NB02 (Poseltinib) Combined Rituximab and Lenalidomide in R/R PCNSL

This study is testing a three-drug combination — poseltinib (NB02), rituximab, and lenalidomide — for patients with primary central nervous system lymphoma (PCNSL), a rare brain lymphoma that has come back or stopped responding to treatment. **You may be eligible if...** - You are between 19 and 80 years old - You have been diagnosed with CD20-positive primary CNS lymphoma (PCNSL), confirmed by biopsy - Your lymphoma has progressed or returned after prior remission treatment, radiation, or autologous stem cell transplant - You have had no more than two prior systemic treatments and no more than one prior radiation treatment **You may NOT be eligible if...** - You have had more than two prior systemic treatments - Your cancer cells do not express CD20 - You are in very poor health or have serious organ problems Talk to your doctor to see if this trial is right for you.