Synthesis and in vitro evaluations of 6-(hetero)-aryl-imidazo[1,2-b]pyridazine-3-sulfonamide's as an inhibitor of TNF-α production

Tumor necrosis factor-α is an important pro-inflammatory cytokine having a key role in hosts defensive process of immune systems and its over expression led to a diverse range of inflammatory diseases such as Rheumatoid arthritis, Cronh's disease, psoriasis, etc. This paper describes our medicinal chemistry efforts on imidazo[1,2-b]pyridazine scaffold: design, synthesis and biological evaluation. By the introducing sulfonamide functionality at 3 positions and substituting 6 positions with (hetero)-aryl groups', a small library of compounds was prepared. All synthesized compounds were screened for lipopolysaccharide (LPS) mediated TNF-α production inhibitory activity. Biological data revealed that the majority of the compounds of this series showed moderate to potent TNF-α production inhibitory activity. Compound 5u and 5v are the most potent compounds from the series with activity of IC₅₀ = 0.5 µM and 0.3 µM respectively. A short SAR demonstrates that 3-sulfonyl-4-arylpiperidine-4-carbonitrile moiety on imidazo[1,2-b]pyridazine showed better activity compared to the 3-(4-aryllpiperazin-1-yl) sulfonyl) in hPBMC assay. The molecular modeling studies revealed that the potent TNF-α production inhibitory activity 5v due to the extra stability of complex because of an extra pi-pi (π-π) stacking, hydrogen-bonding interactions.

Imidazo [1,2-b]pyridazine; RA (rheumatoid arthritis); Sulfonamide; Tumor necrosis factor-alpha (TNF-α); hPBMC (human peripheral blood mononuclear cells).