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ObjectivesMacrophage activation syndrome (MAS) is a severe, life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) and adult onset Still’s disease (AOSD). The objective of this study was to confirm the adequacy of an emapalumab dosing regimen in relation to interferon-γ (IFNγ) activity by assessing efficacy and safety. The efficacy outcome was MAS remission by week 8, based on clinical and laboratory criteria.MethodsWe studied emapalumab, a human anti–IFNγ antibody, administered with background glucocorticoids, in a prospective open-label, single-group trial involving patients who had MAS secondary to sJIA or AOSD and had previously failed high-dose glucocorticoids. The study foresaw 4-week treatment that could be shortened or prolonged based on investigator’s assessment of response. Patients could enter a long-term (12 months) follow-up study.ResultsFourteen patients received emapalumab. All patients completed the trial, entered the long-term follow-up and were alive at the end of the follow-up. The investigated dosing regimen, based on an initial loading dose followed by maintenance doses, was appropriate, as shown by rapid neutralisation of IFNγ activity, demonstrated by prompt decrease in serum C-X-C motif chemokine ligand 9 (CXCL9) levels. By week 8, remission of MAS was achieved in 13 of the 14 patients at a median time of 25 days. Viral infections and positive viral tests were observed during the trial and during the long-term follow-up.ConclusionsNeutralisation of IFNγ with emapalumab was efficacious in inducing remission of MAS secondary to sJIA or AOSD in patients who had failed high-dose glucocorticoids.KEY MESSAGESWhat is already known on this topic?Macrophage activation syndrome (MAS) is a severe and potentially life-threatening complication of systemic juvenile idiopathic arthritis and adult-onset Still’s disease. There are no therapeutic options that have been prospectively investigated in MAS. Data in animal models andex vivodata from humans with MAS led to the hypothesis that interferon-γ (IFNγ) has a pathogenic role in MAS.What does this study add?This open-label multicentre trial using emapalumab, an anti–IFNγ antibody, in patients who have failed to respond to high-dose glucocorticoids, demonstrates that IFNγ has a pathogenic role in MAS and that its neutralisation leads to MAS remission.How might this affect research, clinical practice or policy?The results of this study show that neutralisation of IFNγ with emapalumab is a therapeutic option for patients with severe MAS who have failed standard of care with high-dose glucocorticoids.

Macrophage activation syndrome (MAS) is a subtype of haemophagocytic lymphohistiocytosis (HLH), and a well-described complication of systemic juvenile idiopathic arthritis (SJIA), triggered by disease onset or flare, infection, or some medications. Here, we report a 20-year-old man with previously well-controlled SJIA, who developed first time MAS after acute Epstein-Barr virus (EBV) infection, with MAS recurrence due to a drug reaction, ‘3-week sulfasalazine syndrome’, secondary to prophylactic trimethoprim/sulfamethoxazole. Both episodes of MAS were minimally responsive to pulse corticosteroids. Initial EBV-driven MAS was treated with multiple doses of emapalumab prior to resolution, while MAS secondary to sulfasalazine-induced 3-week syndrome required the initiation of ruxolitinib. This case exhibits two rare but life-threatening causes of MAS/secondary HLH in a single patient and the difficulties in their diagnosis and management.

ObjectiveMacrophage activation syndrome (MAS) is a life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) characterised by a vicious cycle of immune amplification that can culminate in overwhelming inflammation and multiorgan failure. The clinical features of MAS overlap with those of active sJIA, complicating early diagnosis and treatment. We evaluated adenosine deaminase 2 (ADA2), a protein of unknown function released principally by monocytes and macrophages, as a novel biomarker of MAS.MethodsWe established age-based normal ranges of peripheral blood ADA2 activity in 324 healthy children and adults. We compared these ranges with 173 children with inflammatory and immune-mediated diseases, including systemic and non-systemic JIA, Kawasaki disease, paediatric systemic lupus erythematosus and juvenile dermatomyositis.ResultsADA2 elevation beyond the upper limit of normal in children was largely restricted to sJIA with concomitant MAS, a finding confirmed in a validation cohort of sJIA patients with inactive disease, active sJIA without MAS or sJIA with MAS. ADA2 activity strongly correlated with MAS biomarkers including ferritin, interleukin (IL)-18 and the interferon (IFN)-γ-inducible chemokine CXCL9 but displayed minimal association with the inflammatory markers C reactive protein and erythrocyte sedimentation rate. Correspondingly, ADA2 paralleled disease activity based on serial measurements in patients with recurrent MAS episodes. IL-18 and IFN-γ elicited ADA2 production by peripheral blood mononuclear cells, and ADA2 was abundant in MAS haemophagocytes.ConclusionsThese findings collectively identify the utility of plasma ADA2 activity as a biomarker of MAS and lend further support to a pivotal role of macrophage activation in this condition.

