C25-140 is a small-molecule inhibitor of TRAF6-Ubc13 interaction. C25-140 directly binds to TRAF6, thereby blocking the interaction of TRAF6 with Ubc13, and as a consequence lowers TRAF6 activity. C25-140 impedes NF-κB activation in various immune and inflammatory signaling pathways also in primary human and murine cells.