Geranylgeranyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway derived directly from farnesyl pyrophosphate and used in the biosynthesis of terpenes and terpenoids.{8343} It is also serves as a substrate in the prenylation of a variety of critical intracellular proteins including small GTPases.{24323} This post-translational modification is necessary for correct localization of proteins to intracellular membranes for proper functionality and has become a focus of anticancer drug discovery.{24334,24333}