A Phase 1 Safety and Dose Finding Study of GLIX1 in Adults With Recurrent or Progressive High-grade Glioma

Main Inclusion Criteria: * Adult patients aged ≥18 years at the time of informed consent * Participants must have histologically confirmed Grade 3 or Grade 4 glioma * Recurrent or progressive disease * A maximum of two prior treatment lines * Interval of at least 3 months since the last day off of radiotherapy, unless tumor progression and index lesion is outside the prior radiation field. * Interval since last dose of systemic therapy and Baseline MRI of ≥28 days, except: * for nitrosoureas (e.g., lomustine, carmustine, fotemustine): 42 days (6 weeks) * for monoclonal antibodies: 42 days (6 weeks) * for small molecules, 4 weeks or at least 5 half-lives (whatever is longer) * Recovered from all toxicities from prior treatments to Grade 1 or less by NCI CTCAE v6.0: * Participants receiving corticosteroids must be on a stable or decreasing dose of ≤6 mg daily dexamethasone (or ≤40 mg prednisone) for the 7 days prior to the start of study treatment. * Participants with seizures must be adequately controlled on a stable regimen of anti-epileptic drugs. * Adequate performance status: Eastern Cooperative Oncology Group (ECOG) 0 or 1. * Ability to swallow tablets or capsules. * Adequate hematological, liver and renal function. * Women of childbearing potential must have a negative serum pregnancy test result within 7 days prior to first dosing. Women must use a highly effective form of contraception (with Pearl Index \<1%) for the duration of the study and for at least 3 months after the last dose of study medication. * Men with partners of childbearing potential must be willing to use condoms in combination with a second effective method of contraception by the partner during the study and for at least 3 months after the last dose of study medication. Main Exclusion Criteria: * Known contraindication for gadolinium (Gd) based, contrast-enhanced MRI * Prior history of another invasive malignancy unless a complete remission was achieved at least 3 years prior to enrolment AND no additional therapy is required during the study period, except for anti-estrogen or androgen therapy and/or bisphosphonates or denosumab. * Participants with known active or uncontrolled infection, and/or unexplained fever \>38°C in the 3 days prior to the start of study treatment. * Major non-tumor related surgical procedure or significant traumatic injury within 28 days prior to signing of consent. * Receiving any investigational products (defined as treatment for which there is currently no regulatory authority-approved indication) within 4 weeks or 5 half-lives (whichever is the longest) prior to Baseline MRI.