Patients will be eligible for the study if they meet all of the following inclusion criteria and none of the exclusion criteria.

Inclusion criteria

1. Written informed consent from the patient or their legally authorized representative (LAR) prior to any study-related procedure, and willing and able to comply with the protocol and aware of the investigational nature of this study. 2. At least 18 years of age. 3. KPS score of ≥ 60 4. A confirmed GBM diagnosis must be based on local review of tumor tissue from the initial biopsy, surgery, or re-resection. A formal pathology report confirming GBM is acceptable. It is not a requirement for slides to be sent to a central reviewer. 5. Recurrent or progressive GBM as evaluated by central review applying RANO criteria on contrast MRI scans of the Baseline/Screening MRI scan obtained up to six weeks prior to C1D1 and a historical scan taken before the Baseline/Screening scan that meets at least 1 of the following criteria: 1. In the case of measurable disease, progression will be documented by ≥ 25% increase in the sum of the perpendicular diameter products (SPDPs) of the measurable contrast-enhancing (target) lesions or any new measurable lesions. 2. If the SPDPs cannot be reliably estimated due to the lesion's complex conspicuity, shape, and contrast enhancement pattern, the volume of all measurable and non-measurable lesions may be used instead, applying the same threshold (≥ 25% increase) to confirm disease progression. 3. In the case of non-measurable lesions in the historical scan, any transformation into measurable lesions (≥10 mm in both maximum perpendicular diameters) in the Baseline/Screening scan will be evidence of progression. 4. If there are only non-measurable (non-target) lesions in the Baseline/Screening scan, additional lesions/sites will be considered evidence of progression based on the historical scan. Patients with new cerebrospinal fluid (CSF) seeding will not be considered eligible. 5. If historical scans are unavailable, a radiology report of a scan taken before the Baseline/Screening scan documenting the SPDPs from a previous scan of the enhancing disease or its volume can be used by the central reviewer to assess eligibility if it demonstrates the quality standards and acquisition guidelines required. 6. If the scan obtained during standard of care (prior to initiation of formal clinical screening and patient enrollment) is being used as the Baseline/Screening scan and does not entirely conform to central reader quality standards and acquisition guidelines (ie, artifacts or missing sequences), this can be used for the purpose of inclusion if the central reader in discussion with the sponsor and PI agree it provides evidence based on standard clinical practices of recurrence or progression. 7. Patients at first progression who are treated by re-resection or biopsy to confirm progression do not require measurable disease at their post-operative screening scan as their Baseline/Screening scan. These patients must be medically stable after the procedure as assessed by the PI and have the Baseline/Screening scan available by 7 days before starting treatment. 6. The tumor is localized supratentorially with no leptomeningeal (local or distant), spinal or CSF metastases, and no ventricular invasion (explicit documentation of the disease progression that would be problematic in evaluating the efficacy of this drug). 7. O[6] methylguanine-DNA methyltransferase (MGMT) methylation status must be available; results of routinely used methods for MGMT methylation testing (eg, methylation-specific polymerase chain reaction or quantitative polymerase chain reaction) are acceptable. 8. No more than 1 prior line of treatment (eg, surgery followed by radiation with concomitant chemotherapy, followed by adjuvant chemotherapy is considered as 1 line of treatment). In addition, treatment with tumor treating fields (TTFields; Optune) is acceptable if provided as first line therapy prior to progression or recurrence of disease. 9. A second debulking surgery, additional radiation or gamma knife surgery during the first line treatment or after progression, and for which the investigator does not suspect pseudoprogression is acceptable, as long as no chemotherapy or immunotherapy has been provided. 10. Recovery from toxicity/side effects of all prior therapy to Grade 1 or less, subject to the investigator's discretion, except for alopecia; the following time intervals from previous treatments are required to be eligible: 1. 12 weeks from the completion of radiation (to reduce risk of pseudoprogression), unless progression is confirmed by biopsy 2. 4 weeks from the end of any previous of chemotherapy 3. 2 weeks from tumor biopsy if wound completely healed 4. 4 weeks from any major surgery (maximal debulking surgery, either gross total resection or partial resection), gamma knife surgery or significant traumatic injury. Any surgery incisions or wounds must be completely healed 11. A stable or decreasing dose of corticosteroids (or none) for brain edema for at least 5 days prior to baseline MRI and enrollment in the study to document disease progression such that changes in the MRI are not related to the use of corticosteroids. 12. Eligible for chemotherapy based on adequate bone marrow function and organ function within 2 weeks of study treatment as defined by the following laboratory guidelines, subject to the investigator's discretion: 1. Hematopoietic function: total white blood cell (WBC) count ≥3 × 103/µL, absolute neutrophil count (ANC) ≥1.5 × 10³/µL, platelet count ≥75 × 10³/µL, hemoglobin ≥10 g/dL 2. Hepatic function: bilirubin ≤1.5 × × the upper limit of normal (ULN) (excluding Gilberts Syndrome, for which bilirubin must be ≤4 × ULN); aspartate aminotransferase (AST) and alanine aminotransferase (ALT) <3 × ULN, and alkaline phosphatase ≤2.5 × ULN 3. Renal function: serum creatinine ≤1.5 × ULN or for patients with creatinine levels above the ULN, estimated creatinine clearance of ≥60 mL/min, calculated using the Cockcroft-Gault equation35 4. Activated partial thromboplastin time (aPTT) ≤1.5 × ULN 13. Women of childbearing potential must agree to practice a highly effective method of contraception beginning at least 28 days before the start of treatment until at least 6.25 months after the last dose of study drug. Male study patients and their female sexual partners of childbearing potential must agree to practice a highly effective method of contraception starting from the time of informed consent until at least 3.5 months (no less than 104 days) after the last dose of study drug. 1. A woman of childbearing potential is defined as a woman who is not permanently sterilized or postmenopausal. Postmenopausal is defined as 12 months with no menses without an alternative medical cause. 2. Women of childbearing potential must have a negative serum or urine pregnancy test at Screening. 3. A highly effective method of birth control is defined as one which results in a low failure rate (ie, less than 1% per year) when used consistently and correctly, such as implants, injectables, combined oral contraceptives, some intrauterine devices (IUDs), sexual abstinence, or vasectomized partner. For patients using a hormonal contraceptive method, information regarding all medications being administered to the patient and their potential effects on the contraceptive should be addressed. 14. Patients with prior malignancies must be disease-free for ≥5 years. Curatively treated basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix, breast, or bladder; or prostate cancer as well as benign tumors that will not interfere with the treatment plan at the time of screening are allowed.

