before the lymphodepletion). Subjects who have
        received bridging chemotherapy must have imaging and bone marrow study results at least 3
        weeks after most recent therapy.

        3.4.3 Adequate organ function as defined in the table below:

        System Laboratory Value Hematological* Absolute Neutrophil Count (ANC) ≥ 0.8 x 10^9/L
        Platelets (transfusion independent) ≥ 50 x 10^9/L Renal** Age Maximum Serum Creatinine
        (mg/dL) Male Female

          1. to <2 years ≤0.6 ≤0.6

          2. to <6 years ≤0.8 ≤0.8

        6 to <10 years ≤1 ≤1 10 to <13 years ≤1.2 ≤1.2 13 to <16 years ≤1.5 ≤1.4

        ≥16 years ≤1.7 ≤1.4

        Hepatic Total Bilirubin ≤ 1.5 × upper limit of normal (ULN) for age Alanine
        aminotransferase (ALT) ≤ 500 U/L

          -  Subjects with known bone marrow involvement are eligible even if they have not met the
             above Hematological eligibility criteria. However, those subjects must be able to be
             supported with transfusions to prevent life-threatening bleeding as per investigator
             discretion. NB: Bone marrow involvement is only relevant to neuroblastoma subjects.

               -  Subjects with moderate impairment of renal function (normalized creatinine
                  clearance 30-70 mL/min/1.73m^2) should have their fludarabine dose reduced by 20%
                  and be monitored closely for excessive toxicity.

        3.4.4 Treatment with any investigational drug within 21 days of lymphodepletion or any
        tumor vaccines within the previous six weeks prior to lymphodepletion.

        3.4.5 Adequate performance status as defined by Lansky or Karnofsky performance status of ≥
        60 (Lansky for <16 years of age).

        3.4.6 Females of childbearing potential must have a negative serum pregnancy test within 72
        hours prior to lymphodepletion. NOTE: Premenarchal females do not require pregnancy
        testing.

        3.4.7 Available autologous transduced activated T cells product meets the certificate of
        analysis.

        3.4.8 Subject has not received aldesleukin (IL-2) within 28 days of starting
        lymphodepletion.

        3.4.9 Subject has not received:

          -  filgrastim (G-CSF) (or biosimilar) within 7 days of starting lymphodepletion;

          -  sargramostim (GM-CSF) within 14 days of starting lymphodepletion;

          -  pegfilgrastim within 21 days of starting lymphodepletion.

        3.4.10 Systemic steroid use is prohibited, except as below:

        • Physiologic replacement for adrenal insufficiency is allowed at doses of hydrocortisone
        6-12 mg/m^2/day or equivalent.

          -  Inhaled steroids are allowed.

          -  Other than the above, systemic steroids must be stopped 48 hours prior to
             lymphodepletion and not used after infusion unless clinically required.

        3.4.11 Prior autologous stem cell transplant is allowed as long as it occurred ≥4 weeks
        prior to lymphodepletion.

        3.4.12 Prior therapeutic ^131 I-MIBG is allowed as long as it is completed ≥4 weeks prior
        to lymphodepletion.

        3.4.13 Prior anti-GD2 therapy (such as dinutuximab) is allowed as long as it is completed
        ≥4 weeks prior to lymphodepletion.

        3.4.14 Subject did not have major surgery within 14 days of starting lymphodepletion.

        3.4.15 Subjects that have received bridging therapy with murine antibodies must have
        documentation of absence of human anti-mouse antibodies (HAMA) prior to lymphodepletion.

        3.4.16 Subject is not taking a prohibited or contraindicated medication listed in Section
        4.2.12 prior to lymphodepletion. Contraindicated medications should be discontinued at
        least two weeks prior to the scheduled lymphodepletion or by at least 5 half-lives of the
        contraindicated medication, whichever is shorter.

        3.4.17 Subject does not have disease progression that would, in the opinion of the treating
        physician, place the subject at significant potential risk, such as location of lesion that
        would have high risk with tumor swelling (examples include airway or spinal canal).

