Proactive therapeutic drug monitoring of infliximab: a comparative study of a new point-of-care quantitative test with two established ELISA assays

Fluorescence-Based Lateral Flow Immunoassay for Quantification of Infliximab: Analytical and Clinical Performance Evaluation

BACKGROUND

Therapeutic drug monitoring of infliximab (IFX) can improve treatment outcomes; however, the temporal gap between drug concentration monitoring and subsequent availability restricts its practical application. To address this issue, an automated monitoring method, AFIAS IFX, was developed to rapidly and accurately analyze IFX concentration in blood. The analytical and clinical performances of this method were assessed to establish its clinical utility.

METHODS

The analytical performance of AFIAS IFX was evaluated according to Clinical and Laboratory Standard Institute guidelines. For clinical validation, AFIAS IFX was compared with 3 established enzyme-linked immunosorbent assay kits (LISA TRACKER, RIDASCREEN, and ImmunoGuide) using 100 consecutive samples from 28 patients treated with IFX. Passing-Bablok regression and Bland-Altman analyses were performed to compare the methods.

RESULTS

The detection and quantification limits of AFIAS IFX were 0.12 and 0.20 mcg/mL, respectively. Furthermore, AFIAS IFX analyzed samples within 10 minutes for concentrations up to 50 mcg/mL, exhibiting reproducibility (coefficient of variation [CV] ≤7.8%) and accuracy (recovery 98%-101%) with serum, plasma, and whole blood samples. Clinically, it exhibited a good correlation with the 3 established enzyme-linked immunosorbent assay kits. For patients treated with Remicade (IFX), the Passing-Bablok regression slope was 1.001-1.259, with a mean difference of -1.48 to 0.28 mcg/mL. For patients treated with CT-P13, the Passing-Bablok regression slope was 0.974-1.254, with a mean difference of -2.44 to 0.15 mcg/mL.

CONCLUSIONS

AFIAS IFX, a novel fluorescence-based lateral flow assay, exhibited excellent performance in analyzing IFX trough levels and is a potentially powerful tool for therapeutic drug monitoring in clinical settings, with opportunities for further development.

Therapeutic drug monitoring in inflammatory bowel diseases. Position statement of the Spanish Working Group on Crohn's Disease and Ulcerative Colitis

The treatment of inflammatory bowel disease has undergone a significant transformation following the introduction of biologic drugs. Thanks to these drugs, treatment goals have evolved from clinical response and remission to more ambitious objectives, such as endoscopic or radiologic remission. However, even though biologics are highly effective, a significant percentage of patients will not achieve an initial response or may lose it over time. We know that there is a direct relationship between the trough concentrations of the biologic and its therapeutic efficacy, with more demanding therapeutic goals requiring higher drug levels, and inadequate exposure being common. Therapeutic drug monitoring of biologic medications, along with pharmacokinetic models, provides us with the possibility of offering a personalized approach to treatment for patients with IBD. Over the past few years, relevant information has accumulated regarding its utility during or after induction, as well as in the maintenance of biologic treatment, in reactive or proactive strategies, and prior to withdrawal or treatment de-escalation. The aim of this document is to establish recommendations regarding the utility of therapeutic drug monitoring of biologics in patients with inflammatory bowel disease, in different clinical practice scenarios, and to identify areas where its utility is evident, promising, or controversial.

Performance of a New Rapid Point-of-Care Test for Infliximab Levels in Patients with Inflammatory Bowel Disease: A Comparison to ELISA

BACKGROUND

Therapeutic drug monitoring of infliximab levels in patients with inflammatory bowel disease (IBD) optimizes patients' treatment. The reference technique is based on enzyme-linked immunosorbent assay (ELISA) although point of care (POC) assays are being developed.

AIMS

To assess the performance of a new rapid immunochromatographic POC assay (Promonitor Quick IFX) compared with ELISA technique to measure infliximab levels in patients with IBD.

METHODS

A prospective, observational, unicentric study was performed on capillary blood samples from patients with IBD before infliximab infusion (trough levels). Infliximab levels and anti-infliximab antibodies were measured using the ELISA technique (Promonitor IFX) and the POC assay. Correlation between both techniques was assessed by Pearson's coefficient. Quantitative differences were evaluated by Bland-Altman analysis. Samples were stratified according to infliximab therapeutic ranges (< 3 μg/mL, 3-8 μg/mL, and > 8 μg/mL).

RESULTS

A total of 135 experimental samples were assessed. Infliximab levels showed a high correlation between POC and ELISA tests (r = 0.84, P < 0.001). The mean difference between tests was 1.46 μg/mL (P < 0.001), being minimal for concentrations < 8 μg/mL. POC and ELISA assays showed an overall concordance of 87.4%. Most samples were in the same therapeutic range, which lead to equivalent therapeutic decisions. POC and ELISA assays detected the presence of anti-infliximab antibodies in 2.2% and 3.7% of the samples, respectively.

CONCLUSIONS

POC assay results in blood samples from patients with IBD were comparable to those obtained with the reference ELISA technique. The POC assay could be considered for routine testing based on its ease of use and rapidity.

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.

Validation Study of Novel Point-of-Care Tests for Infliximab, Adalimumab and C-Reactive Protein in Capillary Blood and Calprotectin in Faeces in an Ambulatory Inflammatory Bowel Disease Care Setting

Background and aims: Point-of-care tests (POCT) allow instant measurement of inflammatory markers and drug concentrations. Here, we studied agreement between a novel POCT device and reference methods of measuring infliximab (IFX) and adalimumab (ADL) serum concentrations and C-reactive protein (CRP) and faecal calprotectin (FCP) concentrations of patients with inflammatory bowel disease (IBD). Methods: In this single-centre validation study, IBD patients were recruited in which IFX, ADL, CRP and/or FCP tests were required. IFX, ADL and CRP POCT were performed on capillary whole blood (CWB), obtained via finger prick. Additionally, IFX POCT was performed on serum samples. FCP POCT was performed on stool samples. Agreement between POCT and reference methods was tested using Passing-Bablok regression, intra-class correlation coefficients (ICC) and Bland-Altman plots. Results: In total, 285 patients participated. Passing-Bablok regression identified differences between the reference method and IFX CWB POCT (intercept = 1.56), IFX serum POCT (intercept = 0.71, slope = 1.10) and ADL CWB POCT (intercept = 1.44). There were also differences in the Passing-Bablok regressions of CRP (intercept = 0.81, slope = 0.78) and FCP (intercept = 51 and slope = 0.46). Bland-Altman plots demonstrated that IFX and ADL concentrations were slightly higher with the POCT and CRP and FCP were slightly lower with POCT. The ICC demonstrated almost perfect agreement with IFX CWB POCT (ICC = 0.85), IFX serum POCT (ICC = 0.96), ADL CWB POCT (ICC = 0.82) and CRP CWB POCT (ICC = 0.91) and moderate agreement with FCP POCT (ICC = 0.55). Conclusions: IFX and ADL results were slightly higher with this novel rapid and user-friendly POCT, whereas CRP and FCP results were slightly lower compared to the reference methods.

Recent Advances in the Optimization of Anti-TNF Treatment in Patients with Inflammatory Bowel Disease

Despite the evolution in inflammatory bowel disease (IBD) management during the last 20 years owing to the advent of new advanced therapies, anti-TNF agents still remain the cornerstone of therapy for both Crohn's disease and ulcerative colitis. However, this does not only secure favorable outcomes for patients considering the progressive disease character and the high likelihood of primary or secondary loss of response. Therefore, trying to reach a better treatment approach and maximize the benefits anti-TNF agents offer, optimization strategies should be examined. It has been indicated that optimizing treatment with anti-TNF enhances drug efficacy and has been associated with improved disease outcomes and a complication-free disease course. From this perspective, we aim to provide an overview of currently available data and recent advances in the practices of anti-TNF treatment optimization. Special focus has been given to the role of therapeutic drug monitoring (TDM), as well as the utility of combining anti-TNF with an immunomodulator and the treat-to-target approach.

