CA19-9 is a tumor-associated carbohydrate antigen and the most widely used serum biomarker for pancreatic cancer. Elevated CA19-9 expression is strongly associated with pancreatic ductal adenocarcinoma (PDAC) as well as gastrointestinal malignancies including colorectal, gastric, and bile duct cancers. Clinically, serum CA19-9 levels are routinely measured to evaluate tumor burden, predict surgical resectability, monitor treatment response, and detect recurrence. Preoperative CA19-9 concentrations above 1000 U/mL often correlate with unresectable disease, while postoperative normalization is linked to improved survival outcomes. As a glycan epitope expressed on mucin-type glycoproteins and glycolipids, CA19-9 represents a valuable target for antibody-based diagnostics, imaging, and therapeutic development. Anti-CA19-9 antibodies have demonstrated high tumor specificity, making them essential tools for molecular pathology, biomarker validation, and translational oncology. Catalina offers high-quality CA19-9 antibodies with high sensitivity and reproducibility that support advanced research in pancreatic cancer biology, biomarker discovery, and antibody-based therapy development.