Dynamics of circulating TNF during adalimumab treatment using a drug-tolerant TNF assay

Patients with rheumatoid arthritis (RA) can be successfully treated with tumor necrosis factor (TNF) inhibitors, including the monoclonal antibody adalimumab. Once in remission, a proportion of patients can successfully discontinue treatment, indicating that blocking TNF is no longer required for disease control. To explore the dynamics of circulating TNF during adalimumab treatment, we developed a competition enzyme-linked immunosorbent assay that can quantify TNF in the presence of large amounts of TNF inhibitor, i.e., a “drug-tolerant” assay. In 193 consecutive adalimumab-treated patients with RA, we demonstrated that circulating TNF increased in average of &gt;50-fold upon treatment and reached a stable concentration in time for most patients. A similar increase in TNF was found in 30 healthy volunteers after one dose of adalimumab. This implies that TNF in circulation during anti-TNF treatment is not primarily associated with disease activity. During treatment, TNF was in complex with adalimumab and could be recovered as inactive 3:1 adalimumab-TNF complexes. No quantitative association was found between TNF and adalimumab concentrations. Low TNF concentrations at week 4 were associated with a higher frequency of antidrug antibodies (ADAs) at subsequent time points, less frequent methotrexate use at baseline, and less frequent remission after 52 weeks. Also in healthy volunteers, early low TNF concentrations are associated with ADAs. In conclusion, longitudinal TNF concentrations are mostly stable during adalimumab treatment and may therefore not predict successful treatment discontinuation. However, early low TNF is strongly associated with ADA formation and may be used as timely predictor of nonresponse toward adalimumab treatment.</p

Immunogenicity of TNF-Inhibitors

Tumor necrosis factor inhibitors (TNFi) have significantly improved treatment outcome of rheumatic diseases since their incorporation into treatment protocols two decades ago. Nevertheless, a substantial fraction of patients experiences either primary or secondary failure to TNFi due to ineffectiveness of the drug or adverse reactions. Secondary failure and adverse events can be related to the development of anti-drug antibodies (ADA). The earliest studies that reported ADA toward TNFi mainly used drug-sensitive assays. Retrospectively, we recognize this has led to an underestimation of the amount of ADA produced due to drug interference. Drug-tolerant ADA assays also detect ADA in the presence of drug, which has contributed to the currently reported higher incidence of ADA development. Comprehension and awareness of the assay format used for ADA detection is thus essential to interpret ADA measurements correctly. In addition, a concurrent drug level measurement is informative as it may provide insight in the extent of underestimation of ADA levels and improves understanding the clinical consequences of ADA formation. The clinical effects are dependent on the ratio between the amount of drug that is neutralized by ADA and the amount of unbound drug. Pharmacokinetic modeling might be useful in this context. The ADA response generally gives rise to high affinity IgG antibodies, but this response will differ between patients. Some patients will not reach the phase of affinity maturation while others generate an enduring high titer high affinity IgG response. This response can be transient in some patients, indicating a mechanism of tolerance induction or B-cell anergy. In this review several different aspects of the ADA response toward TNFi will be discussed. It will highlight the ADA assays, characteristics and regulation of the ADA response, impact of immunogenicity on the pharmacokinetics of TNFi, clinical implications of ADA formation, and possible mitigation strategies

Capillary blood microsampling to determine serum biopharmaceutical concentration: Mitra® microsampler vs dried blood spot

Aim: For assessment of concentrations of biopharmaceuticals, for example, therapeutic drug monitoring, dried blood sampling of capillary blood is a convenient alternative to traditional venepuncture sampling. We investigated an alternative to dried blood spot collection on filter paper: sampling capillary blood using the Mitra® microsampler. Materials and Methods: Therapeutic monoclonal antibodies were spiked in whole blood, sampled using filter paper and Mitra microsampler and concentrations measured using specific ELISAs. Results: Good recoveries of adalimumab, infliximab, ustekinumab, vedolizumab, tocilizumab, natalizumab and rituximab were found up to 1 month of storage at room temperature, averaging 95.2% for the Mitra microsampler and 92.9% for Whatman® paper. Both hemoglobin and potassium yield satisfactory estimates for the volume of the cellular fraction of blood samples in combination with the Mitra microsampler. Conclusion: We established practical protocols for the estimation of serum/plasma concentrations of therapeutic antibodies via capillary blood microsampling

Antibodies to constant domains of therapeutic monoclonal antibodies: Anti-hinge antibodies in immunogenicity testing

Rheumatoid factors are antibodies directed against IgG that may confound immunogenicity testing for therapeutic monoclonal antibodies. We developed antigen-binding assays to monitor anti-drug-antibody (ADA) responses against infliximab and adalimumab using F(ab')2 fragments of the drug. This avoids possible detection of rheumatoid factor activity. During development of these assays, a number of sera from patients before treatment as well as several healthy control sera were tested positive. None of these sera contained antibodies specific for the therapeutic mAb. Instead, they were found to contain anti-hinge antibodies. We demonstrate that this aspecific antibody binding can be inhibited by adding F(ab')2 of intravenous immunoglobulin (IVIG), which consists of pooled polyclonal IgG derived from plasma. Using this protocol, anti-infliximab antibodies can be measured specifically without interference by anti-hinge antibodies. (C) 2011 Elsevier B.V. All rights reserve