EULAR points to consider for therapeutic drug monitoring of biopharmaceuticals in inflammatory rheumatic and musculoskeletal diseases

OBJECTIVE

To develop EULAR points-to-consider for therapeutic drug monitoring (TDM) of biopharmaceuticals in inflammatory rheumatic and musculoskeletal diseases (RMDs).

METHODS

The points-to-consider were developed in accordance with EULAR standardised operation procedures by a multidisciplinary task force from eight European countries, based on a systematic literature review and expert consensus. Level of evidence and strength of the points-to-consider were determined, and mean levels of agreement among the task force were calculated using a 10-point rating scale.

RESULTS

Six overarching principles and 13 points-to-consider were formulated. The level of agreement among the task force for the overarching principles and points-to-consider ranged from 8.4 to 9.9.The overarching principles define TDM and its subtypes, and reinforce the underlying pharmacokinetic/pharmacodynamic principles, which are relevant to all biopharmaceutical classes. The points-to-consider highlight the clinical utility of the measurement and interpretation of biopharmaceutical blood concentrations and antidrug antibodies in specific clinical scenarios, including factors that influence these parameters. In general, proactive use of TDM is not recommended but reactive TDM could be considered in certain clinical situations. An important factor limiting wider adoption of TDM is the lack of both high quality trials addressing effectiveness and safety of TDM and robust economic evaluation in patients with RMDs. Future research should focus on providing this evidence, as well as on further understanding of pharmacokinetic and pharmacodynamic characteristics of biopharmaceuticals.

CONCLUSION

These points-to-consider are evidence-based and consensus-based statements for the use of TDM of biopharmaceuticals in inflammatory RMDs, addressing the clinical utility of TDM.

Early Infliximab Clearance Predicts Remission in Children with Crohn's Disease

BACKGROUND AND AIMS

Children with Crohn's disease have lower response rates to infliximab, lower infliximab levels, and higher infliximab clearance on weight-based dosing than adults. We hypothesize infliximab clearance is a predictive of later outcomes on infliximab in children with Crohn's disease.

METHODS

In this single-center retrospective study, data were collected from charts on diagnosis, anthropometry, routine labs, infliximab therapeutic drug monitoring, infliximab dosing, disease activity, and other treatments. With these data we generated a population pharmacokinetic model using non-linear mixed effects modeling and calculated infliximab clearance for each patient over time. Patients were classified as in remission, responder-only or non-responder at 5, 10 and 16 months. Regression and ROC analyses were used to assess for early predictors of remission and response to infliximab.

RESULTS

Eighty-five subjects were included, with a median follow-up of 22.3 months (IQR 10.1-36.8). Our pharmacokinetic model showed infliximab clearance was positively associated with CRP and weight, while negatively associated with albumin. In regression analyses, early infliximab clearance was the only significant, consistent predictor of remission. A 0.1 L/day increase in infliximab clearance predicted remission with an OR between 0.179 and 0.426. Differences in dosing did not account for differences in outcome. Infliximab clearance alone had moderate predictive accuracy of remission, with an AUC between 0.682 and 0.738.

CONCLUSIONS

Early infliximab clearance is strongly associated with remission in children with Crohn's disease. It may be useful as a marker of response in proactive therapeutic drug monitoring to guide early dose optimization and/or changes in treatment for betterment of long-term outcomes.

Quantification of infliximab and adalimumab in human plasma by a liquid chromatography tandem mass spectrometry kit and comparison with two ELISA methods

Background: This study compared the performance of plasma infliximab and adalimumab quantification using a commercially available kit (mAbXmise kit) and mass spectrometry readout to that of two ELISA methods in patients treated for inflammatory bowel disease. Methods & results: The mAbXmise method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was linear from 2 to 100 μg/ml. It was validated according to international guidelines. Regarding cross-validation for infliximab (n = 70), the mean bias with LC-MS/MS assay was approximately threefold higher with the commercial ELISA assay compared with the in-house ELISA (-6.1 vs -1.8 μg/ml, respectively). The mean bias between the LC-MS/MS assay and in-house ELISA was -1.2 μg/ml for adalimumab (n = 35). Conclusion: The LC-MS/MS method is a powerful alternative to immunoassays to monitor concentrations of infliximab and adalimumab.

Therapeutic drug monitoring of biopharmaceuticals in inflammatory rheumatic and musculoskeletal disease: a systematic literature review informing EULAR points to consider

The objectives of this review were to collect and summarise evidence on therapeutic drug monitoring (TDM) of biopharmaceuticals in inflammatory rheumatic and musculoskeletal diseases and to inform the EULAR Task Force for the formulation of evidence-based points to consider. A systematic literature review (SLR) was performed, covering technical aspects and (clinical) utility of TDM, to answer 13 research questions. MEDLINE, Embase and Cochrane were searched until July 2020. American College of Rheumatology and EULAR abstracts were also considered for inclusion. Data were extracted in evidence tables and risk of bias assessment was performed. For the search on technical aspects, 678 records were identified, of which 22 papers were selected. For the clinical utility search, 3846 records were identified, of which 108 papers were included. Patient-related factors associated with biopharmaceutical blood concentrations included body weight, methotrexate comedication and disease activity. The identification of a target range was hampered by study variability, mainly disease activity measures and study type. Evidence was inconsistent for multiple clinical situations in which TDM is currently applied. However, for some particular scenarios, including prediction of future treatment response, non-response to treatment, tapering and hypersensitivity reactions, robust evidence was found. There is currently no evidence for routine use of proactive TDM, in part because published cost-effectiveness analyses do not incorporate the current landscape of biopharmaceutical costs and usage. This SLR yields evidence in favour of TDM of biopharmaceuticals in some clinical scenarios, but evidence is insufficient to support implementation of routine use of TDM.

Therapeutic drug monitoring for biological medications in inflammatory bowel disease

Therapeutic drug monitoring (TDM) is the measurement of serum drug concentrations and anti-drug-antibodies (ADA) for biologic therapies used to treat inflammatory bowel disease (IBD). The aim of this article is to review the current literature concerning reactive and proactive TDM for both adults and children with IBD. Although optimal trough concentration windows for some of these medications are not well defined, there is mounting evidence to suggest that reactive TDM is associated with favorable therapeutic outcomes, including less immunogenicity, greater drug exposure, and a decreased risk of treatment failure. Moreover, while the exact mechanism of loss of response is not fully elucidated, the vast majority of studies have reported a decreased incidence of nonresponse and secondary loss of response when TDM is implemented. Proactive TDM, while even less understood in the literature, employs a schedule of preemptive analysis of serum trough concentrations to accordingly adjust the patient's biologic dosage. Proactive TDM may decrease the need for IBD-related surgery/hospitalization, and therefore merits future studies of investigation.

Patient-led Remote IntraCapillary pharmacoKinetic Sampling (fingerPRICKS) for Therapeutic Drug Monitoring in patients with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Because of COVID-19 public health restrictions, telemedicine has replaced conventional outpatient follow up for most patients with chronic immune-mediated inflammatory disorders treated with biologic drugs. Innovative solutions to facilitate remote therapeutic drug monitoring are therefore required. Low-volume intracapillary blood sampling can be undertaken by patients at home and samples returned by post to central laboratories. We sought to report the effect of the COVID-19 pandemic on requests for therapeutic drug monitoring and the equivalence, acceptability and effectiveness of low volume Patient-led Remote IntraCapillary pharmacoKinetic Sampling [fingerPRICKS] compared to conventional venepuncture.

METHODS

We undertook a cross-sectional blood sampling methods comparison study and compared sample types using linear regression models. Drug and antidrug antibody levels were measured using standard ELISAs. Acceptability was assessed using a purpose-designed questionnaire.

