Based on the short-term efficacy and plasma EBV DNA levels following immuno-induction chemotherapy, patients with locally advanced nasopharyngeal carcinoma who derive different benefits from this treatment can be identified. For high-risk patients who do not respond to immuno-induction chemotherapy (defined as EBV DNA >0 copies/mL or imaging response evaluation showing SD/PD after immuno-induction chemotherapy), the addition of becotatug vedotin, which has a different mechanism of action, during concurrent radiotherapy and the adjuvant phase may improve patient survival. Based on the above research and background, the investigators plan to conduct the first prospective, single-arm, phase II clinical study of becotatug vedotin in patients with locally advanced nasopharyngeal carcinoma who are suboptimal responsive to immuno-induction chemotherapy, aiming to obtain sufficient evidence-based medical data to provide an additional treatment option for the concurrent and adjuvant phases of nasopharyngeal carcinoma.

Inclusion Criteria:

• Voluntary participation and written informed consent must be signed.
• Age between 18 and 70 years, male or non-pregnant female.
• Pathologically confirmed nasopharyngeal non-keratinizing carcinoma (differentiated or undifferentiated type, i.e., WHO type II or type III).
• Stage Any T N2-3 or T4N1 (AJCC 9th edition), with no distant metastasis, and previously untreated nasopharyngeal carcinoma.
• Efficacy after 3 cycles of induction immunochemotherapy assessed as stable disease (SD) or progressive disease (PD) by nasopharyngoscopy and contrast-enhanced MRI of the nasopharynx and neck.
• ECOG performance status score of 0 or 1.
• Adequate hematological function: Hemoglobin (HGB)≥90g/L, White Blood Cell (WBC) ≥ 4.010^9/L, and Platele (PLT) ≥10010^9/L.
• Adequate hepatic function: ALT and AST≤2.5Upper Limit of Normal (ULN), total bilirubin ≤2.0ULN, and serum albumin≥30g/L.
• Adequate renal function: Serum creatinine ≤ 1.5*ULN or calculated creatinine clearance (CrCl) ≥ 60 mL/min (using the Cockcroft-Gault formula).
• International Normalized Ratio (INR) and Activated Partial Thromboplastin Time (APTT) ≤ 1.5 *ULN (unless the subject is receiving anticoagulant therapy and the coagulation parameters (PT/INR and APTT) are within the expected therapeutic range for the anticoagulant at the time of screening).

Exclusion Criteria:

• Patients with recurrent or distant metastatic nasopharyngeal carcinoma.
• Pathological diagnosis of keratinizing squamous cell carcinoma (WHO Type I).
• Patients who have previously received radiotherapy or systemic chemotherapy.
• Women who are pregnant or breastfeeding, or individuals of childbearing potential who are not using effective contraception.
• HIV positive.
• History of other malignancies (except for cured basal cell carcinoma or cervical carcinoma in situ).
• Patients who have previously received immune checkpoint inhibitors (e.g., CTLA-4, PD-1, PD-L1 inhibitors).