This phase II trial determines if the combination of ONC201 with different drugs is effective for treating participants with diffuse midline gliomas (DMGs). Despite years of research, little to no progress has been made to improve outcomes for participants with DMGs, and there are few treatment options. This trial will utilize an adaptive platform design in that the different treatment arms for each cohort will be opened and closed based on ongoing preclinical investigation as well as evolving outcome data from the trial.

Novel agents will be continuously added to this study as pre-clinical data emerge to suggest additive or synergistic activity when combined ONC201. Should a novel agent not have an RP2D at the time of incorporation into this study, a phase 1 lead-in will be performed prior to initiation of combination therapy (via study amendment).

OUTLINE:

This is a multi-arm/cohort, multi-institutional, open-label trial. The study is divided into cohorts based on stage of disease (newly-diagnosed, post-radiation therapy without disease progression, and at disease progression).

---THIS STUDY IS NOT ENROLLING ON COHORTS 1, 2, 3, and 4 --

COHORT DESCRIPTIONS:

--ENROLLING-- COHORT 5: Includes participants whose tumor demonstrates specific molecular alterations of interest considered targetable by an approved/available agent(s) and recommended by the PNOC022 tumor board. Participants are also allowed to receive ONC201 monotherapy with radiation or re-irradiation therapy.

Cohort 5^1: Includes newly diagnosed participants who have already undergone tumor tissue collection and have not yet completed radiation therapy.

Cohort 5^2: Includes newly diagnosed participants who have already undergone tumor tissue collection and have completed radiation therapy.

Cohort 5^3: Includes participants with progressive DMG who are not planned for SOC tumor collection and will undergo re-irradiation.

--ENROLLING-- COHORT 6: Includes participants with DMGs who have completed focal radiation therapy and are within 4-14 weeks from completion of radiation therapy without evidence of progression, who will undergo repeated intratumor DNX-2401 infusions.

-NOT CURRENTLY ENROLLING- COHORTS 1A & 2A (Target Validation cohorts); Includes newly diagnosed participants that have not yet undergone tumor tissue collection. Cohort 1A will include participants with DMG who have not yet completed radiation therapy and Cohort 2A will include participants with DMG who have completed radiation therapy.

-NOT CURRENTLY ENROLLING - COHORTS 1B & 2B: Includes newly-diagnosed participants who have already undergone tumor tissue collection. Cohort 1B will include participants with DMG who have not yet completed radiation therapy and Cohort 2B will include participants with DMG who have completed radiation therapy.

-NOT CURRENTLY ENROLLING- COHORTS 3A & 3B: Includes participants with progressive DMG. Cohort 3A will include participants planned for standard of care (SOC) tumor tissue collection. Cohort 3B will include participants not planned for SOC tumor tissue collection. The nomenclature will delineate participants previously enrolled in Cohorts 1 or 2.

-NOT CURRENTLY ENROLLING - COMBINATION COHORTS 1, 2 and 3: Participants are randomized to 1 of 3 arms (Arm 2,4,6)

ARM 2: During the trial validation phase, participants without prior biopsy receive ONC201 on day -1 prior to standard of care biopsy. During the radiation/re-irradiation phase, participants without prior radiation therapy or have disease progression after radiation therapy undergo weekly radiation therapy and receive ONC201 weekly during radiation therapy. During the maintenance phase, participants receive ONC201 weekly and paxalisib daily. Cycles repeat every 28 days (4 weeks) in the absence of adverse events of unacceptable toxicity.

ARM 4: During the trial validation phase, participants without prior biopsy receive ONC201 on days -2 and -1 prior to standard of care biopsy. During the radiation/re-irradiation phase, participants may receive ONC201 weekly during radiation therapy. During the maintenance phase, participants receive ONC201 weekly and paxalisib. Cycles repeat every 28 days (4 weeks) in the absence of adverse events or unacceptable toxicity.

ARM 6: During trial validation phase, participants without prior biopsy receive paxalisib on day -1 prior to standard of care biopsy. During the radiation/re-irradiation phase, participants without prior radiation therapy or have disease progression after radiation therapy undergo radiation therapy five times a week and receive paxalisib during radiation therapy. During the maintenance phase, participants receive ONC201 and paxalisib during each cycle. Cycles repeat every 28 days (4 weeks) in the absence of adverse events of unacceptable toxicity.

-NOT CURRENTLY ENROLLING - COHORT 4A and 4B: Includes patients who are currently not eligible for defined combination arms of PNOC022 or other clinical trials investigating ONC201, such as ONC201-108 ACTION trial.

