The purpose of this study is to determine whether Nivolumab given intrathecally is effective in the treatment of Relapsed/Refractory Primary Central Nervous System Lymphoma (PCNSL)

This is a case study aiming to recruit 1 patient. This study is indicated for relapsed/refractory primary central nervous system lymphoma. Primary objective is to explore the safety.

Inclusion Criteria:

• Subjects with ECOG 0,1,2,3
• Subjects with pathologically confirmed PCNSL with lesion in brain who progressed after or did not respond to at least 1 line of systemic therapy. PCNSL prior therapy may include HD-MTX, HD-MTX-based regimen, high-dose cytarabine, radiation therapy alone as treatment or as part of consolidation therapy, high-dose therapy with autologous stem cell transplant as part of consolidation therapy, and/or intraocular MTX alone or as part of consolidation therapy
• Subject with sufficient function of liver, kidney, heart, lung and hematopoiesis
• Subjects with relapsed PCNSL and are able to receive biopsy

Exclusion Criteria:

• Subjects that are not DLBCL type pathologically
• Intraocular PCNSL without evidence of brain disease
• Subjects who cannot undergo MRI assessments
• Relapsed PCNSL patients who cannot undergo biopsy
• Biopsy suggests no significant tumor-infiltration T cell or poor PD-1 expression
• Subjects with other malignancy
• Subjects with history of any inflammatory CNS diseases
• Subjects with an active, known, or suspected autoimmune disease
• Subjects with a condition requiring systemic treatment with either corticosteroids or other immunosuppressive medications within 14 days of start of study treatment
• Prior treatment with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or anti-CTLA-4 antibody, or any other antibody or drug specifically targeting T-cell co-stimulation or checkpoint pathways

Other protocol defined inclusion/exclusion criteria could apply