SJDAWN: St. Jude Children's Research Hospital Phase 1 Study Evaluating Molecularly-Driven Doublet Therapies for Children and Young Adults With Recurrent Brain Tumors

Patients will be stratified by the molecular and histologic characteristics of their tumor to
one of three treatment strata.

STRATUM A:

- Combination Treatment: ribociclib and gemcitabine.

- Patient Population: Participants with a diagnosis of refractory or recurrent
medulloblastoma (Group 3/4) or refractory or recurrent ependymoma (including:
ependymoma, not otherwise specified (NOS), WHO Grade III; ependymoma, RELA fusion
positive; anaplastic ependymoma; ependymoma, NOS, WHO grade II).

STRATUM B:

- Combination Treatment: ribociclib and trametinib.

- Patient Population: Participants with a diagnosis of one of the following refractory or
recurrent CNS diseases: medulloblastoma [sonic hedgehog (SHH)], medulloblastoma (WNT),
high grade glioma (including: high grade glioma, (NOS), WHO Grade III or IV; anaplastic
astrocytoma, IDH mutant; glioblastoma, IDH-wildtype; glioblastoma, IDH-mutant; diffuse
midline glioma, H3K27-mutant; anaplastic oligodendroglioma, IDH mutant and
1p/19q-codeleted; anaplastic pleomorphic xanthoastrocytoma) or select central nervous
system (CNS) embryonal tumors (including: embryonal tumors with multilayered rosettes,
C19MC-altered; embryonal tumors with multilayered rosettes, not otherwise specified
(NOS); medulloepithelioma; CNS neuroblastoma; CNS ganglioneuroblastoma; CNS embryonal
tumor, NOS; atypical teratoid/rhabdoid tumor; CNS embryonal tumor with rhabdoid
features).

STRATUM C:

- Combination Treatment: ribociclib and sonidegib.

- Patient Populations: Participants with refractory or recurrent medulloblastoma (SHH) >6
months off smoothened inhibitor, presence of 9q loss or PTCH1 mutant, skeletally mature.

The rolling 6 design will be used separately in each stratum to estimate the MTD or RP2D and
determine the dose-limiting toxicity (DLT) of the combination of escalating doses. Therapy
will be administered in cycles of 28 days and may be continued for up to 24 months (26
cycles) in the absence of disease progression or unacceptable toxicity.

Patients will receive doublet therapy in cycles of 28 days. The dose-limiting toxicity
(DLT)-evaluation period will consist of the first cycle (i.e. first 4 weeks of therapy).
Research participants will be evaluated at least once a week during the DLT-evaluation period
and at regular intervals thereafter. Standard (e.g., physical exam, blood tests, and disease
evaluations) tests will be obtained at regular intervals. Research-associated evaluations
(e.g., pharmacokinetic studies, etc.) will also be obtained during therapy. Treatment may be
continued for up to 2 years in the absence of disease progression or unacceptable toxicity.

Potential participants will first be screened using the screening inclusion/exclusion shown
below. If they meet the requirements of the screening phase, they will then be evaluated
for enrollment based on the overall study's inclusion criteria as well as the
stratum-specific inclusion/exclusion criteria for the applicable stratum, all of which are
shown below.

SCREENING INCLUSION CRITERIA - ALL PARTICIPANTS:

- Participants with recurrent, progressive, or refractory brain tumors.

- Age ≥ 1 year and < 25 years at the time of screening. Exception: Participants with
recurrent, progressive, or refractory Medulloblastoma and are ≥ 1 and < 40 years of
age at the time of study screening are eligible for screening.

- Participants and/or guardian have the ability to understand and the willingness to
sign a written informed consent document according to institutional guidelines.

SCREENING EXCLUSION CRITERIA - ALL PARTICIPANTS:

- Participants with a diagnosis of recurrent, progressive, or refractory low grade
glioma (LGG).

- Previous exposure to a CDK4/6 inhibitor (palbociclib, abemaciclib, or ribociclib).

- Participants with a history of clinically significant, uncontrolled heart disease
and/or repolarization abnormalities.

- Participants with any history of QTc prolongation (i.e. QTc interval of > 450 msec).

Participants who meet the requirements of the screening phase will then be evaluated for
enrollment based on the overall study's inclusion criteria as well as the stratum-specific
inclusion/exclusion criteria for the applicable stratum, all of which are shown below.

INCLUSION CRITERIA - OVERALL STUDY - ALL PARTICIPANTS:

- Evaluable disease, as defined as meeting any of the following:

- Patients who have measurable disease

- Patients with radiologically discernible but non-measurable lesions (i.e.
leptomeningeal disease)

- Patients with CSF positive disease

- Participants must have received their last dose of anticancer therapy (including
experimental) at least 4 weeks prior to study enrollment.

- Participants must have had their last fraction of radiation at least 4 weeks prior to
study enrollment. Participants who received radiation therapy for palliation must have
had their last fraction of radiation at least 2 weeks prior to study enrollment.

- Participants who are receiving corticosteroids must be on a stable or decreasing dose
for at least 1 week prior to study enrollment with no plans for escalation.

- Participants who are receiving known strong inducers and/or strong inhibitors of
CYP3A4/5, drugs that have a narrow therapeutic window and are predominantly
metabolized through CYP3A4/5, and medications that carry a known risk for QT
prolongation must discontinue these drugs at least 7 days prior to study enrollment.

- Participants must discontinue herbal preparations, herbal medication, and dietary
supplements, with the exception of multivitamins, at least 7 days prior to study
enrollment.

- Participants must be able to swallow medication. It is acceptable to administer
medication via a g-tube if participant has a g-tube. It is not acceptable to place a
g-tube for the purpose of delivering study medication.

