Determination of Serum Infliximab Concentration by Point-of-care Devices in Children With Inflammatory Bowel Disease

Monoclonal antibodies against pediatric ulcerative colitis: a review of clinical progress

INTRODUCTION

In children, ulcerative colitis (UC) is often more severe and extensive than in adults and hospitalization for acute exacerbations occurs in around a quarter of subjects. There is a need for effective drugs, which could avoid or reduce the use of corticosteroids which, especially in children, are burdened by a number of severe side effects. The introduction in therapy of monoclonal antibodies has completely changed the therapeutic scenario and the prognosis of the disease.

AREAS COVERED

In this review, the use of the monoclonal antibodies directed against tumor necrosis factor (TNF)α or other inflammatory targets for the treatment of pediatric UC will be discussed. A search of the literature was done using the keywords 'pediatric,' 'ulcerative colitis,' 'inflammatory bowel disease,' 'monoclonal antibodies;' 'infliximab,' 'adalimumab,' 'golimumab,' vedolizumab," 'ustekinumab' and 'risankizumab.'

EXPERT OPINION

The use of monoclonal antibodies has greatly increased in recent years in pediatric UC, both in patients who did not respond to conventional therapies, and, more often, as initial therapy. Thanks to therapeutic drug monitoring and to the availability of biologics with different targets, therapy has become more targeted and personalized, with a significant improvement in response, in quality of life, and with a good safety profile.

Enhancing Therapeutic Drug Monitoring in Inflammatory Bowel Disease: A Comparative Analysis of Rapid Point-of-Care Infliximab, Adalimumab and Anti-Drug Antibodies' Determination against ELISA

The introduction of point-of-care (POC) assays into clinical practice in patients with inflammatory disease enables on-demand therapeutic decision making. The aim of this study was to compare the POC test Quantum blue (Bühlmann Laboratories) for infliximab (IFX), adalimumab (ADL), and its anti-drug antibodies with the traditional ELISA assay (Promonitor). A total of 200 serum samples were analyzed. Samples were classified into the following three different groups; sub-therapeutic range (IFX < 3 μg/mL and ADL < 5 μg/mL); therapeutic range (IFX: 3-7 μg/mL and ADL: 5-12 μg/mL) and supra-therapeutic range (IFX levels > 7 μg/mL and ADL levels > 12 μg/mL). Significant higher values were measured using the POC test (p < 0.001) for IFX results but no differences in ADL trough levels were observed (p = 0.3101). Spearman's correlation indicated a good correlation between the two assays (rs = 0.88 for ADL and rs = 0.93 for IFX), and McNemar's test revealed significant differences (p = 0.016) when classifying IFX samples between therapeutic and supra-therapeutic ranges but no significant differences were found among the other ranges for either IFX or ADL. These results show that we should be cautious when using these rapid measurement methods, and new targets should probably be defined for IFX when using this new analytical method.

Development and validation of enzyme-linked immunosorbent assays for the measurement of infliximab and anti-drug antibody levels

Infliximab and its anti-drug antibody (ADA) serum concentrations exhibit a strong correlation with clinical response and loss of response. The use of therapeutic drug monitoring to measure the concentration of infliximab and ADA can facilitate clinical decision-making, helping patients attain optimal therapeutic effects. However, there are still limitations to the existing infliximab and its ADA detection methods. Therefore, this study aimed to develop and validate enzyme-linked immunosorbent assay (ELISA)-based methods for measuring infliximab and its ADA levels in human plasma according to the general recommendations for immunoassays. Free infliximab is bound by recombinant TNF-α and detected using HRP-labeled anti-human antibody. The ADA is captured by on-plate-coated infliximab and recognized by biotin-labeled infliximab. Two bridging ELISA assays were developed and after assay optimization and validation, these assays have been applied in ten patients with inflammatory bowel disease (IBD). In infliximab detection assay, a standard curve ranging from 0.10 μg/mL to 8.0 μg/mL with great precision and accuracy has been established. Drug tolerance of the ADA assay was that 100 ng/mL ADA could tolerate at least 5.0 μg/mL infliximab in the plasma using a commercially available monoclonal anti-infliximab antibody as the positive control. The ADA screening and confirmatory assays achieved a sensitivity of 36.74 ng/mL and 37.15 ng/mL, respectively. All other assay characteristics met the requirements. The mean concentration of infliximab in eight patients with IBD was 7.88 (1.87-21.1) μg/mL, and the ADA levels were all negative. Moreover, the concentrations of infliximab in the remaining two patients were below the LLOQ and the ADAs were positive. Thus, accurate and sensitive ELISA methods have been developed and validated for the detection of infliximab and its ADA concentrations and have been successfully applied to clinical therapeutic drug monitoring.

