Selection of Anti-TIGIT Affibody Molecules Blocking the Interaction between TIGIT and CD155

T cell immunoglobulin and ITIM domain (TIGIT) is an immune checkpoint receptor expressed on T and NK cells that, upon interaction with its ligand CD155, suppresses immune cell activation. Tumor cells sometimes upregulate CD155 to evade detrimental immune reactions, and TIGIT is therefore an attractive target for the development of novel checkpoint inhibitor therapies. TIGIT has also been shown to be upregulated on tumor-infiltrating lymphocytes (TILs), enabling imaging of TILs for patient stratification for immune checkpoint therapy. Here, we have selected so-called affibody molecules targeting TIGIT from a combinatorial affibody library displayed on the surface ofEscherichia coli. The two most promising candidates had equilibrium dissociation constants (K _D values) of 2.5 and 6.5 nM, and were found to specifically interact with TIGIT-expressing cells. Furthermore, the affibody candidates were found to successfully block the interaction between TIGIT and CD155, suggesting future application as immune checkpoint inhibitors. Using an ensemble of general language models for in silico evolution, a variant with a 4.4 °C increased melting temperature could be derived, albeit with a 2-fold weaker affinity. The promising results justify further development of the anti-TIGIT affibodies for in vivo TIL-imaging and immune checkpoint therapy.