        3.4.18 No evidence of uncontrolled infection or sepsis.

        3.5 Eligibility criteria to be met prior to cell infusion after lymphodepletion

        3.5.1 Subject is a good candidate for treatment per investigator's discretion. 3.5.2 No
        evidence of uncontrolled infection or sepsis.

        3.6 Eligibility Criteria Prior to Lymphodepltion for Second Infusion (Optional) 3.6.1
        Subjects must not have received bridging therapy after their initial iC9.GD2.CAR.IL-15 cell
        infusion.

        3.6.2 Adequate organ function as defined in the table below:

        System Laboratory Value Hematological* Absolute Neutrophil Count (ANC) ≥ 0.8 x 10^9/L
        Platelets (transfusion independent) ≥ 50 x 10^9/L Renal** Age Maximum Serum Creatinine
        (mg/dL) Male Female 1 to <2 years ≤0.6 ≤0.6 2 to <6 years ≤0.8 ≤0.8 6 to <10 years ≤1 ≤1 10
        to <13 years ≤1.2 ≤1.2 13 to <16 years ≤1.5 ≤1.4

        ≥16 years ≤1.7 ≤1.4

        Hepatic Total Bilirubin ≤ 1.5 × upper limit of normal (ULN) for age Alanine
        aminotransferase (ALT) ≤ 500 U/L

        *Subjects with known bone marrow involvement are eligible even if they have not met the
        above Hematological eligibility criteria. However, those subjects must be able to be
        supported with transfusions to prevent life-threatening bleeding as per investigator
        discretion. NB: Bone marrow involvement is only relevant to neuroblastoma subjects.

        **Subjects with moderate impairment of renal function (normalized creatinine clearance
        30-70 mL/min/1.73m2) should have their fludarabine dose reduced by 20% and be monitored
        closely for excessive toxicity.

        3.6.3 Adequate performance status as defined by Lansky or Karnofsky performance status of ≥
        60 (Lansky for <16 years of age).

        3.6.4 Females of childbearing potential must have a negative serum pregnancy test within 72
        hours prior to lymphodepletion. NOTE: Premenarchal females do not require pregnancy
        testing.

        3.6.5 Subject has not received:

          -  filgrastim (G-CSF) (or biosimilar) within 7 days of starting lymphodepletion;

          -  sargramostim (GM-CSF) within 14 days of starting lymphodepletion;

          -  pegfilgrastim within 21 days of starting lymphodepletion.

        3.6.6 Systemic steroid use is prohibited, except as below:

          -  Physiologic replacement for adrenal insufficiency is allowed at doses of
             hydrocortisone 6-12 mg/m2/day or equivalent.

          -  Inhaled steroids are allowed.

          -  Other than the above, systemic steroids must be stopped 48 hours prior to
             lymphodepletion and not used after infusion unless clinically required.

        3.6.7 Subject did not have major surgery within 14 days of starting lymphodepletion.

        3.6.8 Subject is not taking a prohibited or contraindicated medication listed in Section
        4.2.12 prior to lymphodepletion. Contraindicated medications should be discontinued at
        least two weeks prior to the scheduled lymphodepletion or by at least 5 half-lives of the
        contraindicated medication, whichever is shorter.

        3.6.9 No evidence of uncontrolled infection or sepsis. 3.6.10 Subject has completed the
        initial safety evaluation period without DLTs. 3.6.11 Subject has not experienced
        additional toxicity(ies) directly attributable to the initial T-cell infusion that would
        place them at excessive risk with re-infusion. 3.6.12 Subject has derived clinical benefit
        from the initial infusion as assessed by the investigator (stable disease or better to the
        initial infusion). 3.6.13 Subject has sufficient stored iC9.GD2.CAR.IL-15 T-cells for
        re-infusion.

        3.7 Eligibility Criteria Prior to Second Infusion (Optional) 3.7.1 Subject is a good
        candidate for treatment per investigator's discretion. 3.7.2 No evidence of uncontrolled
        infection or sepsis.