The designed siRNA sequences silenced 70–75% of the lipopolysaccharide-induced IL-1β, IL-6 and IL-18 mRNA expression in macrophages compared with a control siRNA. Each siRNA affected the targeted cytokine specifically, without modifying other proinflammatory cytokine mRNAs. In the collagen-induced arthritis model, weekly injections of siRNA lipoplexes significantly reduced the incidence and severity of arthritis, abrogating joint swelling, and destruction of cartilage and bone, in both preventive and curative settings. The most striking therapeutic effect was observed when combining the three siRNAs targeting IL-1β/IL-6/IL-18 at once. Such tritherapy was associated with downregulation of both inflammatory and autoimmune components of the disease, and overall parameters were improved compared with the TNFα siRNA lipoplex-based treatment. The siRNA formulation was widely distributed, delivering the siRNA to several organs with a strong efficacy in the liver and spleen.