Cohort 4A^1: Includes newly diagnosed participants that have not yet undergone tumor tissue collection and have not yet completed radiation therapy.

Cohort 4A^2: Includes newly diagnosed participants that have not yet undergone tumor tissue collection and have completed radiation therapy. Cohort 4A^3: Includes participants with progressive DMG who are planned for SOC tumor collection and will undergo re-irradiation.

Cohort 4B^1: Includes newly diagnosed participants who have already undergone tumor tissue collection and have not yet completed radiation therapy.

Cohort 4B^2: Includes newly diagnosed participants who have already undergone tumor tissue collection and have completed radiation therapy. Cohort 4B^3: Includes participants with progressive DMG who are not planned for SOC tumor collection and will undergo re-irradiation.

All Cohorts: After completion of study treatment, participants are followed at 30 days and then every 3 months for up to 5 years, until withdrawal of consent, or until death, whichever occurs first.

PRIMARY OBJECTIVES:

I. To assess efficacy of combination therapy with ONC201 (ONC201) and novel agent in participants with DMG based on median progression-free survival at 6 months (PFS6) (Cohorts 1 and 2).

II. To assess efficacy of combination therapy with ONC201 and novel agent in participants with recurrent DMG based on overall survival at 7 months (OS7) (Cohort 3).

III. To assess the safety and toxicity of a revised ONC201 dose and dosing schedule in participants with DMG. (Cohort 4).

IV. To assess the safety and toxicity of a revised ONC201 dosing schedule in combination with radiation or re-irradiation in participants with DMG. (Cohort 4).

V. To evaluate the pharmacokinetic profile of a revised ONC201 dose and dosing schedule in participants with DMG. (Cohort 4).

VI. To assess the safety and toxicity of ONC201 with agent(s) that will be determined by a specialized tumor board recommendation that is based on molecular assessments of tumor tissue or cerebrospinal fluid (CSF). (Cohort 5).

VII. To determine the maximum tolerated number of intratumor infusions of DNX-2401, with a maximum of 6, in participants with thalamic or pontine DMG who completed radiotherapy. (Cohort 6, Phase 1) VIII. To assess efficacy of repeated intratumor infusions with DNX-2401 in participants with DMG based on overall survival at 15 months. (Cohort 6, expansion cohort)

EXPLORATORY OBJECTIVES:

I. To confirm blood brain barrier (BBB) penetration of ONC201 in DMGs by measuring the concentration of ONC201 in tumor tissue (All cohorts except Cohort 6; target validation phase).

II. To confirm BBB penetration of novel agents in DMGs by measuring the concentration of drug (or metabolite) in tumor tissue All cohorts except Cohort 6; target validation phase).

III. To assess changes in immune cell infiltration in DMG tumor tissue after 1 or 2 doses of ONC201 (All cohorts except Cohort 6; target validation phase).

IV. To assess correlation of intratumoral concentration of ONC201 with clinical outcome (All cohorts except Cohort 6; target validation phase).

V. To assess correlation of intratumoral drug concentration of novel agents with clinical outcome. (All cohorts except Cohort 6; target validation phase).

VI. To assess if intratumoral ONC201 concentrations differ in irradiated versus nonirradiated tumor tissue. (All cohorts except Cohort 6; target validation phase).

VII. To assess if intratumoral concentrations of novel agents differ in irradiated versus nonirradiated tumor tissue. (All cohorts except Cohort 6; target validation phase).

VIII. To assess tumor tissue biomarkers in the context of clinical outcome, such as PFS6 and/or OS12. (All cohorts except Cohort 6; target validation phase).

IX. To assess efficacy of combination therapy ONC201 and novel agent based on overall survival at 12 months (OS12). (All cohorts except Cohort 6; maintenance combinations).

X. To assess toxicity of combination therapy ONC201 and novel agents. (All cohorts except Cohort 6; maintenance combinations).

XI. To assess the toxicity of weekly ONC201 in combination with up-front radiation therapy. (Cohort 1; radiation therapy phase).

XII. To assess the toxicity of twice weekly ONC201 in combination with up-front radiation therapy. (Cohort 1; radiation therapy phase).

XIII. To assess the toxicity of novel agents in combination with up-front radiation therapy. (Cohort 1; radiation therapy phase).

XIV. To assess the toxicity of weekly ONC201 in combination with re-irradiation after progression. (Cohort 3).

XV. To assess the toxicity of twice weekly ONC201 in combination with re-irradiation therapy after progression. (Cohort 3).

