Antibody cysteine residues (Cys)

Antibody cysteine residues are specific amino acid components within the structure of an immunoglobulin, primarily responsible for forming the disulfide bonds that stabilize the antibody's architecture (UniProt, 2024). In the context of pharmaceutical development, these residues are not biological targets for treating disease but are instead utilized as chemical handles for the construction of antibody-drug conjugates (ADCs) (Behrens & Liu, 2014, PMC6113581). By reducing the interchain disulfide bonds, researchers can expose free thiol groups that react with linker-payload molecules, such as those containing maleimide groups (Tsuchikama & An, 2018). This process allows for the targeted delivery of highly potent cytotoxic drugs to specific cells, such as cancer cells, by leveraging the antibody's specificity (Nature Reviews Drug Discovery, 2021). However, conjugation at these sites can lead to a mixture of species with different drug-to-antibody ratios (DAR), which can influence the pharmacokinetics and therapeutic index of the resulting drug (Sun et al., 2017). Consequently, while they are vital for the structural and functional integrity of the therapeutic antibody, they represent a manufacturing site rather than a traditional therapeutic receptor or enzyme (FDA, 2023).

Other names

Cysteine thiolsInterchain cysteinesThiol groupsAntibody cysteines

Serves as a site for covalent attachment of cytotoxic payloads via thiol-reactive linkers (e.g., maleimide) to create antibody-drug conjugates (ADCs).