Infliximab Concentrations during Induction Are Predictive for Endoscopic Remission in Pediatric Patients with Inflammatory Bowel Disease under Combination Therapy.

OBJECTIVES: To study infliximab (IFX) pharmacokinetics in children with inflammatory bowel disease (IBD) during induction therapy to predict outcome and explore if other covariates influenced outcome. STUDY DESIGN: All children with IBD starting IFX therapy (5 mg/kg at weeks 0, 2, 6, and 12) for active luminal disease from May 2017 to May 2019 were included and followed prospectively. Patients were sampled at multiple timepoints during induction (trough concentrations and peak concentration at weeks 0, 2, 6, and 12, and intermediate concentration at weeks 1-4). IFX concentrations and cumulative drug exposure were correlated with outcome at 6 months. Endoscopic remission was defined as Simple Endoscopic Score for Crohn's Disease of <3 or Mayo endoscopic subscore of 0, and deep remission as endoscopic with clinical remission (Pediatric Ulcerative Colitis Activity Index/Pediatric Crohn's Disease Activity Index of <10). RESULTS: There were 252 serum induction concentrations obtained from 32 patients (81% on concomitant thiopurines). Children in endoscopic remission (all in deep remission) at 6 months had significantly higher drug concentrations from week 4 onward. A receiver operating characteristics curve analysis identified IFX trough concentrations at week 12 of ≥5.0 µg/mL and area under the curve at weeks 0-12 of ≥4056.0 µg∗day/mL as the minimal target to achieve endoscopic remission at 6 months (area under the receiver operating characteristics curve, 0.796 [95% CI, 0.62-0.97] and area under the receiver operating characteristics curve, 0.778 [95% CI, 0.61-0.94], respectively). In addition, our findings suggest that proteomic analysis may help to understand IFX response. CONCLUSIONS: Higher IFX exposure during induction therapy in pediatric patients with IBD is associated with significantly better endoscopic and deep remission rates at 6 months. Drug concentrations differentiate remitters from nonremitters from week 4 after induction onward.

Modelling of the relationship between infliximab exposure, faecal calprotectin and endoscopic remission in patients with Crohn's disease.

AIMS: Evidence for the benefits of pharmacokinetic (PK) and pharmacodynamic (PD) monitoring of infliximab in patients with Crohn's disease (CD) remains scarce. We aimed to develop a population (pop)PK/PD model to characterise the infliximab dose-exposure-biomarker-response (faecal calprotectin [fCal] and endoscopic remission [ER]) relationship. METHODS: Data were obtained from 116 patients with CD in a phase 4 dose-escalation study. Three sequential models were developed: a 2-compartment popPK model linking infliximab dose to exposure; an indirect response popPK/PD model describing the inhibitory effect of infliximab exposure on fCal; and a first-order Markov popPD model linking fCal to transitions between states of ER, no ER and dropout. RESULTS: Infliximab clearance increased with increasing fCal, decreasing albumin, increasing CD activity index and presence of anti-drug antibodies. Baseline fCal increased with increasing C-reactive protein and decreasing platelet count. Lower fCal increased the probability of attaining ER and decreased the probability of losing ER. Probability of dropping out given an earlier state of absence of ER increased with time. Large interpatient PK and PD variability resulted in a flat dose-response curve. Predicted fraction of patients achieving ER was 45% [30-61] (median [interquartile range], n = 50 000) when on 5 mg/kg infliximab (~46% observed in data). Simulations with 10 mg/kg induction doses predicted an increase to 48% [32-63]. This minor benefit at the population level argues against systematic 10 mg/kg induction dosing in all patients. CONCLUSION: Model-informed infliximab dose optimisation towards a predefined fCal concentration (while accounting for PK and PD variability) may improve effectiveness of infliximab therapy.

The effect of aging on infliximab exposure and response in patients with inflammatory bowel diseases.