Exclusion Criteria

1. Unable or not willing to comply with the protocol regulations. 2. Any additional chemotherapy (including but not limited to TMZ or immunotherapy) for recurrent or progressive GBM after a first line treatment. 3. Prior treatment with bevacizumab. 4. Prior treatment with lomustine. 5. Known to have an IDH mutation prior to enrollment 6. Screening/Baseline MRI showing a mass effect defined as significant compression of the ventricular system and/or a midline shift with associated clinical symptoms deemed inappropriate for the patient to enter a clinical trial. If there is otherwise asymptomatic compression and/or midline shift and the patient fulfills all other criteria, these patients are considered eligible. 7. Any condition (medical, social, psychological) that would prevent adequate information and follow-up, including but not limited to clinically relevant psychiatric disorders, legal incapacity, dementia, adults protected by law or altered mental status. 8. Presence of poorly controlled seizures, defined as occurring despite SOC or requiring hospitalization. 9. Prior anthracycline cumulative dose more than 550 mg/m2. 10. Heart disease: 1. LVEF <50% 2. Unstable angina 3. CHF with New York Heart Association (NYHA) classification of 3 or 4 4. Patients with baseline QT/QTc interval >480 msec, a history of additional risk factors for torsades de pointes (TdP) (eg, heart failure, hypokalemia, family history of long QT syndrome) and using concomitant medications that significantly prolong the QT/QTc interval 5. History of myocardial infarction within 12 months of enrollment 6. Severe arrhythmia not controlled by medication 11. Uncontrolled hypertension (systolic blood pressure [BP] >150 mmHg and/or diastolic BP >100 mmHg) sustained over 2 measurements. 12. Known to be positive for hepatitis B virus surface antigen (HBsAg), hepatitis C virus (HCV), human immunodeficiency virus (HIV), COVID-19 (currently positive at time of screening), or any other acute viral, bacterial, or fungal infection (testing not required unless symptomatic or suspected disease). 13. Patients with any other uncontrolled intercurrent medical conditions, including but not limited to diabetes mellitus or chronic obstructive pulmonary disease that have not been well controlled by medical management over the prior 3 months are ineligible unless approved by the sponsor. 14. Women who are lactating or breastfeeding

Inclusion Criteria:

