• Age of 18 years or older on the date of signing the informed consent.

• Understand and be willing to sign a written informed consent.

• Patients with recurrent/metastatic head and neck squamous cell carcinoma confirmed by histology or cytology (the primary tumor is located in the oral cavity, oropharynx, hypopharynx, or larynx) that cannot be resected and cannot be cured by local treatment.

• The status of head and neck squamous cell carcinoma meets one of the following requirements: a. There is still residual tumor, local recurrence, or metastatic cancer within 6 months after platinum-containing neoadjuvant treatment, adjuvant treatment, or curative concurrent chemoradiotherapy, or b. Any residual tumor, local recurrence, or metastatic cancer should receive first-line systemic therapy, but this first-line systemic therapy is not suitable for platinum-containing regimens.

• Have measurable lesions as defined by the RECIST 1.1.

• ECOG PS 0 or 1.

• Life expectancy estimated at ≥3 months.

• The functions of important organs within 1 week before the first dose meet all the following requirements: a. Hb ≥9.0 g/dL (90 g/L), b. ANC ≥1500/μL (1.5×109/L), c. Platelet count (PLT) ≥100,000/μL (100×109/L), d. Total bilirubin ≤ upper limit of normal laboratory value (ULN), e. AST ≤1.5× ULN and ALT ≤1.5× ULN, f. International normalized ratio (INR)/prothrombin time (PT) and activated partial thromboplastin time (aPTT) ≤1.5× ULN, g. Serum amylase and lipase ≤1.5× ULN, h. serum albumin ≥3.0 g/dL (30 g/L), and i. CCR ≥30 ml/min.

• Female patients of childbearing potential should have a negative blood pregnancy test or urine pregnancy test within 72 hours before the first dose of study treatment.

⁃ Male patients should agree to take adequate contraceptive measures from the first dose of study treatment to 180 days after the last dose.