Infliximab Concentrations Research Articles

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.

Simultaneous quantification and structural characterization of monoclonal antibodies after administration using capillary zone electrophoresis-tandem mass spectrometry

Monoclonal antibodies (mAbs) are demonstrating major success in various therapeutic areas such as oncology and the treatment of immune disorders. Over the past two decades, novel analytical methodologies allowed to address the challenges of mAbs characterization in the context of their production. However, after administration only their quantification is performed and insights regarding their structural evolution remain limited. For instance, clinical practice has recently highlighted significant inter-patient differences in mAb clearance and unexpected clinical responses, without providing alternative interpretations. Here, we report the development of a novel analytical strategy based on capillary zone electrophoresis coupled to tandem mass spectrometry (CE-MS/MS) for the simultaneous absolute quantification and structural characterization of infliximab (IFX) in human serum. CE-MS/MS quantification was validated over the range 0.4–25 µg·mL-1 corresponding to the IFX therapeutic window and achieved a LOQ of 0.22 µg·mL-1 (1.5 nM) while demonstrating outstanding specificity compared to the ELISA assay. CE-MS/MS allowed structural characterization and estimation of the relative abundance of the six major N-glycosylations expressed by IFX. In addition, the results allowed characterization and determination of the level of modification of post-translational modifications (PTMs) hotspots including deamidation of 4 asparagine and isomerization of 2 aspartate. Concerning N-glycosylation and PTMs, a new normalization strategy was developed to measure the variation of modification levels that occur strictly during the residence time of IFX in the patient’s system, overcoming artefactual modifications induced by sample treatment and/or storage. The CE-MS/MS methodology was applied to the analysis of samples from patients with Crohn’s disease. The data identified a gradual deamidation of a particular asparagine residue located in the complementary determining region that correlated with IFX residence time, while the evolution of IFX concentration showed significant variability among patients.

Therapeutic Drug Monitoring of Infliximab in Acute Severe Ulcerative Colitis.

Therapeutic drug monitoring (TDM) is a useful strategy in ulcerative colitis (UC). Nearly a quarter of UC patients will experience acute severe UC (ASUC) in their lifetime, including 30% who will fail first-line corticosteroid therapy. Steroid-refractory ASUC patients require salvage therapy with infliximab, cyclosporine, or colectomy. Fewer data are available for the use of TDM of infliximab in ASUC. The pharmacokinetics of ASUC make TDM in this population more complex. High inflammatory burden is associated with increased infliximab clearance, which is associated with lower infliximab drug concentrations. Observational data support the association between increased serum infliximab concentrations, lower clearance, and favorable clinical and endoscopic outcomes, as well as decreased rates of colectomy. Data regarding the benefit of accelerated or intensified dosing strategies of infliximab-as well as target drug concentration thresholds-in ASUC patients remain more equivocal, though limited by their observational nature. Studies are underway to further evaluate optimal dosing and TDM targets in this population. This review examines the evidence for TDM in patients with ASUC, with a focus on infliximab.

The Impact of Early Optimization of Infliximab Blood Concentrations >1 μg/mL on Therapeutic Effectiveness in Rheumatoid Arthritis

Infliximab is a human-murine chimeric monoclonal IgG antibody against tumor necrosis factor that is used in combination with methotrexate for the treatment of moderate to severe rheumatoid arthritis (RA). The trough concentration of serum infliximab required to control disease activity in RA is ≥1 μg/mL, and we investigated whether this trough concentration can predict the effectiveness of RA treatment. We retrospectively analyzed the cases of 76 patients with RA. The REMICHECK Q® (REMIQ) is a kit that can check for serum infliximab concentrations. Infliximab concentrations >1 μg/mL at 14 weeks after an initial infliximab induction is considered REMIQ-positive, otherwise considered REMIQ-negative. Here, we determined the retention rates and investigated the clinical and serologic features of REMIQ-positive and REMIQ-negative patients. At 14 weeks, significantly more of the REMIQ-positive patients (n = 46) were responders compared to the non-responders (n = 30). The retention rate at 54 weeks was also significantly higher in the REMIQ-positive group versus the negative group. After 14 weeks, more patients in the REMIQ-negative group were considered inadequate responders, and their infliximab doses were escalated. At baseline, the REMIQ-positive group had significantly lower C-reactive protein (CRP) levels compared to the negative group. Cox regression analysis with multiple variables showed that the positivity of REMIQ (hazard ratio [HR] 2.10 and 95% confidence interval [CI]: 1.55-5.71) at baseline was associated with the achievement of low disease activity. The positivities of rheumatoid factor and anti-CCP antibody at baseline were associated with the achievement of remission with infliximab treatment (HR 0.44, 95% CI: 0.09-0.82 and HR 0.35, 95% CI: 0.04-0.48, respectively). The results of this study suggest that the control of RA disease activity may be facilitated by using the REMIQ kit at 14 weeks to check whether it is necessary to increase a patient's infliximab dose to ensure a therapeutic blood concentration that will help the patient achieve low disease activity.

One year of experience with combined pharmacokinetic/pharmacogenetic monitoring of anti-TNF alpha agents: a retrospective study.