• STEP 0: Patients must be >= 12 months and =< 21 years of age at the time of enrollment on Step 0.
• Please note:
• This age range includes pre-screening for all HGG patients. Individual treatment protocols may have different age criteria.
• Non-DIPG patients with tumors that do not harbor an H3K27M-mutation and are >= 18 years of age will not be eligible to enroll on ACNS1821 (Step 1).
• STEP 0: Patient is suspected of having localized, newly diagnosed HGG, excluding metastatic disease, OR patient has an institutional diagnosis of DIPG
• STEP 0:
• For patients with non-pontine tumors: Patient and/or their parents or legal guardians have signed informed consent for eligibility screening on APEC14B1 Part A.
• For patients with DIPG: Patient and/or their parents or legal guardians have signed informed consent for ACNS1821.
• STEP 0:
• For patients with non-pontine tumors only, the specimens obtained at the time of diagnostic biopsy or surgery must be submitted through APEC14B1 ASAP, preferably within 5 calendar days of definitive surgery
• STEP 1: Patients must be >= 12 months and =< 21 years of age at the time of enrollment
• STEP 1: Patients must have newly-diagnosed DIPG or HGG (including DMG).
• STEP 1: Stratum DIPG
• Patients with newly-diagnosed typical DIPG, defined as tumors with a pontine epicenter and diffuse involvement of at least 2/3 of the pons on at least 1 axial T2 weighted image, are eligible. No histologic confirmation is required.
• Patients with pontine tumors that do not meet radiographic criteria for typical DIPG (e.g., focal tumors or those involving less than 2/3 of the pontine cross-sectional area with or without extrapontine extension) are eligible if the tumors are biopsied and proven to be high-grade gliomas (such as anaplastic astrocytoma, glioblastoma, high-grade glioma not otherwise specified [NOS], and/or H3 K27M-mutant) by institutional diagnosis.
• STEP 1: Stratum DMG (with H3 K27M mutation)
• Patients must have newly-diagnosed non-pontine H3 K27M-mutant HGG without BRAF V600 or IDH1 mutations as confirmed by Rapid Central Pathology and Molecular Screening Reviews performed on APEC14B1
• Note: Patients need not have either measurable or evaluable disease, i.e., DMG patients may have complete resection of their tumor prior to enrollment. Primary spinal tumors are eligible for enrollment. For rare H3 K27M-mutant HGG in non-midline structures (e.g., cerebral hemispheres), these patients will be considered part of Stratum DMG.
• STEP 1: Stratum HGG (without H3 K27M mutation)
• Patients must have newly-diagnosed non-pontine H3 K27M-wild type HGG without BRAF V600 or IDH1 mutations as confirmed by Rapid Central Pathology and Molecular Screening Reviews performed on APEC14B1
• Please note:
• Patients who fall in this category and who are >= 18 years of age are not eligible due to another standard-of-care regimen (radiation/temozolomide) that is available
• Patients need not have either measurable or evaluable disease, i.e., HGG patients may have complete resection of their tumor prior to enrollment. Primary spinal tumors are eligible for enrollment
• STEP 1: Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1 or 2. Use Karnofsky for patients > 16 years of age and Lansky for patients =<16 years of age. 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.
• STEP 1: Peripheral absolute neutrophil count (ANC) >= 1000/uL (within 7 days prior to step 1 enrollment)
• STEP 1: Platelet count >= 100,000/uL (transfusion independent) (within 7 days prior to step 1 enrollment)
• STEP 1: Hemoglobin >= 8.0 g/dL (may receive red blood cell [RBC] transfusions) (within 7 days prior to step 1 enrollment)
• STEP 1: Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 mL/min/1.73 m^2 (within 7 days prior to step 1 enrollment) or A serum creatinine based on age/gender as follows (within 7 days prior to step 1 enrollment):
• Age / Maximum Serum Creatinine (mg/dL)
• 1 to < 2 years / male: 0.6; female: 0.6
• 2 to < 6 years / male: 0.8; female: 0.8
• 6 to < 10 years / male: 1; female: 1
• 10 to < 13 years / male: 1.2; female: 1.2
• 13 to < 16 years / male: 1.5; female: 1.4
• >= 16 years / male: 1.7; female: 1.4
• STEP 1: Total bilirubin =< 1.5 x upper limit of normal (ULN) for age
• STEP 1: Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 135 U/L. For the purpose of this study, the ULN for SGPT is 45 U/L.
• STEP 1: Serum amylase =< 1.5 x ULN
• STEP 1: Serum lipase =< 1.5 x ULN
• STEP 1: No evidence of dyspnea at rest, no exercise intolerance, and a pulse oximetry > 94% if there is clinical indication for determination.
• STEP 1: Patients with seizure disorder may be enrolled if on anticonvulsants and well controlled.
• STEP 1: Patients must be enrolled and protocol therapy must begin no later than 31 days after the date of radiographic diagnosis (in the case of non-biopsied DIPG patients only) or definitive surgery, whichever is the later date (Day 0). For patients who have a biopsy followed by resection, the date of resection will be considered the date of definitive diagnostic surgery. If a biopsy only was performed, the biopsy date will be considered the date of definitive diagnostic surgery.

Exclusion Criteria:

• STEP 1: Patients must not have received any prior therapy for their central nervous system (CNS) malignancy except for surgery and steroid medications.
• STEP 1: Patients who are currently receiving another investigational drug are not eligible.
• STEP 1: Patients who are currently receiving other anti-cancer agents are not eligible.
• STEP 1: Patients >=18 years of age who have H3 K27M-wild type HGG.
• STEP 1: Patients who have an uncontrolled infection.
• STEP 1: Patients who have received a prior solid organ transplantation.
• STEP 1: Patients with grade > 1 extrapyramidal movement disorder.
• STEP 1: Patients with known macular degeneration, uncontrolled glaucoma, or cataracts.
• STEP 1: Patients with metastatic disease are not eligible; MRI of spine with and without contrast must be performed if metastatic disease is suspected by the treating physician.
• STEP 1: Patients with gliomatosis cerebri type 1 or 2 are not eligible, with the exception of H3 K27M-mutant bithalamic tumors.
• STEP 1: Patients who are not able to receive protocol specified radiation therapy.
• STEP 1:
• Female patients who are pregnant are ineligible since there is yet no available information regarding human fetal or teratogenic toxicities.
• Lactating females are not eligible unless they have agreed not to breastfeed their infants. It is not known whether selinexor is excreted in human milk.
• Female patients of childbearing potential are not eligible unless a negative pregnancy test result has been obtained.
• Sexually active patients of reproductive potential are not eligible unless they have agreed to use two effective methods of birth control (including a medically accepted barrier method of contraception, e.g., male or female condom) for the duration of their study participation and for 90 days after the last dose of selinexor. Abstinence is an acceptable method of birth control.

