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

The purpose of this study is to see if combining silevertinib with temozolomide after surgery and radiotherapy helps treat newly diagnosed glioblastoma (GBM) better than using temozolomide alone in the maintenance setting. Specifically, this study is being done to find answers to the following questions: * How much of the study drugs (silevertinib combined with temozolomide) should be given to participants with GBM? * What are the side effects participants have when taking the study drug (silevertinib combined with temozolomide)? * Can the study drug (silevertinib combined with temozolomide) help participants with GBM live longer without disease progression compared to treatment with temozolomide alone?