- Participants must have a Lansky (≤ 16 years) or Karnofsky (> 16 years) score of at
least 50 at the time of study enrollment. 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.

- Participant must have adequate bone marrow and organ function defined as:

- ANC ≥ 1000/mm3 without growth factor support within 7 days of the test

- Platelet count ≥ 50,000/mm^3 without support of a platelet transfusion within 7
days of the test

- Hemoglobin ≥ 8.0 g/dL without support of a blood transfusion within 7 days of the
test

- Creatinine clearance ≥ 70 mL/min/1.73 m^2 or serum creatinine ≤ the maximum serum
creatinine based on age/gender (threshold creatinine values derived from the
Schwartz formula for estimating GFR utilizing child length and stature data
published by the Centers for Disease Control and Prevention or creatinine
clearance ≥70 mL/min/1.73 m^2).

- Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 x ULN.
For the purposes of eligibility the ULN of ALT and AST is 45 U/L.

- Total bilirubin ≤ ULN or if > ULN then direct bilirubin ≤ 1.5xULN.

- Participants and/or guardian have the ability to understand and the willingness to
sign a written informed consent document according to institutional guidelines.

EXCLUSION CRITERIA - OVERALL STUDY - ALL PARTICIPANTS:

- Participants receiving any other investigational agents.

- Participants with other clinically significant medical disorders (serious infections
or significant cardiac, pulmonary, hepatic, psychiatric, GI disease, or other organ
dysfunction) that in the investigator's judgment could compromise their ability to
tolerate or absorb protocol therapy or would interfere with the study procedures or
results.

- Female participants who are breastfeeding a child.

- Participants with QTc interval of > 450 msec on screening ECG.

- Participants with a pathogenic somatic or known germline retinoblastoma (RB1) gene
mutation.

(A) INCLUSION CRITERIA - STRATUM A PARTICIPANTS ONLY:

- Participants with recurrent, progressive, or refractory Non-WNT Non-SHH (NWNS)
Medulloblastoma or Ependymoma as confirmed through central pathology review.

- Age ≥ 1 year and < 25 years at the time of enrollment.

- Female participants of childbearing potential must have a negative pregnancy test at
the time of enrollment on this study and be willing to use a highly effective method
of contraception throughout the study and for 16 weeks after discontinuation of the
study drug.

- Male participants of child fathering potential must be willing to use medically
acceptable form of contraception during treatment and for 16 weeks after stopping
treatment.

(A) EXCLUSION CRITERIA - STRATUM A PARTICIPANTS ONLY:

- Participants with subependymoma or myxopapillary ependymoma.

(B) INCLUSION CRITERIA - STRATUM B PARTICIPANTS ONLY:

- Participants with recurrent, progressive, or refractory CNS tumors as confirmed
through central pathology review and whose diagnosis is being treated on this study.

- Age ≥ 1 year and < 25 years at the time of study enrollment.

- Must meet the following weight and BSA restrictions:

- For enrollment on dose levels 0A, must have a weight ≥16kg and <32kg.

- For enrollment on dose level 0B, must have a weight of ≥32kg and BSA ≥ 0.55m^2.

- For enrollment on dose level 1, must have a weight ≥16kg and BSA ≥0.55m^2.

- For enrollment on dose level 2, must have a weight ≥16kg and BSA≥ 0.63m^2

- For enrollment on dose levels 3 or 4A, must have a weight ≥16kg

- For enrollment on dose levels 4B or 5, must have a weight ≥20kg and ≤106kg

- Participant must be able to swallow trametinib tablets.

- Female participants of childbearing potential must have a negative pregnancy test at
the time of enrollment on this study and be willing to use a highly effective method
of contraception throughout the study and for 16 weeks after discontinuation of the
study drug.

- Male participants of child fathering potential must be willing to use medically
acceptable form of contraception during treatment and for 16 weeks after stopping
treatment.

(B) EXCLUSION CRITERIA - STRATUM B PARTICIPANTS ONLY: Participants eligible for this study
must NOT meet ANY of the following criteria.

- Participants with Low Grade Glioma (LGG) or Diffuse Intrinsic Pontine Glioma (DIPG).

- Previous exposure to a MEK inhibitor (i.e. trametinib, selumetinib).

- Participants with abnormal LVEF on screening, defined as > 10% below lower limit of
normal on screening.

- Participants with retinal vein occlusion (RVO).

- Previous exposure to a MEK inhibitor (i.e., trametinib, selumetinib.

(C) INCLUSION CRITERIA - STRATUM C PARTICIPANTS ONLY:

- Participants with recurrent, progressive, or refractory SHH Medulloblastoma and
presence of either a or b as confirmed by central pathology review of the tumor
specimen: a) copy number loss of 9q b) PTCH1 mutation and whose diagnosis is being
treated on this study.

- Age ≥ 10 years and <40 years at the time of study enrollment.

- Participant must be skeletally mature as defined as females with a bone age ≥ 15 years
(180 months) and males with a bone age ≥ 17 years (204 months). This includes
participants that are within 2 standard deviations of this value (i.e. if SD = 11
months on bone age; then a male patient who has a bone age of 182 months would be
eligible; or a female patient with a bone age of 158 months.)

- Female participants of childbearing potential must have a negative pregnancy test at
the time of enrollment on this study and be willing to use a highly effective method
of contraception throughout the study and for 8 months after discontinuation of the
study drug.

- Male participants of child fathering potential must be willing to use medically
acceptable form of contraception during treatment and for 8 months after stopping
treatment.

(C) EXCLUSION CRITERIA - STRATUM C:

- Exposure to smoothened inhibitor (vismodegib, sonidegib) within the last 6 months.