This is an open-label, phase Ib study evaluating the combination treatment of sintilimab and linperlisib in patients with relapsed or refractory extranodal natural killer/T-cell lymphoma (NKTCL).

Key Inclusion Criteria:

1. Pathologically confirmed extranodal NKTCL.
2. Voluntary participation in the clinical study; fully understand the study, and have signed the written informed consent form.
3. Age ≥ 18 years.
4. Relapsed or refractory NKTCL after failure of at least one line of asparaginase-based chemotherapy or chemoradiotherapy regimen.
5. ECOG performance status: 0-2.
6. Estimated survival time ≥ 3 months.
7. At least one measurable lesion according to the Lugano 2014 lymphoma evaluation criteria.
8. Adequate organ and bone marrow function.

Key Exclusion Criteria:

1. Patients previously treated with PI3K inhibitors.
2. Patients with hemophagocytic syndrome.
3. Patients known to be allergic to any component of monoclonal antibodies.
4. Patients with a history of other malignancies within the past 5 years or concurrent malignancies (excluding basal cell carcinoma of the skin).
5. Patients with aggressive NK-cell leukemia or central nervous system involvement.
6. Patients who have participated in other drug clinical trials within 4 weeks prior to the start of this study or have received anti-tumor treatment within 4 weeks before the study initiation.
7. Patients with clinically significant gastrointestinal abnormalities that may affect drug intake, transport, or absorption (e.g., inability to swallow, chronic diarrhea, intestinal obstruction) or patients who have undergone total gastrectomy.
8. Patients with a history of interstitial lung disease (except for asymptomatic interstitial lung disease caused by radiotherapy).