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

This is a multicenter, open-label, phase Ib/II clinical trial in relapsed or refractory NK/T-cell lymphoma. In phase Ib, patients with relapsed or refractory NK/T-cell lymphoma after at least 1 prior asparaginase-based chemotherapy-containing regimen will receive tislelizumab 200 mg intravenously every 3 weeks in combination with zeprumetostat at 1 of 2 dose levels: 300 mg orally twice daily or 350 mg orally twice daily. The dose-limiting toxicity observation window is 21 days. If neither dose level is excessively toxic, enrollment will continue until 12 evaluable patients are included in each arm. Dose selection for phase II will be based on dose-limiting toxicity and objective response rate at week 12 assessed by independent blinded imaging review according to Lugano 2014 criteria. If efficacy is similar, the lower dose level will be preferred. In phase II, patients will receive zeprumetostat at the RP2D plus tislelizumab 200 mg intravenously every 3 weeks. Patients will be enrolled into 2 predefined cohorts according to prior exposure to PD-1 inhibitors: Cohort-R (prior PD-1 exposed/refractory) and Cohort-N (PD-1 inhibitor-naive). Treatment will continue until disease progression, unacceptable toxicity, withdrawal of consent, loss to follow-up, death, or study termination. The primary phase II endpoint is objective response rate at week 12 assessed by independent blinded imaging review according to Lugano 2014 criteria. Secondary endpoints include complete response rate, duration of response, progression-free survival, overall survival, and safety. Exploratory endpoints include the association of ctDNA and EBV-DNA dynamics, PD-L1, EZH2/H3K27me3, and tumor microenvironment biomarkers with clinical outcome.