4-Substituted-5-acetyl-2-methyl-6-phenyl-3(2H)pyridazinones as PGE2 and IL-1 release inhibitors from mouse adherent macrophages

A series of 4,5-functionalized 3(2H)-pyridazinones were evaluated as prostaglandin E2 (PGE2) and interleukin-1 (IL-1) release inhibitors from mouse adherent macrophages. Among the tested compounds only 2b was found to be devoid of activity in both the PGE2 and IL-1 tests, whereas the other compounds, showed a significant dose-dependent activity. Compounds 2a, 3 and 4 were able to inhibit PGE2 better than IL-1 release from stimulated macrophages. Compound 4, which showed an IC50 = 5.5 microM in the IL-1 test, appears to be a promising agent in this cell inflammation model. Structure-activity relationship (SAR) studies demonstrated the importance of the presence of a substituent characterized by a positive sigma constant at position 4 of the pyridazine system.