Background:The calcium-binding proteins S100A8/A9 (calprotectin) and S100A12 (extracellular newly identified receptor for advanced glycation end-products binding protein [EN-RAGE]) are involved in multiple signalling pathways to mediate inflammation, can be secreted by activated monocytes/macrophages and exhibit cytokine-like extracellular functions. Circulating levels of these proteins have been associated with disease and clinical responses in systemic juvenile idiopathic arthritis (sJIA), including treatment response.1 Studies suggest that serum S100A8/A9 and S100A12, which are released at inflammation sites, are more specific biomarkers of local inflammation (e.g. in the synovium) than systemic biomarkers such as CRP and ESR.2,3Objectives:To investigate if baseline S100A8/A9 and S100A12 predict clinical response to abatacept treatment in polyarticular JIA (pJIA), and to assess whether changes from baseline in S100A8/A9 or S100A12 can be better prognostic markers for response to abatacept treatment than CRP in pJIA.Methods:Data are from a phase III trial of SC abatacept for the treatment of pJIA (NCT01844518).4 This 24-month, single-arm, open-label, international, multicentre, two-part study included male and female patients with pJIA aged 2–17 years. This analysis examined the correlation between biomarkers (S100A8/A9, S100A12 and high-sensitivity CRP [hsCRP]) and disease activity (measured using Juvenile Arthritis Disease Activity Score [JADAS]) at baseline, baseline biomarker values as predictors of future treatment response (ACR and JADAS endpoints), and the correlation between change from baseline in biomarker values and treatment response at Day 113.Results:Of 219 total patients, 158 (72%) had S100A8/A9 values and 155 (71%) had S100A12 values at baseline. Median S100A8/A9 and S100A12 values were 3295 ng/mL (normal range, 716–3004 ng/mL) and 176 ng/mL (normal range, 32–385 ng/mL), respectively. S100A8/A9, S100A12 and hsCRP (median 0.20 mg/dL; normal ≤0.6 mg/dL) had a low-to-moderate but significant association with disease activity at baseline; coefficients for associations between JADAS71-CRP low disease activity (LDA) and the biomarkers S100A8/A9, S100A12 and hsCRP were 0.23 (p=0.0038), 0.16 (p=0.0448) and 0.26 (p=0.0001), respectively. Baseline S100A8/A9 level above the median was associated with lower odds of ACR100 at Day 113 (p=0.0052). Figure 1 shows the associations of baseline biomarker values with Day 113 ACR and JADAS scores in the overall population. Baseline S100A8/A9 or S100A12 did not significantly influence ACR50 or ACR70 responses at Day 113, but high baseline values were associated with reduced odds of ACR90 (p=0.01), ACR100 (p=0.005), ACR-inactive disease (ID) (p=0.0001), and JADAS71-CRP (LDA) (p=0.02). By Day 477, elevated baseline S100A12 was still significantly associated with lower odds of ACR100 overall (0.467; p=0.0248) but baseline S100A8/A9 was not; at Day 645, neither was significantly associated with ACR100 response. At Day 113, changes from baseline in S100A8/A9 and S100A12 were correlated with ACR100 (coefficients of 0.22 [p=0.0082] and 0.26 [p=0.0015], respectively) and with ACR-ID (0.22 [p=0.0067] and 0.26 [p=0.0014], respectively); change in hsCRP was not significantly correlated with disease response.Conclusion:S100A8/A9 and S100A12 may serve as prognostic biomarkers to predict response to abatacept treatment at Day 113. Changes from baseline S100A8/A9 and S100A12 levels were more highly correlated with efficacy outcomes including ACR100 and ACR-ID at Day 113 compared with hsCRP.References:[1]Aljaberi N, et al. Pediatr Rheumatol Online J 2020;18:7.[2]Hammer H, et al. Arthritis Res Ther 2011;13:R178.[3]Nordal HH, et al. BMC Musculoskelet Disord 2014;15:335.