A carboxamide, the structure of which is that of acetamide substituted on carbon by a 2',3-dimethyl-2,4'-bipyridin-5-yl group and on nitrogen by a 5-(pyrazin-2-yl)pyridin-2-yl group. It is a highly potent, selective and orally bioavailable Porcupine inhibitor (a Wnt signalling inhibitor).