This single-center, open, single-arm study aim to evaluate the efficacy and tolerability of a therapy introducing orelabrutinib on the basis of rituximab and chemotherapy in treating patients with relapsed or refractory B-cell lymphoma invloving central nervous system.

Participants will receive orelabrutinib in addition to second-line therapy consisting of rituximab and recommended chemotherapy according to histopathologic type. After treatment of 6 cycles with the new regimen, the patients achieving CR or PR would go on to receive autologous haematopoietic stem cell transplantation (auto-HSCT) with or without orelabrutinib maintenance of 2 years (if tolerable) or orelabrutinib maintenance alone if intolerant to auto-HSCT.

Inclusion Criteria:

• 14 to 80 years old;
• Histopathologically confirmed CD20 positive B-cell lymphoma according to the 5th edition of the World Health Organization (WHO) Classification of Haematolymphoid Tumours;
• After systemic treatment of the CNS lesions;
• Life expectancy of > 3 months (in the opinion of the investigator);
• No non-haematologic adverse events, except alopecia, higher than grade 1 according to Common Terminology Criteria for Adverse Events (CTCAE) v5.0;
• Absolute Neutrophil Count (ANC) ≥ 1.0×10^9/L, Platelet Count ≥ 50×10^9/L and Haemoglobin ≥ 60 g/L, without transfusion or any use of pharmacologically hematopoietic drugs in 2 weeks;
• Serum Creatinine (SCr) ≤ 1.5 times the Upper Limit of Normal (ULN) or Creatinine Clearance Rate (CCR) ≥ 30 mL/min;
• Serum total Bilirubin (tBil) ≤ 1.5 × ULN and both Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) ≤ 2.5 × ULN without hepatic metastases, otherwise tBil ≤ 3 × ULN and AST, ALT ≤ 5 × ULN respectively;
• International Normalized Ratio (INR) ≤ 1.5 and activated Partial Thromboplastin Time (aPTT) ≤ 1.5 × ULN;
• Left Ventricular Ejection Fraction (LVEF) ≥ 50%;
• Agreeing to provide written informed consent prior to any special examination or procedure for the research on their own or legal representative.

Exclusion Criteria:

• Pregnant or lactating women;
• Known Hepatitis B Virus (HBV) and/or Hepatitis C Virus (HCV) infection (HBV infection refers to HBV-DNA > detectable limit);
• With acquired or congenital immunodeficiency;
• With congestive heart failure in 6 months before enrollment, New York Heart Association (NYHA) heart function class III or IV, or LVEF < 50%;
• Known to be allergic to the test drug ingredients;
• Diagnosed with or being treated for malignancy other than lymphoma;
• With severe infection;
• Substance abuse, medical, psychological, or social conditions that may interfere with the subjects' participation in the study or evaluation of the study results;
• Deemed unsuitable for the group.