Anti-histamine-succinyl-glycine (HSG) antibody fragment (Anti-HSG arm)

The Anti-HSG arm of TF2 and TF12 is a recombinant antibody fragment, typically derived from the humanized 679 antibody (h679), that specifically recognizes the synthetic hapten histamine-succinyl-glycine (HSG). It serves as the capture mechanism in a multi-step pre-targeting strategy designed to improve the efficacy and safety of radioimmunotherapy and diagnostic imaging in oncology (Sharkey RM, et al., 2008, PMID: 18381681). In this system, a bispecific antibody—such as TF2, which targets carcinoembryonic antigen (CEA), or TF12, which targets MUC1—is first administered to the patient to bind to tumor-associated antigens. Once the bispecific antibody has localized to the tumor and cleared from the blood, a small, fast-clearing radiolabeled peptide carrying the HSG hapten (e.g., IMP288) is injected (Schoffelen R, et al., 2013, PMID: 23303603). The Anti-HSG arm then binds this peptide with high affinity, effectively locking the radioactive payload onto the tumor cells. This approach significantly reduces the radiation dose to bone marrow and other healthy organs compared to traditional radioimmunoconjugates, as the radioactive component does not circulate for extended periods attached to a full-sized antibody (Janevik-Ivanovska E, et al., 1997, PMID: 9143949).

Other names

h679679 antibodyAnti-HSG FabAnti-HSG scFvHistamine-succinyl-glycine binding arm

The anti-HSG arm functions as a molecular bridge in a pre-targeting strategy, where it captures a radiolabeled HSG-peptide payload at the tumor site after a bispecific antibody has already bound to a tumor-associated antigen.