This study is designed to evaluate the efficacy and safety of rimegepant in combination with glofitamab and CD19 CAR-T cell therapy in patients with high-risk relapsed/refractory large B-cell lymphoma. Eligible patients will be randomized to receive glofitamab plus CD19 CAR-T cell therapy with or without rimegepant. The primary endpoint is complete response rate at 6 months after CAR-T cell infusion.

Inclusion Criteria:

• Able to understand and voluntarily sign the written informed consent form.
• Age 18 years or older.
• Histologically confirmed large B-cell lymphoma with CD19 and CD20 expression.
• Relapsed or refractory disease after at least one prior line of systemic therapy.
• Prior treatment must have included an anthracycline-containing chemotherapy regimen and an anti-CD20 monoclonal antibody.
• Considered suitable by the investigator to receive glofitamab and CD19 CAR-T cell therapy.
• Presence of at least one high-risk feature, including extranodal involvement, bulky disease, or TP53 abnormality.
• ECOG performance status of 0 to 2.
• Life expectancy of at least 12 weeks.
• Adequate bone marrow, hepatic, renal, pulmonary, and cardiac function as determined by the investigator.
• Participants of reproductive potential must agree to use effective contraception during the study period.
• Able and willing to comply with the study protocol, in the investigator's judgment.

Exclusion Criteria:

• History of hypersensitivity to any study treatment or related compounds.
• Active or uncontrolled infection requiring systemic treatment.
• History of allogeneic hematopoietic stem cell transplantation or organ transplantation.
• Uncontrolled or clinically significant viral infection as defined by the protocol.
• Known central nervous system involvement by lymphoma or clinically significant central nervous system disease that may interfere with study treatment or safety assessment.
• Severe or uncontrolled cardiovascular disease.
• Severe autoimmune disease or immune-mediated disease that may interfere with study treatment or safety assessment.
• Known or suspected history of hemophagocytic lymphohistiocytosis.
• Recent thromboembolic event before screening.
• History of another malignancy within 5 years before screening, except adequately treated carcinoma in situ or non-melanoma skin cancer.
• Receipt of prohibited anticancer therapy, immunosuppressive therapy, live attenuated vaccine, or other prohibited treatment within the protocol-specified period before enrollment.
• Pregnant or breastfeeding women, or participants planning pregnancy during the study period.
• Concurrent participation in another interventional clinical trial.
• Need for prohibited concomitant medications that cannot be discontinued or substituted.
• Any condition that, in the investigator's judgment, makes the participant unsuitable for study treatment or study participation.