KL-A167 Injection in Recurrent or Metastatic Nasopharyngeal Carcinoma

Inclusion Criteria: * Aged ≥ 18 years old, male or female; * Subjects with histopathologically confirmed recurrent/metastatic nonkeratinizing differentiated or undifferentiated NPC; * Subjects with diseases of clinical stage IVB \[Staging System of American Joint Committee on Cancer (AJCC) (8th edition)\] who have received first line of platinum-containing combination chemotherapy and second line of monotherapy or failure of combination therapy; * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 1; * Expected survival ≥ 12 weeks; * Subjects with at least one measurable lesion according to RECIST 1.1, and lesions that have been treated with local therapies, such as radiotherapy, cannot be considered as measurable lesions; * Tissue or tissue samples must be provided for biomarker analysis. Newly obtained tissues are preferred, and archived paraffin slices are acceptable for patients who do not have newly obtained tissues; * Adequate organ and bone marrow function, as defined below: a) Hematology: neutrophil count (NEUT #) ≥ 1.5 × 10\^9/L; platelet count (PLT) ≥ 90 × 10\^9/L; hemoglobin concentration ≥ 9 g/dL; b) Hepatic function: aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3 × upper limit of normal (ULN); total bilirubin (TBIL) ≤ 1.5 × ULN; ALT and AST ≤ 5 × ULN for subjects with liver metastases; TBIL ≤ 2 × ULN for subjects with liver metastases or Gilbert's syndrome; c) Renal function: creatinine clearance (CCR) ≥ 50 mL/min…