OBJECTIVES CLIPPER2 was an 8-year, open-label extension of the phase 3 b, 2-year CLIPPER study on the safety and efficacy of etanercept in patients with juvenile idiopathic arthritis (JIA), categorized as extended oligoarticular arthritis (eoJIA), enthesitis-related arthritis (ERA), or psoriatic arthritis (PsA). METHODS Participants with eoJIA (2-17 years old), ERA, or PsA (each 12-17 years old) who received ≥1 etanercept dose (0.8 mg/kg weekly; maximum 50 mg) in CLIPPER could enter CLIPPER2. Primary end point was occurrence of malignancy. Efficacy assessments included proportions achieving JIA American College of Rheumatology (ACR) 30/50/70/90/100 criteriaand ACR inactive disease criteria, and clinical remission (ACR criteria) or Juvenile Arthritis Disease Activity Score (JADAS) ≤1. RESULTS Overall, 109/127 (86%) CLIPPER participants entered CLIPPER2 (n = 55 eoJIA, n = 31 ERA, n = 23 PsA; 99 [78%] on active treatment); 84 (66%) completed 120 months' follow-up (32 [25%] on active treatment). One malignancy (Hodgkin's disease in 18-year-old patient with eoJIA treated with methotrexate for 8 years) was reported; there were no cases of active tuberculosis or deaths. Numbers and incidence rates [events per 100 patient-years] of TEAEs (excluding infections/ISRs) decreased from 193 [173.81] in Year 1-9 [27.15] in Year 10; TE infections and serious infections also decreased. Over 45% of participants (N = 127) achieved JIA ACR50 responses from Month 2 onwards; 42 (33%) and 17 34 (27%) participants achieved JADAS and ACR clinical remission, respectively. CONCLUSIONS Etanercept treatment up to 10 years was well tolerated, consistent with the known safety profile, with durable response in the participants still on active treatment. The benefit-risk assessment of etanercept in these JIA categories remains favorable. CLINICALTRIALS.GOV IDS CLIPPER (NCT00962741); CLIPPER2 (NCT01421069).

Introduction Although children seem to be less susceptible to COVID-19, some of them develop a rare but serious hyperinflammatory condition called multisystem inflammatory syndrome in children (MIS-C). While several studies describe the clinical conditions of acute MIS-C, the status of convalescent patients in the months after acute MIS-C is still unclear, especially the question of persistence of changes in the specific subpopulations of immune cells in the convalescent phase of the disease. Methods We therefore analyzed peripheral blood of 14 children with MIS-C at the onset of the disease (acute phase) and 2 to 6 months after disease onset (post-acute convalescent phase) for lymphocyte subsets and antigen-presenting cell (APC) phenotype. The results were compared with six healthy age-matched controls. Results All major lymphocyte populations (B cells, CD4 + and CD8+ T cells, and NK cells) were decreased in the acute phase and normalized in the convalescent phase. T cell activation was increased in the acute phase, followed by an increased proportion of γ/δ-double-negative T cells (γ/δ DN Ts) in the convalescent phase. B cell differentiation was impaired in the acute phase with a decreased proportion of CD21 expressing, activated/memory, and class-switched memory B cells, which normalized in the convalescent phase. The proportion of plasmacytoid dendritic cells, conventional type 2 dendritic cells, and classical monocytes were decreased, while the proportion of conventional type 1 dendritic cells was increased in the acute phase. Importantly the population of plasmacytoid dendritic cells remained decreased in the convalescent phase, while other APC populations normalized. Immunometabolic analysis of peripheral blood mononuclear cells (PBMCs) in the convalescent MIS-C showed comparable mitochondrial respiration and glycolysis rates to healthy controls. Conclusions While both immunophenotyping and immunometabolic analyzes showed that immune cells in the convalescent MIS-C phase normalized in many parameters, we found lower percentage of plasmablasts, lower expression of T cell co-receptors (CD3, CD4, and CD8), an increased percentage of γ/δ DN Ts and increased metabolic activity of CD3/CD28-stimulated T cells. Overall, the results suggest that inflammation persists for months after the onset of MIS-C, with significant alterations in some immune system parameters, which may also impair immune defense against viral infections.