KRAS and cancer: These inhibitors failed in the clinic, due to alternative prenylation of K‐Ras and N‐Ras by geranylgeranyl transferase I, the two Ras isoforms most frequently mutated in cancer.[10,11] Given that PDE6D facilitates plasma membrane localization of K‐Ras,[12,13] a number of small molecule inhibitors were developed against PDE6D,[10] including our own Deltaflexin1, ‐2, and ‐3.[14,15] Deltaflexin3 is a highly water‐soluble, low nanomolar inhibitor of the prenyl‐binding pocket of PDE6D.