Histamine-succinyl-glycine binding site (Anti-HSG) (HSG binding site)

The Histamine-succinyl-glycine (HSG) binding site is an engineered molecular target used in Pre-targeted Radioimmunotherapy (PRIT) systems to improve the therapeutic index of radionuclides. It is typically incorporated as a single-chain variable fragment (scFv), derived from the 679 monoclonal antibody, into a bispecific monoclonal antibody (bsAb). In the PRIT clinical workflow, the bsAb is administered first to bind a specific tumor-associated antigen, such as Carcinoembryonic Antigen (CEA). After the bsAb has localized at the tumor site and cleared from the blood, a small radiolabeled peptide containing the HSG hapten (e.g., IMP288) is administered. This peptide rapidly docks with the anti-HSG binding site on the tumor-bound antibody, delivering a concentrated dose of radiation for imaging or therapy while minimizing exposure to healthy tissues. This system effectively decouples the slow pharmacokinetics of large antibodies from the fast distribution of small-molecule radiopharmaceuticals (Goldenberg et al., 2012; Sharkey et al., 2003). Clinical studies using bsAbs like TF2 have demonstrated that targeting the HSG binding site allows for high tumor-to-background ratios and reduced bone marrow toxicity compared to conventional radioimmunotherapy (Schoffelen et al., 2013).

Other names

Anti-HSG scFvAnti-HSG binding arm679 antibody binding siteHSG-hapten binding siteAnti-HSG epitope-binding domain

Pre-targeted radioimmunotherapy (PRIT) via high-affinity capture of radiolabeled HSG-haptens by a pre-localized bispecific antibody.