This study aims to find safe and effective doses of two drugs, defactinib and VS-6766, for treating glioblastoma, a type of brain cancer. Researchers are interested in how these drugs work in the brain and their safety. **Glioblastoma** is a fast-growing brain tumor, and these drugs might slow its growth by blocking certain proteins that help tumors grow. **Defactinib** and **VS-6766** are kinase inhibitors, which means they block specific proteins in cells to stop tumor growth. In the study, patients will receive one dose of either defactinib or VS-6766 before planned surgery to remove the tumor. They will need to give blood and tumor tissue samples for research. The study checks how much of the drug gets into the brain and if it affects tumor growth pathways. - **Key Points:** - The study involves a single dose of medication before surgery. - Participants must be over 21 years old and have a good health status. - Patients must not have had major surgery or certain therapies recently and must be able to swallow pills. This study is for adults diagnosed with glioblastoma who meet specific health criteria.