Additional Study Information: This study is being done to test the orally administered study drug, CA-4948 alone, in combination with ibrutinib, or ibrutinib alone in adult patients ages 18 and over diagnosed with relapsed or refractory (RR)Primary Central Nervous System Lymphoma (PCNSL). This study will take place at multiple centers globally. The study drug, CA-4948, is thought to work by blocking a protein in your body called interleukin-1receptor-associated kinase 4 (IRAK4). IRAK4 plays an essential role in some of the signaling pathways that are frequently not controlled in non-Hodgkins Lymphoma (NHL) and other hematological malignancies. When these signals are not working properly, they can trigger cancer growth. By blockingIRAK4, the study drug may stop or reduce these signals and help fight your cancer. Ibrutinib is a medication used to treat adults with certain kinds of leukemia and is commercially available. It has been approved by the United States Food and Drug Administration (FDA) for the treatment of various types of cancer. Ibrutinib is also not FDA approved to treat PCNSL.CA-4948 taken alone, in combination with ibrutinib, and ibrutinib alone are all considered Investigational treatments as the use of these study drugs to treat PCNSL are experimental and has not been approved as a marketed product (i.e., available to be prescribed or sold) by any regulatory authorities, such as the FDA.