• Histologic diagnosis of a primary central nervous system (CNS) tumor with documented BRAF-V600E mutation by a Clinical Laboratory Improvement Amendments (CLIA) approved DNA or RNA (Ribonucleic acid )-based sequencing test (NGS (Next generation sequencing) or RNAseq). Immunohistochemistry alone is insufficient.

• Patient must have received prior BRAF and/or Mitogen-activated protein kinase kinase (MEK) inhibitor therapy.

• Karnofsky performance status ≥ 70.

• Patient is 18 years of older.

• Measurable disease by RANO2.0 criteria on screening MRI. Leptomeningeal disease allowed.

• Willing to submit archival tumor sample if available.

• The following intervals from previous treatments should have elapsed prior to cycle 1 day 1:

‣ 12 weeks from the completion of radiation.

⁃ 12 weeks from an anti- vascular endothelial growth factor therapy (VEGF)

⁃ 4 weeks from a nitrosourea chemotherapy

⁃ 3 weeks from a non-nitrosourea chemotherapy

⁃ 2 weeks or 5 half-lives from any investigational (not FDA-approved) agents (whichever is shorter)

⁃ 2 weeks from administration of a non-cytotoxic, FDA-approved agent (e.g., erlotinib, hydroxychloroquine, dabrafenib, etc.)

• Patients must have the following organ and marrow function:

‣ Absolute neutrophil count \>1,000/micro liter (mcL)

⁃ Platelets \>100,000/mcL

⁃ Hemoglobin \> 9 g/dL

⁃ Total bilirubin \</= 1.5 x institutional upper limit of normal (ULN) OR total bilirubin \>1.5 × ULN with direct bilirubin \<1.5 × ULN

⁃ (aspartate aminotransferase (AST) and alanine transaminase (ALT) \</= 2.5 x institutional ULN

⁃ prothrombin time (PT) or Partial thromboplastin time (PTT) \< 1.5 x institutional ULN

⁃ Creatinine ≤ 1.5 x institutional ULN OR Creatinine clearance (Cockcroft-Gault Formula) \> 50 ml/min/1.73m2

• Patient must be able to provide written informed consent.

⁃ All adverse events related to prior therapies (chemotherapy; radiotherapy; surgery) must have resolved to Grade 1 or baseline except for

∙ Alopecia (Grade ≤2)

‣ Sensory neuropathy (Grade ≤2)

‣ Lymphopenia (Grade 2)

‣ Other adverse events that have resolved to Grade ≤2 that, according to the clinical judgment of the investigator, do not constitute a safety risk to the participant.

⁃ Patients must be maintained on a stable or decreasing dose of systemic corticosteroid regimen (no increase for 5 days) prior to screening MRI. Topical and inhaled steroid treatment is allowed.

⁃ Ability to swallow and retain orally administered medications, including a liquid suspension.

⁃ Female participants of childbearing potential must have a negative serum pregnancy test prior to study start. Female participants of childbearing potential must agree to use highly effective contraception and not to donate ova from screening through 30 days after the last dose of study drug. Highly effective contraception is defined as 1) intrauterine device, 2) abstinence, or 3) combined estrogen and progesterone or progesterone only containing implants, injectables, transdermal, or intravaginal contraceptives. Male participants must also agree to use adequate contraception and not to donate sperm from screening until 90 days after the last dose of study drug.

⁃ Patients must have no concurrent malignancy except curatively treated basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix, breast, or bladder. Patients with other malignancies must be disease-free for \>/=2 years.

⁃ Life expectancy equal or greater than six months.