A Phase Ib/II Clinical Study Evaluating the Safety and Efficacy of Tislelizumab in Combination With Golidocitinib and Selinexor for the Treatment of R/R NKTCL

Inclusion Criteria: * Voluntarily participate in the clinical study; fully understand and provide informed consent (via a signed Informed Consent Form, ICF); willing and able to comply with all trial procedures. * Histopathologically confirmed diagnosis of extranodal NK/T-cell lymphoma, nasal type (NKTCL) by the participating study center. * Relapsed or refractory NKTCL after failure of asparaginase-based chemotherapy ± radiotherapy: * Relapse: Disease recurrence \>6 months after achieving complete response (CR) to prior therapy. * Refractory: Failure to achieve CR or disease progression after adequate systemic therapy (≥4 cycles of a combination regimen). * For Phase II: Patients must have received prior anti-PD-1 monoclonal antibody therapy and remain refractory. * At least one measurable or evaluable lesion per Lugano 2014 criteria: * Measurable lesion: CT/MRI: Longest diameter ≥1.5 cm (lymph nodes) or ≥1.0 cm (extranodal lesions).Post-radiation lesions require radiological evidence of progression. * Evaluable lesion: FDG-PET: Lymph node/extranodal lesion with uptake \> liver and imaging consistent with lymphoma. * Age ≥18 years at the time of ICF signing. * Life expectancy \>12 weeks. * ECOG performance status 0-2. * Adequate organ and bone marrow function: * Hematology (no transfusion/G-CSF support within 14 days): ANC ≥1.5×10⁹/L (≥0.5×10⁹/L if bone marrow involvement)；Platelets ≥100×10⁹/L (≥50×10⁹/L if bone marrow involvement)；Hemoglobin ≥8.0 g/dL. * L…