AIMS: Controversies regarding infliximab treatment in elderly patients with inflammatory bowel diseases remain. We evaluated the effect of patient's age on infliximab exposure, efficacy and safety. METHODS: Retrospective case-control data of patients receiving infliximab induction treatment were analysed. A population pharmacokinetic model was developed to estimate individual pharmacokinetic parameters. A logistic regression model was used to investigate the effect of exposure on endoscopic remission. Repeated time-to-event models were developed to describe the hazard of safety events over time. RESULTS: A total of 104 patients (46 elderly, ≥65 years) were included. A two-compartment population pharmacokinetic model with linear elimination adequately described the data. Infliximab clearance decreased with older age, higher serum albumin, lower fat-free mass, lower C-reactive protein and absence of immunogenicity. Yet, infliximab exposure was not significantly different between elderly and nonelderly. Regardless of age, an infliximab trough concentration at week (w)14 of 15.6 mg/L was associated with a 50% probability of attaining endoscopic remission between w6 and w22. Infliximab exposure during induction treatment was not a risk factor of (severe) adverse events. The hazard of severe adverse events and malignancy increased by 2% and 7%, respectively, with increasing year of age. Concomitant immunomodulator use increased the hazard of infection by 958%, regardless of age. CONCLUSIONS: Elderly patients attained infliximab exposure and endoscopic remission similarly to nonelderly patients. Therefore, the same infliximab trough concentration target can be used in therapeutic drug monitoring. The hazards of severe adverse events and malignancy increased with age, but not with infliximab exposure.

Adaptive antibody diversification through N-linked glycosylation of the immunoglobulin variable region.

A hallmark of B-cell immunity is the generation of a diverse repertoire of antibodies from a limited set of germline V(D)J genes. This repertoire is usually defined in terms of amino acid composition. However, variable domains may also acquire N-linked glycans, a process conditional on the introduction of consensus amino acid motifs (N-glycosylation sites) during somatic hypermutation. High levels of variable domain glycans have been associated with autoantibodies in rheumatoid arthritis, as well as certain follicular lymphomas. However, the role of these glycans in the humoral immune response remains poorly understood. Interestingly, studies have reported both positive and negative effects on antibody affinity. Our aim was to elucidate the role of variable domain glycans during antigen-specific antibody responses. By analyzing B-cell repertoires by next-generation sequencing, we demonstrate that N-glycosylation sites are introduced at positions in which glycans can affect antigen binding as a result of a specific clustering of progenitor glycosylation sites in the germline sequences of variable domain genes. By analyzing multiple human monoclonal and polyclonal (auto)antibody responses, we subsequently show that this process is subject to selection during antigen-specific antibody responses, skewed toward IgG4, and positively contributes to antigen binding. Together, these results highlight a physiological role for variable domain glycosylation as an additional layer of antibody diversification that modulates antigen binding.

Monitoring a Combination of Calprotectin and Infliximab Identifies Patients With Mucosal Healing of Crohn's Disease.

BACKGROUND & AIMS: In the TAILORIX trial, no benefit could be shown by infliximab dose escalation based on pharmacokinetic (infliximab serum concentrations) and pharmacodynamic (biomarkers and symptoms) monitoring compared with dose escalation based on symptoms alone in patients with Crohn's disease (CD). We investigated whether integration of pharmacokinetic and pharmacodynamic monitoring can be used to evaluate responses to infliximab induction and maintenance therapy, based on findings from endoscopy. METHODS: We performed a post hoc analysis of patients with CD included in a trial to test the effects of infliximab dose escalation, based on biomarkers and serum concentrations of infliximab, on symptoms (the Study Investigating Tailored Treatment With Infliximab for Active Crohn's Disease trial; n = 122). We analyzed data from this study to determine whether concentrations of biomarkers and serum concentrations of infliximab were associated with endoscopic outcomes (n = 116). The primary end points were endoscopic response (CD endoscopic index of severity decrease ≥50% from baseline), endoscopic remission (CD endoscopic index of severity, <3), and absence of ulcers at weeks 12 and 54 of infliximab treatment. RESULTS: Infliximab trough concentrations greater than 23.1 mg/L at week 2 and greater than 10.0 mg/L at week 6 were associated with endoscopic remission at week 12 (positive predictive values, 72% and 76%; negative predictive values, 65% and 59%, respectively). During maintenance therapy, we found evidence for an exposure-response relationship only after dose escalation; trough concentrations greater than 10.6 mg/L were associated with the absence of ulcers at week 54 (positive predictive value, 49%; negative predictive value, 92%). Low fecal concentrations of calprotectin during therapy were associated with endoscopic response and remission (P < .05). Dose escalations increased trough concentrations of infliximab; persistent increase in fecal concentration of calprotectin, despite dose escalation, was associated with a lack of endoscopic response and remission. A significantly higher proportion of patients with antibodies to infliximab, identified by a drug-tolerant assay, dropped out of the study compared with patients without antibodies (P < .0001). CONCLUSIONS: In a post hoc analysis of data from a trial to test the effects of infliximab dose escalation on symptoms, we found that during maintenance therapy, the combination of fecal concentration of calprotectin and trough concentration of infliximab can guide dose adjustment and increase the chances for endoscopic response and remission. ClinicalTrialsRegister.eu EudraCT no: 2011-003038-14.

