Histamine-succinyl-glycine (HSG) hapten (HSG)

Histamine-succinyl-glycine (HSG) is a synthetic hapten that serves as a high-affinity target for the capture arm of bispecific antibodies in pre-targeted radioimmunotherapy (PRIT) and diagnostic imaging (Sharkey et al., 2003, Cancer Research). In this therapeutic strategy, a bispecific antibody—often constructed using the Dock-and-Lock (DNL) platform—is designed with one arm targeting a tumor-associated antigen (e.g., CEA, MUC1, or CD74) and the other arm targeting the HSG hapten (Goldenberg et al., 2012, Journal of Nuclear Medicine). The HSG moiety is typically conjugated to a small, rapidly clearing peptide carrier such as IMP-205 or IMP-288, which can be chelated with radioisotopes like Indium-111, Lutetium-177, or Yttrium-90 (Rossi et al., 2006, PNAS). The clinical workflow involves administering the bispecific antibody first, allowing it to localize at the tumor and clear from the circulation, followed by the administration of the radiolabeled HSG-peptide. This approach significantly reduces off-target radiation exposure, particularly to the bone marrow, compared to directly labeled antibodies, thereby enhancing the therapeutic window for treating various malignancies (Sharkey and Goldenberg, 2011, Accounts of Chemical Research). The HSG hapten was specifically designed to be a stable, non-immunogenic mimic of metal-chelate complexes, allowing for efficient and specific binding by therapeutic antibodies like the 679 clone (Janevik-Ivanovska et al., 1997, Bioconjugate Chemistry).

Other names

HSG haptenHistamine-succinyl-glycylIMP-205 ligandDTPA-In mimicDivalent HSG peptide

Pre-targeted capture of radiolabeled haptens by bispecific antibodies for localized radiotherapy and imaging