Description_x000D_ Biochem/physiol Actions_x000D_ APC366 is a selective inhibitor of mast cell tryptase, which is involved with allergenic response. It thereby also inhibits protease-activated receptor PAR2, a G-protein-coupled receptor that is activated by mast cell tryptase. Tryptase has been proposed to be involved in fibrosis, joint inflammation and also in promoting breast cancer angiogenesis, all of which APC366 inhibited.