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IntroductionA proportion of patients receiving infliximab have antibodies toward infliximab (ATI), which are associated with increased risk of infusion reaction and reduced response to treatment. We studied the association of infliximab concentration at treatment initiation and development of ATI as well as the association of the presence of ATI and maintenance of infliximab.MethodsAll patients with rheumatoid arthritis (RA) or spondyloarthritis (SpA) receiving infliximab beginning in December 2005 were retrospectively followed until January 2009 or until infliximab discontinuation. Trough serum infliximab and ATI concentrations were measured at each visit. The patients were separated into two groups: ATIpos if ATI were detected at least once during the follow-up period and ATIneg otherwise. Repeated measures analysis of variance was used to study the association of infliximab concentration at treatment initiation and the development of ATI. Maintenance of infliximab in the two groups was studied by using Kaplan-Meier curves.ResultsWe included 108 patients: 17 with RA and 91 with SpA. ATI were detected in 21 patients (19%). The median time to ATI detection after initiation of infliximab was 3.7 months (1.7 to 26.0 months). For both RA and SpA patients, trough infliximab concentration during the initiation period was significantly lower for ATIpos than ATIneg patients. RA patients showed maintenance of infliximab at a median of 19.5 months (5.0 to 31.0 months) and 12.0 months (2.0 to 24.0 months) for ATIneg and ATIpos groups, respectively (P = 0.08). SpA patients showed infliximab maintenance at a median of 16.0 months (3.0 to 34.0 months) and 9.5 months (3.0 to 39.0 months) for ATIneg and ATIpos groups, respectively (P = 0.20). Among SpA patients, those who were being treated concomitantly with methotrexate had a lower risk of developing ATI than patients not taking methotrexate (0 of 14 patients (0%) vs. 25 of 77 patients (32%); P = 0.03).ConclusionsHigh concentrations of infliximab during treatment initiation reduce the development of ATI, and the absence of ATI may be associated with prolonged maintenance of infliximab. Thus, trough serum infliximab concentration should be monitored early in patients with rheumatic diseases.

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NCT00597623.

Objective Rituximab, a monoclonal antibody specifically targeting CD20, induces B cell depletion and is effective in the treatment of rheumatoid arthritis (RA). This study was undertaken to evaluate whether routine monitoring of lymphocyte subpopulations, especially T cells, may be useful in patients receiving rituximab for RA. Methods We examined data on all RA patients receiving rituximab between July 2007 and November 2012 in our center. Peripheral blood CD3+, CD4+, CD8+, CD3−CD56+, and CD19+ lymphocyte counts before and during the first course of rituximab were measured by flow cytometry. The Mann‐Whitney nonparametric test was used to compare lymphocyte subpopulation counts before and during treatment. Results Data on 52 patients were examined. Rituximab induced unexpected and substantial depletion of T cells, mainly CD4+ cells, in most patients. The CD4+ cell count decreased by a mean ± SD of 37 ± 33% as compared to baseline at week 12, reaching <200 cells/μl in 3 patients. Importantly, lack of CD4+ cell depletion was associated with no clinical response. Therefore, the mechanism of action of rituximab may depend at least in part on T cells. Conclusion Rituximab induces substantial T cell depletion, mainly of CD4+ cells, which is associated with the clinical response in RA. Routine monitoring of T cells may be useful in the clinical setting of RA.

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Monoclonal antibodies (mAbs) are increasingly used to treat rheumatoid arthritis (RA). At present, anti-tumor necrosis factor-α drugs (infliximab, adalimumab, certolizumab pegol, and golimumab), rituximab, and tocilizumab are approved for RA treatment. This review focuses on the pharmacokinetics and pharmacodynamics of mAbs approved in RA. Being large proteins, mAbs exhibit complex pharmacokinetic and pharmacodynamic properties. In particular, owing to the interactions of mAbs with their antigenic targets, the pharmacokinetics of mAbs depends on target turnover and exhibits non-specific (linear) and target-mediated (often nonlinear) clearances. Their volume of distribution is low (3-4 L) and their elimination half-life usually ranges from 2 to 3 weeks. The inter-individual pharmacokinetic variability of mAbs is usually large and is partly explained by differences in antigenic burden or by anti-drug antibodies, which accelerate mAb elimination. The inter-individual variability of clinical response is large and influenced by the pharmacokinetics. The analysis of mAbs concentration-effect relationship relies more and more often on pharmacokinetic-pharmacodynamic modeling; these models being suitable for dosing optimization. Even if adverse effects of mAbs used in RA are well known, the relationship between mAb concentration and adverse effects is poorly documented, especially for anti-tumor necrosis factor-α mAbs. Overall, RA patients treated with mAbs should benefit from individualized dosing strategies. Because of the complexity of their pharmacokinetics and mechanisms of action, the current dosing strategy of mAbs is not based on sound knowledge. New studies are needed to assess individual dosing regimen, adjusted notably to disease activity.

Objective. To evaluate the efficacy and tolerability of a single intraarticular (IA) injection of hyaluronic acid (HA) for the treatment of hip osteoarthritis (OA).Methods. A multicenter, randomized, parallelgroup, placebo-controlled trial was conducted over 3 months. Patients (older than 30 years) with symptomatic hip OA (pain score of >40 mm on a visual analog scale [VAS]) and a Kellgren/Lawrence grade of 2 or 3 were randomly assigned to receive 1 fluoroscopically guided IA injection of HA (2.5 ml) or placebo (2.5 ml). Patients were followed up for 3 months. The main outcome measure was pain score on a VAS (100 mm) at month 3 compared with baseline. Secondary outcome measures were the proportion of responders defined by Osteoarthritis Research Society International criteria; Western Ontario and McMaster Universities Osteoarthritis Index subscores for pain, stiffness, and disability; and patient and physician global assessment. Randomization was computer generated. HA and placebo preparations were placed in numbered identical containers, and syringes were covered with masking tape. Physicians assessing outcomes were blinded with regard to group assignment.Results. Eighty-five patients were randomized to the HA group (n ‫؍‬ 42) or placebo group (n ‫؍‬ 43). Baseline characteristics were similar between the 2 groups. At 3 months, the decrease in pain score did not differ between the HA and placebo groups in the intentto-treat analysis (mean ؎ SD decrease 7.8 ؎ 24.9 mm with HA versus 9.1 ؎ 27.4 mm with placebo; P ‫؍‬ 0.98). The responder rates were 33.3% and 32.6% in the HA and placebo groups, respectively (P ‫؍‬ 0.94). Other secondary end points did not differ between the groups, nor did use of rescue medication or frequency of adverse events.Conclusion. Our findings indicate that a single IA injection of HA is no more effective than placebo in treating the symptoms of hip OA.Osteoarthritis (OA) is the most common type of arthritis and the major cause of disability in elderly populations worldwide. Hip OA is the second most frequent form of OA affecting a large joint, and its prevalence ranges from 3% to 11% in populations older than 35 years (1-3).Current therapies for hip OA include a combination of nonpharmacologic and pharmacologic treatments (4-6). Viscosupplementation is an intraarticular (IA) therapeutic modality that is based on the physiologic importance of hyaluronic acid (HA) in synovial ClinicalTrials.gov identifier: NCT00330135.