XVI. To assess the toxicity of novel agents in combination with re-irradiation after progression. (Cohort 3).

XVII. To assess the toxicity of ONC201 in combination with novel agents in participants after re-irradiation after progression. (Cohort 3).

XVIII. To assess efficacy of a revised ONC201 dose and dosing schedule board based on median progression free survival (PFS) and overall survival (OS). (Cohort 4).

XIX. To assess efficacy of ONC201 in combination with targeted agent(s) that will be determined by a specialized tumor board based on median OS. (Cohort 5).

XX. To assess cerebrospinal fluid (CSF) biomarkers in the context of clinical outcome, such as PFS6 and/or OS12. (All cohorts except Cohort 6) XXI. To assess levels of circulating tumor deoxyribonucleic acid (ctDNA) in the context of imaging response criteria and clinical outcome, such as PFS6 and/or OS12. (All cohorts except Cohort 6) XXII. To assess single cell ribonucleic acid (RNA) sequencing in the context of clinical outcome, such as PFS6 and/or OS12. (All cohorts except Cohort 6) XXIII. To assess microbiome and flow cytometry studies in the context of imaging and clinical outcomes using descriptive statistics.(All cohorts except Cohort 6) XXIV. To assess Health-Related Quality of Life (HRQOL) and cognitive measures.(All cohorts except Cohort 6) XXV. To assess participants and/or proxy satisfaction with study participation via participant-reported outcome (PRO) measures. (All cohorts except Cohort 6) XXVI. To assess on therapy toxicity and survival in the context of race, ethnicity and other health related social risks. (All cohorts except Cohort 6) XXVII. To assess volumetric measurements of tumor in correlation with median OS. (All cohorts except Cohort 6) XXVIII. To assess MR spectroscopy of tumor in correlation with radiographic response, ONC201 exposure and median PFS and OS. (All cohorts except Cohort 6) XXIX. To assess the therapeutic benefit including overall survival (OS), progression-free survival (PFS), the tumor objective response rate (ORR) and proportion of pseudoprogression (PSP) (Cohort 6) XXX. To assess the persistence of DNX-2401 antigen, DNA and transcripts in the tumor in the context of imaging response criteria and clinical outcome. (Cohort 6) XXXI. To assess the changes in cellular, molecular, and immunologic variables in the tumor in context of imaging response criteria and clinical outcome. (Cohort 6) XXXII. To assess the microbiome in the context of imaging response and clinical outcome. (Cohort 6) XXXIII. To assess peripheral blood biomarkers and cfDNA studies in the context of imaging and clinical outcome. (Cohort 6) XXXIV. To assess CSF biomarkers and cfDNA studies in the context of imaging and clinical outcomes. (Cohort 6) XXXV. To assess changes in functional status and in quality of life applying the PedsQLTM (Generic Score Scale). (Cohort 6) XXXVI. To assess patient and/or proxy satisfaction with study participation via patient-reported outcome (PRO) measures. (Cohort 6) XXXVII. To assess on therapy toxicity in the context of race, ethnicity and other health related social risks. (Cohort 6) XXXVIII. To assess volumetric measurements of tumor in correlation with median OS. (Cohort 6) XXXIX. To assess MR spectroscopy of tumor in correlation with radiographic response. (Cohort 6)

--COHORTS 1, 2, AND 3 CLOSED---

INCLUSION CRITERIA:

COHORT 1A AND 1B:

• New diagnosis of DMG with imaging and/or pathology consistent with a DMG, including spinal cord tumors. In cohort 1B, previous tumor tissue confirmation of DMG is mandatory and pathology must be consistent with a DMG including diffuse midline glioma Histone 3 lysine 27 - mutant (H3K27M); World Health Organization (WHO) grade III and IV H3 wildtype gliomas.
• Must be within 6 weeks of diagnosis to begin standard of care radiation therapy on study.

COHORT 2A AND 2B:

• Diagnosis of DMG with imaging and/or pathology consistent with a DMG, including spinal cord tumors, who have complete standard-of-care radiation therapy. In Cohort 2B, previous tumor tissue confirmation of DMG is mandatory and pathology must be consistent with a DMG including diffuse midline glioma H3K27M mutant; WHO grade III and IV H3 wildtype gliomas.
• Participants must be within 4-14 weeks of completion of radiation. Radiation should have started within 6 weeks of diagnosis.

COHORT 3A AND 3B:

• Diagnosis of recurrent DMG with imaging and/or pathology consistent with a DMG, including spinal cord tumors, who have complete standard-of-care radiation therapy. In cohort 3B, previous tumor tissue confirmation of DMG is mandatory and pathology must be consistent with a DMG including diffuse midline glioma H3K27M mutant; WHO grade III and IV H3 wildtype gliomas.
• Participants must have evidence of progression and not have received any treatment for this progression and have not previously received re-irradiation.