Inclusion Criteria:

• Patients must be greater than or equal to 3 years and less than 22 years of age at the time of enrollment
• Patients must be newly diagnosed and have:
• Eligibility confirmed by rapid central pathology and molecular screening review on APEC14B1 and via the Molecular Characterization Initiative:
• Classical histologic type (non LC/A) WNT medulloblastoma
• Positive nuclear beta-catenin by immunohistochemistry (IHC)
• Positive for CTNNB1 mutation
• Negative for MYC and MYCN by fluorescence in situ hybridization (FISH)
• Patient must have negative lumbar cerebrospinal fluid (CSF) cytology
• Note: CSF cytology for staging should be performed no sooner than 14 days post operatively to avoid false positive CSF; ideally, CSF should be obtained between day 14 and day 21 to allow for final staging status before enrollment onto the study; patients with positive CSF cytology obtained 0 to 14 days after surgery should have cytology repeated to determine eligibility and final CSF status; patients with negative CSF cytology from lumbar puncture obtained 0 to 14 days after surgery do not need cytology repeated; patients with negative CSF cytology from lumbar puncture obtained prior to surgery do not need cytology repeated post-operatively
• Patients must have eligibility confirmed by Rapid Central Imaging Review on APEC14B1; patients must have =< 1.5 cm^2 maximal cross-sectional area of residual tumor; whole brain magnetic resonance imaging (MRI) with and without gadolinium and spine MRI with gadolinium must be performed
• Patients must be enrolled, and protocol therapy must be projected to begin, no later than 36 days after definitive diagnostic surgery (day 0)
• Peripheral absolute neutrophil count (ANC) >= 1000/uL
• Platelet count >= 100,000/uL (transfusion independent)
• Hemoglobin >= 8.0 g/dL (may receive red blood cell [RBC] transfusions)
• Creatinine clearance or radioisotope glomerular filtration rate (GFR) >= 70 mL/min/1.73 m^2 or a serum creatinine based on age/gender as follows:
• 3 to < 6 years of age: maximum (max) serum creatinine 0.8 mg/dL (males and females)
• 6 to < 10 years of age: max serum creatinine 1 mg/dL (males and females)
• 10 to < 13 years of age: max serum creatinine 1.2 mg/dL (males and females)
• 13 to < 16 years of age: max serum creatinine 1.5 md/dL (males) and 1.4 md/dL (females)
• >= 16 years of age: max serum creatinine 1.7 mg/dL (males) and 1.4 mg/dL (females)
• The threshold creatinine values were derived from the Schwartz formula for estimating GFR utilizing child length and stature data published by the Centers for Disease Control and Prevention (CDC)
• Total or direct bilirubin =< 1.5 x upper limit of normal (ULN) for age, and
• Serum glutamate pyruvate (SGPT) (alanine aminotransferase [ALT]) =< 135 U/L (3x ULN); for the purpose of this study, the ULN for SGPT is 45 U/L
• Central nervous system function defined as:
• Patients with seizure disorder may be enrolled if on anticonvulsants and well controlled
• Patients must not be in status epilepticus, a coma or on assisted ventilation at the time of study enrollment
• Patients must have receptive and expressive language skills in English, French, or Spanish to complete the QoL and neurocognitive assessments; if a patient meets these criteria but the parent/guardian speaks a language other than English, French, or Spanish, the patient may still be enrolled and tested, and the parent-report measures should be omitted
• All patients and/or their parents or legal guardians must sign a written informed consent; assent, when appropriate, will be obtained according to institutional guidelines
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met

Exclusion Criteria:

• Patients with metastatic disease by either MRI evaluation (brain and spine) or lumbar CSF cytology are not eligible; patients who are unable to undergo a lumbar puncture for assessment of CSF cytology are ineligible
• Patients must not have received any prior radiation therapy or chemotherapy (tumor-directed therapy) other than surgical intervention and/or corticosteroids
• Pregnancy and Breast Feeding
• Female patients who are pregnant are ineligible due to risks of fetal and teratogenic adverse events as seen in animal/human studies
• Lactating females are not eligible unless they have agreed not to breastfeed their infants
• Female patients of childbearing potential are not eligible unless a negative pregnancy test result has been obtained
• Sexually active patients of reproductive potential are not eligible unless they have agreed to use an effective contraceptive method for the duration of their study participation
• Patients with a history of moderate to profound intellectual disability (i.e., intelligence quotient [Q)]=< 55) are not eligible for enrollment; PLEASE NOTE: Children with a prior history of attention deficit hyperactivity disorder (ADHD) or a specific learning disability (e.g., dyslexia) are eligible for this study. Children with posterior fossa syndrome (also known as cerebellar mutism) are eligible for this study

