A Phase II Clinical Study of HLX22 in Combination With Trastuzumab and Chemotherapy

Inclusion Criteria: * Voluntary Participation Willingly participate in the clinical study; fully comprehend the study details and sign the Informed Consent Form (ICF); commit to and demonstrate capacity to complete all trial procedures. * Age and Gender Any gender; age ≥18 and ≤75 years at the time of ICF signing. * Diagnosis Histologically or cytologically confirmed metastatic pancreatic ductal adenocarcinoma (PDAC). * Prior Therapy \*No prior systemic antitumor therapy for metastatic PDAC. \*Exception: Patients who received one cycle of chemotherapy (nab-paclitaxel + gemcitabine) as initial treatment for newly diagnosed PDAC may enroll. \*Prior neoadjuvant/adjuvant therapy is permitted if completed \>6 months before enrollment, and treatment-related adverse events (AEs) have recovered to NCI-CTCAE ≤ Grade 1 (alopecia excluded). * Measurable Disease At least one measurable lesion per RECIST v1.1, assessed by the investigator. Target lesions must not be exclusively bone metastases. * HER2 Status \*HER2-positive defined by ASCO/CAP gastric cancer HER2 testing guidelines: IHC 3+ (primary or metastatic lesion), or IHC 2+ with ISH/FISH-positive confirmation. \*Note: ≤15 patients with IHC 2+/FISH-positive status may enroll. * Performance Status ECOG performance status 0 or 1 within 7 days prior to first dose. * Life Expectancy Expected survival ≥3 months. * Hepatitis B \*HBsAg-negative and HBcAb-negative. \*If HBsAg-positive or HBcAb-positive, HBV-DNA must be \<2500 copi…