Glofitamab Plus Gemcitabine and Oxaliplatin (GemOx) in Relapsed or Refractory Primary and Secondary Central Nervous System Lymphoma

Inclusion Criteria: * 1\. Histopathologically confirmed relapsed/refractory primary central nervous system lymphoma (PCNSL), or secondary central nervous system lymphoma (SCNSL) with isolated central nervous system relapse * 2\. Written informed consent obtained, and the participant is able to comply with the protocol-specified visits and procedures * 3\. Whole-body PET/CT and brain MRI (plain plus contrast) performed within 28 days before enrolment must show at least one measurable lesion in two perpendicular dimensions (according to the Lugano 2014 criteria) * 4\. Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 4 * 5\. Adequate organ and bone marrow function, defined as: complete blood count - absolute neutrophil count (ANC) \>= 1.0 x 10\^9/L, platelet count (PLT) \>= 50 x 10\^9/L, and haemoglobin (HGB) \>= 8.0 g/dL; no granulocyte growth factor, platelet transfusion or red blood cell transfusion within 7 days before testing * 6\. Hepatic function: serum total bilirubin (TBIL) \<= 1.5 x upper limit of normal (ULN); alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \<= 2.5 x ULN * 7\. Renal function: serum creatinine (Cr) \<= 2 x ULN, or creatinine clearance (CCR) \>= 60 mL/min * 8\. Cardiac function: New York Heart Association (NYHA) class below III; left ventricular ejection fraction \>= 50% on echocardiography * 9\. Coagulation function: international normalised ratio (INR) \<= 1.5 x ULN, activated partial thromboplastin time (APTT) \<= ULN + 10 s, and prothrombin time (PT) \<= ULN + 3 s * 10\. Life expectancy of more than 3 months * 11\. Age 18 years or older * 12\. Women of childbearing potential and male participants with a female partner of childbearing potential must use effective contraception throughout the treatment period and for 90 days after the last dose of study treatment Exclusion Criteria: * 1\. Involvement of any site outside the central nervous system * 2\. A second primary malignancy (except non-melanoma in-situ skin cancer, superficial bladder cancer, in-situ cervical cancer, gastrointestinal intramucosal carcinoma, or breast cancer that has been cured with no recurrence within 5 years) * 3\. Previous allogeneic organ transplantation or allogeneic haematopoietic stem cell transplantation * 4\. Anticipated need for any other systemic anticancer therapy during the study period * 5\. Anti-tumour vaccine or other immunostimulatory anticancer therapy within 3 months before the first dose * 6\. Severe acute or chronic infection requiring systemic treatment * 7\. Human immunodeficiency virus antibody (HIV-Ab) positivity, active hepatitis, or any other uncontrolled infectious disease * 8\. Current or prior idiopathic pulmonary fibrosis or idiopathic pneumonia * 9\. Known active pulmonary tuberculosis * 10\. Grade \>= 3 immune-related adverse events during previous immunotherapy * 11\. Documented history of neurological or psychiatric disorders * 12\. Receipt of any live vaccine for infectious diseases (e.g., influenza vaccine, varicella vaccine) within 4 weeks before the first dose, or planned use during the study period * 13\. Documented history of alcohol or drug abuse * 14\. Pregnant or breastfeeding women * 15\. Receipt of any other investigational active drug within 1 month before the first dose * 16\. Any other condition that, in the investigator's opinion, may affect the efficacy or safety assessment of this study