However, genes such as avirulence genes are not essential for the organism and many potential targets lack known inhibitors. Examples of this procedure include the search for new herbicidal compounds of the nonmevalonate, such as the discovery of new inhibitors of 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (IspD, Enzyme Commission (EC) number 2.7.7.60) with the best expressing a half-maximal inhibitory concentration (IC50) of 140 nM in the greenhouse at 3 kg/ha (2.7 lb/acre). Thanks to an x-ray crystal structure of Arabidopsis thaliana, IspD enzyme cocrystallized with the inhibitor, a more potent inhibitor with an IC50 of 35 nM was designed.