COHORT 4A AND 4B:

• Diagnosis of DMG with imaging and/or pathology consistent with a DMG, including spinal cord tumors. In cohort 4B^1, previous tumor tissue confirmation of DMG is mandatory and pathology must be consistent with a DMG diffuse midline glioma H3K27-altered.
• Not currently eligible for any other clinical trials that include administration of ONC201.

Cohort 4A^1 and 4B^1 (participants with newly diagnosed DMG prior to radiation): Must be able to begin standard of care radiation therapy on study within 6 weeks of diagnosis.

Cohort 4A^2 and 4B^2 (participants with newly diagnosed DMG who have completed radiation): Participants must be within 4-14 weeks of completion of radiation and not have received additional therapy beyond completion of radiation therapy. Radiation should have started within 6 weeks of diagnosis.

Cohort 4A^3 and 4B^3 (participants with DMG at progression): Participants must have evidence of progression and not have received any treatment for this progression and have not previously received re-irradiation.

COHORT 5

• Diagnosis of DMG with imaging and/or pathology consistent with a DMG, including spinal cord tumors. In cohort 5^1, previous tumor tissue confirmation of DMG is mandatory and pathology must be consistent with a DMG diffuse midline glioma H3K27-altered.

• Not currently eligible for any other clinical trials that include administration of ONC201.

• Multifocal and leptomeningeal disease will be eligible for Cohort 5.

• Participant's tumor must demonstrate one of the following molecular alterations considered targetable by an approved agent:

  • BRAFV600E
  • PDGFRA (DNA point mutation or amplification with >=5 copy numbers)
  • FGFR1 (DNA point mutation, gene fusions, or amplification with >=5 copy numbers)
  • NF1

Cohort 5^1 (participants pre-radiation): Must be able to begin standard of care radiation therapy on study within 6 weeks of diagnosis.

Cohort 5^2 (participants post-radiation): Participants must be within 4-14 weeks of completion of radiation and not have received additional therapy beyond completion of radiation therapy. Radiation should have started within 6 weeks of diagnosis.

Cohort 5^3 (participants with progression): Participants must have evidence of progression and not have received any treatment for this progression and have not previously received re-irradiation.

All Cohorts (except Cohort 6):

• Age 2 to 39 years

• Participants must have recovered from all acute side effects of prior therapy and be beyond the window for expected ongoing acute toxicities. Any number of prior therapies are allowed.

• Prior ONC201 exposure is allowed, except in participants who have participated in Chimerix trials investigating ONC201 in the upfront setting. Participants who participated in trials investigating ONC201 in the upfront setting will not be eligible at any time, with the exception if participants received ONC201 as part of PNOC022 or other expanded access programs such as German sources of ONC201.

• Participant body weight must be above the minimum necessary for the participant to receive ONC201 (at least 10 kilograms (kg))

• From the projected start of scheduled study treatment, the following time periods must have elapsed: At least 7 days after last dose of a biologic agent or beyond time during which adverse events are known to occur for a biologic agent, 5 half-lives from any investigational agent, 4 weeks from cytotoxic therapy (except 23 days for temozolomide and 6 weeks from nitrosoureas), 6 weeks from antibodies (21 days for bevacizumab when used for tumor-directed therapy, guidance on use for pseudo-progression is below), or, or 4 weeks (or 5 half-lives, whichever is shorter) from other anti-tumor therapies.

  o The use of bevacizumab to control radiation therapy-induced edema is allowed (if used for tumor-directed therapy, please see required time period above).

  • Dosing limitations are as follows:
  • * Bevacizumab (or equivalent) for up to a maximum of 5 doses, dosing per institutional standard. There is no required washout period.

• Prior use of temozolomide during radiation at maximum of the standard pediatric dosing (defined as 90 mg/m2 /dose continuously during radiation therapy for 42 days) or dexamethasone is allowed. Any other agent given throughout radiation therapy must be discussed with the study chairs prior to beginning the agent.

• Corticosteroids: Participants who are receiving dexamethasone must be on a stable or decreasing dose for at least 3 days prior to baseline magnetic resonance imaging (MRI) scan.

