A Study of Becotatug Vedotin (MRG003) Combined With Epirubicin as Neoadjuvant Therapy for EGFR-Positive, Unresectable Recurrent Sinonasal Adenoid Cystic Carcinoma

Inclusion Criteria: Age ≥ 18 years, male or female. Histopathologically confirmed sinonasal adenoid cystic carcinoma (SNACC) with measurable recurrent disease located in the sinonasal/skull base region, irrespective of the presence of regional lymph node or distant metastases. EGFR expression positive by immunohistochemistry (IHC) performed at a central laboratory. Multidisciplinary team (MDT) assessment at baseline confirms that the tumor is not amenable to radical (R0) surgical resection. At least one measurable lesion in the skull base/sinonasal region according to RECIST v1.1 (longest diameter ≥ 10 mm). Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Adequate bone marrow, hepatic, renal, and cardiac function as defined by protocol-specified laboratory parameters. Willing to provide written informed consent (including consent for clinical treatment and biospecimen research) and able to comply with study procedures. Exclusion Criteria: Prior treatment with any antibody-drug conjugate (ADC) that contains monomethyl auristatin E (MMAE) as the payload. Prior systemic chemotherapy containing epirubicin or any other anthracycline within 6 months before study enrollment. Active uncontrolled infection, or active autoimmune disease requiring systemic therapy. Symptomatic or urgent (e.g., requiring radiotherapy or surgery) central nervous system (CNS) metastases. Known severe hypersensitivity to any component of the study drugs. Pregnant or breastfeeding women, or men/women planning to become pregnant within 6 months after the last dose of study treatment. Any medical or psychosocial condition that, in the investigator's judgment, may interfere with study participation, increase patient risk, or confound data interpretation.