Nuclear factor (NF)-kappaB is a transcription factor that induces the immunoglobulin kappa chain, cytokines such as interleukin (IL)-1, IL-2, IL-6, IL-8, tumor necrosis factor (TNF)-alpha and interferon gamma, and cell adhesion proteins. It also induces anti-apoptotic proteins, and inhibits TNF-alpha and anticancer drug-induced apoptosis. Therefore, NF-kappaB function inhibitors may be useful as anti-inflammatory and anticancer agents. Microbial products such as panepoxydone, cycloepoxydon and gliotoxin are known to inhibit activation of NF-kappaB. We have designed and synthesized new NF-kappaB inhibitors from the structure of an antibiotic, epoxyquinomicin C. The designed compound, DHM2EQ, inhibited TNF-alpha-induced activation of NF-kappaB and showed a therapeutic effect in mouse rheumatoid arthritis model.