Are pyridazines privileged structures?

One can estimate that about 50% of all the drug molecules used in medicine contain a phenyl ring which can be substituted or not. The bioisosteric replacement of these phenyl rings by the corresponding pyridazine rings opens an access to several thousands of diaza analogues presenting more interaction possibilities, lower Log P values and improved crystalline salts. The use of pyridazine scaffolds in place of phenyl scaffolds entails additional interaction possibilities. Another interest of pyridazines is their capacity to act as original functional surrogates. Thus, aminopyridazines can be used as carboxamide, as well as amine surrogates. Finally, the many examples of pyridazines used either as a structural element or as a main scaffold, justify largely their status as privileged structures.