5G-RUBY: Avutometinib and Defactinib in Malignant Brain Tumours

Inclusion Criteria for Phase 1b: 1. Patients with histologically confirmed advanced WHO Stage IV glioblastoma (per fourth edition 2016). Per the new 2021 fifth edition of WHO Classification of Tumours of the Central Nervous System, this will include: * Glioblastoma, IDH-wildtype Grade 4 * Astrocytoma, IDH-mutant, Grade 4 (lower Grade 2/3 are not included) * Diffuse hemispheric glioma, H3 G34 mutant Grade 4 Patients with any other CNS tumours will only be eligible for defined Phase 2 biomarker arms once a Phase 1b GO decision has been met. Specific eligibility criteria for these tumours will be defined following an amendment. 2. Patients for Phase 1 will need to have consented to the Minderoo Precision Brain Tumour Programme and have available whole genome, and transcriptome data available. 3. Patients for the relapsed cohorts will be eligible at first relapse following completion of optimal surgery, and Stupp based adjuvant chemo-radiotherapy (or equivalent). They will need to have measurable disease per RANO or evaluable disease. 4. Patients for the front line minimal residual disease (mrd) cohort will be eligible following completion of optimal surgery and Stupp based adjuvant chemoradiotherapy as long as they meet all other inclusion/exclusion criteria. 5. 16 years or over 6. Life expectancy of at least 12 weeks. 7. World Health Organisation (WHO) performance status of 0-1 8. Neurologically stable (e.g., without a progression of neurological symptoms or requiring escalating doses of systemic steroid therapy within the last week) 9. Written (signed or dated) informed consent and be capable of co-operating with treatment and follow up 10. Haematological and biochemical indices within the ranges shown below. These measurements must be performed within one week prior to the first dose of either IMP Haemoglobin (Hb): ≥ 9.0 g/dL; Absolute neutrophil count: ≥1.5 x 10\^9/L; Platelet count: ≥100 x 10\^9/L; Coagulation: INR \<1.5 and APTT \<1.5x if not anticoagulated, INR stable \> 7 days within intended therapeutic range if anticoagulated; Bilirubin: Within institution normal ranges; Alanine aminotransferase (ALT) and aspartate aminotransferase (AST): \<3 x ULN; Albumin: ≥ 28 g/dL; Creatinine: \<1.5 x ULN; Sodium: ≥130 mmol/L; Potassium, Calcium, Magnesium, phosphate: Within institution normal ranges (replacement is permitted); Urinary protein: \< 1+ on dipstick. 11. Female patients with reproductive potential must have a negative serum pregnancy test within 14 days prior to start of trial. 12. Men and women of childbearing potential must agree to comply with the use of a highly effective method of contraception to avoid impregnating a partner or becoming pregnant, respectively, during the study, and for at least 150 days after the last dose of either investigational drug. Exclusion Criteria for Phase 1b: 1. Receipt of treatment before the first dose of study drug (Cycle 1 Day 1) within an interval shorter than the following, as applicable: * Cytotoxic chemotherapy during the prior 2 weeks or 6 weeks for nitrosoureas * Bevacizumab during the prior 6 weeks * Five half-lives of any small molecule investigational or licensed medicinal product. 2. Prior immune checkpoint inhibitor therapy or vaccine therapy is not permitted. Prior use of any other immune-modulatory investigational agent must be discussed with sponsor team and CI. Prior use of BRAF or MEK inhibitors is not permitted. 3. Ongoing Grade 2 or greater toxicities from pre-existing conditions or from previous treatments. 4. Patients with carcinomatous meningitis, leptomeningeal spread of tumour, spread of tumour to the brain stem or spinal cord. 5. Has evidence of recent intratumoural or peritumoural haemorrhage on baseline MRI. Patients with radiological findings that are stable on at least 2 consecutive MRI scans at least 3 weeks apart will be eligible. 6. History of clinically relevant bleeding disorders, including significant GI bleeding within last 6 months. 7. History of arterial thromboembolism. 8. Recent (within 3 months) deep vein thrombosis or pulmonary embolism or another significant thromboembolism. Venous port of catheter thrombosis or superficial thrombosis are not considered significant. Patients with prior thrombosis (\> 3 months ago) on stable anticoagulation are permitted to be enrolled. Patients on Warfarin will need to be converted onto low-molecular weight-based heparin therapy. 9. History of clinically significant cardiac disorders: * Myocardial infarction, or New York Heart Association Class II to IV congestive heart failure, within 6 months of the first dose of study drug * Concurrent and clinically significant abnormalities on ECG at Screening, including a corrected QT interval (QTcF \>460ms). 10. History of malabsorption syndrome or other conditions that may interfere with enteral absorption. Patients with a history of or active inflammatory bowel disease (e.g., Crohn's disease or ulcerative colitis). Patients with acute or chronic pancreatitis. History of gastrointestinal perforation or fistulae. Patients with known Gilbert's syndrome will be excluded from this study. 11. Concurrent ocular disorders: 1. Patients with history of glaucoma, history of retinal vein occlusion (RVO), predisposing factors for RVO, including uncontrolled hypertension, uncontrolled diabetes 2. Patient with history of retinal pathology or evidence of visible retinal pathology that is considered a risk factor for RVO, intraocular pressure \> 21 mm Hg as measured by tonometry, or other significant ocular pathology, such as anatomical abnormalities that increase the risk for RVO. 3. Patients with a history of corneal erosion (instability of corneal epithelium), corneal degeneration, active or recurrent keratitis, and other forms of serious ocular surface inflammatory conditions. 12. Has urine protein \> 1g/24 hours. Participants with \>1+ on urine dipstick testing will undergo 24-hour urine