Tislelizumab Plus Zeprumetostat for Relapsed or Refractory NK/T-Cell Lymphoma

Inclusion Criteria: * Age 18 years or older. * Pathologically confirmed NK/T-cell lymphoma. * Relapsed or refractory disease after at least 1 prior asparaginase-based chemotherapy-containing regimen, with or without radiotherapy. * At least 1 measurable or evaluable lesion according to Lugano 2014 criteria. * ECOG performance status 0 to 2. * Life expectancy greater than 12 weeks. * Adequate hematologic, hepatic, renal, coagulation, and cardiac function. * Recovery from prior anti-cancer treatment-related toxicities to CTCAE grade 1 or baseline, except for specified stable irreversible toxicities allowed by the investigator. * Negative pregnancy test for women of childbearing potential. * Willingness to use effective contraception. * Written informed consent. Exclusion Criteria: * Prior treatment with any EZH1/2 or EZH2 inhibitor. * Allogeneic hematopoietic stem cell transplantation within 5 years before study treatment. * Autologous hematopoietic stem cell transplantation within 3 months before study treatment. * Requirement for high-dose systemic corticosteroids or other immunosuppressive therapy within 14 days before study treatment, except permitted local/inhaled or short-course use. * Cytotoxic chemotherapy not discontinued within 14 days before study treatment. * Systemic anti-cancer therapy or investigational therapy within 4 weeks before study treatment. * Major surgery within 4 weeks or radiotherapy within 90 days before study treatment. * Active infection, including active/latent tuberculosis, HIV infection, active hepatitis B or C with detectable viral nucleic acid, or other clinically significant active viral infection. * Uncontrolled cardiovascular disease. * Persistent unresolved toxicities greater than CTCAE grade 1 from prior therapy, except alopecia. * Gastrointestinal disorders or prior intestinal surgery that may impair oral drug absorption. * Pregnancy or breastfeeding. * Psychiatric illness or inability to provide informed consent. * Any other condition that, in the investigator's judgment, makes the patient unsuitable for the study.