Inclusion Criteria:

• Patients must be >= 2 years and =< 21 years at the time of enrollment
• Patients must have a body surface area (BSA) of >= 0.5 m^2 at enrollment
• Patients must have neurofibromatosis type 1 (NF1) based on clinical criteria and/or germline genetic testing
• Patients must be newly diagnosed or have previously diagnosed NF-1 associated LGG that has not been treated with any modality other than surgery
• For patients with optic pathway gliomas (OPGs):
• Newly-diagnosed patients with OPG are eligible if there are neurologic symptoms (including visual dysfunction, as defined below) or other exam findings associated with the tumor
• Previously-diagnosed patients with OPG are eligible if they have new or worsening neurologic symptoms (including visual dysfunction, as defined below) or have tumor growth
• For both newly-diagnosed and previously-diagnosed OPG, the patient may be eligible, irrespective of whether there has been tumor growth or other neurological symptoms or worsening, if they meet at least one of the following visual criteria:
• Visual worsening, defined as worsening of visual acuity (VA) or visual fields (VF) documented within the past year (by examination or history); OR
• Significant visual dysfunction (defined as VA worse than normal for age by 0.6 logMAR [20/80, 6/24, or 2.5/10] or more in one or both eyes)
• For patients with LGG in other locations (i.e., not OPGs):
• Newly-diagnosed patients with LGG are eligible if there are neurologic symptoms or other exam findings associated with the tumor
• NOTE: Newly-diagnosed patients with LGG without associated neurologic symptoms or exam findings are not eligible
• Previously-diagnosed patients with LGG are eligible if they have new or worsening neurologic symptoms or have tumor growth
• Although not required, if a biopsy/tumor resection is performed, eligible histologies will include all tumors considered LGG or low-grade astrocytoma (World Health Organization [WHO] grade I and II) by 5th edition WHO classification of central nervous system (CNS) tumors with the exception of subependymal giant cell astrocytoma
• Patients must have two-dimensional measurable tumor >= 1 cm^2
• Patients with metastatic disease or multiple independent primary LGGs are allowed on study
• Creatinine clearance or radioisotope glomerular filtration Rate (GFR) >= 70 mL/min/1.73 m^2 OR a serum creatinine based on age/gender (within 7 days prior to enrollment) as follows:
• Age; maximum serum creatinine (mg/dL)
• 2 to < 6 years; 0.8 (male) and 0.8 (female)
• 6 to < 10 years; 1 (male) and 1 (female)
• 10 to < 13 years; 1.2 (male) and 1.2 (female)
• 13 to < 16 years; 1.5 (male) and 1.4 (female)
• >= 16 years; 1.7 (male) and 1.4 (female)
• Total bilirubin =< 1.5 x upper limit of normal (ULN) for age (within 7 days prior to enrollment) (children with a diagnosis of Gilbert's syndrome will be allowed on study regardless of their total and indirect [unconjugated] bilirubin levels as long as their direct [conjugated] bilirubin is < 3.1 mg/dL)
• Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase [ALT]) =< 3 x upper limit of normal (ULN) = 135 U/L (within 7 days prior to enrollment). For the purpose of this study, the ULN for SGPT is 45 U/L
• Albumin >= 2 g/dL (within 7 days prior to enrollment)
• Left ventricular ejection fraction (LVEF) >= 53% (or institutional normal; if the LVEF result is given as a range of values, then the upper value of the range will be used) by echocardiogram (within 4 weeks prior to enrollment)
• Corrected QT (QTc) interval =< 450 msec by electrocardiography (EKG) (within 4 weeks prior to enrollment)
• Absolute neutrophil count >= 1,000/uL (unsupported) (within 7 days prior to enrollment)
• Platelets >= 100,000/uL (unsupported) (within 7 days prior to enrollment)
• Hemoglobin >= 8 g/dL (may be supported) (within 7 days prior to enrollment)
• Patients with a known seizure disorder should be stable and should have not experienced a significant increase in seizure frequency within 2 weeks prior to enrollment
• Patients 2-17 years of age must have a blood pressure that is =< 95th percentile for age, height, and gender at the time of enrollment. Patients >= 18 years of age must have a blood pressure =< 130/80 mmHg at the time of enrollment (with or without the use of antihypertensive medications).
• Note: Adequate blood pressure can be achieved using medication for the treatment of hypertension
• All patients must have ophthalmology toxicity assessments performed within 4 weeks prior to enrollment
• For all patients, an MRI of the brain (with orbital cuts for optic pathway tumors) and/or spine (depending on the site(s) of primary disease) with and without contrast must be performed within 4 weeks prior to enrollment
• For patients who undergo a surgery on the target tumor (not required), a pre- and post-operative* MRI of the brain (with orbital cuts for optic pathway tumors) or spine (depending on the site(s) of primary disease) with and without contrast must also be performed within 4 weeks prior to enrollment
• The post-operative MRIs should be performed ideally within 48 hours after surgery if possible
• Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1, or 2. Use Karnofsky for patients > 16 years of age and Lansky for patients =< 16 years of age
• Patients must have the ability to swallow whole capsules
• Patients must have receptive and expressive language skills in English or Spanish to complete the quality of life (QOL) and neurocognitive assessments
• All patients and/or their parents or legal guardians must sign a written informed consent.
• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met.

