Difficult-to-Treat Gouty Arthritis

Abstract

Gouty arthritis is the most common inflammatory arthritis in adults and is characterized by very painful flares. Gouty arthritis results from an elevated body uric acid pool, which leads to deposition of monosodium urate crystals, mainly in the joints. These crystals trigger the release of proinflammatory cytokines, in particular interleukin (IL)-1β, which stimulates inflammation. Gouty arthritis can progress to a chronic, deforming and physically disabling disease through the development of disfiguring tophi, joint destruction and persistent pain. Standard treatments are effective in most patients. Acutely, anti-inflammatory therapies provide rapid pain relief and resolution of flares. Chronically, urate-lowering therapies reduce serum urate levels and, in combination with anti-inflammatory prophylaxis, reduce the risk of flares. However, for a growing number of patients, current standard treatments are ineffective or are contraindicated, largely due to the presence of co-morbidities. Indeed, metabolic syndrome, hypertension, dyslipidaemia, cardiovascular disease, diabetes mellitus and renal impairment are all highly prevalent in individuals with gouty arthritis, and may lead to standard treatments being ineffective or inappropriate. Such patients with difficult-to-treat disease require alternative therapies. Gouty arthritis can have a major impact on health-related quality of life (HR-QOL), especially in patients with difficult-to-treat disease, as revealed by recent studies comparing HR-QOL for patients with gouty arthritis with that of the general population. All studies revealed clinically significant reductions in physical functioning for individuals with gouty arthritis compared with the general population. The difference was particularly marked for patients with difficult-to-treat disease. Gouty arthritis also constitutes an important economic burden through absence from work and medical costs. Again, the burden is greater in patients with difficult-to-treat disease. The development of difficult-to-treat disease reflects the short-comings of current standard treatments in a growing number of gouty arthritis patients. This has been recognized by the pharmaceutical industry and has promoted the development of innovative therapies. An appreciation of the key role of IL-1β in inflammation in gouty arthritis has led to the development of a new class of anti-inflammatory agents that block IL-1β signal transduction. The current IL-1β blockers in trials are rilonacept and canakinumab. Canakinumab, a fully human anti-IL-1β monoclonal antibody, has been shown to produce rapid and sustained pain relief from acute flares in patients with difficult-to-treat disease, and both rilonacept and canakinumab have been shown to reduce the risk of recurrent flares. Promising new therapies for reducing serum urate levels are also being developed. These include the recently approved therapies pegloticase (a pegylated form of the enzyme uricase that converts urate to allantoin), inhibitors of renal urate transporter proteins, and inhibitors of purine nucleotide phosphorylase, an enzyme involved in purine metabolism. Further studies are warranted to establish the value and role of these new therapies in the management of gouty arthritis. These new options should help reduce the growing human burden associated with gouty arthritis, lowering the tophaceous burden, minimizing the risk of flares, and enabling patients to achieve rapid and effective pain relief when flares do occur.