Evaluation of dose-tapering strategies for intravenous tocilizumab in rheumatoid arthritis patients using model-based pharmacokinetic/pharmacodynamic simulations

Purpose: Tocilizumab is a humanized monoclonal antibody approved for rheumatoid arthritis treatment. In clinical practice, empirical dose-tapering strategies are implemented in patients showing sustained remission or low disease activity (LDA) to avoid overtreatment and reduce costs. Since rational adaptive-dosing algorithms taking the full pharmacokinetic (PK)/pharmacodynamic (PD) characteristics into account are currently lacking, we aimed to develop novel tapering strategies and compare them with currently used empirical ones. Methods: Four strategies were simulated on a virtual population. In all of them, the same initial dose was administered every 28 days for six consecutive months. Then, different strategies were considered: (1) label-dosing; (2) mild empirical dose-tapering; (3) intense empirical dose-tapering; (4) therapeutic drug monitoring (TDM)-guided dose-tapering. The different strategies were evaluated on the proportion of patients who maintain remission/LDA 1 year after the intervention. Cost-savings of direct drug costs were also estimated as relative dose intensity. Results: The overall proportion of simulated patients in remission/LDA after 1 year of the intervention was comparable between the mild empirical and the TDM-guided dose-tapering strategies, and much lower for the intense empirical dose-tapering strategy (80.3%, 78.2%, and 69.0%, respectively). Likewise, 1-year flare rates were lower for the mild empirical and TDM-guided tapering strategies. The relative dose intensity was lowest for the intense empirical dose-tapering, followed by the TDM-guided and the mild empirical dose-tapering approaches (61.2%, 71.0%, and 80.4%, respectively). Conclusion: We demonstrated that the TDM-guided strategy using model-based algorithms performed similarly to mild empirical dose-tapering strategies in overall remission/LDA rates but is superior in cost-savings

The effect of methotrexate on tumour necrosis factor concentrations in etanercept-treated rheumatoid arthritis patients

Recently, we demonstrated that early low concentrations of circulating, adalimumab-bound TNF in RA patients treated with adalimumab was associated with future anti-drug antibody formation. Furthermore, low TNF was associated with less frequent baseline MTX use. This is remarkable, because of the anti-inflammatory effects of MTX and a potential inhibiting effect on cytokine production. We hypothesized an indirect effect of non-MTX use on low TNF concentrations via immunogenicity. To investigate the effect of MTX on TNF concentrations independent of anti-drug antibody formation, we measured TNF in RA patients treated with etanercept, a drug with low immunogenicity. Methods: TNF was quantified in 186 consecutive etanercept-treated RA patients at baseline and at weeks 4, 16 and 28. The dynamics of TNF during etanercept treatment were compared with dynamics recently published for adalimumab. Results: We demonstrated that TNF concentrations at week 4 did not associate with baseline MTX or remission after 28 weeks. Furthermore, median (interquartile range) TNF increased from <112 (<112-<112) pg/ml at baseline to 548 (344-688) pg/ml at week 4 and remained stable at week 16 and 28 [598 (442-756) and 568 (444-755) pg/ml, respectively]. Conclusion: Circulating TNF did not associate with MTX usage in etanercept-treated patients. This implies that MTX does not have a direct effect on TNF concentrations in circulation and that the association between early low TNF and non-use of MTX for adalimumab is thus most likely due to anti-drug antibody formation

Successful reduction of overexposure in patients with rheumatoid arthritis with high serum adalimumab concentrations: an open-label, non-inferiority, randomised clinical trial

OBJECTIVE: High adalimumab serum concentrations do not result in better response in patients with rheumatoid arthritis (RA), suggesting overexposure. We investigated whether patients with adalimumab concentrations >8 µg/mL can prolong their dosing interval by 50% without a clinically relevant change in disease activity. METHODS: Consecutive patients with RA, treated with adalimumab 40 mg every other week for at least 28 weeks, were approached for this randomised, open-label, non-inferiority trial. Patients with adalimumab trough concentrations >8 µg/mL were randomly (1:1) assigned to dose-interval prolongation of once every 3 weeks or continuation of every other week. Primary outcome was the change in disease activity score of 28 joints (ΔDAS28-ESR) after 28 weeks, with a non-inferiority margin of 0.6 points. RESULTS: In total, 147 patients were screened. Fifty-five patients had concentrations >8 µg/mL and were randomised. Mean ΔDAS28 after 28 weeks was -0.14±SD 0.61 in the prolongation group and 0.30±0.52 in the continuation group. Mean difference was significantly in favour of the prolongation group: 0.44 (95% CI 0.12 to 0.76, p=0.01). CONCLUSIONS: Adalimumab-treated patients with RA with trough concentrations >8 µg/mL can prolong their standard dosing interval to once every 3 weeks without loss of disease control. TRIAL REGISTRATION NUMBER: NTR3509; Results