Therapeutic Drug Monitoring of Anti-TNFα Inhibitors: A Matter of Cut-Off Ranges

Therapeutic drug monitoring (TDM) is a useful tool for optimising the use of anti-TNFα inhibitors in patients with inflammatory bowel diseases (IBDs). Recently, point-of-care methods for the quantification of drug levels and anti-drug antibodies (ADAs) have been developed to overcome the limitations of conventional enzyme-linked immunoabsorbent assays (ELISAs). Here, we evaluated the performance, interchangeability, and agreement between an automated ELISA-based immunoassay (CHORUS Promonitor) and the lateral flow assay (RIDA^®QUICK) for the quantification of infliximab (IFX, n = 65) and adalimumab (ADM, n = 58) plasma levels in IBD patients. Thirty-two samples for IFX and twenty-three samples for ADM that tested positively for the presence of ADAs were also used. Overall, data analysis showed a good agreement of ADM trough concentrations (R² = 0.75) between the two assays as well as for ADA measurement (K > 0.8). However, IFX levels highlighted a weak correlation (R² = 0.58) between the two kits, with the RIDA^®QUICK assay overestimating IFX plasma values by 30% when compared to the CHORUS Promonitor kit. Results from this study show that the two assays are not quantitatively and qualitatively interchangeable due to substantial discrepancies in some results. Accordingly, the same assay should be used for the longitudinal follow-up of IBD patients.

Therapeutic drug monitoring in Crohn's disease patients treated with anti-TNF: a comparison of two techniques

BACKGROUND

Therapeutic drug monitoring is a useful clinical decision aid in managing patients with inflammatory bowel disease treated with anti-tumor necrosis factor (anti-TNF). Various techniques are available to evaluate drug trough levels, and among these a point-of-care (POC) method has been proposed to overcome the limitations inherent to other methodologies. In this study we aimed to evaluate the capability of POC to discriminate between relapse and remission disease phases, and to assess the concordance of the POC and homogeneous mobility shift assay (HMSA) results.

METHODS

Drug trough level of 46 Crohn's disease patients treated with either adalimumab or infliximab were evaluated with both a POC technique and an HMSA at various time points (week-16 and -48) during anti-TNF treatment.

RESULTS

Median adalimumab trough level of patients in remission were significantly higher as compared to relapsing patients using both HMSA (week 16, P = 0.0001; week48, P = 0.001) and POC (week 16, P = 0.0003; week 48, P = 0.0012), and similar results were observed with infliximab trough level at week 16 (HMSA, P = 0.019; POC, P = 0.0072). Overall, we observed a good correlation between the techniques for both infliximab (r = 0.76; P  < 0.0001) and adalimumab (r = 0.75; P  < 0.0001), with no difference in discriminatory accuracy between assays (infliximab: HMSA versus POC c-index, 0.921 versus 0.895, P =0.149; adalimumab: HMSA versus POC c-index, 0.817 versus 0.850, P = 0.197).

CONCLUSION

Both POC and HMSA assays are able to reliably differentiate relapse and remission phases in Crohn's disease patients treated with anti-TNF. These techniques showed good concordance and we feel that their preferential use should be based on local accessibility, physicians' experience and preference, and the need for timeliness availability of results.

Pharmacogenetic variants of infliximab response in young patients with inflammatory bowel disease

Infliximab is commonly used in inflammatory bowel disease (IBD), however, differences in clinical response among patients are common. Several studies have considered the possibility that these differences are caused by genetic variability even if no unique marker has been yet identified in pediatric patients. We evaluated the impact of two candidate single-nucleotide polymorphisms (SNPs) rs396991 in FCGR3A and rs1800629 in TNFα genes on infliximab response in an Italian cohort of 76 pediatric patients with IBD. Results showed that patients with the variant FCGR3A allele had a reduced clinical response at the end of induction (p value = 0.004), at 22 weeks (p value = 0.001), and at 52 weeks of treatment (p value = 0.01). A significant association between the FCGR3A variant and median infliximab levels measured during maintenance therapy was also observed: patients with wild type genotype had higher infliximab levels compared to patient with variant allele. Furthermore, patients with the variant allele had a higher probability to produce antidrug antibodies (ADAs). No association was found among the TNFα SNP, clinical response, and infliximab levels. This study addressed for the first time in pediatric patients with IBD, the association of FCGR3A SNP, infliximab response, and ADA production.

