Junctional Epitope

Junctional Epitope refers to an antigenic region created at the interface where two protein domains are joined, such as in fusion proteins, bispecific antibodies, or antibody-drug conjugates. These epitopes may not exist in natural proteins and can be recognised as foreign by immune systems. Junctional epitopes contribute to immunogenicity risk and require careful design consideration in engineered therapeutic proteins.

The biopharmaceutical industry evaluates junctional epitopes during protein engineering to minimise immune responses. Computational prediction tools identify potential T-cell epitopes at junction regions, while in vitro assays assess immune activation potential. Clinical immunogenicity monitoring measures anti-drug antibodies that may target junction regions, affecting efficacy or safety. Design strategies include optimised linker sequences, human-like frameworks, and removal of high-risk immunogenic motifs. As engineered biologics including bispecific antibodies, fusion proteins, and conjugated therapeutics increase in number and complexity, junctional epitope management remains critical for ensuring long-term safety, sustained clinical performance, and durable therapeutic responses.