Histamine-succinyl-glycine (HSG) epitope (HSG)

The Histamine-succinyl-glycine (HSG) epitope is a synthetic hapten used in pre-targeted radioimmunotherapy (PRIT) and diagnostic imaging. It is the specific molecular target for the 679 antibody arm of the TF2 bispecific antibody, which is a trivalent Dock-and-Lock (DNL) construct designed to bind both Carcinoembryonic Antigen (CEA) on tumor cells and the HSG epitope on a carrier peptide (Schoffelen et al., 2014, J Nucl Med). In a typical clinical workflow, TF2 is administered first to saturate tumor-associated CEA; once the antibody has cleared from the circulation, a small HSG-containing peptide (such as IMP288) labeled with a radionuclide is injected (Goldenberg et al., 2012, Bioconjug Chem). This system allows for rapid localization of the therapeutic or imaging agent at the tumor site with high contrast and minimal systemic toxicity, as the small peptide is either captured by the pre-localized TF2 or quickly excreted via the kidneys (Sharkey et al., 2003, Cancer Res). The HSG-pre-targeting platform has been investigated primarily for the treatment of CEA-expressing malignancies, including colorectal, medullary thyroid, and pancreatic cancers (Kraeber-Bodéré et al., 2006, J Nucl Med).

Other names

HSGHistamine-succinyl-glycineHSG haptenHSG-peptide epitope

The HSG epitope serves as a synthetic docking site in a multi-step pre-targeting strategy. A bispecific antibody (e.g., TF2) is used to bridge a tumor-associated antigen (like CEA) and the HSG-bearing payload carrier, enabling high-affinity capture of diagnostic or therapeutic agents at the tumor site.