Exclusion Criteria:

• Patients must not have received any prior tumor-directed therapy including chemotherapy, radiation therapy, immunotherapy, or bone marrow transplant. Prior surgical intervention is permitted
• Patients with a concurrent malignancy or history of treatment (other than surgery) for another tumor within the last year are ineligible
• Patients may not be receiving any other investigational agents
• Patients with any serious medical or psychiatric illness/ condition, including substance use disorders likely in the judgement of the investigator to interfere or limit compliance with study requirements/treatment are not eligible
• Patients who, in the opinion of the investigator, are not able to comply with the study procedures are not eligible
• Female patients who are pregnant are not eligible since fetal toxicities and teratogenic effects have been noted for several of the study drugs. A pregnancy test is required for female patients of childbearing potential
• Lactating females who plan to breastfeed their infants are not eligible
• Sexually active patients of reproductive potential who have not agreed to use an effective contraceptive method for the duration of their study participation and for 12 weeks after stopping study therapy are not eligible
• Note: Women of child-bearing potential and males with sexual partners who are pregnant or who could become pregnant (i.e., women of child-bearing potential) should use effective methods of contraception for the duration of the study and for 12 weeks after stopping study therapy to avoid pregnancy and/or potential adverse effects on the developing embryo
• Cardiac conditions:
• Known genetic disorder that increases risk for coronary artery disease. Note: The presence of dyslipidemia in a family with a history of myocardial infarction is not in itself an exclusion unless there is a known genetic disorder documented
• Symptomatic heart failure
• New York Heart Association (NYHA) class II-IV prior or current cardiomyopathy
• Severe valvular heart disease
• History of atrial fibrillation
• Ophthalmologic conditions:
• Current or past history of central serous retinopathy
• Current or past history of retinal vein occlusion or retinal detachment
• Patients with uncontrolled glaucoma
• If checking pressure is clinically indicated, patients with intraocular pressure (IOP) > 22 mmHg or ULN adjusted by age are not eligible
• Ophthalmological findings secondary to long-standing optic pathway glioma (such as visual loss, optic nerve pallor, or strabismus) or longstanding orbito-temporal plexiform neurofibroma (PN), such as visual loss, strabismus) will NOT be considered a significant abnormality for the purposes of the study
• Treatments and/or medications patient is receiving that would make her/him ineligible, such as:
• Supplementation with vitamin E greater than 100% of the daily recommended dose. Any multivitamin containing vitamin E must be stopped prior to study enrollment even if less than 100% of the daily recommended dosing for vitamin E
• Surgery within 2 weeks prior to enrollment, with the exception of surgical placement for vascular access or cerebrospinal fluid (CSF) diverting procedures such as endoscopic third ventriculostomy (ETV) and ventriculo-peritoneal (VP) shunt.
• Note: Patients must have healed from any prior surgery prior to enrollment
• Patients who have an uncontrolled infection are not eligible

Inclusion Criteria:

