4-Hydroxy- N-[3,5-bis(trifluoromethyl)phenyl]-1,2,5-thiadiazole-3-carboxamide: a novel inhibitor of the canonical NF-κB cascade

Abstract

The NF-κB signaling pathway is a validated oncological target. Here, we applied scaffold hopping to IMD-0354, a presumed IKKβ inhibitor, and identified 4-hydroxy-N-[3,5-bis(trifluoromethyl)phenyl]-1,2,5-thiadiazole-3-carboxamide (4) as a nM-inhibitor of the NF-κB pathway. However, both 4 and IMD-0354, being potent inhibitors of the canonical NF-κB pathway, were found to be inactive in human IKKβ enzyme assays.

Fig. 1. PS-1145, BMS-345541 and IMD-0354 as examples of IKKβ inhibitors.

Fig. 2. The bioisosteric scaffold hopping strategy applied to IMD-0354 using hydroxyoxadiazole, hydroxythiadiazole, hydroxytriazole and hydroxypyrazole scaffolds.

Scheme 1. Synthesis of 1,2,5-oxadiazole and thiadiazole analogues 1–6: i) a) oxalyl chloride, DMF, dry THF, b) substituted aniline, dry pyridine, dry THF; ii) H₂, Pd/C, dry THF; iii) CH₃I, Cs₂CO₃, dry THF; iv) HBTU, DMAP, 3,5-bis(trifluoromethyl)aniline, dry DMF.

Scheme 2. Synthesis of triazole and pyrazole analogues (7–11). i) a) Oxalyl chloride, DMF, dry THF; b) 3,5-bis(trifluoromethyl)aniline, dry pyridine, dry THF; ii) H₂, Pd/C, dry THF; iii) TFA, 45 °C.

Fig. 3. Effects of compound 4 on IκBα degradation in Jurkat cells stimulated by TNF-α. IκBα protein expression was evaluated by immunoblotting. One representative immunoblot of three independent experiments is shown. Graphs represent IκBα relative band intensity quantified by densitometric analysis after normalization using β-actin as reference. Values are means ± SD of three independent experiments.

Fig. 4. Effects of PS-1145, IMD-0354 and compound 4 on NF-κB gene reporter assay in Jurkat and MDA-MB-231 cells.

Fig. 5. Effects of compound 4, IMD-0354, PS-1145, aspirin (ASA) and indomethacin (Indo) on IκBα degradation in THP-1 cells stimulated by LPS. IκBα protein expression was evaluated by immunoblotting. One representative immunoblot of three independent experiments is shown.