[4]Brunner H, et al. Arthritis Rheumatol 2018;70:1144–1154.Acknowledgements:Professional medical writing and editorial assistance was provided by Rob Coover, MPH, at Caudex and was funded by Bristol Myers Squibb.Disclosure of Interests:Nicolino Ruperto Speakers bureau: NR has received honoraria for consultancies or speaker bureaus (< 10.000 USD each) from the following pharmaceutical companies in the past 3 years: Ablynx, Astrazeneca-Medimmune, Bayer, Biogen, Boehringer, Bristol Myers Squibb, Celgene, Eli Lilly, EMD Serono, GlaxoSmithKline, Hoffmann-La Roche, Janssen, Merck, Novartis, Pfizer, R-Pharma, Sinergie, Sobi and UCB, Consultant of: NR has received honoraria for consultancies or speaker bureaus (< 10.000 USD each) from the following pharmaceutical companies in the past 3 years: Ablynx, Astrazeneca-Medimmune, Bayer, Biogen, Boehringer, Bristol Myers Squibb, Celgene, Eli Lilly, EMD Serono, GlaxoSmithKline, Hoffmann-La Roche, Janssen, Merck, Novartis, Pfizer, R-Pharma, Sinergie, Sobi and UCB, Grant/research support from: The IRCCS Istituto Giannina Gaslini (IGG), where NR works as full-time public employee has received contributions (>10.000 USD each) from the following industries in the last 3 years: Bristol Myers Squibb, Eli Lilly, F Hoffmann-La Roche, GlaxoSmithKline, Janssen, Novartis, Pfizer, Sobi. This funding has been reinvested for the research activities of the hospital in a fully independent manner, without any commitment with third parties., Grant Schulert Speakers bureau: Novartis, Consultant of: SOBI, Alyssa Sproles: None declared, Sherry Thornton: None declared, Gabriel Vega Cornejo Speakers bureau: AbbVie, Grant/research support from: Bristol Myers Squibb, Eli Lilly, Janssen, Parexel, Sanofi, Jordi Anton Speakers bureau: AbbVie, Gebro, GlaxoSmithKline, Novartis, Pfizer, Roche, Sobi, Consultant of: AbbVie, Gebro, GlaxoSmithKline, Novartis, Pfizer, Roche, Sobi, Grant/research support from: AbbVie, Amgen, Gebro, GlaxoSmithKline, Lilly, Novartis, Novimmune, Pfizer, Roche, Sanofi, Sobi, Ruben Cuttica Speakers bureau: AbbVie, Bristol Myers Squibb, GlaxoSmithKline, Lilly, Novartis, Pfizer, Roche, UCB, Paid instructor for: AbbVie, Novartis, Pfizer, Roche, Consultant of: AbbVie, Bristol Myers Squibb, GlaxoSmithKline, Lilly, Novartis, Pfizer, Roche, UCB, Michael Henrickson: None declared, Ivan Foeldvari Consultant of: Bristol Myers Squibb, Gilead, Hexal, MEDAC, Novartis, Pfizer, Sanofi, Daniel Kingsbury Consultant of: Pfizer, Margarita Askelson Consultant of: Currently working for Syneos Health providing services to Bristol Myers Squibb, Jinqi Liu Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Sumanta Mukherjee Shareholder of: Bristol Myers Squibb, GlaxoSmithKline, Employee of: Bristol Myers Squibb, GlaxoSmithKline, Robert Wong Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Daniel J Lovell Speakers bureau: Genentech, Wyeth Pharm, Consultant of: Abbott, Amgen, AstraZeneca, Boehringer Ingelheim, Celgene, GlaxoSmithKline, Hoffman-La Roche, Novartis, Pfizer, Regeneron, Takeda, UBC, Wyeth Pharma, Xoma, Alberto Martini Speakers bureau: AbbVie, Novartis, Consultant of: AbbVie, Eli Lilly, EMD Serono, Idorsia, Janssen, Novartis, Pfizer, Alexei Grom Consultant of: AB2Bio, Novartis, Sobi (NovImmune), Grant/research support from: AB2Bio, Novartis, Sobi (NovImmune), Hermine Brunner Speakers bureau: GlaxoSmithKline, Novartis, Pfizer, Roche, Paid instructor for: Novartis, Pfizer (funds go to CCHMC/employer), Consultant of: Boehringer Ingelheim, Bristol Myers Squibb, GlaxoSmithKline, Janssen, Merck, Novartis, Pfizer, Roche, UCB (funds go to CCHMC/employer), Grant/research support from: Bristol Myers Squibb, Pfizer (funds go to CCHMC/employer).

