• 19 years of age or older

• Histologically confirmed, advanced or metastatic, HPV-positive (positive on p16 immunohistochemistry and positive on HPV-16 or HPV-18 nucleic acid test) R/M HNSCC patients

• Patients with disease progression after platinum-based chemotherapy are eligible for participation.

• Patients with recurrence within 6 months after conventional platinum-based chemotherapy are considered platinum-based treatment failure.

• Patients who have received first-line or second-line chemotherapy are eligible to participate. That is, patients whose treatment in this trials is the second or third lince chemotherapy can be enrolled.

• PD-L1 (DAKO 28-8 TPS) ≥1%

• Eastern Cooperative Oncology Group (ECOG) Activity Status 0-1

• Patients with a life expectancy of at least 6 months

• Patients must agree to provide a storage tumor tissue sample or a fresh biopsy sample for baseline biomarker tissue analysis including PD-L1 staining. Patients without tissue for storage and without tumor lesions for which biopsies can be obtained will be excluded from the study.

⁃ The patient must have adequate organ function as defined below. Specimens must be collected within 28 days prior to be administered the investigational drug.

⁃ \[hematology\]

‣ Absolute neutrophil count (ANC) ≥1,500/μL

‣ Platelets ≥100,000/μL

‣ Hemoglobin ≥9.0 g/dL or ≥5.6 mmol/L1 \[kidney\]

‣ Creatinine or creatinine clearance measured or calculated2 (GFR may be used instead of creatinine or CrCl) ≤1.5 × ULN or, For subjects with creatinine \> 1.5x laboratory ULN, ≥30 mL/min \[liver\]

‣ Total bilirubin ≤1.5 × ULN or direct bilirubin ≤ULN for subjects with total bilirubin concentration \>1.5 × ULN (except for subjects with Gilbert syndrome, total bilirubin \<3xULN and ALT \<3xULN)

‣ AST (SGOT) and ALT (SGPT) ≤2.5 × ULN (≤5 × ULN, for subjects with liver metastases) \[Blood coagulation\]

‣ As long as the international standardized ratio (INR) or prothrombin time (PT), activated partial thromboplastin time (aPTT) ≤1.5 × ULN, PT, or aPTT is within the therapeutic range of the intended use of anticoagulants, the subject is anticoagulant If you are not receiving

⁃ Patients with RECIST measurable disease defined as:

⁃ Tumor lesions with a long axis diameter (LD) ≥1 cm on axial CT or MRI images (reconstruction interval ≤5 mm) or lymph nodes ≥1.5 cm in the short axis on CT (reconstruction interval ≤5 mm)

⁃ For women of childbearing potential (WOCBP), a patient with a negative serum or urine pregnancy test result within 72 hours prior to the first administration of the investigational drug. If the urine test result cannot be confirmed as positive or negative, a serum pregnancy test should be performed.

⁃ A woman who has started menarche and has not reached amenorrhea for at least 12 consecutive months without a postmenopausal condition, an identified cause other than menopause, and who has not undergone surgical sterilization (removal of the ovaries and/or uterus) is considered a woman of childbearing potential.

⁃ Women of childbearing potential must agree to use an appropriate double contraceptive method for the entire course of this study and up to 120 days after the last administration of the study drug. Women who are menopausal (over 45 years of age and have not menstruated for more than 1 year) and women who are surgically infertile are exempt from this requirement. Note: Abstinence is acceptable as long as it is the subject's normal lifestyle and the subject's preferred method of contraception.

⁃ A patient who is willing to participate in a clinical trial in accordance with the guidelines of each laboratory and can give written consent through the subject consent form.