In vitro activity: SC-514 inhibits the native IKK complex or recombinant human IKK-1/IKK-2 heterodimer and IKK-2 homodimer similarly. SC-514 inhibits transcription of NF-κB-dependent IL-6, IL-8, and COX-2 genes in IL-1β-induced rheumatoid arthritis-derived synovial fibroblasts (RASFs) with IC50s of 20, 20 and 8 μM. 100 μM SC-514 blocks the phosphorylation and degradation of IκBα and also reduces the level of translocation of p65 into the nucleus in IL-1β-treated RASFs SC-514 does not inhibit the phosphorylation and activation of the IKK complex. SC-514 induces a delay but not a complete blockade in IκBα phosphorylation and degradation. SC-514 treatment cells shows a slightly slowed, decreased import of p65 into the nucleus and a faster export of p65 from the nucleus. SC-514 inhibits the phosphorylation of either IκBα or p65 similarly.

Kinase Assay: IKK complexes are immunoprecipitated from IL-1β-treated RASF cell lysates (0.5-2 mg) using a NEMO antibody (3-10 μg) followed by the addition of protein A-agarose beads. Antibody complexes are pelleted by centrifugation and washed 3 times with 1 mL of cold whole-cell lysis buffer followed by 2 washes in kinase buffer (25 mM HEPES, pH 7.6, 2 mM MgCl2, 2 mM MnCl2, 10 mM NaF, 5 mM DTT, and 1 mM phenylmethylsulfonyl fluoride). 100-200 μg of immunoprecipitated IKK is analyzed for kinase activity in a reaction containing 10 μM biotinylated IκBα peptide as substrate and 1 μM [γ-33P]ATP (2500 Ci/mmol). After incubation at room temperature for 30 min, 25 μL of the reaction mixture is withdrawn and added to a SAM 96 biotin capture plate. After successive wash steps the plate was allowed to air-dry, and 25 μL of scintillation fluid is added to each well. Incorporation of [γ-33P]ATP is measured using a Top-Count NXT

Cell Assay: SC-514 inhibits all forms of recombinant human IKK-2 with IC50 values in the 3–12μM range. It also inhibits the native IKK complex. SC-514 specifically binds at the ATP-binding site of IKK-2 and exerts a reversible and competitive inhibition with ATP. However, SC-514 shows non-competitive inhibition with the IκB site. As an inhibitor of IKK-2, SC-514 is found to block the phosphorylation and degradation of IκBα and reduce the translocation level of p65 into the nucleus in IL-1β-treated RASFs. Additionally, SC-514 shows dose-dependent inhibition in the transcription of NF-κB-induced genes, including IL-6, IL-8, and COX-2. Moreover, SC-514 shows efficacious in reduction of LPS-induced TNFα production in the acute model of inflammation. SC-514 is also reported to inhibit the osteoclastogenesis in BMM cells through attenuating RANKL-induced activation of NF-κB.

J Biol Chem. 2003 Aug 29;278(35):32861-71.