Whitlow linker peptide (218 linker)

The Whitlow linker, also known as the 218 linker, is a synthetic 18-amino acid peptide sequence (GSTSGSGKPGSGEGSTKG) designed to connect the variable heavy (VH) and variable light (VL) domains of single-chain variable fragments (scFvs) (Whitlow et al., 1993). Developed to overcome the limitations of standard glycine-serine (G4S) linkers, it provides enhanced proteolytic stability and significantly reduces the tendency of scFvs to aggregate, thereby improving the overall stability and affinity of the antigen-binding domain (Sino Biological; Whitlow et al., 1993). This linker is a critical structural component of several FDA-approved chimeric antigen receptor (CAR) T-cell therapies, including tisagenlecleucel (Kymriah), axicabtagene ciloleucel (Yescarta), and lisocabtagene maraleucel (Breyanzi), which utilize the FMC63-derived scFv (Kimble et al., 2025; Cell Signaling Technology). While the linker itself is not a therapeutic target for disease treatment, it serves as a vital "universal" epitope for anti-linker monoclonal antibodies used in research and clinical diagnostics (Miltenyi Biotec). These antibodies allow for the precise detection, quantification, and spatial characterization of CAR-T cells in patient samples, such as peripheral blood or tumor biopsies, regardless of the CAR's specific antigen target (Kimble et al., 2025; AcroBiosystems).

Other names

218 linkerWhitlow 218 linkerGSTSGSGKPGSGEGSTKG linkerscFv 218 linker

The Whitlow linker provides structural flexibility and stability to the scFv domain of chimeric antigen receptors, facilitating proper folding and reducing aggregation. It also serves as a universal epitope for anti-linker antibodies used in CAR-T cell detection and monitoring.