This is a randomized, open-label, multicenter Phase III study evaluating the efficacy and safety of TR115, an EZH2 inhibitor, versus investigator's choice (chidamide, golidocitinib, mitoxantrone liposome, or gemcitabine) in patients with relapsed and/or refractory peripheral T/NK-cell lymphoma. Approximately 180 patients will be randomized in a 1:1 ratio. The primary endpoint is progression-free survival (PFS) assessed by an Independent Review Committee (IRC). The key secondary endpoint is overall survival (OS). The study is being conducted at approximately 40 to 60 centers across China.