Becotatug Vedotin (MRG003) With PD-1 Blockade and Chemoradiotherapy in High-Risk Locoregionally Advanced Nasopharyngeal Carcinoma

Inclusion Criteria:

* 1\. Age ≥ 18 years at the time of diagnosis, regardless of sex

  2\. Histologically confirmed newly diagnosed nasopharyngeal carcinoma (NPC) of non-keratinizing carcinoma histology (WHO classification)

  3\. Locoregionally advanced NPC staged as T4N2 or T1-4N3 according to the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) 9th edition staging system. All patients must undergo the following evaluations prior to initiation of any treatment to confirm clinical staging: complete medical history and physical examination, complete blood count (CBC) and biochemistry panel, plasma Epstein-Barr virus (EBV) DNA titer and serology, nasopharyngoscopy, magnetic resonance imaging (MRI) of the head and neck, chest X-ray or computed tomography (CT) of the chest, abdominal ultrasound, and bone scintigraphy. 18F-fluorodeoxyglucose positron emission tomography/CT (¹⁸F-FDG PET/CT) may be used as a substitute for the latter three imaging modalities.

  4\. At least one measurable lesion as defined by Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1)

  5\. Willing to provide archived tumor tissue (primary or metastatic lesion, obtained within 2 years prior to enrollment) or fresh biopsy specimen. Patients unable to provide tumor tissue may still be enrolled at the investigator's discretion, provided all other eligibility criteria are met.

  6\. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 within 7 days prior to first dose

  7\. Adequate organ function, as defined by the following laboratory parameters, obtained within 4 weeks prior to screening, with no blood transfusions, hematopoietic growth factors, or thrombopoietic agents administered during this period: a) Hematology: Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L; white blood cell count \> 4 × 10⁹/L; hemoglobin \> 90 g/L; platelet count \> 100 × 10⁹/L; b) Hepatic and renal function: Serum total bilirubin (TBIL) ≤ 1.5 × upper limit of normal (ULN); aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) ≤ 2.5 × ULN; alkaline phosphatase (ALP) ≤ 2.5 × ULN; creatinine clearance ≥ 60 mL/min; urinary protein ≤ 2+ or ≤ 1000 mg/24 hours; c) Coagulation: International normalized ratio (INR) ≤ 1.5 × ULN and activated partial thromboplastin time (APTT) ≤ 1.5 × ULN (patients receiving stable low-dose anticoagulation therapy, such as aspirin 100 mg/day, are permitted)

  8\. Normal findings on thyroid function tests, serum amylase and lipase, pituitary function tests, inflammatory and infectious markers, cardiac enzyme panel, and electrocardiogram (ECG): a) Patients aged \> 50 years with a smoking history must have normal pulmonary function test results; b) Patients with ECG abnormalities or a prior cardiovascular history (not meeting exclusion criteria) must additionally undergo myocardial function testing and echocardiography, with normal results required for enrollment

  9\. Willing and able to provide written informed consent and to comply with all protocol-specified requirements, including scheduled visits, treatment administration, laboratory assessments, and other study procedures

  10\. Patients of reproductive potential must agree to use effective contraception from the time of informed consent through 6 months after the last dose of study treatment. Women of childbearing potential (WOCBP), defined as premenopausal women and women within 2 years of menopause, must have a negative serum pregnancy test within 7 days prior to the first dose of study treatment.

