DAY101 In Gliomas and Other Tumors

This is a Phase I clinical trial. A Phase I clinical trial tests the safety of an investigational drug and also tries to define the appropriate dose of the investigational drug to use for further studies. "Investigational" means that the drug is being studied. The U.S. Food and Drug Administration (FDA) has not approved DAY101 as a treatment for any disease. This is the first time that DAY101 will be given to children. There is limited experience with DAY101 in humans. The purpose of this study is to test the safety DAY101 in children and adolescent participants with brain tumors. The investigators want to find out what effects, good and/or bad, it has on participants and the participant's brain tumor, and find the dose of DAY101 that is tolerated by participants without too many side effects to use in Phase II of the study. Research in the laboratory has shown that DAY101 may have activity against cancer cells. DAY101 belongs to a group of drugs called type II BRAF inhibitors. BRAF abnormalities are found in cancer cells. There are no type II BRAF inhibitors approved by the FDA for humans at the time of this study's start. DAY101 functions by binding the mutant BRAF molecule and causing a conformation change in the molecule thereby blocking the signal that tells the tumor cell to divide.