Three loop vertices with massive particles

Vertex corrections, or form factors, are important building blocks for higher order calculations, since they describe virtual corrections to the tree level process. In flavor physics, especially $B$ meson decays, vertex corrections with flavor changes, and therefore asymmetric mass assignements on the external legs are important. In these processdings I present recent results for these kind of corrections focusing on the generic heavy-to-light form factor and the inclusive decay of $b \to s \gamma$.