Successful Infliximab Treatment is Associated With Reversal of Clotting Abnormalities in Inflammatory Bowel Disease Patients.

BACKGROUND AND GOALS: Active inflammatory bowel diseases (IBD) represent an independent risk factor for venous thromboembolism. The authors investigated the hemostatic profile of IBD patients before and after induction treatment with infliximab, vedolizumab, and methylprednisolone. STUDY: This prospective study included 62 patients with active IBD starting infliximab, vedolizumab, and/or methylprednisolone, and 22 healthy controls (HC). Plasma was collected before (w0) and after induction therapy (w14). Using a clot lysis assay, amplitude (marker for clot intensity), time to peak (Tmax; marker for clot formation rate), area under the curve (AUC; global marker for coagulation/fibrinolysis), and 50% clot lysis time (50%CLT; marker for fibrinolytic capacity) were determined. Plasminogen activator inhibitor-1 (PAI-1) and fibronectin were measured by ELISA. Clinical remission was evaluated at w14. RESULTS: At baseline, AUC, amplitude, and 50%CLT were significantly higher in IBD patients as compared with HC. In 34 remitters, AUC [165 (103-229)% vs. 97 (78-147)%, P=0.001], amplitude [119 (99-163)% vs. 95 (82-117)%, P=0.002], and 50%CLT [122 (94-146)% vs. 100 (87-129)%, P=0.001] decreased significantly and even normalized to the HC level. Vedolizumab trough concentration correlated inversely to fibronectin concentration (r, -0.732; P=0.002). The increase in Tmax for infliximab-treated remitters was significantly different from the decrease in Tmax for vedolizumab-treated remitters (P=0.028). The 50%CLT increased (P=0.038) when remitters were concomitantly treated with methylprednisolone. CONCLUSIONS: Control of inflammation using infliximab most strongly reduced those parameters that are associated with a higher risk of venous thromboembolism.

Increasing Infliximab Dose Based on Symptoms, Biomarkers, and Serum Drug Concentrations Does Not Increase Clinical, Endoscopic, and Corticosteroid-Free Remission in Patients With Active Luminal Crohn's Disease.

BACKGROUND & AIMS: A combination of infliximab and immunomodulators is the most efficacious treatment for Crohn's disease (CD). Patients have the best outcomes when their serum concentrations of these drugs are above a determined therapeutic threshold. We performed a prospective, randomized trial to determine whether therapeutic drug monitoring (TDM) to maintain serum levels of infliximab above 3 µg/mL produced higher rates of clinical and endoscopic remission than adapting dose based only on symptoms. METHODS: We performed a double-blind trial in which 122 biologic-naïve adult patients with active CD (71 female, median age 29.8 years) received induction treatment with infliximab in combination with an immunosuppressant, from July 2012 through September 2015 at 27 centers in Europe. At week 14 of treatment, patients were randomly assigned (1:1:1) to 3 infliximab maintenance groups: dose increases (2 maximum) in steps of 2.5 mg/kg based on clinical symptoms and biomarker analysis and/or serum infliximab concentrations (dose intensification strategy [DIS]1 group); dose increase from 5 to 10 mg/kg based on the same criteria (DIS2 group); dose increase to 10 mg/kg based on clinical symptoms alone (controls). Patients' CD activity index scores, levels of C-reactive protein, fecal levels of calprotectin, and serum concentrations of infliximab were determined at baseline and at weeks 2, 4, 6, 12, and 14 of treatment, and then every 4 weeks thereafter until week 54. The primary endpoint was sustained corticosteroid-free clinical remission (CD activity index <150) from weeks 22 through 54 with no ulcers at week 54. RESULTS: The primary endpoint was reached by 15 (33%) of 45 patients in the DIS1 group, 10 (27%) of 37 patients in the DIS2 group, and 16 (40%) of 40 patients in the control group (P = .50). CONCLUSIONS: In a prospective randomized exploratory trial of patients with active CD, we found increasing dose of infliximab based on a combination of symptoms, biomarkers, and serum drug concentrations does not lead to corticosteroid-free clinical remission in a larger proportion of patients than increasing dose based on symptoms alone. EUDRACT NUMBER: 2011-003038-14.

Optimising infliximab induction dosing for patients with ulcerative colitis.

