PR1A3

PR1A3 is a monoclonal antibody that targets membrane-bound carcinoembryonic antigen (mCEA), specifically binding to a conformational epitope formed by parts of the glycosyl-phosphatidylinositol anchor and the B3 domain of CEA. It has unique properties that differentiate it from other anti-CEA antibodies, particularly its preferential binding to cell-surface CEA rather than soluble CEA found circulating in the blood of cancer patients. This selective binding makes PR1A3 an ideal candidate for antibody-targeted tumor therapy, especially for colorectal cancers. The antibody has been humanized while retaining its cell-surface specificity and affinity. In 2014, Roche developed RG7813, a drug based on PR1A3 that delivers a cytokine (engineered IL2) to the specific part of CEA exposed only on cancer cell surfaces.