Synthesis and evaluation of novel dimethylpyridazine derivatives as hedgehog signaling pathway inhibitors.

We report herein the design and synthesis of a series of structural modified dimethylpyridazine compounds as novel hedgehog signaling pathway inhibitors. The bicyclic phthalazine core and 4-methylamino-piperidine moiety of Taladegib were replaced with dimethylpyridazine and different azacycle building blocks, respectively. The in vitro Gli-luciferase assay results demonstrate that the new scaffold still retained potent inhibitory potency. Piperidin-4-amine moiety was found to be the best linker between pharmacophores dimethylpyridazine and fluorine substituted benzoyl group. Furthermore, the optimization of 1-methyl-1H-pyrazol and 4-fluoro-2-(trifluoromethyl)benzamide by different aliphatic or aromatic rings were also investigated and the SAR were described. Several new derivatives were found to show potent Hh signaling inhibitory activity with nanomolar IC50 values. Among these compounds, compound 11c showed the highest inhibitory potency with an IC50 value of 2.33 nM, which was comparable to the lead compound Taladegib. In vivo efficacy of 11c in a ptch+/- p53-/- mouse medulloblastoma allograft model also indicated encouraging results.