AIMS: The therapeutic failure of infliximab therapy in patients with ulcerative colitis remains a challenge even 2 decades after its approval. Therapeutic drug monitoring (TDM) has shown value during maintenance therapy, but induction therapy has still not been explored. Patients may be primary nonresponders or underexposed with the standard dosing regimen. We aimed to: (i) develop a population pharmacokinetic-pharmacodynamic model; (ii) identify the best exposure metric that predicts mucosal healing; and (iii) build an exposure-response (ER) model to demonstrate model-based dose finding during induction therapy with infliximab. METHODS: Data were retrospectively collected from a clinical database. A total of 583 samples, from 204 patients, was used to develop a population pharmacokinetic model to generate exposure metrics for subsequent ER modelling. A subset of 159 patients was used to develop a logistic regression ER model, describing the relationship between infliximab exposure and ordered transitions between Mayo endoscopic subscore (MES) 3, 2 and ≤1 (baseline to post-induction). RESULTS: A 1-compartment population pharmacokinetic model with interindividual and interoccasion variability was found to fit the data best. Covariates influencing exposure were C-reactive protein, albumin, baseline MES, fat-free mass, concomitant corticosteroid use and pancolitis. The cumulative area under the infliximab concentration-time curve until endoscopy (CAUCendoscopy ) was found to be the best exposure metric for predicting mucosal healing (baseline MES >1 and post-induction MES ≤1). The model predicted that 70% of patients will attain mucosal healing with infliximab administered at days 0, 14 and 42 and a target CAUCendoscopy of 3752 mg/L*day at day 84. CONCLUSIONS: TDM-based dose individualisation targeting CAUCendoscopy has the potential to improve the effectiveness of infliximab during induction therapy.

Pharmacodynamic Monitoring of Biological Therapies in Chronic Inflammatory Diseases.

BACKGROUND: Psoriasis, psoriatic arthritis, spondyloarthritis, rheumatoid arthritis, ulcerative colitis, and Crohn disease share similar underlying pathophysiological processes, providing the opportunity to treat the patients using similar biological therapies. Failure of biological treatments due to underexposure can be managed by therapeutic drug monitoring. Adjusting the treatment based on pharmacokinetic monitoring can be further improved by taking pharmacodynamic parameters such as clinical and molecular markers into account. METHODS: Here, we critically evaluate the existing evidence, the hurdles to be taken, and the opportunities for a widespread implementation of pharmacodynamic monitoring. RESULTS: Pharmacodynamic monitoring typically is the monitoring of biochemical markers. A pharmacodynamic marker preferably is specific for the pharmacological action of a drug, but most of the time nonspecific pharmacodynamic markers are used, such as C-reactive protein and the erythrocyte sedimentation rate. Clinical pharmacodynamic markers typically evaluate physical variables or symptoms. Although physician-reported outcomes have been studied for a longer time and often have been shown to correlate well with molecular pharmacodynamic markers and treatment outcomes, the introduction of mobile health or mHealth technologies caused a shift toward patient-reported outcomes, with the associated challenge to consistently reflect the inflammatory state, thereby preventing undertreatment or unnecessary overdosing of patients. CONCLUSIONS: The primary goal of pharmacodynamic monitoring is to optimize the response, but it can also have an impact on safety, costs, patient adherence, etc. Ideally, the constant remote monitoring of patient-reported disease activity is expected to become the standard, facilitated by mHealth technologies.

Efficacy, Pharmacokinetics, and Immunogenicity is Not Affected by Switching From Infliximab Originator to a Biosimilar in Pediatric Patients With Inflammatory Bowel Disease.

BACKGROUND: Rising evidence demonstrates that there are no differences in efficacy and safety between infliximab (IFX) originator and IFX biosimilar CT-P13 in the treatment of inflammatory bowel diseases (IBDs). However, most data are derived from adult patients, and data on pharmacokinetics are limited. The authors evaluated long-term IFX trough levels, immunogenicity, and remission rates in children with IBD who switched from IFX originator to biosimilar CT-P13. METHODS: In this single-center study, all children with Crohn disease and ulcerative colitis receiving maintenance IFX therapy were switched from originator to biosimilar CT-P13. Demographics, disease activity indices, and IFX drug levels were collected from 6 months before (baseline) till 6 months after switching to CT-P13. All data are presented as median (interquartile range). RESULTS: A total of 42 children (26 Crohn disease and 16 ulcerative colitis), with a median duration on IFX originator of 13.5 (6.8-35.5) months before switching to CT-P13, were included. No significant changes in IFX trough levels occurred after switching. The median baseline IFX trough level was 5.7 mcg/mL (3.8-9.3) versus 6.5 mcg/mL (3.9-8.6) at month 6 after switching (P = 0.900). Antibodies to IFX appeared in one patient after switching. The proportion of patients in clinical and/or biological remission did not significantly change after switching (all P > 0.05). No significant changes were observed in C-reactive protein, erythrocyte sedimentation rate, albumin, weight, and body mass index after the switch. Safety profile was also comparable. CONCLUSIONS: Pediatric patients with IBD on IFX originator can be successfully switched during maintenance to biosimilar CT-P13 without affecting efficacy, pharmacokinetics, immunogenicity, or safety.

