The Therapeutic Role of Interleukin-1 Inhibition in Idiopathic Recurrent Pericarditis: Current Evidence and Future Challenges

IL-1 is a master cytokine of local and systemic inflammation. With the availability of specific IL-1 targeting therapies, a broadening list of diseases has revealed the pathologic role of IL-1-mediated inflammation. Although IL-1, either IL-1α or IL-1β, was administered to patients in order to improve bone marrow function or increase host immune responses to cancer, these patients experienced unacceptable toxicity with fever, anorexia, myalgias, arthralgias, fatigue, gastrointestinal upset and sleep disturbances; frank hypotension occurred. Thus it was not unexpected that specific pharmacological blockade of IL-1 activity in inflammatory diseases would be beneficial. Monotherapy blocking IL-1 activity in a broad spectrum of inflammatory syndromes results in a rapid and sustained reduction in disease severity. In common conditions such as heart failure and gout arthritis, IL-1 blockade can be effective therapy. Three IL-1blockers have been approved: the IL-1 receptor antagonist, anakinra, blocks the IL-1 receptor and therefore reduces the activity of IL-1α and IL-1β. A soluble decoy receptor, rilonacept, and a neutralizing monoclonal anti-interleukin-1β antibody, canakinumab, are also approved. A monoclonal antibody directed against the IL-1 receptor and a neutralizing anti-IL-1α are in clinical trials. By specifically blocking IL-1, we have learned a great deal about the role of this cytokine in inflammation but equally important, reducing IL-1 activity has lifted the burden of disease for many patients.

Interleukin (IL)-1, first described ∼35 years ago as a secreted product of monocytes and neutrophils, refers to IL-1α and IL-1β, two key cytokines in the activation of innate immunity. These cytokines were among the first proteins identified as orchestrators of leukocyte communication, creating the class of secreted products now known as interleukins. The IL-1 family comprises a total of 11 members, including the two activating cytokines IL-1α and IL-1β as well as an inhibitory mediator, the IL-1 receptor antagonist. IL-1 is processed and activated by a caspase-1 dependent mechanism in conjunction with inflammasome assembly, as well as by caspase-1 independent processes that involve neutrophil proteases. Once activated, IL-1α and IL-1β act as potent proinflammatory cytokines at the local level, triggering vasodilatation and attracting monocytes and neutrophils to sites of tissue damage and stress. Importantly, these cytokines are crucial for the induction of matrix enzymes and serve as potent mediators of tissue damage by altering cartilage and bone homeostasis. Systemically, IL-1 cytokines foster the hypothalamic fever response and promote hyperalgesia. Uncontrolled IL-1 activation is a central component of some inflammatory diseases, including rare hereditary syndromes with mutations in inflammasome-associated genes or more frequent diseases such as gout, characterized by neutrophil infiltration and IL-1 activation. Apart from these connections to inflammatory diseases, an important role for IL-1 in inflammatory atherogenesis is also predicted. To date, four potent inhibitors of IL-1 are available for clinical use or in late-stage clinical development, which not only constitute efficacious therapies, but also helped improve our understanding of the role of IL-1 in human disease.