Neoadjuvant Presurgical Becotatug Vedotin (MRG003) Plus Pucotenlimab (HX008) in Oral Cavity Squamous Cell Carcinoma

This is a phase 2, open-label, single-arm clinical trial evaluating neoadjuvant therapy with Becotatug vedotin (MRG003) combined with Pucotenlimab (HX008) in patients with previously untreated, resectable stage III-IVA oral cavity squamous cell carcinoma (OSCC) with a PD-L1 Combined Positive Score (CPS) of 1 or higher. Eligible participants will receive 3 cycles of neoadjuvant treatment (Becotatug vedotin 2.3 mg/kg plus Pucotenlimab 200 mg, intravenously, every 3 weeks), followed by radical surgery 2-3 weeks after the last cycle of neoadjuvant therapy. Postoperative adjuvant radiotherapy will be stratified based on pathological response and risk factors: patients achieving major pathological response (MPR, defined as ≤10% residual viable tumor) with negative margins and no extranodal extension (ENE) will receive de-escalated radiotherapy (50-54 Gy); patients not achieving MPR or with high-risk features will receive standard radiotherapy (60-66 Gy) with or without concurrent cisplatin chemotherapy. The primary endpoint is major pathological response (MPR). Secondary endpoints include objective response rate (ORR), pathological complete response (pCR), event-free survival (EFS), overall survival (OS), and safety profile. Exploratory biomarkers will be assessed in tumor tissue and peripheral blood. A total of 32-33 participants will be enrolled using a Simon two-stage optimal design (α=0.05, power=80%).