RESULTS

Therapeutic drug monitoring requests for adalimumab (96.5 [70.5-106] per week to 52 [33.5-57.0], p < 0.001) but not infliximab (184.5 [161.2-214.2] to 161 [135-197.5], p = 0.34) reduced during the first UK stay-at-home lockdown compared with the preceding 6 months. Fingerprick sampling was equivalent to conventional venepuncture for adalimumab, infliximab, vedolizumab and ustekinumab drug, and anti-adalimumab and anti-infliximab antibody levels. The median [interquartile range] volume of serum obtained using intracapillary sampling was 195 µL [130-210]. More than 87% [90/103] of patients agreed that intracapillary testing was easy and 69% [71/103] preferred it to conventional venepuncture. In routine care, 75.3% [58/77] of patients returned two blood samples within 14 days to permit remote assessment of biologic therapeutic drug monitoring.

CONCLUSIONS

Therapeutic drug monitoring can be undertaken using patient-led remote intracapillary blood sampling and has the potential to be a key adjunct to telemedicine in patients with immune-mediated inflammatory diseases.

Proactive therapeutic drug monitoring is more effective than conventional management in inducing fecal calprotectin remission in inflammatory bowel disease

BACKGROUND

Proactive therapeutic drug monitoring (pTDM) may improve treatment outcomes in inflammatory bowel disease.

AIMS AND METHODS

We compared 135 patients following a prospective pTDM protocol aiming at an infliximab trough level (IFXTL) between 5 and 10 μg/ml with sequential measurements of Fc, with 108 patients from a retrospective group under conventional management. We evaluated the rates of Fc remission (<250 μg/g) and other clinical outcomes at 2-year of follow-up.

RESULTS

pTDM associated with higher rates of Fc remission (69.6% vs. 50.0%; P = 0.002), and steroid-free clinical remission (78.4% vs. 55.2%, P = 0.028) with a trend for clinical remission (79.3% vs. 68.5%, P = 0.075). There was no difference in treatment discontinuation (P = 0.195), hospitalization (P = 0.156), and surgery (P = 0.110). Higher IFXTL associated with Fc remission at week 14 (6.59 vs. 2.96 μg/ml, P < 0.001), and at the end of follow-up (8.10 vs. 5.03 μg/ml, P = 0.001). In patients reaching Fc remission after week 14, IFXTL increased from week 14 to the end of follow-up (2.71 vs. 8.54 μg/ml, P < 0.001). Fc remission associated with higher rates of clinical (85.8% vs. 56.8% P < 0.001) and steroid-free clinical remission (86.9% vs. 50.0% P < 0.001), lower IFX discontinuation (8.8% vs. 36.8%, P < 0.001), and hospitalization (13.5% vs. 33.7%, P < 0.001), without significance for surgery (6.1% vs. 12.6%, P = 0.101).

CONCLUSION

pTDM was more effective than conventional management in inducing Fc remission which was associated with improved outcomes.

Comparison of a Point-of-Care Testing with Enzyme-Multiplied Immunoassay Technique and Liquid Chromatography Combined With Tandem Mass Spectrometry Methods for Therapeutic Drug Monitoring of Mycophenolic Acid: A Preliminary Study

BACKGROUND

For mycophenolic acid (MPA), therapeutic drug monitoring is an essential tool for dosage optimization in transplant recipients and autoimmune diseases. In China, a new commercial kit using an immunochromatographic assay (FICA) with a point-of-care testing system was approved for therapeutic drug monitoring of MPA. However, corroboration between FICA and clinically used assays remains unknown. The authors evaluated MPA concentrations in heart transplant recipients obtained by FICA, high-performance liquid chromatography combined with tandem mass spectrometry (LC-MS/MS), and enzyme-multiplied immunoassay technique (EMIT).

METHODS

Nine heart transplant recipients administered a single mycophenolate mofetil (MMF) dose, and 4 administered multiple MMF doses were enrolled. MPA samples were collected before administration, and after 0.5, 1, 1.5, 2, 4, 6, 8, 10, and 12 hours, and assessed by 2 immunoassays (EMIT and FICA) and LC-MS/MS. Consistency between methods was evaluated using Passing-Bablok regression and Bland-Altman analysis.

RESULTS

For Passing-Bablok regression between FICA and LC-MS/MS, FICA = 0.784 LC-MS/MS + 0.360 (95% CI slope: 0.739 to 0.829, 95% CI intercept: 0.174-0.545). Regardless of a significant observed correlation coefficient (R2 = 0.9126), statistical analyses revealed a significant difference between FICA and the reference LC-MS/MS method. The mean absolute bias was 0.69 mcg/mL between FICA and LC-MS/MS. Bland-Altman plots showed a mean bias of -0.23 mcg/mL (±1.96 SD, -2.19 to 1.72 mcg/mL) and average relative bias of 14.73% (±1.96 SD, -67.91% to 97.37%) between FICA and LC-MS/MS. Unsatisfactory consistency was observed between EMIT and LC-MS/MS, and FICA and EMIT. Differences between pharmacokinetic parameters after a single or 7 days of MMF administration, by LC-MS/MS and FICA, were not statistically significant.

CONCLUSIONS

The consistency of the new FICA using a point-of-care testing device with LC-MS/MS and EMIT was inadequate, and the accuracy of EMIT and LC-MS/MS was inappropriate. Clinicians should be informed when switching MPA detection methods to avoid misleading results.

Therapeutic Drug Monitoring of Tumor Necrosis Factor Antagonists in Crohn Disease: A Theoretical Construct to Apply Pharmacokinetics and Guidelines to Clinical Practice

Therapeutic drug monitoring (TDM) is the measurement of drug and antidrug antibody concentrations in individuals to guide treatment decisions. In patients with Crohn disease (CD), TDM, used either reactively or proactively, is emerging as a valuable tool for optimization of tumor necrosis factor (TNF) antagonist therapy. Reactive TDM is carried out in response to treatment failure, whereas proactive TDM involves the periodic monitoring of patients responding to TNF antagonist therapy to allow treatment optimization. In patients with CD, most of the available data for TDM relate to the first-to-market TNF antagonist infliximab and, to a lesser extent, to adalimumab and certolizumab pegol. Several gastroenterology associations, including the American Gastroenterology Association, have endorsed the use of reactive TDM in patients with active CD. However, fewer recommendations currently exist for the use of proactive TDM, although several new prospective randomized controlled trials evaluating proactive TDM strategies have been published. In this review, the current evidence for reactive and proactive TDM is discussed, and a proactive treatment algorithm for certolizumab pegol based on previously published threshold concentrations is proposed.

Point-of-Care Therapeutic Drug Monitoring for Precision Dosing of Immunosuppressive Drugs

BACKGROUND

Immunosuppressive drugs (ISD) are an essential tool in the treatment of transplant rejection and immune-mediated diseases. Therapeutic drug monitoring (TDM) for determination of ISD concentrations in biological samples is an important instrument for dose personalization for improving efficacy while reducing side effects. While currently ISD concentration measurements are performed at specialized, centralized facilities, making the process complex and laborious for the patient, various innovative technical solutions have recently been proposed for bringing TDM to the point-of-care (POC).

CONTENT

In this review, we evaluate current ISD-TDM and its value, limitations, and proposed implementations. Then, we discuss the potential of POC-TDM in the era of personalized medicine, and provide an updated review on the unmet needs and available technological solutions for the development of POC-TDM devices for ISD monitoring. Finally, we provide concrete suggestions for the generation of a meaningful and more patient-centric process for ISD monitoring.

SUMMARY

POC-based ISD monitoring may improve clinical care by reducing turnaround time, by enabling more frequent measurements in order to obtain meaningful pharmacokinetic data (i.e., area under the curve) faster reaction in case of problems and by increasing patient convenience and compliance. The analysis of the ISD-TDM field prompts the evolution of POC testing toward the development of fully integrated platforms able to support clinical decision-making. We identify 4 major areas requiring careful combined implementation: patient usability, data meaningfulness, clinicians' acceptance, and cost-effectiveness.