Advances in Therapeutic Drug Monitoring in Biologic Therapies for Pediatric Inflammatory Bowel Disease

In the current era of treat-to-target strategies, therapeutic drug monitoring (TDM) has emerged as a potential tool in optimizing the efficacy of biologics for children diagnosed with inflammatory bowel disease (IBD). The incorporation of TDM into treatment algorithms, however, has proven to be complex. "Proactive" TDM is emerging as a therapeutic strategy due to a recently published pediatric RCT showing a clear benefit of "proactive" TDM in anti-TNF therapy. However, target therapeutic values for different biologics for different disease states [ulcerative colitis (UC) vs. Crohn's disease (CD)] and different periods of disease activity (induction vs. remission) require further definition. This is especially true in pediatrics where the therapeutic armamentarium is limited, and fixed weight-based dosing may predispose to increased clearance leading to decreased drug exposure and subsequent loss of response (pharmacokinetic and/or immunogenic). Model-based dosing for biologics offers an exciting insight into dose individualization thereby minimizing the chances of losing response. Similarly, point-of-care testing promises real-time assessment of drug levels and individualized decision-making. In the current clinical realm, TDM is being used to prolong drug durability and efficacy and prevent loss of response. Ongoing innovations may transform it into a personalized tool to achieve optimal therapeutic endpoints.

Infliximab Level Between Venous and Capillary Blood Using Novel Device Strongly Correlate in Paediatric Inflammatory Bowel Disease Patients

OBJECTIVES

Blood to measure infliximab (IFX) levels is typically obtained with venipuncture. Dried blood sampling (DBS), using capillary blood obtained from a finger prick, would be an alternative to measure IFX blood levels while being more patient friendly. The aim of this study is to compare IFX blood level measured by venipuncture versus DBS in patients with paediatric inflammatory bowel disease (PIBD) to assure accuracy.

METHODS

A prospective clinical pilot study was performed in patients with PIBD. Before IFX infusion, blood was collected simultaneously through venipuncture and DBS from a finger prick, using Mitratips (Neoteryx). All IFX concentrations were measured by an enzyme-linked immunosorbent assay. The Bland-Altman analysis was used to measure limits of agreement. The interrater reliability was measured with the interclass correlation coefficient and Cohen kappa. To calculate Cohen kappa, IFX levels were categorized into 3 groups; low <5 μg/mL, adequate 5 to 10 μg/mL, and high >10 μg/mL.

RESULTS

Twenty patients were included. Median age was 12.1 year (interquartile range 8-16 year). The mean difference between the 2 methods was -0.14 as calculated with Bland-Altman plot. The limits of agreement were between -1.39 and 1.12. The interclass correlation coefficient was with 0.998 excellent. The Cohen kappa between 3 IFX level categories was strong K = 0.911 (P = 0.0001). There was a strong correlation between venous IFX serum levels and DBS (r = 0.991, P = 0.0001) in the included patients.

CONCLUSIONS

This is the first study in patients with PIBD to show that bloodspot technology is a patient friendly alternative method to measure IFX blood levels in PIBD.

Therapeutic drug monitoring to improve outcome of anti-TNF drugs in pediatric inflammatory bowel disease

Introduction: Medical treatment of pediatric inflammatory bowel diseases (IBD) has been greatly changed by the introduction of a number of biologic agents that are able to target various players of the immune response. In particular, monoclonal antibodies against the pro-inflammatory cytokine TNF-alpha (TNF) such as infliximab, adalimumab, and golimumab are now in the clinics both in induction and maintenance therapy, and several efforts are currently ongoing to optimize the use of these drugs in children. Areas covered: This review focuses on therapeutic drug monitoring (TDM) of anti-TNF levels and antidrug antibodies (ADAs), in IBD children. A revision of the analytical assays used for assessing anti-TNF plasma levels is also provided. Expert opinion: Although there is a consensus across studies that higher anti-TNF trough levels are associated with a better clinical outcome, and that early anti-TNF serum measurements could be predictive of long-term response, it is still not clear what the best predictive time of sampling is and what the ideal target drug plasma concentration to achieve. Indeed, there are a number of published studies, particularly in pediatric cohorts, limited by the population size analyzed and more prospective large studies are needed to examine the value of these predictive markers.