• STEP 1 REGISTRATION: No known IDH mutation. (If tested before step 1 registration, patients known to have IDH mutation in the tumor on local or other testing are ineligible and should not be registered)
• STEP 1 REGISTRATION: Availability of formalin-fixed paraffin-embedded (FFPE) tumor tissue block and hematoxylin and eosin (H&E) stained slide to be sent for central pathology review for confirmation of histology and MGMT promoter methylation status. Note that tissue for central pathology review and central MGMT assessment must be received by the NYU Center for Biospecimen Research and Development (CBRD) on or before postoperative calendar day 23. If tissue cannot be received by postoperative calendar day 23, then patients may NOT enroll on this trial as central pathology review will not be complete in time for the patient to start treatment no later than 6 weeks following surgery. Results of central pathology review and central MGMT analysis will generally be conveyed to NRG Oncology within 10 business days of receipt of tissue. Note: In the event of an additional tumor resection(s), tissue must be received within 23 days of the most recent resection and the latest resection must have been performed within 30 days after the initial resection. Surgical resection is required; stereotactic biopsy alone is not allowed because it will not provide sufficient tissue for MGMT analysis
• STEP 1 REGISTRATION: Contrast-enhanced brain MRI within 4 days after surgery
• Magnetic resonance imaging (MRI) with Axial T2 weighted FLAIR or T2 TSE/FSE and 3D contrast-enhanced T1 sequences are required.
• 3-dimensional (3D) pre contrast-enhanced T1 sequences are strongly suggested
• STEP 1 REGISTRATION: Willing to use highly effective method of contraception for participants of childbearing potential (participants who may become pregnant or who may impregnate a partner) during therapy and for 6 months after completing treatment; this inclusion is necessary because the treatment in this study may be significantly teratogenic
• STEP 1 REGISTRATION: The patient or a legally authorized representative must provide study-specific informed consent prior to study entry and, for patients treated in the United States (U.S.), authorization permitting release of personal health information
• STEP 2 REGISTRATION: Histopathologically proven diagnosis of glioblastoma (or gliosarcoma as a subtype of glioblastoma) confirmed by central pathology review
• STEP 2 REGISTRATION: MGMT promoter with methylation confirmed by central pathology review (See Section 10 for details). Note: Patients with tissue that is insufficient or inadequate for analysis, fails MGMT testing, or has indeterminate or unmethylated MGMT promoter are excluded. Patients with unmethylated MGMT may be considered for enrollment on NRG-BN007
• STEP 2 REGISTRATION: IDH mutation testing by at least one method (such as immunohistochemistry for IDH1 R132H) must be performed as part of standard of care and no mutation must be found (i.e IDH wildtype). (If a mutation is identified then the patient will be ineligible and must be registered as ineligible at Step 2.)
• STEP 2 REGISTRATION: History/physical examination within 28 days prior to Step 2 registration
• STEP 2 REGISTRATION: Karnofsky performance status (KPS) >= 70 within 28 days prior to Step 2 registration
• STEP 2 REGISTRATION: Neurologic function assessment within 28 days prior to Step 2 registration
• STEP 2 REGISTRATION: Age 18-70 years
• STEP 2 REGISTRATION: Hemoglobin >= 10 g/dl (Note: the use of transfusion or other intervention to achieve hemoglobin (Hgb) >= 10.0 g/dl is acceptable)
• STEP 2 REGISTRATION: Leukocytes >= 2,000/mm^3
• STEP 2 REGISTRATION: Absolute neutrophil count >= 1,500/mm^3
• STEP 2 REGISTRATION: Platelets >= 100,000/mm^3
• STEP 2 REGISTRATION: Total bilirubin =< 1.5 x institutional/lab upper limit of normal (ULN)
• STEP 2 REGISTRATION: Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT]) =< 2.5 x ULN
• STEP 2 REGISTRATION: Alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) =< 2.5 x ULN
• STEP 2 REGISTRATION: Serum creatinine =< 1.5 x ULN OR creatinine clearance (CrCl) >= 50 mL/min (if using the Cockcroft-Gault formula
• STEP 2 REGISTRATION: For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated
• Note: Known positive test for hepatitis B virus surface antigen (HBV sAg) indicating acute or chronic infection would make the patient ineligible unless the viral load becomes undetectable on suppressive therapy. Patients who are immune to hepatitis B (anti-hepatitis B surface antibody positive) are eligible (e.g. patients immunized against hepatitis B)
• STEP 2 REGISTRATION: For patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load
• Note: Known positive test for hepatitis C virus ribonucleic acid (HCV ribonucleic acid [RNA]) indicating acute or chronic infection would make the patient ineligible unless the viral load becomes undetectable on suppressive therapy
• STEP 2 REGISTRATION: Known human immunodeficiency virus (HIV) infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months prior to step 2 registration are eligible for this trial. Testing is not required for entry into protocol
• STEP 2 REGISTRATION: Negative serum or urine pregnancy test (in persons of childbearing potential) within 7 days prior to Step 2 registration
• Childbearing potential is defined as any person who has experienced menarche and who has not undergone surgical sterilization (hysterectomy or bilateral oophorectomy) or who is not postmenopausal

Exclusion Criteria:

