Interleukin-1 antagonists in the treatment of autoinflammatory syndromes, including cryopyrin-associated periodic syndrome

Cryopyrin-associated periodic syndrome (CAPS) include a group of rare autoinflammatory disorders, the spectrum of which ranges from the mildest form, ie, familial cold autoinflammatory syndrome to more severe phenotypes, ie, Muckle-Wells syndrome, and chronic infantile neurological cutaneous and articular syndrome, also known as neonatal-onset multisystem inflammatory disease. Three interleukin (IL)-1 antagonists have been tested in adults and children with CAPS, ie, anakinra, a recombinant homolog of the human IL-1 receptor antagonist; rilonacept, a fusion protein comprising the extracellular domains of IL-1 receptor I and the IL-1 adaptor protein, IL-1RAcP, attached to a human immunoglobulin G molecule; and canakinumab, the anti-IL-1β monoclonal antibody. Following rapid clinical development, rilonacept and canakinumab were approved by both the US Food and Drug Administration and the European Medicines Agency for use in adults and children. This review describes how the study of CAPS has helped us to understand better the way the innate immune system works, the pathogenesis of autoinflammatory syndromes, and the key role of IL-1. It also reviews the effects of IL-1 blockade in CAPS and other disorders, in particular systemic juvenile idiopathic arthritis, adult-onset Still's disease, and gout. Finally, this review covers some issues addressed by very recent and ongoing work regarding treatment indications, from orphan diseases to common disorders, continuous versus intermittent treatment, the pharmacokinetics, pharmacodynamics, and optimal dosages of the different drugs, as well as the need for Phase IV trials, exhaustive registries, and long-term follow-up of several patient cohorts.