Comparison of Immunoassays for Measuring Serum Levels of Golimumab and Antibodies Against Golimumab in Ulcerative Colitis: A Retrospective Observational Study.

BACKGROUND: Golimumab is a monoclonal anti-tumor necrosis factor alpha antibody, which is used in ulcerative colitis with an exposure-response relationship. The goal of this study was to compare results obtained with different immunoassays (golimumab and antigolimumab antibodies trough levels). METHODS: This study was based on samples from 78 ulcerative colitis patients on golimumab treatment. Golimumab was quantified by either an anti-IgG detection antibody (Theradiag, Marne la Vallée, France) or an antibody directed against golimumab (Sanquin, Amsterdam, The Netherlands, KU Leuven, Leuven, Belgium, and Janssen R&D, San Diego, CA). Bridging drug-sensitive enzyme-linked immunosorbent assays (Theradiag, Janssen R&D, and KU Leuven), a bridging drug-tolerant enzyme-linked immunosorbent assay (Janssen R&D), and a radioimmunoassay (Sanquin) were used to quantify antidrug antibody. RESULTS: Median serum golimumab levels were 4.5, 3.5, 4.9, and 2.4 mcg/mL with Theradiag, Sanquin, KU Leuven, and Janssen R&D assay, respectively (P < 0.05). Correlation coefficients between assays ranged from 0.9 to 0.97. When using the KU Leuven and Janssen R&D assays, 86% of samples were in the same quartile of distribution of values, and for Sanquin and Janssen R&D assays, this overlap was 80%. The concordance observed for the other pairs was 83% (Sanquin/KU Leuven R&D), 71% (Theradiag/KU Leuven), and 68% (Theradiag/Janssen R&D and Theradiag/Sanquin). The specificity of assays for golimumab was demonstrated. Antidrug antibodies were detected in 28.2% of the samples with the Janssen R&D drug-tolerant assay and in the same 2 patients by the 3 other assays. CONCLUSIONS: Performances of these immunoassays were similar in terms of quality, but differences in the quantitative results point to the importance of using the same assay consistently to monitor a patient's treatment.

Immunogenicity is not the driving force of treatment failure in vedolizumab-treated inflammatory bowel disease patients.

BACKGROUND AND AIM: The pivotal GEMINI trials reported low immunogenicity of vedolizumab. However, anti-vedolizumab antibodies (AVA) are frequently underestimated because most assays are not drug-tolerant and unable to detect antidrug antibodies while there is drug in the circulation. This study aimed to explore which antidrug antibody assay is best suited to detect AVA and investigated immunogenicity of vedolizumab in inflammatory bowel disease (IBD) patients discontinuing vedolizumab therapy. METHODS: A drug-tolerant affinity capture elution (ACE) assay was developed for the measurement of AVA in the presence of vedolizumab and compared with the previously established drug-resistant and drug-sensitive assays. Vedolizumab and AVA were measured at week 6, at the last infusion, and 12-20 weeks after treatment discontinuation in a cohort of 40 vedolizumab-treated IBD patients who stopped treatment due to primary non-response, loss of response, or adverse events. RESULTS: The drug-tolerant ACE assay could detect AVA in samples that the drug-resistant and drug-sensitive assays were unable to. Using the drug-tolerant ACE assay, 3 (8%) out of 40 vedolizumab-treated IBD patients who discontinued therapy were AVA positive at week 6, whereas no AVA were detected at the last infusion nor after treatment discontinuation. Primary non-responders had numerically lower median vedolizumab concentrations at week 6 compared with patients with loss of response (20.3 vs 30.7 µg/mL, respectively, P = 0.0570). CONCLUSIONS: Immunogenicity of vedolizumab is not the driving force of treatment failure, and AVA do not increase upon treatment discontinuation in vedolizumab-treated IBD patients. Underexposure during induction might partially be responsible for primary non-response.

Adequate Infliximab Exposure During Induction Predicts Remission in Paediatric Patients With Inflammatory Bowel Disease.

