The transcription of several cytokines, cell adhesion molecules, and enzymes involved in the inflammatory and destructive mechanisms of rheumatoid arthritis is dependent on nuclear factor κB (NF‐κB). Because IκB kinase (IKK) is critical in transducing the signal‐inducible activation of NF‐κB, we examined whether the highly selective and orally bioavailable IKK inhibitor BMS‐345541 is efficacious against collagen‐induced arthritis (CIA) in mice.

Arthritis in DBA/1LacJ male mice was induced by subcutaneous immunization with bovine type II collagen on day 0 and day 21. BMS‐345541 was administered perorally daily, either prophylactically (before disease onset) or therapeutically (after disease onset). Clinical assessment of the incidence and severity of disease was conducted throughout the study, and histologic evaluation was performed at the time of study termination (day 42).

When administered prophylactically, BMS‐345541 (in a dose range of 10–100 mg/kg) was effective, in a dose‐dependent manner, in reducing the incidence of disease and inhibiting clinical signs of disease. Histologic evaluation of the joints showed that both inflammation and joint destruction were blocked by the IKK inhibitor. Message levels of interleukin‐1β in the joints were also dose‐dependently inhibited in the mice that received BMS‐345541. Dose‐dependent efficacy in terms of both disease severity and histologic end points was observed with the therapeutic dosing regimen of BMS‐345541, with use of the 100‐mg/kg dose resulting in resolution of disease.

IKK plays a key role in CIA in mice, and inhibitors of this enzyme represent a promising target for the development of novel agents to treat rheumatoid arthritis and other inflammatory diseases. BMS‐345541 represents the first example of an inhibitor of IKK that has antiinflammatory activity in vivo.