Comparison of a new rapid method for determination of serum anti-adalimumab and anti-infliximab antibodies with two established ELISA kits

BACKGROUND

Adalimumab (ADL), infliximab (IFX) and their biosimilars are widely used biological drugs. Some patients, however, generate neutralizing antibodies that hamper the effectiveness of these drugs. Evidence shows therapeutic drug monitoring of serum levels ADL/IFX and anti-drug antibodies (ADA) is useful to improve treatment effectiveness. We evaluated a new rapid quantitative method, Quantum Blue (QB), for determining serum anti-ADL and anti-IFX antibodies (Research Use Only labelling) by comparing it with two established ELISA kits, Promonitor (PM) and Lisa-Tracker (LT).

METHODS

Eighty samples (40 for each drug type) were analysed. Percentage of agreement and kappa statistic were used to compare positive/negative ADA results. Clinical implications for drug treatment in the patients with discordant results were evaluated. The Chi-square test was used to analyze differences for ADA detection in patients with disease flare and without concomitant immunosuppressant treatment.

RESULTS

Agreement exceeded 80 % among anti-ADL methods. Although LT ELISA showed a lower capacity in detecting anti-ADL antibodies, discrepancies were found for levels close to the cut-off concentration, thus having minimal impact on clinical decisions. Conversely, QB anti-IFX displayed low agreement with PM and LT ELISA kits (67.5 % and 50 %, respectively), and was unable to detect high levels of antibodies, therefore having major clinical implications. Agreement between PM and LT ELISA anti-IFX kits was 82.5 % with all discordant results being undetected for PM and slightly positive for LT.

CONCLUSION

QB anti-ADL shows similar performance to ELISA kits while QB anti-IFX needs further improvements to achieve reliable antibody detection.

Monitoring vedolizumab and ustekinumab drug levels in patients with inflammatory bowel disease: hype or hope?

Therapeutic drug monitoring (TDM) plays a vital role in implementing precision medicine in inflammatory bowel disease (IBD), and may contribute to increased effectiveness, lower rates of drug toxicity and cost savings. While expert panels advocate the use of reactive TDM for anti-tumor necrosis factor (anti-TNF) agents, TDM is not yet widely recommended for non-anti TNF biologicals. We provide an overview of the observational evidence of the value of TDM in case of vedolizumab and ustekinumab. We also shed light on obstacles that need to be addressed before establishing wide acceptance of TDM in the field of IBD. In this respect, new analytical techniques and modelling approaches are being developed to further optimize efficacy of TDM and to facilitate general acceptance of this tool in personalizing IBD management.

Point-of-Care Assays Could Be Useful for Therapeutic Drug Monitoring of IBD Patients in a Proactive Strategy with Adalimumab

The objective of the study was to evaluate whether Point-of-Care (POC) assays are equivalent to ELISAs for measuring residual trough levels of adalimumab (ADA) in a cohort of Inflammatory Bowel Disease (IBD) patients. ADA trough levels obtained by POC assays were used to optimize patients in daily clinical practice. Different assays (three ELISAs (Enzyme-Linked ImmunoSorbent Assay) from two different suppliers and two POC assays) were compared to measure ADA trough levels in a first cohort of 31 IBD patients. All assays revealed a high correlation within the assays, ranging from 0.86 to 0.99. Cut-off values were always higher with ELISAs than with POC assays. Then, a small prospective clinical study with a second cohort of 37 IBD patients was performed to compare POC assays and ELISAs for their ability to optimize patients on the basis of the measured ADA trough levels. The use of a POC assay to monitor ADA trough levels did not improve the follow-up of patients with loss of response, as they were always optimized whatever their ADA residual rate. For patients in clinical remission, a POC assay can be useful in some clinical situations to maintain or de-escalate ADA doses according to the measured trough levels. In conclusion, different assays for ADA monitoring are quite equivalent. A POC assay could be only useful for a proactive strategy for asymptomatic patients with a sub-therapeutic dose of ADA, but new therapeutic thresholds need to be identified.

Infliximab trough levels: A comparison between the Quantum Blue Infliximab assay and the established ELISA

BACKGROUND AND AIM

Therapeutic drug monitoring of infliximab (IFX) using the established laboratory-based enzyme-linked immunosorbent assay (ELISA) cannot produce results fast enough to allow IFX dose adjustments prior to each IFX infusion. We investigate the validity of IFX trough levels obtained through the Quantum Blue IFX (QB-IFX) rapid assay compared with the established ELISA.

METHODS

Adult inflammatory bowel disease patients receiving maintenance IFX infusions at Middlemore Hospital and Dunedin Public Hospital were prospectively recruited from July to October 2016. Serum samples were stored at -40 °C until processed using QB-IFX by a clinician at Middlemore Hospital and a research staff at Dunedin Public Hospital strictly following the manufacturers' instructions in an open label fashion.

RESULTS

Forty four inflammatory bowel disease patients were recruited. Median duration of IFX therapy was 21 months (interquartile range: 12-44). Overall, the correlation between ELISA and QB-IFX trough levels was 0.73 (95% confidence interval [CI]: 0.53-0.85). The sensitivity and specificity of a QB-IFX level < 7 in detecting an ELISA level < 7 were 0.79 (95% CI: 0.59-0.92) and 0.75 (95% CI: 0.48-0.93), respectively. Conversely, the sensitivity and specificity of a QB-IFX level < 2 detecting an ELISA level < 2 were 1.00 (95% CI: 0.52, 1.00) and 0.97 (95% CI: 0.85, 1.00), respectively.

CONCLUSION

The QB-IFX had excellent sensitivity and specificity for IFX levels < 2 obtained with the established ELISA. Therefore, QB-IFX could be used for real time dosing decisions when the IFX level is low and dose escalation is required.

How, When, and for Whom Should We Perform Therapeutic Drug Monitoring?

The implementation of therapeutic drug monitoring (TDM) in the inflammatory bowel disease practice has evolved over the years. In the early days, the focus was merely on measuring and reporting drug concentrations. Later, these concentrations were considered in light of target concentrations that are related to clinical response. This not only allowed passively predicting a patient's future response, but it also triggered physicians and pharmacists to actively use the information to optimize the drug dosage to induce and maintain a clinical response in the future. Although reactive TDM, testing at time of loss of response, is widely accepted in practice, especially for anti-tumor necrosis factor antibodies, there are less data for the other monoclonal antibodies belonging to other classes. Besides reactive testing, there is a movement toward proactively adjusting biologic dosing to prevent loss of response, in keeping with the tight control philosophy of inflammatory bowel disease care. This review highlights the various assays available to measure drug concentrations and antidrug antibodies, as well as algorithmic approaches to TDM, the unmet needs and required studies to enable pharmacokinetics principles to be applied in the future.

Laboratory Monitoring of Biological Therapies in Rheumatology: The Role of Immunogenicity

Biological drugs, such as proteins and immunogens, are increasingly used to treat various diseases, including tumors and autoimmune diseases, and biological molecules have almost completely replaced synthetic drugs in rheumatology. Although biological treatments such as anti-tumor necrosis factor (TNF) drugs seem to be quite safe, they cause some undesirable effects, such as the onset of infections due to weakening of the immune system. Given the biological nature of these drugs, they might be recognized as extraneous; this would induce an immune reaction that neutralizes their effectiveness or lead to more serious consequences. Laboratories play a pivotal role in appropriate therapeutic management. The aim of this review was to underline the production of anti-drug antibodies during treatment with biological drugs and highlight the role of laboratories in ensuring appropriate use of these drugs.

Proactive Infliximab Drug Monitoring Is Superior to Conventional Management in Inflammatory Bowel Disease

BACKGROUND

Increasing evidence supports the use of reactive therapeutic drug monitoring (TDM) in Crohn's disease (CD) and ulcerative colitis (UC) following secondary loss of response. It is still unknown if proactive TDM can improve clinical outcomes.

METHODS

Consecutive patients completing infliximab (IFX) induction therapy were prospectively allocated into a proactive TDM protocol (pTDM). Before the fourth infusion and every 2 infusions, IFX trough levels and antidrug antibodies were measured using a drug-sensitive assay (Theradiag, Lisa Tracker). Treatment was proactively escalated aiming at an IFX trough level between 3 and 7 ug/mL (CD) and 5 and 10 ug/mL (UC). A retrospective cohort treated with IFX but without TDM served as the reference group. End points included the need for surgery, hospitalization, treatment discontinuation, and mucosal healing at 2 years of follow-up.

