Ureido-pyridazinone derivatives : insights into the structural and conformational properties for STAT3 inhibition

Three new ureido-pyridazinone derivatives, which are structurally related to the known STAT3 inhibitor AVS-0288, were designed by taking into account the structure–activity relationships determined for several ureido-oxadiazole derivatives previously studied by our group. Their synthesis was first attempted through suitable 5-aminopyridazinone intermediates (6a and 6b), which molecular structures were confirmed by means of X-ray diffraction data on 6a. Amine functionalization was unsuccessful, therefore, an alternative method was devised. Dual-luciferase and AlphaScreen-based assays were used to test their activity. The obtained data were rationalized on the basis of a modeling study, which focused our attention on the geometrical preferences of the ureido moiety. Computational results seem to indicate that both the 1,2,5-oxadiazole ring and the extended ZZ arrangement are essential and probably act in a synergistic way to confer significant activity against STAT3.