Exclusion Criteria:

* 1\. History of any other malignancy within the past 5 years, with the exception of curatively treated cervical carcinoma in situ, papillary thyroid carcinoma, or basal cell carcinoma of the skin

  2\. Prior receipt of any anti-tumor therapy for nasopharyngeal carcinoma, or any of the following: a) Any ADC drug with a monomethyl auristatin E (MMAE) payload within 3 months prior to first dose; b) Any investigational drug from another clinical trial within 28 days prior to first dose; c) Major surgery within 28 days prior to first dose without full recovery, or planned major surgery within the first 12 weeks after initiation of study treatment

  3\. Positive human immunodeficiency virus antibody (HIV-Ab); active tuberculosis; active hepatitis B virus infection (HBV-DNA \> 1 × 10³ copies/mL); or active hepatitis C virus infection (HCV antibody positive and HCV-RNA above the lower limit of detection)

  4\. History of primary immunodeficiency, or active autoimmune disease requiring immunosuppressive therapy or systemic corticosteroids (≥ 10 mg/day prednisone or equivalent) within 2 weeks prior to enrollment. The following conditions are exempt: type 1 diabetes mellitus; hypothyroidism (including autoimmune thyroid disease) stable on hormone replacement therapy; psoriasis, vitiligo, or alopecia not requiring systemic treatment; and use of topical or inhaled corticosteroids, or short-term (≤ 7 days) systemic corticosteroids for prophylaxis or treatment of non-autoimmune, non-recurrent allergic conditions

  5\. Uncontrolled cardiac disease, including any of the following: (1) heart failure of New York Heart Association (NYHA) Class ≥ 2; (2) unstable angina; (3) myocardial infarction within the past 1 year; (4) prolonged QT interval (QTc \> 450 ms in males or QTc \> 470 ms in females), complete left bundle branch block, third-degree atrioventricular block, or supraventricular or ventricular arrhythmia requiring treatment or intervention

  6\. Hypertension inadequately controlled with two antihypertensive agents (systolic blood pressure \> 150 mmHg or diastolic blood pressure \> 100 mmHg)

  7\. Poorly controlled blood glucose, defined as: (a) fasting blood glucose \> 10 mmol/L on two occasions, or (b) glycated hemoglobin (HbA1c) \> 8%; or concurrent diabetic gangrene

  8\. History of interstitial lung disease (ILD) or pulmonary inflammation requiring steroid treatment (including pulmonary fibrosis and radiation pneumonitis), current ILD or pulmonary inflammation, or imaging findings at screening that cannot exclude suspected ILD or pulmonary inflammation

  9\. Concurrent pulmonary disease causing clinically severe respiratory impairment, including but not limited to: (a) any underlying pulmonary condition (e.g., pulmonary embolism, severe asthma, or severe chronic obstructive pulmonary disease \[COPD\] within 3 months prior to screening); (b) restrictive lung disease; (c) history of or concurrent interstitial pneumonitis, radiation pneumonitis, severe COPD, severe pulmonary insufficiency, or symptomatic bronchospasm

  10\. Unstable thromboembolic events requiring therapeutic intervention within 6 months prior to screening, including deep vein thrombosis, arterial thrombosis, or pulmonary embolism; catheter-related thrombosis is exempt

  11\. Pregnant or breastfeeding women (pregnancy testing should be considered for sexually active women of childbearing potential)

  12\. Known hypersensitivity to any component of Pucotenlimab or Becotatug Vedotin (MRG003) (including histidine, histidine hydrochloride, sucrose, mannitol, and polysorbate 80), or a history of Grade ≥ 3 hypersensitivity reaction to any macromolecular protein preparation or monoclonal antibody

  13\. Serious infection (CTCAE Grade \> 2) within 4 weeks prior to first dose, including but not limited to severe pneumonia, bacteremia, sepsis, or active tuberculosis

  14\. Pre-existing peripheral neuropathy of Grade \> 1

  15\. Receipt of a live vaccine within 30 days prior to first dose of Becotatug Vedotin (MRG003)

  16\. Prior solid organ transplantation or allogeneic hematopoietic stem cell transplantation (Allo-HSCT)

  17\. Any other condition judged by the investigator to potentially compromise patient safety or compliance, including but not limited to serious medical conditions requiring urgent treatment (including psychiatric disorders), significantly abnormal laboratory findings, or other psychological, familial, or social high-risk factors