Combination Regimen of Teniposide, PD-1 Monoclonal Antibody and Selinixor for Patients With Relapsed or Refractory PCNSL

This study is testing a new combination of three drugs — teniposide (chemotherapy), a PD-1 immune checkpoint blocker, and selinexor (a targeted drug) — for people with primary central nervous system lymphoma (brain lymphoma) that has come back or not responded to prior treatment. **You may be eligible if...** - You are between 18 and 75 years old - You have a confirmed B-cell lymphoma in the brain or spinal fluid (primary CNS lymphoma) - Your cancer has come back or not responded to at least one prior treatment that included high-dose methotrexate - You have measurable disease visible on MRI scan - Your life expectancy is at least 3 months - Your blood counts and organ function are at acceptable levels **You may NOT be eligible if...** - You have significant ongoing side effects from previous treatments - Your overall health or organ function is too poor for the study - You are outside the 18–75 age range Talk to your doctor to see if this trial is right for you.