Pyridazine is a heterocyclic aromatic compound that consists of a six-membered ring with the formula C4H4N2. As a phenyl bioisostere, pyridazine's two nitrogen atoms are capable of forming hydrogen bonds with target proteins. Pyridazine has also been frequently used as an isostere of pyridine, pyrimidine, and pyrazine in drug discovery. Pyridazine derivatives have been identified as potential anticancer agents with high selectivity and low toxicity.