RESULTS

Two hundred five patients were included, 56 in the proactive regimen. Treatment escalation was more common in pTDM patients (76.8% vs 25.5%; P < 0.001), who also required less surgery (8.9% vs 20.8%; P = 0.032) and presented higher rates of mucosal healing (73.2% vs 38.9%; P < 0.0001). Proactive TDM significantly decreased the odds of reaching any unfavorable outcome (odds ratio, 0.358; 95% confidence interval, 0.188-0.683; P = 0.002).

CONCLUSIONS

Proactive TDM is associated with fewer surgeries and higher rates of mucosal healing than conventional non-TDM-based management.

Mass spectrometry-based metabolomics in health and medical science: a systematic review

Metabolomics is the study of the investigation of small molecules derived from cellular and organism metabolism, which reflects the outcomes of the complex network of biochemical reactions in living systems.

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

OBJECTIVES

Therapeutic drug monitoring is becoming increasingly important in clinical decision-making in children with inflammatory bowel disease (IBD). However, enzyme-linked immunosorbent assay (ELISA) assays do not allow results to be provided in real-time. We sought to compare 2 point-of-care (POC) devices for quantification of serum infliximab concentration with 2 validated ELISA assays in children with IBD.

METHODS

We studied 32 serum samples from 19 children with IBD treated with infliximab. Serum samples were collected immediately before drug infusion (trough level). Infliximab was measured using 2 POC infliximab assays, Quantum Blue (POC IFX/QB) and Rida Quick (POC IFX/RQ), and 2 ELISA assays: Lisa-Tracker (used as primary reference), and Promonitor (used as second control). Intraclass correlation coefficient (ICC) was assessed for quantitative comparison. Qualitative analysis was also performed to evaluate whether POC assays would correctly classify infliximab serum according to a target window (between 3 and 7 μg/mL).

RESULTS

ICC was 0.82 and 0.87 for POC IFX/QB and POC IFX/RQ with the primary reference ELISA assay, respectively; ICC between the 2 ELISA assays was 0.87. Classification of results according to therapeutic intervals showed good agreement between pairs of assays, with kappa of 0.67 and 0.80 for POC IFX/QB and POC IFX/RQ, respectively, with reference ELISA, and 0.81 between the 2 ELISAs. Accuracy of POC assays was better for drug levels <3 μg/mL.

CONCLUSIONS

POC infliximab assays showed good agreement with traditional ELISA assays. POC devices may represent a viable option for real-time therapeutic drug monitoring in children treated with infliximab.

Comparison of a new rapid method for the determination of adalimumab serum levels with two established ELISA kits

Background

Therapeutic drug monitoring (TDM) of adalimumab (ADA) in inflammatory bowel diseases (IBDs) has gained increased attention since several studies showed a correlation between drug levels and mucosal healing. The limitations of routine usage of enzyme-linked immunoabsorbent assay (ELISA) kits for measuring serum ADA concentrations have prompted the development of rapid methods, such as Quantum Blue (QB). We evaluated the interchangeability and agreement between the QB method and two established ELISA kits, Promonitor (PM) and Lisa-Tracker (LT).

Methods

Fifty samples from patients with IBD were included. Quantitative analysis was performed using the ANOVA test for repeated measures, Deming regression and the Bland-Altman plot. Clinical implications were evaluated by concordance in classifying patients into therapeutic windows according to the proposed cut-off levels for subtherapeutic (either <5 or <7.5 μg/mL) and supratherapeutic (>12 μg/mL) ranges.

Results

Statistical differences were detected between the QB method and the two ELISA kits, with QB overestimating ADA serum values compared to them. A lack of interchangeability was observed between methods, with greater differences as ADA levels increased. An analysis of a sub-set of samples with ADA values below 9 μg/mL (n = 25) showed that QB fulfilled the criteria to be interchangeable with the LT assay. Concordance for patient classification into ADA therapeutic windows was better for QB vs. LT than for QB vs. PM, with high agreement (>75%) for subtherapeutic levels among the three methods.

Conclusions

Although quantitative differences existed between the rapid method and ELISA kits that hampered their interchangeability, the agreement for identifying patients with subtherapeutic values of ADA was high.

Accuracy of the new rapid test for monitoring adalimumab levels

BACKGROUND

The loss of response to adalimumab (ADL) has been related to low serum concentrations at trough. Currently, most methods commercially available for the quantification of ADL are enzyme-linked immunosorbent assay (ELISA) based, with a turnaround time of approximately 8 h, delaying the target dosage adjustment to the subsequent infusion. In this study, we aimed to evaluate the performance of the newly available rapid-test ADL quantification assay by comparing it with three established ELISA methods, using spiked samples and a set of clinical samples.

METHODS

Spiked samples from control donors and 120 serum samples from inflammatory bowel disease (IBD) patients undergoing ADL therapy were quantified using lateral flow Quantum Blue^® Adalimumab and, the ELISA formats from Immundiagnostik, R-Biopharm and an in-house assay.

RESULTS

The rapid-test assay had intraclass correlation coefficients of 0.590, 0.864 and 0.761 when comparing with the Immundiagnostik, R-Biopharm and in-house assays, respectively. For the five therapeutic windows, the accuracy was high: ADL rapid test compared with the Immundiagnostik (58-88%); R-Biopharm, 68-89%; and in house, 60-88%; and kappa statistics revealed 0.492-0.602, 0.531-0.659 and 0.545-0.682, respectively.

CONCLUSIONS

The Quantum Blue^® Adalimumab assay can replace the commonly used ELISA-based ADL quantification kits and it is a reliable alternative to these methods. This rapid-test assay enables the quantitative determination of ADL serum trough level in only 15 min. The developed assay allows measurement of ADL over a wide range. Hence, it represents a valuable tool for the clinician to assess the ADL trough level.

Advances in Therapeutic Drug Monitoring for Small-Molecule and Biologic Therapies in Inflammatory Bowel Disease

PURPOSE OF REVIEW

Therapeutic drug monitoring (TDM) is increasingly utilized as a strategy to optimize inflammatory bowel disease (IBD) therapeutics. As management paradigms have evolved towards treat-to-target strategies, there has been growing interest in expanding the role of TDM to guide drug optimization for achieving objective endpoints. This review summarizes the evidence for using TDM with biologic and oral small-molecule therapies, evaluates the role of reactive versus proactive TDM in treatment algorithms, and identifies potential future applications for TDM.

RECENT FINDINGS

Achieving therapeutic drug concentrations has been associated with important clinical, endoscopic, and histologic outcomes in IBD. However, the optimal drug concentration varies by therapeutic agent, disease phenotype, inflammatory burden, phase of treatment, and target outcome. Traditionally, TDM has been used reactively to define pharmacokinetic versus mechanistic failures after loss of response to a tumor necrosis factor-α (TNF) antagonist and while observational data suggests a benefit to proactive TDM, this has not been definitively confirmed in prospective randomized controlled trials. The role of TDM in optimizing vedolizumab, ustekinumab, and tofacitinib remains unclear, given differences in pharmacokinetics and immunogenicity compared to TNF antagonists. Measuring drug action at the site of inflamed tissue may provide additional insights into treatment optimization. The use of TDM offers the possibility of a more personalized treatment approach for patients with IBD. High-quality studies are needed to delineate the role of proactive TDM for maintaining remission, for optimizing induction regimens, and for novel agents.

Analytical and clinical performance evaluation of two POC tests for therapeutic drug monitoring of infliximab

Background

Infliximab (IFX) is an effective therapy in patients with inflammatory bowel disease. Serum IFX trough concentrations correlate well with clinical, biological and endoscopic outcomes. Therefore, therapeutic drug monitoring (TDM) of infliximab is useful for dose optimization and prevention of secondary treatment failure. In the present study, analytical and clinical performance of two point-of-care (POC) tests, RIDA®QUICK IFX Monitoring assay (R-biopharm) and Quantum Blue® Infliximab assay (Bühlmann), have been evaluated and compared to our established enzyme-linked immunosorbent assay (ELISA) (apDia IFX ELISA).

