Study of Silevertinib With Temozolomide for the Treatment of Newly Diagnosed GBM With Unmethylated MGMT and EGFRvIII

Key Inclusion Criteria: * Newly diagnosed histologically confirmed glioblastoma that is isocitrate dehydrogenase wild type (IDH-WT). * Positive EGFR status in the brain tumor as determined by a commercially available test or validated laboratory assay (CLIA or comparable certification). * For Part 1 (Safety Lead-in) ONLY: EGFR alterations. * For Part 2 (Randomized, Controlled Trial) ONLY: EGFRvIII. * For Part 2 (Randomized, Controlled Trial) ONLY: Unmethylated MGMT promoter tumor status based on a validated assay. * No treatment for newly diagnosed GBM other than surgery followed by standard-of-care adjuvant postoperative radiation (54 to 60 Gy) and TMZ chemotherapy. * At least 4 weeks since completion of radiation therapy, with a post-radiation MRI showing no progression. Key Exclusion Criteria: * Recurrent multifocal disease, metastatic, leptomeningeal, or extracranial GBM, or gliomatosis cerebri. * Progression of GBM prior to Enrollment, Screening, or Randomization. * Biopsy-only/no resectional surgery. * Prior or concomitant treatment for GBM with an EGFR-targeting agent, including silevertinib, bevacizumab, cytotoxic chemotherapy, immunotherapy, experimental therapies, Gliadel wafers, GammaTile®, or other intratumoral or intracavitary antineoplastic therapy. * Intent to use Optune® (TTF). * Significant other uncontrolled health conditions or other malignancies.