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ObjectiveTo investigate the pharmacokinetics, effectiveness, and safety of subcutaneous (SC) abatacept treatment over 24 months in patients with polyarticular‐course juvenile idiopathic arthritis (JIA).MethodsIn this phase III, open‐label, international, multicenter, single‐arm study, patients with polyarticular JIA (cohort 1, ages 6–17 years and cohort 2, ages 2–5 years) in whom treatment with ≥1 disease‐modifying antirheumatic drug was unsuccessful received weight‐tiered SC abatacept weekly: 10 to <25 kg (50 mg), 25 to <50 kg (87.5 mg), ≥50 kg (125 mg). Patients who had met the JIA–American College of Rheumatology 30% improvement criteria (achieved a JIA‐ACR 30 response) at month 4 were given the option to continue SC abatacept to month 24. The primary end point was the abatacept steady‐state serum trough concentration (Cminss) in cohort 1 at month 4. Other outcome measures included JIA‐ACR 30, 50, 70, 90, 100, and inactive disease status, the median Juvenile Arthritis Disease Activity Score in 71 joints using the C‐reactive protein level (JADAS‐71–CRP) over time, safety, and immunogenicity.ResultsThe median abatacept Cminss at month 4 (primary end point) and at month 24 was above the target therapeutic exposure (10 μg/ml) in both cohorts. The percentage of patients who had achieved JIA‐ACR 30, 50, 70, 90, or 100 responses or had inactive disease responses at month 4 (intent‐to‐treat population) was 83.2%, 72.8%, 52.6%, 28.3%, 14.5%, and 30.1%, respectively, in cohort 1 (n = 173) and 89.1%, 84.8%, 73.9%, 58.7%, 41.3%, and 50.0%, respectively, in cohort 2 (n = 46); the responses were maintained to month 24. The median (interquartile range) JADAS‐71–CRP improved from baseline to month 4: cohort 1, from 21.0 (13.5, 30.3) to 4.6 (2.1, 9.4); cohort 2, from 18.1 (14.0, 23.1) to 2.1 (0.3, 4.4). Improvements were sustained to month 24, at which time 27 of 173 patients (cohort 1) and 11 of 22 patients (cohort 2) had achieved JADAS‐71–CRP remission. No unexpected adverse events were reported; 4 of 172 patients (2.3%) in cohort 1 and 4 of 46 (8.7%) in cohort 2 developed anti‐abatacept antibodies, with no clinical effects.ConclusionWeight‐stratified SC abatacept yielded target therapeutic exposures across age and weight groups, was well tolerated, and improved polyarticular JIA symptoms over 24 months.

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Matrix metalloproteinase-3 (MMP-3) is involved in the immunopathogenesis of rheumatoid arthritis (RA), but little is known about its relationship to genetic susceptibility and biomarkers of disease activity, especially acute phase reactants in early RA. MMP-3 was measured by ELISA in serum samples of 128 disease-modifying, drug-naïve patients and analysed in relation to shared epitope genotype, a range of circulating chemokines/cytokines, acute phase reactants, autoantibodies, cartilage oligomeric protein (COMP), and the simplified disease activity index (SDAI). MMP-3 was elevated >1.86 ng/ml in 56.25% of patients (P < 0.0001), correlated with several biomarkers, notably IL-8, IL-6, IFN γ, VEGF and COMP (r values = 0.22–0.33, P < 0.014–0.0001) and with CRP and SAA levels (r = 0.40 and 0.41, resp., P < 0.0000) and SDAI (r = 0.29, P < 0.0001), but not with erosions or nodulosis. However, the correlations of CRP and SAA with SDAI were stronger (respective values of 0.63 and 0.54, P < 0.001 for both). COMP correlated with smoking, RF, and MMP-3. MMP-3 is significantly associated with disease activity, inflammatory mediators and cartilage breakdown, making it a potential biomarker of disease severity, but seemingly less useful than CRP and SAA as a biomarker of disease activity in early RA.

Smoking is now well recognised not only as a risk factor for rheumatoid arthritis (RA), but also as a determinant of disease activity, severity, response to therapy, and possibly mortality. Recent studies have provided significant insights into the molecular and cellular mechanisms which underpin the pathogenesis of smokingrelated RA. These involve release of the enzymes, peptidylarginine deiminases (PADs) 2 and 4 from smoke-activated, resident and infiltrating pulmonary phagocytes. PADs, in turn, mediate the conversion of various endogenous proteins to putative citrullinated autoantigens. In genetically susceptible individuals, these autoantigens trigger the production of anti-citrullinated peptide/protein pathogenic autoantibodies (ACPA), an event which precedes the development of RA. This review is focused primarily on smoking-mediated harmful chronic inflammatory responses, both local and systemic, which promote the formation of ACPA, as well as the possible involvement of other types of outdoor and indoor pollution in the pathogenesis of RA. This is preceded by a brief overview of the evidence implicating smoking as a risk factor for development of ACPA-positive RA.Keywords: Anti-citrullinated peptide/protein antibodies; airway microbiota; atmospheric pollution; heavy metals; peptidylarginine deiminases; smoking cessation strategies. ImplicationsChronic inflammatory mechanisms operative in the lungs of smokers lead to the production of anti-citrullinated protein antibodies which, in turn, drive the development of rheumatoid arthritis. These mechanistic insights not only reinforce the association between smoking and risk for rheumatoid arthritis, but also the necessity to increase the level of awareness in those at highest risk.