Background CD163 is a hemoglobin scavenger receptor and serves as a marker of activated monocytes and macrophages. It is also expressed on monocytes from children with active systemic juvenile idiopathic arthritis, and highly enriched on hemophagocytic macrophages that characterize the emergence of macrophage activation syndrome. However, the regulation of CD163 expression during monocyte and macrophage polarization is poorly understood. MicroRNA are small non-coding RNA that post-transcriptionally regulate gene expression, often serving as feedback loops to “fine tune” gene expression programs. Objectives Determine microRNA regulation of CD163 at the protein and mRNA levels using novel flow cytometry techniques. Methods Human THP-1 monocytic cells and primary monocytes and monocyte-derived macrophages (MDMs) from healthy donors were polarized with activating conditions including M1 (LPS and IFNg), M2a (IL-4), M2b (LPS and immune complexes) and M2c (TGFb or IL-10). CD163 expression was determined by quantitative RT-PCR or on a single-cell level using RNA flow cytometry. Transcripts were detected using the PrimeFlow kit, with probes specific for CD163 mRNA and other cell surface markers. Cells were also transfected with specific microRNA mimics. Results Significantly increased CD163 mRNA levels were detected only in monocytes and macrophages polarized towards M2c by IL-10 treatment. Similarly, single-cell RNA analysis showed markedly increased CD163 mRNA upon IL-10 treatment, with more modest increases in protein expression. Several candidate microRNA may regulate CD163. As such, our studies indicate that overexpression of miR-125a and miR-181c significantly reduced CD163 mRNA expression in IL-10 polarized macrophages. Notably, both of these microRNAs were significantly increased in monocytes from children with active systemic JIA. In vitro , miR-125a and miR-181c were both elevated in polarizing conditions that restrict CD163 expression. Interestingly, these microRNAs regulated CD163 expression through distinct mechanisms. Computationally, miR-181 is predicted to bind directly to CD163 mRNA. Indeed, using RNA immunoprecipitation (RIP) we found that overexpression of miR-181c significantly increased delivery of CD163 mRNA to the RNA-induced silencing complex. In contrast, CD163 does not have a predicted miR-125a binding site. Using whole transcriptome analysis of macrophages overexpressing miR-125a-5p, significantly reduced levels of mRNA encoding several macrophage receptors, including IL10RA and TGFbR2, was observed. This suggests that miR-125a-5p exerts more global effects to restrict M2c polarization. Conclusions These data show that microRNAs regulate the IL-10-induced expression of CD163 in human macrophages through distinct mechanisms, directly targeting of CD163 mRNA and indirectly inhibiting cytokine receptor expression. These findings illustrate how microRNA “fine-tune” innate immune activation during inflammatory responses, and expand the understanding of the phenotype of activated monocytes and macrophages in systemic JIA. Disclosure of Interest S. Thornton: None declared, T. Do: None declared, R. Tan: None declared, A. Sproles: None declared, M. Bennett: None declared, M. Medvedovic: None declared, M. DeLay: None declared, N. Shen: None declared, A. Grom Grant/research support from: Novartis, Novimmune, Consultant for: Novartis, Novimmune, G. Schulert: None declared

Background Systemic juvenile idiopathic arthritis (SJIA) is an autoinflammatory disease of childhood, characterized by a predominance of mononuclear phagocytic effector cells, compared to the lymphocyte driven pathogenesis seen in other autoimmune JIA subtypes. Monocytes respond to their local cytokine milieu by adopting specific polarization phenotypes with distinct functions. These phenotypes include M1 (classical) activation as well as several forms of alternative activation, including M2b and M2c which have potent immunoregulatory properties. Previous data has shown that monocytes in SJIA patients have a novel phenotype, with features of both classical activation and immunoregulatory phenotypes. Controlling factors of monocyte/macrophage differentiation in SJIA are unknown. MicroRNA serve as transcriptional negative regulators which fine-tune gene expression programs, and have been implicated in the differentiation of monocytes/macrophages. However, miRNA expression in SJIA has not been examined. Methods CD14+ monocytes were isolated from children with active SJIA and clinically inactive disease (CID), and quantified miRNA expression using TaqMan MicroRNA Array (Life technologies). Freshly isolated human monocytes or THP1 macrophage-like cells were polarized in vitro using LPS and interferon-γ (M1), IL-4 (M2a), LPS plus immune complexes (M2b), and IL-10 or TGF-β (M2c). For experiments modulating expression of mir125a-5p, THP1 cells were treated with either mir125a-5p-specific or negative control antagomir (RiboBio) or transfected with miR125a-5p or negative control mimic (Dharmacon) prior to polarization with the indicated conditions. Gene expression was determined using real-time PCR or TaqMan assays. Results We identified mir125a-5p as the most highly upregulated microRNA in monocytes from children with active SJIA compared to those with CID (relative expression 16.8 vs. 3.0, p Conclusions Our data demonstrated increased levels of mir125a-5p in active SJIA and correlation with disease activity. We also showed that mir125a-5p serves as a key regulator of the polarization of immunomodulatory macrophages. Taken together, these data suggest that mir125a-5p could serve as an important diagnostic and therapeutic target in SJIA. Disclosure of Interest G. Schulert: None declared, N. Fall: None declared, N. Shen: None declared, S. Thornton: None declared, A. Grom Grant/research support from: Novartis, NovImmune, Consultant for: Novartis, Roche