Secondary central nervous system lymphoma (SCNSL) occurred in about 5% of patients with diffuse large B-cell lymphoma (DLBCL). The prognosis of SCNSL is very poor. A number of retrospective studies have shown that the median overall survival (mOS) since the diagnosis of CNSL is only 2.5-3.5 months, and the 2-year OS rate is only 20%. At present, there is no consensus on the treatment of SCNSL, and new therapeutic strategies are urgently needed. Zanubrutinib is a new second-generation BTK inhibitor, which has showed good efficacy and safety in a variety of B-NHL. Zanubrutinib has showed good blood-brain barrier permeability in preclinical studies. This study attempts to evaluate the efficacy and safety of zanubrutinib combined with rituximab and high-dose methotrexate in the treatment of SCNSL in patients with DLBCL.

Inclusion Criteria:

• Men and women ≥ 18, and ≤75 years of age

• Histologically documented systemic diffuse large B-cell lymphoma(DLBCL)

• Central nervous system (CNS) relapse (meningeal or /and intraparenchymal) with or without systemic lymphoma manifestations

• All patients need to have received at least one and ≤4 lines of prior therapy systemic lymphoma directed therapy.

• ECOG performance score 0-3

• Participants must have adequate bone marrow and organ function shown by:

  • Absolute neutrophil count (ANC) ≥ 1.5 x 109/L, Hemoglobin (Hgb) ≥ 9 g/dL, Platelets ≥ 75 x 109/L(≥ 50 x 109/L if bone marrow involvement)
  • Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 times the upper limit of normal, total bilirubin ≤ 2 times the upper limit of normal
  • International Normalized Ratio (INR) ≤ 1.5 and PTT (aPTT) ≤ 1.5 times the upper limit of normal
  • serum creatinine (mg/dL)) ≤ 1.5 times the upper limit of normal ; calculated creatinine clearance(CrCl) ≥ 40ml/min using the Cockcroft-Gault equation

• Expected survival greater than 3 months

• Did not receive targeting agents within 10 days or receive chemortherapy, radiotherapy, or monoclonal antibody within 3 weeks

• Woman of reproductive potential must agree to use highly effective methods of birth control during the period of therapy and for 30 days after the last dose of the study drug. Men who are sexually active must agree to use highly effective contraception during the period of therapy and for 3 months after the last dose

• Ability of participants or Legally Authorized Representative (LAR) to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

• Newly diagnosed DLBCL with CNS involvement
• Previous treatment with Bruton's Tyrosine Kinase (BTK) inhibitors
• Received targeting agents within 10 days or received chemortherapy, radiotherapy, or monoclonal antibody within 3 weeks
• Patient has significant abnormalities on screening electrocardiogram (EKG) and active and significant cardiovascular disease such as uncontrolled or symptomatic arrhythmias, congestive heart failure, hypertension, valvular disease, pericarditis, or myocardial infarction within 6 months of screening
• History of severe bleeding diseases
• Patient is using warfarin or any other Coumadin-derivative anticoagulant or vitamin K antagonists. Patients must be off warfarin-derivative anticoagulants for at least seven days prior to starting the study drug. Low molecular weight heparin is allowed. Patients with congenital bleeding diathesis are excluded
• Patient is taking a drug known to be a moderate and strong inhibitor or inducers of the P450 isoenzyme CYP3A. Participants must be off P450/CYP3A inhibitors and inducers for at least two weeks prior to starting the study drug
• Patient is known to have human immunodeficiency virus (HIV) infection
• Patient is known to have a history of active or chronic infection with hepatitis C virus (HCV) or hepatitis B virus (HBV) as determined by serologic tests
• Patient is known to have an uncontrolled active systemic infection
• Patients with serous cavity effustion
• Patient underwent major systemic surgery ≤ 4 weeks prior to starting the trial treatment or who has not recovered from the side effects of such surgery
• Women who are pregnant or nursing (lactating)
• The patient is unwell or unable to participate in all required study evaluations and procedures