A Phase I Trial of T Cells Expressing an Anti-GD2 Chimeric Antigen Receptor in Children and Young Adults With GD2+ Solid Tumors

Background

GD2 is a well-characterized tumor antigen in neuroblastoma, which is also expressed on
osteosarcomas and some other sarcomas. T cells expressing 1st generation anti-GD2 chimeric
antigen receptors (CARs) were safe and mediated modest antitumor activity in some patients
with refractory neuroblastoma.

A 3rd generation anti-GD2-CAR (GD2-CAR.OX40.28.z.ICD9) has been produced and holds promise
for increased activity compared to the 1st generation GD2-CAR already studied in clinical
trials. As an added safety measure, the vector includes a suicide switch comprising a caspase
dimerization domain (ICD9) that can be activated by a small molecule to induce death of the
genetically engineered cells if they were induce untoward toxicity.

Objectives

- Primary:Determine the feasibility of producing anti GD2-CAR cells meeting the
established release criteria and to assess the safety of administering escalating doses
of anti-GD2-CAR engineered T cells in children and young adults with GD2+ solid tumors,
including neuroblastoma, following cyclophosphamide-based lymphodepletion.

- Seconday: 1) Determine if administration of anti-GD2-CAR engineered T cells mediate
antitumor effects in children and young adults with GD2+ solid tumors; 2) Measure
persistence of adoptively transferred anti-GD2-CAR T cells and correlate this with
antitumor effects; 3) Extend information regarding the prevalence and intensity of GD2
expression in non-neuroblastoma, non- osteosarcoma solid tumors in children and young
adults; 4) If unacceptable toxicity occurs that is possibly, probably or likely related
to anti-GD2-CAR T cells, assess the capacity for AP1903, a dimerizing agent, to mediate
clearance of the genetically engineered cells and resolve toxicity; and 5) Assess
toxicity of AP1903 if administered to mediate clearance of anti-GD2-CAR T cells.

Eligibility

Patients 1-35 years of age, at least 15 kg, with osteosarcoma or a GD2+ solid tumor
(including neuroblastoma) that has recurred after or not responded to standard therapy and is
deemed incurable by standard therapy.

Design

After apheresis to collect T cells for transduction, patients receive cyclophosphamide
1800mg/m(2)/d as a lymphodepleting regimen. A phase I cell dose escalation scheme will used
at 4 dose levels (1 x 10(5) transduced T cells/kg; 1 x 10(6) transduced T cells/kg; 3 x 10(6)
transduced T cells/kg; and 1 x 10(7) transduced T cells/kg), using a standard 3 plus 3 dose
escalation design. An expanded group of a total of 12 patients will be treated at the highest
dose, comprising at least 6 osteosarcoma patients.

Patients will be monitored for toxicity, antitumor effects and persistence of anti-GD2-CAR T
cells.

Patients with a PR, SD may receive a 2nd cycle at the next higher dose level a minimum of 60
days following completion of the first cycle if eligibility criteria are met.

A maximum of 36 patients may be treated on this study. Given that there is likelihood that
some patients with non-osteosarcoma will not meet the criteria for GD2 expression to be
eligible for enrollment, up to 72 subjects will be screened to enroll a maximum of 36
patients for treatment. Up to 2-3 patients will be accrued per month, and therefore this
study may require up to 2-3 years to complete enrollment and treatment.

- INCLUSION CRITERIA:

1. Diagnosis

(a) Osteosarcoma, neuroblastoma and melanoma that have been treated with standard
frontline therapy and are judged to be incurable with standard therapy, based
upon the fact that they are unresectable, metastatic, progressive/persistent or
recurrent.

Evaluable disease must be present.

i) For all histologies except osteosarcoma and neuroblastoma, pathologic review
of frozen tissue must document GD2+ expression. Positive expression is defined as
at least 2+ expression (0-4+ scale) in >50 percent of the tumor cells using
anti-GD2 mAb 14G2a. If adequate archived frozen tissue is available, this may be
utilized, or if not, patients may undergo biopsy following enrollment to obtain
tissue to assess GD2 expression, with the following restrictions.

ii) Patients with histologies other than osteosarcoma or neuroblastoma must have
adequate accessible tumor for biopsy (at least 1 cm diameter).

iii) Procedures employed to acquire biopsies for tumor lysates will be limited to
percutaneous needle or core biopsies, thoracoscopic excision or open biopsies of
readily accessible lesions. Pulmonary lesions may be biopsied but extensive
surgery such as thoracotomy or laparotomy should not be employed.

iv) Patients who will require biopsy should not be enrolled if in the opinion of
the principal investigator, the tumor site places the patient at substantial risk
from the biopsy procedure.

