This prospective clinical study aims to evaluate and observe the efficacy and safety of Serplulimab Monotherapy in Elderly Patients with NSCLC and PD-L1 TPS ≥ 50% using a multicenter, single-arm, phase II design.

The study is planned to be conducted in Shaanxi Province, China, with an initial target enrollment of 60 patients. The study commenced in May 2026, and recruitment is expected to conclude around May 2026, with the trial anticipated to end by May 2027.

Assuming no occurrences such as withdrawal of informed consent by subjects, intolerable adverse drug reactions, or investigator-assessed unsuitability for further participation, each participant's estimated duration of study treatment will continue until radiographically confirmed tumor progression.

Inclusion Criteria:

• 1.Voluntary participation and informed consent: Subjects must voluntarily join the study, sign the written informed consent form (ICF), and demonstrate good compliance.

  2.Age and Gender: Aged ≥65 years at the time of signing the ICF, regardless of gender.

  3.Diagnosis and Staging: Histologically or cytologically confirmed Stage IIIB (ineligible for definitive chemoradiotherapy), Stage IIIC, or Stage IV NSCLC according to the AJCC 8th edition staging system.

  4.PD-L1 Expression: Tumor tissue confirmed as PD-L1 TPS≥50% by a central laboratory or a validated local laboratory, using SP263 or 22C3 assays (a formal test report must be provided).

  5.Driver Gene Status: Known absence of actionable driver mutations, including but not limited to EGFR sensitive mutations, ALK fusions, and ROS1 fusions.

  6.Measurable Disease: At least one measurable target lesion per RECIST v1.1 criteria (lesions must not have received prior radiotherapy).

  7.Prior Treatment History: No prior systemic therapy for advanced or metastatic disease. For patients who received adjuvant or neoadjuvant chemotherapy, inclusion is permitted if disease recurrence occurred ≥6 months after the completion of the last dose.

  8.Performance Status: Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0-2.

  9.Adequate organ and bone marrow function (no blood transfusions or hematopoietic stimulating factor therapy within 14 days prior to the first dose):

  • Absolute Neutrophil Count (ANC)≥1.5 x 10^9//L
  • Platelet Count (PLT)≥100 x 10^9//L
  • Hemoglobin (Hb)≥90 g/L
  • Serum Creatinine (Cr) ≤ 1.5 x Limit of Normal (ULN) or Creatinine Clearance ≥ 50mL/min
  • Total Bilirubin (TBIL) ≤ 1.5 x ULN
  • Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT)≤ 2.5 x ULN(≤ 5 x ULN for patients with liver metastases)

Exclusion Criteria:

• 1. Hypersensitivity: Known hypersensitivity to serplulimab or any of its excipients.

  2. Prior Immunotherapy: Prior treatment with any anti-PD-1, anti-PD-L1, anti-CTLA-4, or other immune checkpoint inhibitors (ICIs).

  3. Autoimmune Disease: Active autoimmune disease requiring systemic treatment (e.g., corticosteroids or immunosuppressants) within the past 2 years. Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid replacement for adrenal or pituitary insufficiency) is permitted.

  4. Lung Disease/Pneumonitis: Active interstitial lung disease (ILD) or pneumonitis, or a history of (non-infectious) pneumonitis requiring steroid treatment.

  5. Infections: Active infection requiring systemic therapy. 6. CNS Metastases: Known active central nervous system (CNS) metastases and/or carcinomatous meningitis. However, patients with treated (via surgery or radiotherapy) and stable brain metastases are eligible, provided they are radiographically stable for at least 4 weeks prior to the first dose, have no evidence of new or enlarged brain lesions, and have discontinued glucocorticoids for at least 14 days.

  7. Pregnancy and Breastfeeding: Pregnant or breastfeeding women. 8. Investigator Discretion: Any other condition that, in the investigator's opinion, may interfere with the evaluation of the study drug, jeopardize subject safety, or confound the interpretation of study results.