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

The **histamine-succinyl-glycine epitope tag** is an artificial peptide sequence—often referred to as the "HSG" motif—used primarily as a small-molecule hapten in pretargeting strategies for molecular imaging and radioimmunotherapy. It is not a natural receptor, enzyme, or therapeutic target but rather serves as an engineered recognition element. The HSG motif consists of histamine conjugated to succinic acid and glycine residues; it can be further extended with additional amino acids such as lysine or tyrosine to facilitate chemical modifications like dye labeling or chelator attachment[4]. In clinical research settings, this tag is incorporated into peptides such as IMP288. Bispecific antibodies are designed with one arm recognizing the tumor antigen and another arm specifically binding the HSG motif. This allows for highly selective delivery of radiolabeled haptens (bearing the HSG sequence) after initial antibody localization at tumor sites—a strategy known as pretargeted radioimmunotherapy or imaging[6]. The use of such tags enables modular approaches where different payloads can be attached to the same targeting system without altering antibody specificity. However, since this entity is not itself a biological target but rather an engineered tool for detection/purification/imaging purposes, it should not be classified alongside canonical therapeutic targets like receptors or enzymes. There are no drugs that directly interact with this molecule in terms of inhibition/activation; instead, it acts solely as a recognition site for anti-HSG arms on bispecific antibodies[6]. Safety concerns may include possible immunogenic responses against non-native peptide sequences introduced into patients. This entry appears incorrect if interpreted strictly within drug discovery/therapeutic target frameworks—it describes an **artificial tagging system**, not a native protein/receptor/enzyme involved in disease biology. > "The TF10 bsmAb is divalent for binding to MUC1 and monovalent for binding to a histamine-succinyl-glycine (HSG) motif containing hapten..." [6] > "The hapten consists of histamine conjugated to succinic acid... The hapten-peptide...can incorporate chelators for radiometals or near-infrared dyes through conjugation..." [4]

Other names

HSG taghistamine-succinyl-glycine haptenHim-Suc-Gly epitopeHSG motif

Acts as an artificial antigenic determinant recognized by anti-HSG antibodies for targeted delivery or detection[4][6]