2. Weight greater than or equal to 15 kg

3. Age less than or equal to 35 years old at the time of enrollment.

4. Prior Therapy:

1. The patient s malignancy must have relapsed after or failed to respond to
frontline curative therapy and/or there must not be any curative treatment
options available at the time of study entry.

2. There is no limit to the number of prior treatment regimens. However,
patients must have fully recovered from the acute toxic effects of prior
chemotherapy, immunotherapy, or radiotherapy prior to study enrollment. Any
grade 3 or 4 non-hematologic toxicity of any previous therapy must have
resolved to grade 2 or less.

3. Myelosuppressive chemotherapy: Patients must not have received
myelosuppressive chemotherapy within 3 weeks of enrollment (6 weeks if prior
nitrosourea).

4. Hematopoietic growth factors: At least 7 days must have elapsed since the
completion of therapy with a growth factor. At least 14 days must have
elapsed after receiving pegfilgrastim.

5. At least 7 days must have elapsed since the completion of therapy with a
biologic agent, targeted agent, tyrosine kinease inhibitor or a metronomic
nonmyelosuppressive regimen.

6. Monoclonal antibodies: At least 4 weeks must have elapsed since prior
therapy that included a monoclonal antibody.

7. Radiotherapy: 3 weeks must have elapsed since XRT

5. Performance status:

ECOG 0, 1 or 2, or for children less than or equal to 10 years of age, Lansky
greater than or equal to 60.

6. Cardiac function:

Left ventricular ejection fraction greater than or equal to 40 percent or
fractional shortening greater than or equal to 28 percent.

7. Liver function:

Serum total bilirubin < 2 mg/dl, serum AST and ALT less than or equal to 3 x
upper limit of normal. Patients with Gilbert s syndrome are excluded from the
requirement of a normal bilirubin and patients will not be excluded if liver
enzyme elevation is due to tumor involvement. (Gilbert s syndrome is found in
3-10% of the general population, and is characterized by mild, chronic
unconjugated hyperbilirubinemia in the absence of liver disease or overt
hemolysis). NOTE: Adult values will be used for calculating hepatic toxicity and
determining eligibility, as is standard on POB phase I trials.

8. Renal function:

Age-adjusted normal serum creatinine according to the following table or a
creatinine clearance greater than or equal to 60 ml/min/1.73 m(2).

Age less than or equal to 5 Maximum serum creatinine (mg/dl) 0.8

Age greater than 5 and less than or equal to 10 Maximum serum creatinine (mg/dl)
1.0

Age greater than 10 and less than or equal to 15 Maximum serum creatinine (mg/dl)
1.2

Age greater than 15 Maximum serum creatinine (mg/dl) 1.5

9. Marrow function:

ANC must be > 750/mm(3), platelet count must be greater than or equal to
75,000/mm(3) (not achieved by transfusion).

10. Ability to give informed consent.

For patients <18 years of age, their legal guardian must give informed consent.
Pediatric patients will be included in age-appropriate discussion in order to
obtain verbal assent.

11. Durable power of attorney form offered (patients (Bullet)18 years of age only).

12. Birth Control

Female and male patients (and when relevant their partners) must be willing to practice
birth control (including abstinence) during and for two months after treatment, if of
childbearing potential.

EXCLUSION CRITERIA:

1. Concurrent Illnesses

Clinically significant systemic illness (e.g. serious active infections or significant
cardiac, pulmonary, hepatic or other organ dysfunction), that in the judgment of the
PI would compromise the patient s ability to tolerate protocol therapy or
significantly increase the risk of complications.

Peripheral nerve symptoms from prior therapies or from tumor compression > grade 1.

2. Untreated CNS metastasis

Extradural masses that have not invaded the brain parenchyma or parameningeal tumors
without evidence for leptomeningeal spread will not render the patient ineligible.
Patients with previous CNS tumor involvement that has been treated and is stable for
at least 6 weeks following completion of therapy are eligible.

3. Prior Therapy

Previous treatment with genetically engineered GD2-CAR T cells. Previous vaccine
therapy, anti-GD2 mAb therapy or therapy with other genetically engineered T cells is
not an exclusion criteria.

4. Lactating or pregnant females (due to risk to fetus or newborn).

5. Active HIV, HBV or HCV infection.

6. Immune Therapies

Patients who require systemic corticosteroid or other immunosuppressive therapy.
Immunosuppressive therapy must be stopped at least 14 days prior to cell infusion.

INCLUSION OF WOMEN AND MINORITIES:

Both men and women of all races and ethnic groups are eligible for this trial.