What have we learnt from the inhibition of IL-6 in RA and what are the clinical opportunities for patient outcomes?

Rheumatoid arthritis (RA) is an autoimmune disease characterised by persistent inflammation of the synovial joints as well as other tissues and organs. Left untreated, it can lead to joint damage, disability and even increased mortality. The disease is driven by inflammatory cytokines that contribute to the chronic inflammation seen in RA. Interleukin-6 (IL-6) is a key pathological cytokine and a target for treatments aiming to alleviate local and systemic inflammation. Despite advances in understanding RA and the introduction of new treatments, achieving sustained remission remains challenging. This review explores the role of IL-6 in RA pathogenesis, its potential as a treatment target and the significance of personalised medicine in RA management. IL-6 has a dual signalling mechanism, classical and trans-signalling, which influences various intracellular pathways. While several targeted therapies have emerged, no single mechanism-based therapy is universally effective due to the diversity and complexity of the disease. Different approaches to targeting IL-6 have been tested, including biologic blockade of receptors or ligands, and inhibition of IL-6 signalling. IL-6 receptor inhibitors have been validated as RA therapeutics, either alone or in combination with other treatments. Tocilizumab, the first approved IL-6 inhibitor, blocks both soluble and membrane-bound IL-6 receptors, reducing the inflammatory cascade. Clinical trials confirm the efficacy and safety of tocilizumab and its role as a treatment option for patients unresponsive to conventional therapies. The benefits of IL-6 inhibition extend beyond reduced joint inflammation to the amelioration of comorbidities like anaemia, cardiovascular disease, depression and osteoporosis. Tailoring treatment to patients' profiles and comorbidities is essential for optimal outcomes. A 'treat-to-profile' approach, focusing on a holistic view of the patient, could improve personalised medicine strategies. Biosimilars - lower-cost alternatives to biologics - further enhance the accessibility and cost-effectiveness of treatment. IL-6 inhibitors present a valuable treatment option for RA management, particularly for patients with specific comorbidities.