FAP

Fibroblast activation protein (FAP) inhibitors and ligands target a protease of activated fibroblasts. FAP was described in 1990 as a cell surface glycoprotein of reactive stromal fibroblasts in human epithelial cancers. Its cloning in 1994 placed it in the serine protease family, close to dipeptidyl peptidase IV (DPP-IV). FAP cleaves peptides after proline residues, both as a dipeptidyl peptidase and as an endopeptidase. Ac-Gly-BoroPro and talabostat are boronic acid dipeptides, and talabostat also inhibits DPP-IV and related peptidases. FAPI-4, reported in 2018, is a quinoline-based FAP ligand developed for imaging research. Simlukafusp alfa is an immunocytokine that fuses an anti-FAP antibody to a variant interleukin-2 (IL-2).