NCT00851565.

Objective. Infliximab, an anti-tumor necrosis factor ␣ (anti-TNF␣) antibody, is effective in the treatment of several immunoinflammatory diseases. However, many patients experience primary or secondary response failure, suggesting that individualization of treatment regimens may be beneficial. This study was undertaken to investigate whether serologic monitoring of infliximab bioavailability and immunogenicity in individual patients would be useful in optimizing treatment regimens to improve efficacy and tolerability.Methods. To avoid the use of solid-phase assays, two radioimmunoassays were developed: one for measurement of levels of anti-infliximab antibody, and a functional one for measurement of TNF␣ binding due to infliximab. Sera from 106 randomly selected rheumatoid arthritis patients were tested within 6 months of therapy initiation, and associations between findings of serum assays and disease activity, infusion reactions, and treatment failure occurring within 18 months were assessed.Results. Trough serum infliximab levels after the first 2 intravenous infusions of infliximab at 3 mg/kg varied considerably between patients (range 0-22 g/ ml). At this stage, only 13% of the patients were antiinfliximab antibody positive. With subsequent infusions, the frequency of antibody positivity rose to 30% and 44% (at 3 months and 6 months, respectively), accompanied by diminished trough levels of infliximab. Indeed, low infliximab levels at 1.5 months predicted antibody development and later treatment failure. There were highly significant correlations between high levels of antibodies and later dose increases, side effects, and cessation of therapy. High baseline disease activity, judged by C-reactive protein level and Disease Activity Score, was associated with low levels of infliximab at the early stage of treatment and later development of antiinfliximab antibodies. Cotreatment with methotrexate resulted in slightly reduced antibody levels after 6 months; other disease-modifying antirheumatic drugs and prednisolone had no effect.Conclusion. Development of anti-infliximab antibodies, heralded by low preinfusion serum infliximab levels, is associated with increased risk of infusion reaction and treatment failure. Early monitoring may help optimize dosing regimens for individual patients, diminish side effects, and prevent prolonged use of inadequate infliximab therapy.

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Activated mononuclear cells appear to be important effector cells in autoimmune beta cell destruction leading to insulin-dependent (type 1) diabetes mellitus. Conditioned medium from activated mononuclear cells (from human blood) is cytotoxic to isolated rat and human islets of Langerhans. This cytotoxic activity was eliminated from crude cytokine preparations by adsorption with immobilized, purified antibody to interleukin-1 (IL-1). The islet-inhibitory activity and the IL-1 activity (determined by its comitogenic effect on thymocytes) were recovered by acid wash. Purified natural IL-1 and recombinant IL-1 derived from the predominant pI 7 form of human IL-1, consistently inhibited the insulin response. The pI 6 and pI 5 forms of natural IL-1 were ineffective. Natural and recombinant IL-1 exhibited similar dose responses in their islet-inhibitory effect and their thymocyte-stimulatory activity. Concentrations of IL-1 that inhibited islet activity were in the picomolar range. Hence, monocyte-derived pI 7 IL-1 may contribute to islet cell damage and therefore to the development of insulin-dependent diabetes mellitus.

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The clinical response to two anti-TNFalpha biological agents closely follows the trough drug levels and the presence of antibodies directed against the drugs. Further studies that focus on the underlying pathways leading to antibody formation are warranted to predict immunogenicity of these expensive biological agents and treatment outcomes.

Cytokines have been proposed as inducers of fl-cell damage in human insulin-dependent diabetes mellitus via the generation of nitric oxide (NO). This concept is mostly based on data obtained in rodent pancreatic islets using heterologous cytokine preparations. The present study examined whether exposure of human pancreatic islets to different cytokines induces NO and impairs fl-cell function. Islets from 30 human pancreata were exposed for 6-144 h to the following human recombinant cytokines, alone or in combination: IFN-y (1,000 U/ml), TNF-a (1,000 U/ml), IL-6 (25 U/ml), and IL-1if (50 U/ml). After 48 h, none of the cytokines alone increased islet nitrite production, but IFN-'y induced a 20% decrease in glucose-induced insulin release. Combinations of cytokines, notably IL-1,8 plus IFN-y plus TNF-a, induced increased expression of inducible NO synthase mRNA after 6 h and resulted in a fivefold increase in medium nitrite accumulation after 48 h. These cytokines did not impair glucose metabolism or insulin release in response to 16.7 mM glucose, but there was an 80% decrease in islet insulin content. An exposure of 144 h to IL-1if plus IFN-'y plus TNF-a increased NO production and decreased both glucose-induced insulin release and insulin content. Inhibitors of NO generation, aminoguanidine or NG-nitro-L-arginine, blocked this cytokine-induced NO generation, but did not prevent the suppressive effect of IL-1,8 plus IFN-'y plus TNF-a on insulin release and content. In conclusion, isolated human islets are more resistant to the suppressive effects of cytokines and NO than isolated rodent islets. Moreover, the present study suggests that NO is not the major mediator of cytokine effects on human islets. (J. Clin. Invest. 1994. 93:1968-1974

The aim of this study was to characterize the dynamics and functional relevance of interleukin-1 beta (IL-1 beta)-induced nitric oxide production in isolated pancreatic islets. Thus, islets were isolated from adult rats, precultured for 3-5 days in medium RPMI-1640 plus 10% fetal calf serum, and then exposed to IL-1 beta for different time periods, after which islet nitrite production and aconitase activity were determined. IL-1 beta (5 ng/ml) did not increase islet nitrite production during the first hour of incubation. Moreover, the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (Meth-arg; 5 mM) failed to prevent the initial (90 min) IL-1 beta-induced increase in islet insulin release. After 4, 7, and 24 h, however, nitrite production was increased by 50%, 93%, and 139%, respectively. Islet aconitase activity and glucose oxidation rates were decreased by 70% after incubation for 24 h with IL-1 beta. Both Meth-arg and N alpha-p-tosyl-L-lysine chloromethyl ketone (0.1 mM), a protease inhibitor, could completely counteract the IL-1 beta-induced increases in nitrite production and inhibition of aconitase activity and glucose oxidation rates. In a separate series of experiments, islets were incubated for 60 min with or without IL-1 beta and the RNA synthesis inhibitor actinomycin-D (5 micrograms/ml) and subsequently incubated for another 9 h without any additions. The presence of actinomycin-D during the 1-h IL-1 beta incubation period prevented the IL-1 beta-induced rise in nitrite production and the IL-1 beta-induced inhibition of aconitase activity and insulin release. It is concluded that IL-1 beta-induced nitric oxide production is a late event which requires gene transcription and does not mediate the initial stimulatory effects of IL-1 beta on beta-cell function. However, the gradually augmented rate of nitric oxide production may inhibit the enzyme aconitase, leading to a suppressed mitochondrial activity and a defective insulin release in response to nutrient secretagogues.