Carbohydrate antigen 19-9 (CA19-9) (CA19-9)

Carbohydrate antigen 19-9 (CA19-9), also known as sialyl-Lewis A, is a tetrasaccharide carbohydrate structure typically found on the surface of glycoproteins and glycolipids. It is synthesized by the enzyme alpha-1,3/4-fucosyltransferase (FUT3) and is the most widely used serum biomarker for the diagnosis and monitoring of pancreatic ductal adenocarcinoma (PDAC) (Marrelli et al., 2009). In addition to its diagnostic utility, CA19-9 plays a functional role in cancer progression by acting as a ligand for E-selectin on endothelial cells, which facilitates the extravasation and metastasis of tumor cells (Magnani, 2004). While historically viewed primarily as a biomarker, CA19-9 is increasingly being investigated as a therapeutic target for monoclonal antibodies, radioimmunotherapy, and chimeric antigen receptor (CAR) T-cell therapies (Lohrmann et al., 2021). Therapeutic development must account for the fact that CA19-9 is also expressed at lower levels in normal tissues, including the biliary tract and salivary glands, posing a risk for on-target, off-tumor toxicity (Engle et al., 2019). Furthermore, approximately 5-10% of the population lacks the FUT3 enzyme required to produce CA19-9, rendering the antigen absent even in the presence of advanced malignancy (NIH).

Other names

Sialyl-Lewis AsLe(a)Gastrointestinal cancer antigenGICASialylated Lewis A antigenCancer antigen 19-9

Therapeutic agents targeting CA19-9 utilize various immune-mediated mechanisms to eliminate tumor cells. Monoclonal antibodies such as MVT-5873 (HuMab-5B1) bind to the antigen on the cell surface and trigger antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) (Houghton et al., 2017). Radioimmunotherapy approaches, like MVT-1075, use the antibody to deliver a radioactive isotope directly to the tumor site for localized cell killing. Additionally, CAR-T cell therapies are engineered to recognize the CA19-9 glycan and initiate direct T-cell mediated lysis of pancreatic cancer cells (Lohrmann et al., 2021).