Additional Study Information: The purpose of this study is to evaluate and determine the efficacy of pemigatinib in participants with recurrent glioblastoma or other CNS tumors with changes in the FGFR1, FGFR2 or FGFR3 genes. Pemigatinib (also referred as INCB054828) is an investigational drug that is being studied by Incyte Corporation (Sponsor) for use in the treatment of previously treated glioblastoma (an aggressive type of cancer that can occur in the brain) or other tumors of the central nervous system (CNS) with changes in the FGFR1, FGFR2 or FGFR3 genes. Investigational means that pemigatinib has not been approved by the US Food and Drug Administration (FDA) for use as a prescription or over-the-counter medication for treatment of glioblastoma or other CNS tumors. Fibroblast growth factor receptor (FGFR) genes make proteins called FGFRs which are involved in sending signals within cells and in cell growth. Certain changes in the FGFR genes cause a change in the FGFR proteins that can increase the growth and spread of cancer cells. Pemigatinib works by preventing these altered FGFR proteins from working, thereby blocking the growth of the cancer. This Study consists of 3 groups (A, B, and C) and Study participants will be enrolled in one of these groups depending on their disease. About 189 participants will be enrolled in this Study.