OBJECTIVES: Therapeutic drug monitoring has been proposed as a useful tool in the management of infliximab (IFX) treated patients with inflammatory bowel disease. The aim of this retrospective study was to determine whether IFX trough levels after induction therapy are predictive for outcome at week 52. METHODS: All pediatric patients with inflammatory bowel disease receiving maintenance IFX at our centre, with IFX trough level available at their first maintenance infusion and a follow-up of at least 52 weeks were included. IFX induction regimens could be intensified at the discretion of the treating physician. All children received proactive drug monitoring during maintenance with dose adaptation aiming to target a therapeutic window of 3 to 7 µg/mL. RESULTS: We included 35 children (23 with Crohn disease and 12 with ulcerative colitis). Median IFX trough levels just before the first maintenance infusion were significantly higher in children achieving clinical (4.6 µg/mL [2.7-11.8] vs 1.5 µg/mL [0.9-3.0]), biological (4.6 µg/mL [2.5-10.3] vs 2.6 µg/mL [0.3-3.2]) and combined clinical/biological remission (6.0 µg/mL [3.2-12.0] vs 2.6 µg/mL [1.1-3.2]) at week 52 compared to children not meeting these criteria (all P ≤ 0.002). Binary logistic regression identified these trough levels as the only predictor for the same outcomes with an odds ratio (95% confidence interval) of 2.083 (1.085-3.998), 2.203 (1.101-4.408), and 2.264 (1.096-4.680), respectively (all P < 0.05). CONCLUSIONS: Adequate IFX exposure during induction therapy is associated with better clinical and/or biological remission at week 52. Postinduction IFX trough levels were the only predictor for clinical and/or biological remission at week 52.

Clinical relevance of detecting anti-infliximab antibodies with a drug-tolerant assay: post hoc analysis of the TAXIT trial.

OBJECTIVE: To evaluate the clinical relevance of antidrug antibodies (ADAs) measured using a drug-tolerant assay in a post hoc analysis of the Trough Concentration (TC) Adapted Infliximab Treatment (TAXIT) randomised controlled trial. DESIGN: ADA in serum samples (n=221) of 76 patients enrolled in TAXIT, who presented with an infliximab TC <3 µg/mL at screening, were reanalysed after optimisation and at the end of the study using a drug-tolerant ADA assay. Patients underwent dose escalation to achieve therapeutic TCs between 3 µg/mL and 7 µg/mL prior to randomisation. Patients were grouped into quartiles (Q1-4) according to ADA concentration at screening. RESULTS: Using a drug-tolerant assay, the immunogenicity detection rate increased from 21% (drug-sensitive assay) to 63% at screening, from 0% to 51% after optimisation and from 3% to 42% at the end of TAXIT. Patients in ADA Q4 required a higher cumulative infliximab dose (2390 (880-2998) mg) to achieve target TCs, resulting in a higher drug cost (€10 712 (4120-13 596)) compared with ADA-negative patients (€2060 (1648-3296)) and patients in ADA Q1/Q2 (€2060 (1648-4120)/€2060 (1751-3296), p<0.001). However, all but one patient belonging to ADA Q4 were also ADA-positive using a drug-sensitive assay. CONCLUSIONS: Upon dose intensification, low concentration ADAs, not detectable using a drug-sensitive assay, disappear in more than half of the patients over time and are clinically non-relevant. In contrast, high concentration ADAs which are typically also detected in a drug-sensitive assay, persist over time and necessitate a higher cumulative dose and drug cost. In the latter group, proactive drug switching may be more cost-efficient. CLINICAL TRIALS REGISTER: 2011-002061-38; Post-results.

Mucosal Healing and Long-term Outcomes of Patients With Inflammatory Bowel Diseases Receiving Clinic-Based vs Trough Concentration-Based Dosing of Infliximab.

BACKGROUND & AIMS: The Trough Concentration Adapted Infliximab Treatment (TAXIT) trial demonstrated that maintaining infliximab trough concentrations at 3 to 7 µg/mL is most effective at inducing remission in patients with inflammatory bowel diseases (IBDs), with fewer flares than clinic-based dosing. We performed a follow-up analysis of study participants to explore the correlation between trough dosing strategy and mucosal healing, continued infliximab use, and rates of hospitalization, surgery, and steroid use. METHODS: This was a retrospective single-center study of 226 patients with IBD who completed the maintenance phase of TAXIT, performed at the University Hospitals of Leuven in Belgium. Baseline patient characteristics, laboratory test results, and endoscopic data were obtained at the end of that study between June 2012 and December 2013 (n = 125). Long-term outcome data (IBD-related hospitalization, abdominal surgery, and systemic steroid use) were collected from the time of the last TAXIT study visit (August 2012-April 2013) until April 1, 2016. We also collected data on continued use of infliximab and trough concentrations. RESULTS: At baseline, 91% of patients in the clinic-based dosing group and 90% of patients in the trough concentration-based dosing group had mucosal healing. After a median follow-up time of 41 months (interquartile range, 39-42 mo), infliximab treatment was continued by 81 of 108 patients (75%) from the clinic-based dosing group and 86 of 107 (80%) from the trough concentration-based dosing group. However, within 1 year, infliximab was discontinued by 10 of 27 patients (37%) from the clinic-based dosing group and 2 of 21 patients (10%) from the trough concentration-based dosing group (P = .04). The rates of hospitalization, surgery, and steroid use were below 15% in both groups. CONCLUSIONS: At the end of a trial of clinic-based dosing vs trough concentration-based dosing of infliximab in patients with IBD, most patients had mucosal healing. Most patients (≥75%) in both groups continued taking infliximab for more than 3 years after the trial, but a significantly higher proportion of patients in the clinic-based dosing group discontinued infliximab in the first year after the end of the trial. Both groups had low rates of hospitalization, surgery, and steroid use.

