Study of GDC-0084 in Pediatric Patients With Newly Diagnosed Diffuse Intrinsic Pontine Glioma or Diffuse Midline Gliomas

There are two research strata: Stratum A1 and Stratum A2. All subjects will receive standard
RT no later than 14 days after study enrollment and no later than 42 days after the date of
radiographic diagnosis or surgery, whichever date is the later. Four to 12 weeks after the
completion of standard RT, subjects without radiographic evidence of progression will receive
single-agent oral GDC-0084 once daily in cycles of 28 days. Treatment may be continued for up
to 2 years in the absence of disease progression or unacceptable toxicity.

Subjects enrolled on Stratum A1 will be enrolled on the dose-escalation phase of the study.
Up to 4 different dose levels will be evaluated: Dose level 0, 21 mg/m2; Dose level 1, 27
mg/m2; Dose level 2, 35 mg/m2; and Dose level 3, 45 mg/m2. The Rolling 6 design will be used
to determine the maximum tolerated dose (MTD)/recommended phase 2 dosage (RP2D) of GDC-0084.

Subjects enrolled on Stratum A1 must be able to swallow capsules during the first cycle of
therapy (the dose-limiting toxicity (DLT) evaluation period). Subjects who complete the DLT
evaluation period and are no longer able to swallow the whole capsule may take GDC-0084
opened, sprinkled in purée. Subjects enrolled on Stratum A1 who change administration methods
will have mandatory intrapatient pharmacokinetic studies performed. Subjects enrolled on
Stratum A1 who are no longer able to swallow whole capsules of GDC-0084 during the DLT
evaluation period (cycle 1) will be taken off treatment.

Once the MTD has been established in Stratum A1, the Stratum A1 expansion cohort and Stratum
A2 will open simultaneously. Subjects enrolled on the Stratum A1 expansion cohort will be
required to swallow capsules. Subjects enrolled on Stratum A2 will be restricted to subjects
who are unable to swallow capsules until the Stratum A1 expansion cohort is filled. Once the
Stratum A1 expansion cohort has been filled, both subjects who are able to swallow capsules
and those unable to swallow capsules may be enrolled on Stratum A2. Subjects enrolled on
Stratum A2 who are unable to swallow capsules will take GDC-0084 as an open capsule sprinkled
in purée and will undergo mandatory interpatient pharmacokinetic studies.

Inclusion Criteria:

- Age greater than or equal to 2 years and less than 22 years at the time of enrollment.

- Subjects must have a BSA > 0.65 m^2.

- Subjects must have one of the following newly diagnosed tumors:

- Non-biopsied typical DIPG, defined as a tumor with a pontine epicenter and
diffuse intrinsic involvement of the pons. These subjects are eligible without
histologic confirmation.

- Biopsied typical DIPG: WHO grade III anaplastic astrocytoma (IDH WT or IDH NOS),
WHO grade IV glioblastoma (IDH WT or IDH NOS), or diffuse midline glioma, H3 K27M
mutant. Subjects with a typical DIPG who undergo a biopsy may be eligible for the
study if the tumor does not harbor the H3 K27M mutation, yet eligibility is
restricted to anaplastic astrocytoma or glioblastoma, IDH WT or IDH NOS, tumors.

- Atypical brainstem glioma: diffuse midline glioma, H3 K27M mutant.

- Non-brainstem midline glioma, defined as tumors with an epicenter within midline
structures, including the thalamus, spinal cord, and cerebellum: diffuse midline
glioma, H3 K27M mutant.

- Subjects must have localized, non-metastatic disease; MRI of spine must be performed
if disseminated disease is suspected by the treating physician.

- Subjects must be able to start radiation therapy no later than 42 days after
radiographic diagnosis or surgery, whichever date is later.

- Performance score ≥ 50 (Lansky for research subjects aged 16 years or younger and
Karnofsky for subjects older than 16 years). Subjects 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.

- Subjects must not have received any prior therapy, including prior treatment with a
PI3 kinase, mTOR, or PI3K/mTOR inhibitor, other than surgery and/or steroids.

- Subjects must have adequate organ function documented at the time of study enrollment
as follows:

- Bone marrow: Hemoglobin ≥ 8g/dL [may have received packed red blood cell
transfusion], absolute neutrophil count (ANC) ≥ 1000/mm^3, platelets ≥
50,000/mm^3 [transfusion independent].

- Renal: Normal serum creatinine based on age (Age 2 to ≤5: 0.8; Age >5 to <10:
1.0; Age >10 to <15: 1.2; Age ≥15: 1.5) or GFR ≥ 70 mL/min/1.73m^2

- Hepatic: ALT and AST < 3 × the institutional upper limit of normal (ULN), total
bilirubin concentration < 1.5 x the institutional ULN, albumin ≥ 2g/dL.

- Shortening fraction of ≥ 27% by ECHO or ejection fraction of ≥ 50% by gated
radionuclide study.

- Subjects must not have congenital long QT syndrome and QTc < 500 ms.

- Subjects must not require the use of any CYP34A-inducing or -inhibiting agents, with
the exception of corticosteroids.

- Female subjects of childbearing potential must not be pregnant or breastfeeding a
child. Female subjects of childbearing potential aged 10 years or older must have a
negative serum or urine pregnancy test.

- Subjects of childbearing or child-fathering potential must be willing to use a
medically acceptable form of birth control, which can be abstinence, while being
treated on this study and for 3 additional months after completion of therapy.

- Informed consent: All subjects and/or their parents or legally authorized
representatives must sign a written consent. Assent, when appropriate, will be
obtained according to institutional guidelines.

Exclusion Criteria:

- Subjects with evidence of tumor infiltration of three or more cerebral lobes on
diagnostic MRI.

- Subjects with any clinically significant, unrelated systemic illness (serious
infections or significant cardiac, pulmonary, hepatic, or other organ dysfunction)
that would compromise the subject's ability to tolerate protocol therapy or would
probably interfere with the study procedures or results.

- Diabetic subjects who require insulin therapy.

- Subject with a history of clinically significant, uncontrolled heart disease and/or
repolarization abnormalities as documented by a standard 12-lead ECG.

- Subjects receiving any other anticancer (glucocorticoids are acceptable) or
investigational drug therapy.

- Subjects unable to return for follow-up visits or obtain follow-up studies required to
assess toxicity of therapy.

- Subjects with disseminated disease.

- Pregnant subjects or subjects breast-feeding a child.