Methods

Analytical performance was assessed according to the CLSI EP5-A2 protocol using the manufacturer’s kit controls and different serial dilution series. Method comparison with our established ELISA was done using a wide range of consecutive patient samples (n=180). Clinical concordance was evaluated by categorization based on well-known therapeutic cut-off points (3–7 μg/mL).

Results

The analytical performance of both POC tests was inferior to the established ELISA, but acceptable based on the manufacturer’s quality claims. Eight-point serial dilution confirmed the analytical performance data in the low-level measuring range. Eleven-point serial dilution demonstrated linearity for both POC tests over the studied concentration range. Method comparison with the ELISA showed significant negative proportional bias for the RIDA®QUICK IFX Monitoring assay. However, good correlation and clinical concordance were shown. Quantum Blue® Infliximab assay showed a significant positive proportional and a negative systematic bias in comparison with the ELISA, resulting in overestimation of IFX levels with impact on clinical concordance data.

Conclusions

Both POC tests have their own specific benefits and drawbacks but are suitable for therapeutic drug monitoring of IFX. However, long-term monitoring of IFX trough levels requires measurement of IFX concentrations with the same assay.

Comparison of Point-of-Care and Classical Immunoassays for the Monitoring Infliximab and Antibodies Against Infliximab in IBD

OBJECTIVE

The primary objective is to assess whether the POC assays to measure infliximab residual trough level in the serum of IBD patients were non-inferior to the ELISA techniques available on the market, and to determine which of them was the most robust. The second is to compare three different ELISA kits for monitoring anti-infliximab antibodies (ATI).

METHODS

The assays were carried out on patients' sera using four ELISA kits from four different suppliers (three with a monoclonal antibody and one polyclonal) and two rapid techniques provided by BÜHLMANN (Quantum Blue^®) and R-Biopharm (Ridaquick) for monitoring infliximab levels. ATI were measured by three ELISA sets (Grifols, Theradiag, and R-Biopharm) which have different positivity limits and different units.

RESULTS

We measured infliximab residual level and ATI in the serum of 90 IBD patients (85 treated with infliximab and five with adalimumab). All of the infliximab assays were very well correlated when analyzed with Spearman nonparametric correlation (0.93 ≤ r ≤ 0.99), and the two POC assays were also excellently correlated (r = 0.98). The ATI monitoring kits revealed a correlation ranging from 0.73 to 0.96 when comparing positive and negative patients. When normalizing the quantitative values between the different ELISA tests (expressed arbitrarily by using multiples of the positivity limits defined by each supplier), the Spearman r coefficient ranged from 0.81 to 0.93.

CONCLUSION

The available evidence allows us to conclude that all of the infliximab monitoring assays correlate well and may be used for IFX monitoring; albeit variations in measured IFX concentration among different assays remain present, these assays could be interchangeable. The ATI monitoring techniques are all capable of detecting ATI-positive patients, but because of the difference in the positivity limits and the measurement units, it is better to follow a patient rate with one definite kit.

The performance of Remicade®-optimized quantification assays in the assessment of Flixabi® levels

BACKGROUND

The advent of Remicade® biosimilars, Remsima®, Inflectra® and, more recently, Flixabi®, has brought along the potential to decrease the costs associated with this therapy, therefore increasing its access to a larger group of patients. However, and in order to assure a soft transition, one must make sure the assays and algorithms previously developed and optimized for Remicade perform equally well with its biosimilars. This study aimed to: (a) validate the utilization of Remicade-optimized therapeutic drug monitoring assays for the quantification of Flixabi; and (b) determine the existence of Remicade, Remsima and Flixabi cross-immunogenicity.

METHODS

Healthy donors' sera spiked with Remicade, Remsima and Flixabi were quantified using three different Remicade-quantification assays, and the reactivity of anti-Remicade and anti-Remsima sera to Remicade and to its biosimilars was assessed.

RESULTS

The results show that all tested Remicade-infliximab-optimized assays measure Flixabi as accurately as they measure Remicade and Remsima: the intraclass correlation coefficients between theoretical and measured concentrations varied from 0.920 to 0.990. Moreover, the interassay agreement values for the same compounds were high (intraclass correlation coefficients varied from 0.936 to 0.995). Finally, the anti-Remicade and anti-Remsima sera reacted to the different drugs in a similar fashion.

CONCLUSIONS

The tested assays can be used to monitor Flixabi levels. Moreover, Remicade, Remsima and Flixabi were shown to have a high cross-immunogenicity, which supports their high similarity but prevents their switching in nonresponders with antidrug antibodies.

Individualized Dosing of Therapeutic Monoclonal Antibodies-a Changing Treatment Paradigm?

The introduction of monoclonal antibodies (mAbs) to the treatment of inflammatory bowel disease (IBD) was an important medical milestone. MAbs have been demonstrated as safe and efficacious treatments of IBD. However, a large percentage of patients either fail to respond initially or lose response to therapy after a period of treatment. Although there are factors associated with poor treatment outcomes in IBD, one cause for treatment failure may be low mAb exposure. Consequently, gastroenterologists have begun using therapeutic drug monitoring (TDM) to guide dose adjustment. However, while beneficial, TDM does not provide sufficient information to effectively adjust doses. The pharmacokinetics (PK) and pharmacodynamics (PD) of mAbs are complex, with numerous factors impacting on mAb PK and PD. The concept of dashboard-guided dosing based on Bayesian PK models allows physicians to combine TDM with factors influencing mAb PK to individualize therapy more effectively. One issue with TDM has been the slow turnaround of assay results, either necessitating an additional clinic visit for a sample or reacting to TDM results at a subsequent, rather than the current, dose. New point-of-care (POC) assays for mAbs are being developed that would potentially allow physicians to determine drug concentration quickly. However, work remains to understand how to determine what target exposure is needed for an individual patient, and whether the combination of POC assays and dashboards presents a safe approach with substantial outcome benefit over the current standard of care.

Proactive Therapeutic Drug Monitoring of TNF Antagonists in Inflammatory Bowel Disease

BACKGROUND

Proactive therapeutic drug monitoring (TDM) to titrate tumor necrosis factor (TNF) antagonists has emerged recently as a tool to routinely monitor drug concentration to achieve target levels in patients with quiescent inflammatory bowel disease (IBD).

METHODS

The purpose of the present review article was to present available data exploring the concept of proactive TDM.

RESULTS

While several observational studies have identified an association between proactive TDM and better IBD outcomes, 2 randomized controlled studies did not confirm this advantage.

CONCLUSIONS

Based on the evidence to date, proactive TDM cannot be recommended in daily practice. However, analysis is hampered by the low level of evidence for the cutoffs used and the need for point-of-care assays. Regarding economic issues and de-escalating strategies, proactive TDM may have several future indications in IBD. Exploratory studies on proactive TDM with newly available biologic agents in IBD are also awaited.

How to predict response to anti-tumour necrosis factor agents in inflammatory bowel disease

Anti-tumor necrosis factor (TNF) agents have changed the therapeutic approach to inflammatory bowel disease (IBD). However, a considerable proportion of patients either do not primarily respond or lose response to treatment. Despite the long-standing experience in the use of these drugs, still there is the need of identifying the possible predictors of efficacy. Areas covered: We critically review the current knowledge on predictors of response to anti-TNF therapy - both those available in clinical practice and those still under investigation. Multiple factors are involved in treatment success, including disease phenotype and severity, adherence to medications, and pharmacogenomic, pharmacokinetic, and immunologic factors. Literature search was conducted in PubMed using keywords 'inflammatory bowel disease,' 'Crohn's disease,' and 'ulcerative colitis,' matched with 'antitumor necrosis factor,' 'biologic therapy,' 'clinical response,' 'predictors,' and 'efficacy,' Relevant articles were selected for review. Expert commentary: While the role of several factors in clinical practice is clearly established, other investigational markers have been proposed, mostly in small studies, yet for many of them little external validation exists. Therapeutic drug monitoring is emerging as a pivotal strategy to guide decisions in clinical practice. In the near future, novel markers could improve our ability to direct treatment and personalize therapy.