Evidence to Support Monitoring of Vedolizumab Trough Concentrations in Patients With Inflammatory Bowel Diseases.

BACKGROUND & AIMS: Trough concentrations of vedolizumab were found to correlate with clinical response in phase 3 studies of patients with ulcerative colitis (UC) or Crohn's disease (CD). Nevertheless, there are no solid data to support monitoring of vedolizumab trough concentrations in treated patients. We investigated the correlation between vedolizumab exposure and response in a real-world population and aimed to identify patient factors that affect exposure and response. METHODS: We performed a retrospective cohort study of 179 consecutive patients (66 with UC and 113 with CD) who began vedolizumab therapy from September 1, 2015, through October 1, 2016, at University Hospitals Leuven, Belgium. Serum concentrations of vedolizumab were measured before all infusions up to week 30. Effectiveness endpoints included endoscopic healing (UC, Mayo endoscopic sub-score ≤1; CD, absence of ulcers), clinical response (physicians' global assessment), and biologic response or remission (based on level of C-reactive protein) and were assessed at week 14 (for patients with UC) and week 22 (for patients with CD). A stepwise forward addition-backward elimination modeling approach was performed to identify factors independently associated with vedolizumab exposure and response. RESULTS: Vedolizumab trough concentrations >30.0 µg/mL at week 2, >24.0 µg/mL at week 6, and >14.0 µg/mL during maintenance therapy associated with a higher probability of attaining the effectiveness endpoints for patients with UC or CD (P < .05). Higher body mass and more severe disease (based on high level of C-reactive protein and low level of albumin and/or hemoglobin) at the start of vedolizumab therapy associated with lower trough concentrations of vedolizumab over the 30-week period and a lower probability of achieving mucosal healing (P < .05). Mucosal healing was achieved in significantly more patients with UC than patients with CD, even though a diagnosis of UC was not an independent predictor of higher vedolizumab trough concentrations. CONCLUSIONS: In a retrospective study of 179 patients with CD or UC, we observed a correlation between vedolizumab exposure and response. These findings support monitoring of vedolizumab trough concentrations to predict patients' outcome.

Characterization and Application of a Unique Panel of Monoclonal Antibodies Generated against Etanercept.

The clinical response in ankylosing spondylitis (AS) patients treated with biologic agents can be influenced by pharmacokinetic variability among and within these patients. Therapeutic drug monitoring is seen as a valuable tool to improve patient care. The aim of this study was to generate a panel of mAbs toward etanercept (ETN) and to determine ETN and anti-ETN concentrations in AS patients. mAbs against ETN (MA-ETN) were generated using hybridoma technology. For quantification of ETN concentrations, a mAb-based TNF-coated ELISA and a mAb/mAb-based sandwich-type ELISA were developed. For evaluation of the anti-ETN Ab response, a bridging ELISA, as well as a functional cell-based assay, were constructed. Disease activity of the AS patients was measured with the AS Disease Activity Score (ASDAS). Active disease was defined as ASDAS ≥ 2.1. A total of 59 of 76 generated mAbs were ETN specific and were characterized further. Fifty-one mAbs revealed inhibitory properties in a cell-based assay. Analysis of serum concentrations of 21 ETN-treated AS patients with the TNF/MA-ETN68C5-HRP ELISA and the MA-ETN63C8/MA-ETN61C1-HRP ELISA revealed a good Pearson's r (+0.974) but a poor intraclass correlation coefficient (+0.528) as the result of underestimation of the values in the former ELISA. At 24 wk, ETN concentrations were similar in patients with ASDAS < 2.1 and ≥ 2.1. Anti-ETN Abs were not detected in any of the patient samples tested. In conclusion, highly sensitive mAb-based immunoassays were developed for quantification of ETN and anti-ETN concentrations. The impact of these methods needs to be evaluated further in clinical practice.

