This is a multicenter, prospective, open-label Phase II clinical study designed to evaluate the efficacy and safety of sacituzumab govitecan monotherapy in patients with locally advanced or metastatic pancreatic ductal adenocarcinoma who have failed at least one prior line of therapy, and to explore the potential correlation between baseline tumor tissue TROP-2 expression and treatment efficacy. The study plans to enroll 30 eligible subjects, who will receive sacituzumab govitecan at 5 mg/kg via intravenous infusion every 2 weeks as one treatment cycle, until disease progression or intolerable toxicity occurs. The primary endpoint is Objective Response Rate (ORR); secondary endpoints include Progression-Free Survival (PFS), Overall Survival (OS), Disease Control Rate (DCR), Duration of Response (DOR), and the incidence and severity of Treatment-Related Adverse Events (TRAEs).