SERUM INFLIXIMAB MEASUREMENT IN INFLAMMATORY BOWEL DISEASE PATIENTS IN REMISSION: A COMPARATIVE ANALYSIS OF TWO DIFFERENT METHODS IN A MULTICENTRIC BRAZILIAN COHORT

BACKGROUND

Infliximab (IFX) therapeutic drug monitoring is an important tool to guide therapeutic decision in inflammatory bowel disease patients. Currently, there are two methods to measure trough levels of IFX, ELISA assays or rapid tests. Despite that the ELISA assay is the most used method in therapeutic drug monitoring, the results take long to be available for clinical use, and it needs to be performed by trained personnel. In contrary, the results of a rapid test take 20 to 30 minutes to be available and can be performed by non-trained lab personnel.

OBJECTIVE

The aim of the study was to compare a rapid test (QB-IFX) for quantitative determination of IFX level to one ELISA assay in a cohort of inflammatory bowel disease patients.

METHODS

Cross-sectional multicentric study with 49 inflammatory bowel disease patients on maintenance therapy with IFX. Blood samples for IFX serum levels were collected immediately before infusion. IFX serum levels were classified as undetectable, low (<3.0 μg/mL), adequate (3.1-7.0 μg/mL) or high (>7.1 μg/mL). A sensitivity and specificity of each test and a comparison between tests was based on ROC curves.

RESULTS

Thirty-four Crohn's disease patients and 15 ulcerative colitis patients in clinical remission were evaluated. The majority of patients had low or adequate serum levels of IFX. In relation to the serum levels proportions with the two methods, there was no significant difference (P=0.84). The ROC analysis identified a concentration threshold >2.9 μg/mL with the QB-IFX test (area under the ROC, 0.82; P<0.0001, sensitivity, 100%; specificity, 61.9%), and >3.83 μg/mL using the ELISA assay (area under the ROC, 0.96; P<0.0001, sensitivity, 100%; specificity, 92.9%).

CONCLUSION

QB-IFX and ELISA assays to measure IFX levels were comparable. Both methods had accurate sensitivity and specificity to detect undetectable, low and adequate levels, but had showed low specificity for supra therapeutic levels of IFX.

Reliability evaluation of four different assays for therapeutic drug monitoring of infliximab levels

BACKGROUND

The aim of this study was to evaluate reliability of four different assays for measuring infliximab trough levels and antibodies to infliximab (ATI).

METHODS

In this non-interventional, cross-sectional study including IBD patients, infliximab levels and ATI were measured using four different assays: Lisa-Tracker, Promonitor, Q-Inflixi and Sanquin. Reliability and agreement for infliximab levels was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plots. Qualitative agreement for infliximab (based on a pre-established target window of trough levels between 3 µg/ml and 7 µg/ml) and for ATI were estimated by Cohen's kappa.

RESULTS

Serum samples of 84 IBD patients were evaluated for infliximab using the four assays. Reliability was 'substantial' between Lisa-Tracker versus Promonitor and 'almost perfect' between the remaining assay pairs, with ICCs [95% confidence interval (CI)] ranging from 0.93 (0.70-0.97) for Lisa-Tracker versus Promonitor to 0.97 (0.95-0.98) for Q-Inflixi versus Sanquin. Bland-Altman plots showed significant bias between assays except Promonitor versus Q-Inflixi, which had excellent agreement. The greatest differences in mean infliximab were found between Promonitor versus Lisa-Tracker (-0.91 µg/ml) and Lisa-Tracker versus Q-Inflixi (0.69 µg/ml). Qualitative agreement for infliximab was 'almost perfect' for Promonitor versus Q-Inflixi (kappa 0.84) and Q-Inflixi versus Sanquin (kappa 0.81), and 'substantial' for the remaining pairs. More than 10% of patients who had infliximab levels within the target interval by Lisa-Tracker had suboptimal concentrations (<3 µg/ml) with Promonitor and Q-Inflixi. Furthermore, 11% of patients within the target interval by Q-Inflixi had supra-optimal levels (>7 µg/ml) by Lisa-Tracker. In the remaining paired comparisons, fewer than 5% of patients were placed in different subgroups. Qualitative agreement for ATI fluctuated between 'moderate' and 'almost perfect'.

CONCLUSIONS

All four assays seem suitable for therapeutic drug monitoring of infliximab. Promonitor and Q-Inflixi had the best agreement, making those assays fully interchangeable. Systematic biases between Lisa-Tracker with Promonitor and Q-Inflixi suggest that these assays should not be interchanged during the follow up of an individual patient.

Infliximab Trough Levels and Quality of Life in Patients with Inflammatory Bowel Disease in Maintenance Therapy

Objective

Investigate the association between infliximab trough levels and quality of life in inflammatory bowel disease patients in maintenance therapy.

Methods

We carried out a transversal study with inflammatory bowel disease patients in infliximab maintenance therapy. Infliximab trough levels were determined using a quantitative rapid test. Disease activity indices (partial Mayo Score and Harvey-Bradshaw Index) and endoscopic scores (endoscopic Mayo Score or Simple Endoscopic Score in Crohn's disease) were obtained. Quality of life was assessed using the Inflammatory Bowel Disease Questionnaire (IBDQ).

Results

Seventy-one consecutive subjects were included in the study (55 with Crohn's disease and 16 with ulcerative colitis). Drug levels were considered satisfactory (≥3 μg/mL) in 28 patients (39.4%) and unsatisfactory (<3 μg/mL) in 43 (60.6%). Satisfactory trough levels were associated with higher rates of clinical remission and mucosal healing. Higher trough levels were also associated with improved IBDQ scores, particularly regarding bowel symptoms, systemic function, and social function.

Conclusion

Satisfactory trough levels of infliximab were associated with higher rates of clinical remission, mucosal healing, and improved quality of life in inflammatory bowel disease patients on maintenance therapy.

Anti-infliximab antibody concentrations can guide treatment intensification in patients with Crohn's disease who lose clinical response

BACKGROUND

The presence of antibodies towards infliximab (ATI) is associated with lower infliximab (IFX) trough concentrations and loss of response. IFX treatment intensification is effective for restoring response in most, but not all patients with Crohn's disease (CD).

AIM

To compare outcome, pharmacokinetics and immunogenicity of treatment intensification strategies in patients with CD who lost clinical response to IFX.

METHODS

A retrospective cohort study was conducted, including 103 patients with CD who lost clinical response during IFX maintenance therapy and therefore received a double dose IFX (10 mg/kg) and/or a next infusion after a shortened interval. IFX and ATI concentrations were measured in consecutive trough samples, just before (T0) and after (T+1) treatment intensification.

RESULTS

Clinical response (physicians' global assessment) and biological response and remission (CRP) were restored in 63%, 42% and 24% of patients (evaluated at T+1). Treatment intensification increased IFX trough concentrations from 1.2 μg/mL [0.3-3.6] at T0 to 3.6 μg/mL [0.5-10.2] at T+1 (P < .0001). Using a drug tolerant assay, ATI were detected in the T0 sample of 47% of patients. ATI negatively impacted the achieved IFX trough concentration (Spearman r -0.57, P < .0001) and the probability of clinical response (P = 0.034) at T+1. When ATI were quantifiable but <282 ng/mL eq. at T0, combined interval shortening and dose doubling was more effective for restoring therapeutic IFX trough concentrations (≥3 μg/mL at T+1) than dose doubling alone, which in turn was more effective than interval shortening alone (P < .001).

CONCLUSION

Antibodies towards infliximab can guide clinical decision-making on treatment intensification.

