H3.3K27M Peptide Vaccine for Children With Newly Diagnosed DIPG and Other Gliomas

Subjects who are eligible will receive a specific peptide vaccine, along with a helper drug
called poly-ICLC, every 3 weeks for the first 6 months of treatment. Subjects will be
monitored routinely by laboratory assessments, physical evaluation, vital signs, and MRI.
Subjects who tolerate therapy well and have stable or improved disease after 6 months of
treatment can continue to receive treatment, now every 6 weeks, for a total of 96 weeks of
treatment.

Inclusion Criteria:

- Stratum A:

• Newly diagnosed children (3-21 years old) with DIPG who are positive for the
H3.3K27M mutation (positive testing in CLIA laboratory) that underwent standard
radiation therapy.

- Stratum B:

- Newly diagnosed children (3-21 years old) with diagnosis of glioma other than
DIPG who are positive for the H3.3K27M mutation (positive testing in CLIA
laboratory) including spinal cord gliomas that underwent standard radiation
therapy.

The following eligibility criteria apply to both Stratum A and B.

- The patient must test positive for HLA-A2 (tested by a CLIA approved laboratory; only
the HLA A*02:01 subtype is eligible) The patient must be either off systemic steroids
or be on stable dose of dexamethasone (max 0.1 mg/kg/day; maximum 4mg/day) at time of
enrollment.

- Patients must not have received any prior chemotherapy, immunotherapy or bone marrow
transplant for the treatment of their tumor. Prior use of temozolomide during
radiation at maximum of the standard pediatric dosing (defined as 90 mg/m^2/dose
continuously during radiation therapy for 42 days) or dexamethasone is allowed.

- Patients must have undergone radiation therapy and surgery as part of their standard
of care.

- Stratum A: Radiation therapy must have started within 4 weeks of diagnosis by
imaging or surgery, whichever is later.

- Stratum B: For subjects undergoing surgery for more extensive resection,
radiation therapy should be started within 4-6 weeks from surgery.

- H3.3K27 mutation must have been confirmed in the tumor tissue in a CLIA approved
laboratory.

- Karnofsky ≥ 50 for patients ≥ 16 years of age, and Lansky ≥ 50 for patients < 16 years
of age (See Appendix A). Patients who are unable to walk because of paralysis, but who
are up in a wheelchair, will be considered ambulatory for the purpose of assessing the
performance score.

- The patient must have adequate organ function defined as

Adequate Bone Marrow Function Defined as:

- Peripheral absolute neutrophil count (ANC) ≥ 1000/mm3 and

- Platelet count ≥ 100,000/mm3 (transfusion independent, defined as not receiving
platelet transfusions for at least 7 days prior to enrollment).

Adequate Renal Function Defined as:

- Creatinine clearance or radioisotope glomerular filtration rate (GFR) ≥ 70mL/min/1.73
m2 or

- A serum creatinine based on age/gender as follows:

Age Maximum Serum Creatinine (mg/dL) Male Female

1. - 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 The threshold
creatinine values in this table were derived from the Schwartz formula for estimating GFR
utilizing child length and stature data published by the CDC.

Adequate Liver Function Defined as:

- Bilirubin (sum of conjugated + unconjugated) ≤ 1.5 x upper limit of normal (ULN) for
age and

- SGPT (ALT) ≤ 110 U/L and

- Serum albumin ≥ 2 g/dL.

Adequate Neurologic Function Defined as:

- Patients with seizure disorder may be enrolled if seizure disorder is well controlled.

- The effects of the H3.3K27M vaccine on the developing human fetus are unknown. For
this reason, females of child-bearing potential and men must agree to use adequate
contraception. Adequate methods include: hormonal or barrier method of birth control;
or abstinence prior to study entry and for the duration of study participation. Should
a woman become pregnant or suspect she is pregnant while she or her partner is
participating in this study, she should inform her treating physician immediately. Men
treated or enrolled on this protocol must also agree to use adequate contraception
prior to the study and for the duration of study participation.

- Ability to understand a written informed consent document, and the willingness to sign
it. Assent will be obtained when appropriate based on the subjects age.

Exclusion Criteria:

- Investigational Drugs

- Patients who are currently receiving another investigational drug are not
eligible.

- Prior treatment with another investigational drug.

- Anti-cancer Agents

- Patients who are currently receiving other anti-cancer agents are not eligible.

- Prior treatment with other anti-cancer agents.

- Patients with a known disorder that affects their immune system, such as HIV, or an
autoimmune disorder requiring systemic cytotoxic or immunosuppressive therapy are not
eligible. Note: Patients that are currently using inhaled, intranasal, ocular, topical
or other non-oral or non-IV steroids are not necessarily excluded from the study but
need to be discussed with the study chair

- Female patients of childbearing potential must not be pregnant or breast-feeding.
Female patients of childbearing potential must have a negative serum or urine
pregnancy test prior to the start of therapy (as clinically indicated).