Pemetrexed, when used by itself, is beneficial and is a standard of care therapy for RR PCNSL and can be used to treat SCNSL. Zanubrutinib is an oral drug that is approved by the Food and Drug Administration (FDA) as safe and effective to treat certain lymphoma types.
This study is being conducted to evaluate the safety and efficacy of the combination of pemetrexed and zanubrutinib (called induction therapy) followed by zanubrutinib treatment alone (also called maintenance therapy) in people who have relapsed or refractory (RR) primary central nervous system lymphoma (PCNSL) or isolated central nervous system relapse of B cell lymphoma (SCNSL). Assessments include how well people respond to this treatment, whether their disease gets better or worse, and their survival. Safety of this treatment and its side effects also will be assessed.