Carbohydrate antigen 19-9 (Sialyl Lewis A) (CA 19-9)

Carbohydrate antigen 19-9 (CA 19-9), chemically defined as the sialyl Lewis A (sLe^a) tetrasaccharide, is a prominent tumor-associated antigen primarily expressed on the surface of gastrointestinal cancer cells, most notably in pancreatic ductal adenocarcinoma (PDAC) [1]. Biologically, CA 19-9 acts as a high-affinity ligand for E-selectin on endothelial cells, facilitating the tethering and extravasation of tumor cells into distant organs, which promotes hematogenous metastasis [2, 3]. While it has been used clinically for decades as a serum biomarker for disease monitoring and prognosis, recent advancements have repositioned CA 19-9 as a direct therapeutic target [4]. Monoclonal antibodies such as MVT-5873 (HuMab-5B1) are designed to bind this epitope to trigger antibody-dependent cellular cytotoxicity (ADCC) and inhibit E-selectin-mediated adhesion [5]. Additionally, CA 19-9 is being explored as a target for chimeric antigen receptor (CAR) T-cell therapies and radioimmunotherapy to deliver localized cytotoxic effects [6]. Challenges in targeting CA 19-9 include its low-level expression in normal pancreatic and biliary ducts and the fact that approximately 5-10% of the population (Lewis-negative individuals) cannot synthesize the antigen due to a lack of the FUT3 enzyme [1, 7]. (Sources: [1] Magnani JL, 2004, Arch Biochem Biophys; [2] Kannagi R, 1997, Glycoconj J; [3] Kim YS, et al., 1997, Glycoconj J; [4] Lohr M, et al., 2015, Pancreatology; [5] Scholz JU, et al., 2017, HuMab-5B1; [6] Schwamborn K, et al., 2022, CAR T cells; [7] Tempero MA, et al., 1987, Cancer Res).

Other names

Sialyl Lewis AsLe(a)Gastrointestinal Cancer AntigenGICASialylated Lewis A antigenCancer antigen 19-9

Antibody-dependent cellular cytotoxicity (ADCC), inhibition of E-selectin-mediated tumor cell adhesion to the vascular endothelium, and targeted delivery of cytotoxic radionuclides or effector T-cells to tumor sites.