• Age: ≥18 years.

• Diagnosis: Histologically or cytologically confirmed recurrent or metastatic head and neck squamous cell carcinoma, meeting the following conditions:Local treatment methods cannot achieve a cure (including cases where the patient refuses local treatment or is deemed unsuitable for local treatment by the physician, e.g., inability to tolerate anesthesia or other factors precluding local radiotherapy).No prior systemic treatment (targeted therapy, immunotherapy, and/or chemotherapy) after recurrence or metastasis.Primary nasopharyngeal carcinoma is not permitted.

• Cisplatin Intolerance: Patients must have at least one of the following reasons for being unsuitable for cisplatin-based chemotherapy:Age \>70 years.Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 2.Renal function impairment (creatinine clearance \<50 mL/min). If this criterion is met, the creatinine clearance standard in criterion 7 is not applicable.Severe tinnitus or hearing loss (requiring a hearing aid or showing a ≥25 dB shift at two consecutive frequencies on audiometry).Inability to receive intravenous hydration due to cardiac dysfunction or other comorbidities (left ventricular ejection fraction \[LVEF\] \<50%).Patient refusal of cisplatin-based chemotherapy.

• Oropharyngeal Cancer: Availability of tumor tissue for P16/HPV testing (if previously tested, retesting is not required).

• Performance Status: ECOG PS score of 0-2.

• Measurable Disease: At least one measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.

• Adequate organ function：Hematology:Absolute Neutrophil Count (ANC): ≥1500/μL (1.5 × 10⁹/L),Platelets: ≥100,000/μL (100 × 10⁹/L),Hemoglobin: ≥9 g/dL (90 g/L) or ≥5.6 mmol/L.Renal:Serum Creatinine or Creatinine Clearance: Creatinine ≤1.5 × Upper Limit of Normal (ULN); if creatinine \>1.5 × ULN, then creatinine clearance must be ≥60 mL/min.Hepatic:Total Bilirubin: ≤1.5 × ULN,Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT): ≤2.5 × ULN; if liver metastases are present, then ≤5 × ULN.Coagulation:International Normalized Ratio (INR) or Prothrombin Time (PT): ≤1.5 × ULN; if the patient is receiving anticoagulant therapy, PT or Partial Thromboplastin Time (PTT) must be within the therapeutic range for the anticoagulant used.

• PD-L1 Testing: Availability of tumor tissue (from the tumor core or resected tumor) for PD-L1 testing (if previously tested, additional testing is not required).

• Reproductive Status:Female subjects must have a negative pregnancy test within two weeks before starting study treatment and must not be breastfeeding.Female subjects must agree to use effective contraception during the study and for 6 months after the last dose of study drug.Male subjects must agree to use effective contraception during the study and for 6 months after the last dose of study drug.

⁃ Informed Consent: Subjects must voluntarily participate in the study, provide written informed consent, and be able to comply with the protocol-specified visits and procedures.