Durability and Rapidity of Response to Anakinra in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic and progressive inflammatory disease that ultimately leads to disability and functional decline. Because patients usually develop RA in mid-life, they may experience its consequences for 20-30 years or longer. Proinflammatory cytokines, notably interleukin (IL)-1 and tumour necrosis factor-alpha, are believed to play significant pathophysiological roles. Clinical trials of biologicals that block these cytokines confirm their importance.Anakinra, a recombinant human IL-1 receptor antagonist, improves clinical signs and symptoms, and slows radiographic progression in patients with active RA. In clinical trials, patients receiving anakinra doses >1 mg/kg, whether administered alone or in combination with methotrexate, were two to three times more likely than patients receiving placebo to achieve a sustained ACR20 (American College of Rheumatology criteria) response. Notably, bone erosion slows to a greater extent and shows accelerated benefit when anakinra treatment is continued for periods beyond 24 weeks. Anakinra has a rapid onset of action, with substantial improvements in biochemical indices (C-reactive protein) seen within 1 week and clinical responses (ACR20 or joint counts) seen within 4 weeks of starting treatment. Anakinra is generally well tolerated, with injection site reactions being the most common adverse event. These reactions are generally mild and typically resolve within 2-3 weeks of treatment. The anakinra product labelling does include a warning regarding an increased risk of infections of 2% in anakinra-treated patients versus <1% in patients receiving placebo.