Type I interferon signature and cycling lymphocytes in macrophage activation syndrome

JAK inhibitors in refractory juvenile rheumatic diseases: Efficacy, tolerance and type-I interferon profiling, a single center retrospective study

OBJECTIVES

- Janus Kinase inhibitors (JAKi) are a new class of drugs available for pediatric rheumatic diseases. This study aimed to describe the safety and effectiveness of JAKi in these diseases, with a focus on longitudinal interferon-stimulated genes (ISG) assessment.

METHODS

- We present a single-center retrospective study of children with refractory pediatric rheumatic diseases including connective tissue diseases, monogenic type I interferonopathies or juvenile idiopathic arthritis, receiving JAKi. According to physicians' assessment, treatment effectiveness was classified at 12 months as a complete response in the total absence of disease activity, partial response in case of significant (>50%) but incomplete improvement or no response in the case of non-response or improvement of less than 50% of the clinical and biological parameters. ISG were monitored longitudinally using Nanostring technology.

RESULTS

- 22 children were retrospectively included in this study, treated either by baricitinib or ruxolitinib. Complete response was achieved at 12 months in 9/22 (41%) patients. 6/22 (27%) patients were non-responders and treatment had been discontinued in five of them. Within the interferon (IFN)-related diseases group, ISG-score was significantly reduced 12 months after JAKi onset (p = 0.0068). At 12 months, daily glucocorticoid doses had been reduced with a median dose of 0.16 mg/kg/day (IQR 0.11; 0.33) (p = 0.0425). 7/22 (32%) patients had experienced side effects, infections being the most common. Increase of the body mass index was also recorded in children in the first 6 months of treatment.

CONCLUSION

- JAKi represent a promising treatment of immune-mediated pediatric diseases, enabling to decrease type-I IFN transcriptomic signature in responding patients, especially in the context of juvenile dermatomyositis. JAKi represent steroid-sparing drugs but they induce metabolic changes linked to weight gain, posing a concern in the treatment of young patients and teenagers. More data are required to define the efficacy and safety of JAKi in the management of refractory pediatric rheumatic diseases.

Recent advances and evolving concepts in Still's disease

Still's disease is a rare inflammatory syndrome that encompasses systemic juvenile idiopathic arthritis and adult-onset Still's disease, both of which can exhibit life-threatening complications, including macrophage activation syndrome (MAS), a secondary form of haemophagocytic lymphohistiocytosis. Genetic insights into Still's disease involve both HLA and non-HLA susceptibility genes, suggesting the involvement of adaptive immune cell-mediated immunity. At the same time, phenotypic evidence indicates the involvement of autoinflammatory processes. Evidence also implicates the type I interferon signature, mechanistic target of rapamycin complex 1 signalling and ferritin in the pathogenesis of Still's disease and MAS. Pathological entities associated with Still's disease include lung disease that could be associated with biologic DMARDs and with the occurrence of MAS. Historically, monophasic, recurrent and persistent Still's disease courses were recognized. Newer proposals of alternative Still's disease clusters could enable better dissection of clinical heterogeneity on the basis of immune cell profiles that could represent diverse endotypes or phases of disease activity. Therapeutically, data on IL-1 and IL-6 antagonism and Janus kinase inhibition suggest the importance of early administration in Still's disease. Furthermore, there is evidence that patients who develop MAS can be treated with IFNγ antagonism. Despite these developments, unmet needs remain that can form the basis for the design of future studies leading to improvement of disease management.

Treatment of systemic juvenile idiopathic arthritis

Systemic juvenile idiopathic arthritis (sJIA) is an inflammatory disease with hallmarks of severe systemic inflammation, which can be accompanied by arthritis. Contemporary scientific insights set this paediatric disorder on a continuum with its counterpart, adult-onset Still disease (AOSD). Patients with sJIA are prone to complications, including life-threatening hyperinflammation (macrophage activation syndrome (sJIA-MAS)) and sJIA-associated lung disease (sJIA-LD). Meanwhile, the treatment arsenal in sJIA has expanded markedly. State-of-the-art therapeutic approaches include biologic agents that target the IL-1 and IL-6 pathways. Beyond these, a range of novel agents are on the horizon, some of them already being used on a compassionate use basis, including JAK inhibitors and biologic agents that target IL-18, IFNγ, or IL-1β and IL-18 simultaneously. However, sJIA, sJIA-MAS and sJIA-LD still pose challenging conundrums to rheumatologists treating paediatric and adult patients worldwide. Although national and international consensus treatment plans exist for the treatment of 'classic' sJIA, the treatment approaches for early sJIA without arthritis, and for refractory or complicated sJIA, are not well defined. Therefore, in this Review we outline current approaches for the treatment of sJIA and provide an outlook on knowledge gaps.