Immunoassay for Detection of Infliximab in Whole Blood Using a Fiber-Optic Surface Plasmon Resonance Biosensor.

Monitoring the concentration of a therapeutic drug antibody, infliximab (IFX), is recommended for enhancing its efficacy in patients with inflammatory bowel disease (IBD). However, IFX concentrations are currently determined in patients' serum/plasma, which requires sample preparation from blood, hence hampering the turnaround time. In this paper, we present a short immunoassay (10 min) using a fiber-optic surface plasmon resonance (FO-SPR) biosensor for detection of IFX spiked in 100-fold diluted serum, plasma, and whole blood. The calculated limits of detection (LOD) based on calibration curves were 1.42, 1.00, and 1.34 ng/mL, respectively, which coincides with expected IFX concentrations in diluted samples from IBD patients. A linear correlation was established among different matrixes, indicating that the matrix effect was insignificant. The established point-of-care (POC) FO-SPR bioassay was also used to measure IFX in 100-fold diluted extracts of dried blood spots (DBS), and LOD achieved was below 2 ng/mL. Although DBS might be ideal for POC, this is the first report of using an SPR biosensor for measuring DBS samples. Finally, the POC FO-SPR immunoassay was validated by using matching serum and plasma samples from five IBD patients. A Pearson correlation of 0.968 was obtained between serum and plasma samples. IFX concentrations determined with FO-SPR were compared to a clinically validated enzyme-linked immunosorbent assay (ELISA), resulting in excellent Pearson correlation and intraclass correlation coefficient, both being 0.99 for serum and plasma samples. In conclusion, this paper demonstrates that our FO-SPR biosensor can be used as a true POC diagnostic tool for determining IFX concentrations in a variety of matrixes.

Innovative thrombolytic strategy using a heterodimer diabody against TAFI and PAI-1 in mouse models of thrombosis and stroke.

Circulating thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor-1 (PAI-1) are causal factors for thrombolytic failure. Therefore, we evaluated an antibody-engineered bispecific inhibitor against TAFI and PAI-1 (heterodimer diabody, Db-TCK26D6x33H1F7) in several mouse models of thrombosis and stroke. Prophylactic administration of the diabody (0.8 mg/kg) in a thromboplastin-induced model of thromboembolism led to decreased lung fibrin deposition. In a model of cerebral ischemia and reperfusion, diabody administration (0.8 mg/kg, 1 hour postocclusion) led to a mitigated cerebral injury with a 2.3-fold reduced lesion and improved functional outcomes. In a mouse model of thrombin-induced middle cerebral artery occlusion, the efficacy of the diabody was compared to the standard thrombolytic treatment with recombinant tissue-type plasminogen activator (tPA). Early administration of diabody (0.8 mg/kg) caused a twofold decrease in brain lesion size, whereas that of tPA (10 mg/kg) had a much smaller effect. Delayed administration of diabody or tPA had no effect on lesion size, whereas the combined administration of diabody with tPA caused a 1.7-fold decrease in lesion size. In contrast to tPA, the diabody did not increase accumulative bleeding. In conclusion, administration of a bispecific inhibitor against TAFI and PAI-1 results in a prominent profibrinolytic effect in mice without increased bleeding.

The association between etanercept serum concentration and psoriasis severity is highly age-dependent.

The association between etanercept serum concentration and psoriasis disease severity is poorly investigated, and currently etanercept serum concentration monitoring that is aiming to optimize the psoriasis treatment lacks evidence. In this prospective study, we investigated the relation between etanercept exposure and disease severity via measuring etanercept concentrations at five consecutive time points in 56 psoriasis patients. Disease severity assessments included the Psoriasis Area and Severity Index (PASI), body surface area (BSA) and Physician Global Assessment (PGA), and etanercept and anti-etanercept antibody concentrations were determined every 3 months for a period of 1 year. The present study demonstrated that the association between etanercept concentration and psoriasis severity is age-dependent: when patients were stratified into three groups, patients in the youngest age group (-50 years) showed a lower PASI at a higher etanercept concentration (ß = -0.26), whereas patients in the oldest age group (+59 years) showed the opposite trend (ß =0.22). Similar age effects were observed in the relation of etanercept concentration with BSA (P=0.02) and PGA (P=0.02). The influence of age and length of time in therapy on the etanercept concentration-disease severity relation was unaffected by body mass index (BMI) or any other possible confounder. Incidence of anti-etanercept antibodies was low (2%). The age-dependent relation between etanercept serum concentrations is both unexpected and intriguing and needs further investigation.