• The participant must have adequate organ function defined as:

  • Peripheral absolute neutrophil count (ANC) >= 750/mm^3 (1.0g/l) AND
  • Platelet count >= 75,000/mm^3 (100x10^9/l) (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment).
  • Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 mL/min/1.73 m^2 OR
  • A serum creatinine within the normal limits for age
  • Bilirubin (sum of conjugated + unconjugated) =< 1.5 x upper limit of normal (ULN) for age AND
  • Serum glutamate pyruvate transaminase (SGPT)(alanine aminotransferase (ALT)) =< 3 x ULN AND
  • Serum albumin >= 2 g/Dl
  • No evidence of dyspnea at rest, no exercise intolerance due to pulmonary insufficiency, and a pulse oximetry of > 92% while breathing room air.
  • Diarrhea < grade 2 by Common Terminology Criteria for Adverse Events (CTCAE) version (v) 5.0
  • No history of congestive heart failure or family history of long QT syndrome.
  • ECG must be obtained to verify the Corrected QT Interval (QTc). If an abnormal reading is obtained, the ECG should be repeated in triplicate. QTC < 470 msec.
  • Participants with history of congestive heart failure, at risk of having or have underlying cardiovascular disease, or with history of exposure to cardiotoxic drugs must have adequate cardiac function as determined by echocardiogram. Shortening fraction of >= 27%.
  • Participants with seizure disorder may be enrolled if seizure disorder is well controlled

• Females of child-bearing potential and males must agree to use adequate contraception.

• Karnofsky >= 50 for participants > 16 years of age and Lansky >= 50 for participants =< 16 years of age. Participants 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.

• Participants must be willing to provide adequate tissue. A minimum of 10-20 paraffin embedded unstained slides OR 1 block with tumor content of 40% or greater is required. Frozen tissue is also acceptable.

COHORT 6 Inclusion Criteria:

• Diagnosis of newly diagnosed thalamic or pontine located DMG with imaging and/or pathology consistent with a DMG, excluding spinal cord tumors, who have completed standard-of-care radiation therapy. If archival tissue is available prior to first biopsy, participants must be willing to provide adequate tissue. A minimum of 10-20 paraffin embedded unstained slides OR 1 block with tumor content of 40% or greater is required.

• Participants must be within 4-14 weeks of completion of radiation. Radiation should have started within 6 weeks of diagnosis.

• Age 2-39 years.

• Prior use of temozolomide during radiation at maximum of the standard pediatric dosing (defined as 90 mg/m2 /dose continuously during radiation therapy for 42 days) is allowed. Any other agent given throughout radiation therapy must be discussed with the study chairs prior to enrollment.

• Participants must have recovered from all acute side effects of prior therapy and be beyond the window for expected ongoing acute toxicities. Washout requirements from prior therapy include:

  • At least 7 days after last dose of a biologic agent or beyond time during which adverse events are known to occur for a biologic agent, 5 half-lives from any investigational agent, 4 weeks from cytotoxic therapy (except 30 days for temozolomide and 6 weeks from nitrosoureas), 6 weeks from antibodies (28 days for bevacizumab when used for tumor-directed therapy, guidance on use for pseudo-progression is below), or 4 weeks (or 5 half-lives, whichever is shorter) from other anti-tumor therapies.
  • At least 4 weeks prior to study enrollment from last immune therapy

• Corticosteroids: Participants treated with corticosteroids must be on stable or decreasing dose for at least 1 week prior to enrollment, with maximum dexamethasone dose 0.1 mg/kg/day dexamethasone equivalent at time of enrollment.

• The participant must have adequate organ function defined as:

  • Peripheral absolute neutrophil count (ANC) >= 750/mm3 (1.0g/l) and
  • Platelet count >= 75,000/mm3 (100x109/l) (transfusion independent, defined as not receiving platelet transfusions for at least 7 days prior to enrollment.
  • Creatinine clearance or radioisotope GFR >= 70mL/min/1.73 m2 or
  • A serum creatinine within the normal limits for age.
  • Total bilirubin <= 3 x upper limit of normal (ULN); in presence of Gilbert's syndrome, total bilirubin </= 6 x ULN or direct bilirubin <= 3 x ULN
  • ALT <= 5 x ULN
  • AST <= 5 x ULN.
  • Serum albumin >= 2 g/dL
  • Diarrhea < grade 2 by CTCAE v5.0.
  • No history of congestive heart failure or family history of long QT syndrome.
  • Participants with seizure disorder may be enrolled if seizure disorder is well controlled.

• The effects of the study drugs on the developing human fetus are unknown. For this reason, females of child-bearing potential and males must agree to use adequate contraception.

• Karnofsky >/= 70 for Participants > 16 years of age and Lansky >/= 70 for participants \

Individual participant data after de-identification will be shared with study collaborators