• STEP 2 REGISTRATION: Prior therapy for tumor except for resection. For example, prior chemotherapy, immunotherapy, or targeted therapy for GBM or lower grade glioma is disallowed (including but not limited to temozolomide, lomustine, bevacizumab, any viral therapy, ipilimumab or other CTLA-4 antibody, PD-1 antibody, CD-137 agonist, CD40 antibody, PDL-1 or 2 antibody, vaccine therapy, polio or similar viral injection as treatment for the tumor, and/or any other antibody or drug specifically targeting T-cell co-stimulation or immune checkpoint pathways) as is prior Laser interstitial thermal therapy (LITT), Gliadel wafer, radiotherapy, radiosurgery, vaccine or other immunotherapy, brachytherapy, or convection enhanced delivery
• Note: 5-aminolevulinic acid (ALA)-mediated fluorescent guided resection (FGR) photodynamic therapy (PDT) or fluorescein administered prior to/during surgery to aid resection is not exclusionary and is not considered a chemotherapy or intracerebral agent
• STEP 2 REGISTRATION: Current or planned treatment with any other investigational agents for the study cancer
• STEP 2 REGISTRATION: Definitive clinical or radiologic evidence of metastatic disease outside the brain
• STEP 2 REGISTRATION: Prior invasive malignancy (except non-melanomatous skin cancer, cervical cancer in situ and melanoma in situ) unless disease free for a minimum of 2 years
• STEP 2 REGISTRATION: Prior radiotherapy to the head or neck that would result in overlap of radiation therapy fields
• STEP 2 REGISTRATION: Pregnancy and individuals unwilling to discontinue nursing due to the potential teratogenic effects and potential risk for adverse events in nursing infants
• STEP 2 REGISTRATION: History of allergic reactions attributed to compounds of similar chemical or biologic composition to temozolomide or lomustine
• STEP 2 REGISTRATION: History of pulmonary fibrosis
• STEP 2 REGISTRATION: Uncontrolled intercurrent illness including, but not limited to:
• Ongoing or active infection requiring IV antibiotics, IV antiviral, or IV antifungal treatment
• Symptomatic congestive heart failure, defined as New York Heart Association Functional Classification III/IV (Note: Patients with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification)
• Unstable angina pectoris within 6 months prior to Step 2 registration
• Uncontrolled cardiac arrhythmia
• Psychiatric illness/social situations that would limit compliance with study requirements

• Pre-registration: Patients must have local diagnosis of papillary craniopharyngioma and have tissue slides available for submission to central pathology review; central pathology review will include immunohistochemistry (IHC) testing for BRAF V600E mutation (VE1 clone) and beta-catenin IHC (membranous, non-nuclear pattern) if needed to confirm diagnosis of papillary craniopharyngioma
• Histologically proven papillary craniopharyngioma as documented by central pathology review with positive BRAF V600E mutation by IHC
• Measurable disease and/or non-measurable disease
• Measurable disease, defined as bidimensionally measurable lesions with clearly defined margins by magnetic resonance imaging (MRI) scans, with a minimum diameter of 10 mm in both dimensions
• Progressive disease required in cohort B, defined as an increase in the bidirectional area by 25% within the past 13 months after surgery or radiation; progressive or recurrent disease is not required in cohort A, but is allowed provided it is a new diagnosis and patient has not received prior treatment.
• Prior treatment
• Cohort A: No prior therapy received other than surgery
• Cohort B: Prior radiation therapy required (any type of prior radiation is allowed)
• For patients treated with external beam radiation therapy, interstitial brachytherapy or radiosurgery, an interval of >= 3 months must have elapsed from completion of radiation therapy to registration
• Recovered to Common Terminology Criteria for Adverse Events (CTCAE) grade 1 or less toxicity attributed to radiation with exception of alopecia, fatigue
• For patients enrolling on Cohort A or Cohort B:
• For patients treated with surgery, an interval of >= 21 days must have elapsed prior to registration
• No prior treatment with BRAF or MEK inhibitors
• Steroid dosing stable for at least 4 days prior to registration
• Not pregnant and not nursing; for women of childbearing potential only, a negative pregnancy test done =< 7 days prior to registration is required
• ECOG performance status =< 2
• Comorbid conditions
• No evidence of active bleeding, bleeding diathesis, or hemoptysis (>= 1/2 teaspoon of red blood) =< 8 weeks prior to registration
• No evidence of intracranial hemorrhage =< 4 weeks prior to registration
• Patients who have experienced thromboembolic event within 6 months prior to registration must be on stable therapeutic anticoagulation for at least 4 weeks prior to registration
• No symptomatic congestive heart failure (New York Heart Association class II, III, or IV) within 6 months prior to registration
• No current unstable angina or uncontrolled arrhythmia
• No uncontrolled hypertension at time of registration (blood pressure [BP] > 150/95 despite antihypertensive therapy)
• No known history of prolonged QT syndrome
• No known history of ventricular arrhythmia within 6 months of registration
• No known history of uveitis or iritis =< 4 weeks prior to registration
• No known history of or evidence of retinal pathology that is considered a risk factor for neurosensory retinal detachment, retinal vein occlusion (RVO), or neovascular macular degeneration within 12 months of registration
• No known history of chronic lung disease
• Concomitant medications
• Chronic concomitant treatment with strong CYP3A4 inducers or CYP3A4 inhibitors is not allowed; patients must discontinue the drug at least 14 days prior to study registration
• Chronic concomitant treatment with CYP1A2 substrate is not allowed; patients must discontinue the drug at least 14 days prior to study registration
• Absolute neutrophil count >= 1500/mm^3
• Platelets >= 100,000/mm^3
• Creatinine =< 1.5 mg/dL OR creatinine clearance >= 45mL/min
• Bilirubin =< 1.5 upper limit of normal (ULN)
• Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) =< 2.5 ULN