Application of Population Pharmacokinetic Modeling for Individualized Infliximab Dosing Strategies in Crohn Disease

OBJECTIVES

The pharmacokinetics of infliximab (IFX) is highly variable in children with Crohn disease (CD), and a one-size-fits-all approach to dosing is inadequate. Model-based drug dosing can help individualize dosing strategies. We evaluated the predictive performance and clinical utility of a published population pharmacokinetic model of IFX in children with CD.

METHODS

Within a cohort of 34 children with CD who had IFX trough concentrations measured, the pharmacokinetics of each patient was estimated in NONMEM using a published population pharmacokinetic model. Infliximab concentrations were then predicted based on each patient's dosing history and compared with actual measured concentrations (n = 59). In addition, doses 5 to 10 mg/kg and dosing intervals every 4 to 8 weeks were simulated in each patient to examine dose-trough relationships.

RESULTS

Predicted concentrations were within ±1.0 μg/mL of actual measured concentrations for 88% of measurements. The median prediction error (ie, measure of bias) was -0.15 μg/mL (95% confidence interval -0.37 to -0.05 μg/mL) and absolute prediction error (ie, measure of precision) was 0.26 μg/mL (95% confidence interval 0.15 to 0.40 μg/mL). At standard maintenance dosing of 5 mg/kg every 8 weeks, a trough >3 μg/mL was predicted to be achieved in 32% of patients. To achieve a trough >3 μg/mL, a dosing interval ≤every 6 weeks was predicted to be required in 29% of patients.

CONCLUSIONS

A published IFX population pharmacokinetic model demonstrated accurate predictive performance in a pediatric CD population. Individualized IFX dosing strategies in children with CD will be critical to consistently achieve trough concentrations associated with optimal outcomes.

Point-of-care testing (POCT) and evidence-based laboratory medicine (EBLM) - does it leverage any advantage in clinical decision making?

Point-of-care testing (POCT) is the analysis of patient specimens outside the clinical laboratory, near or at the site of patient care, usually performed by clinical staff without laboratory training, although it also encompasses patient self-monitoring. It is able to provide a rapid result near the patient and which can be acted upon immediately. The key driver is the concept that clinical decision making may be delayed when samples are sent to the clinical laboratory. Balanced against this are considerations of increased costs for purchase and maintenance of equipment, staff training, connectivity to the laboratory information system (LIS), quality control (QC) and external quality assurance (EQA) procedures, all required for accreditation under ISO 22870. The justification for POCT depends upon being able to demonstrate that a more timely result (shorter turnaround times (TATs)) is able to leverage a clinically important advantage in decision making compared with the central laboratory (CL). In the four decades since POCT was adapted for the self-monitoring of blood glucose levels by subjects with diabetes, numerous new POCT methodologies have become available, enabling the clinician to receive results and initiate treatment more rapidly. However, these instruments are often operated by staff not trained in laboratory medicine and hence are prone to errors in the analytical phase (as opposed to laboratory testing where the analytical phase has the least errors). In some environments, particularly remote rural settings, the CL may be at a considerable distance and timely availability of cardiac troponins and other analytes can triage referrals to the main centers, thus avoiding expensive unnecessary patient transportation costs. However, in the Emergency Department, availability of more rapid results with POCT does not always translate into shorter stays due to other barriers to implementation of care. In this review, we apply the principles of evidence-based laboratory medicine (EBLM) looking for high quality systematic reviews and meta-analyses, ideally underpinned by randomized controlled trials (RCTs), looking for evidence of whether POCT confers any advantage in clinical decision making in different scenarios.

Clinical performance of an infliximab rapid quantification assay

BACKGROUND

Therapeutic drug monitoring (TDM)-based algorithms can be used to guide infliximab (IFX) adjustments in inflammatory bowel disease (IBD) patients. This study aimed to explore a rapid IFX-quantification test from a clinical perspective.

METHODS

This manuscript describes a prospective cohort study involving 110 ulcerative colitis (UC) patients on the maintenance phase of IFX. IFX trough levels were quantified using a rapid quantification assay and a commonly-used reference kit.

RESULTS

Irrespective of the assay used to measure IFX, its through levels were statistically different between patients with and without endoscopic remission (Mayo endoscopic score = 0), as well as between patients stratified by their faecal calprotectin (FC) levels. Despite the fact that the two methods correlated well with each other [Spearman's rank correlation coefficient = 0.843, p < 0.001; intraclass correlation coefficients = 0.857, 95% confidence interval (CI): 0.791-0.903], there was a discernible systematic variation; values obtained with the reference kit were on average 2.62 units higher than those obtained with the rapid assay. Notwithstanding, 3 µg/ml was shown to be an acceptable cut-off to assess endoscopic status and inflammatory burden levels using both assays. The percentage of patients that had a positive outcome when the IFX concentration measured by the rapid assay ranked above 3 µg/ml was 88% both for a Mayo endoscopic score ⩽ 1 and for an FC concentration <250 µg/g.

CONCLUSIONS

Based on this study, we concluded that using the rapid IFX assessment system with a 3 µg/ml threshold is a reliable alternative to the time-consuming enzyme-linked immunosorbent assays in patients on the maintenance phase of IFX.

Therapeutic drug monitoring of CT-P13: a comparison of four different immunoassays

BACKGROUND

The commercialization of CT-P13, an infliximab (IFX) biosimilar, has the potential to decrease health-related costs and enhance access to biological therapies. This study aimed to address the accuracy and inter-assay agreement of the CT-P13 quantification using four different assays initially developed to assess IFX.

METHODS

The four different methods, one in-house method and three commercially available kits, were used to quantify exogenously-spiked samples and the sera from 185 inflammatory bowel disease (IBD) patients on CT-P13 therapy.

RESULTS

The quantification of the spiked samples unveiled a consistent and accurate behaviour of three of the tested methods, with average percentage recoveries of 90%, 102% and 109%. Results from the clinical samples demonstrated that these three assays were also highly correlated, both concerning Spearman's rank coefficients (range 0.890-0.947) and intraclass correlation coefficients (range 0.907-0.935). There were a few systematic deviations among them, but their impact in the clinical stratification of the patients using different cut-offs was minimal, particularly when these cut-offs were in the 3-4 µg/ml range, for which the strength of agreement (as assessed by the Kappa statistics that ranged from 0.732 to 0.902) was substantial to almost perfect.

CONCLUSIONS

Our results indicate that three of the tested IFX quantification methods can be used to accurately quantify CT-P13 without any adjustments.

Clinical correlations of infliximab trough levels and antibodies to infliximab in South Korean patients with Crohn’s disease

AIM

To investigate the clinical implications of infliximab trough levels (IFX-TLs) and antibodies to infliximab (ATI) levels in Crohn’s disease (CD) patients in Asian countries.

METHODS

IFX-TL and ATI level were measured using prospectively collected samples obtained with informed consent from CD patients being treated at Asan Medical Center, South Korea. We analyzed the correlations between IFX-TLs/ATI levels and the clinical activity of CD (quiescent vs active disease) based on the CD activity index, C-reactive protein level, and physician’s judgment of patients’ clinical status at enrollment. The impact of concomitant immunomodulators was also investigated.

RESULTS

This study enrolled 138 patients with CD (84 with quiescent and 54 with active disease). In patients with quiescent and active diseases, the median IFX-TLs were 1.423 μg/mL and 0.163 μg/mL, respectively (P < 0.001) and the median ATI levels were 8.064 AU/mL and 11.209 AU/mL, respectively (P < 0.001). In the ATI-negative and -positive groups, the median IFX-TLs were 1.415 μg/mL and 0.141 μg/mL, respectively (P < 0.001). In patients with and without concomitant immunomodulator use, there were no differences in IFX-TLs (0.632 μg/mL and 1.150 μg/mL, respectively; P = 0.274) or ATI levels (8.655 AU/mL and 9.017 AU/mL, respectively; P = 0.083).

CONCLUSION

IFX-TL/ATI levels were well correlated with the clinical activity in South Korean CD patients. Our findings support the usefulness of IFX-TLs/ATI levels in treating CD patients receiving IFX in clinical practice.