Anti-tumor necrosis factor alpha (anti-TNFα) inhibitors are used extensively for the management of moderate to severe inflammatory bowel disease (IBD) in both adult and pediatric patients. Unfortunately, not all patients show anoptimal response to induction therapy, while others lose their response over time for reasons yet poorly understood. We report on a pharmacokinetic/pharmacogenetic approach to monitor the therapy with anti-TNFα in a real-world cohort of seventy-nine pediatric patients affected by IBD that was analyzed retrospectively. We evaluated plasma concentrations of infliximab, adalimumab, and related anti-drug antibodies (ADAs), and single nucleotide polymorphisms (SNPs) in genes involved in immune processes and inflammation on theanti-TNFα response. We found a significant association between the SNP in TNFα promoter (-308G>A) and clinical remission without steroids in patients on infliximab therapy. Additionally, a potential connection between HLA-DQA1*05 genetic variant carriers and a higher risk of anti-TNFα immunogenicity emerged.

Comparison of Immunochemical Reactions of Infliximab Innovator and Biosimilars on an Infliximab Detection Kit Used for Therapeutic Drug Monitoring.

Monitoring serum infliximab (INF) concentrations is crucial for designing appropriate doses for patients with rheumatoid arthritis. It is recommended to maintain the serum trough INF level at least 1.0 µg/mL. In Japan, an in vitro diagnostic kit using immunochromatography has been approved to determine whether the serum INF concentration is over 1.0 µg/mL or not, and to support the determination of the necessity of increasing the dose or switching to another drug. Biosimilars (BS) of INF may have immunochemical properties different from those of its innovator product, which may show different reactivities on the diagnostic kit. In this study, the responses of the innovator and five BS products on the kit were compared. Based on visually comparing the intensity of color development between the test and control samples, differences were found in the judgment results depending on the analyst. In particular, 1.0 µg/mL was not determined as positive in some cases, whereas 2.0 µg/mL was reliably determined as positive. Overall, no significant difference in reactivity was found between the innovator and five BS products. To further compare the differences in immunochemical properties, the reactivity of these products with three enzyme-linked immunosorbent assay (ELISA) kits was compared. The results confirmed that there were no significant differences among the innovator and BS products in reactivity with the examined kits. When using that diagnostic kit, the users need to be aware that the judgement around 1.0 µg/mL INF may differ depending on the test conditions, including the analyst.

Pharmacist-Driven Therapeutic Infliximab Monitoring at the Point of Care Using Rapidly Assessed Drug Levels in Patients with Inflammatory Bowel Disease.

Therapeutic monitoring of infliximab is limited by the time lag between drug-level measurement and dose adjustment, along with the cost of dose escalation. Strategies for dose reduction in stable patients on maintenance infliximab at supratherapeutic levels are uncertain. This study determined the feasibility of a pharmacist-driven strategy for immediate dose adjustment using a sliding scale at the point of care in stable patients with inflammatory bowel disease on maintenance therapy. Adult patients with stable disease undergoing maintenance therapy with infliximab infusions, 5 mg/kg every 8 weeks, were prospectively studied. Trough drug levels were assessed by a rapid assay (and later by ELISA) at all infusions for up to 12 months with immediate but quantitatively small dose adjustment according to a sliding scale targeting a therapeutic range of 3-7 mcg/mL. Disease activity was assessed both clinically and biochemically. The rapid assay and ELISA detected similar infliximab levels, and the strategy added approximately 30 minutes to the duration of infusion events. Only 20% of 48 patients (77% with Crohn disease) had baseline trough infliximab concentrations within the therapeutic range. This value increased 3-fold after 24 and 48 weeks of interventions. One in 2 patients had baseline supratherapeutic levels, and most were brought into the therapeutic range without a discernible impact on disease activity by 1 dose adjustment, but 2 or 3 adjustments were generally needed for 29% of patients with subtherapeutic levels. Overall, drug costs were reduced by 4%. Immediate dose adjustment after infliximab rapid assay performed by a pharmacist using a sliding scale is a feasible strategy. Supratherapeutic infliximab levels can be safely and quickly brought into the therapeutic range using small dose adjustments without affecting disease activity, offsetting (at least partly) costs associated with dose escalation.

Comparison of 3 Enzyme-Linked Immunoassay Methods to Evaluate Serum Concentrations of Infliximab and Antibodies to Infliximab in 32 Patients with Moderate to Severe Inflammatory Bowel Disease.

BACKGROUND Monitoring of trough levels and anti-drug antibodies is important when patients with inflammatory bowel disease (IBD) are treated with anti-TNF biologics due to guided therapeutic decisions. The comparability of 3 ELISA tests for detection of the lowest serum concentration of infliximab (IFX) or antibodies to IFX (ATIs) was evaluated. MATERIAL AND METHODS Two commercial assays for measuring IFX levels were compared with the in-house (UHL) test. ATIs were measured with 1 commercial test and compared to the in-house test. According to the guidelines, IFX levels were within the range of 3 to 7 µg/mL. RESULTS The decision to continue therapy would be the same for 11 out of 16 patients when comparing the apDia Infliximab ELISA and UHL test, and for 12 out of 18 patients when comparing the Lisa-Tracker and in-house UHL test. Linear correlations between the tests were R=0.92 (UHL and apDia), R=0.91 (apDia and Lisa-Tracker), and R=0.89 (UHL and Lisa-Tracker) with P<0.001, respectively. CONCLUSIONS As the IFX levels are important for decisions on further therapy, detectable IFX levels realistically reflect the presence of the drug in the patients' blood and thus control inflammatory activity. The tests were found as comparable and performed well in this aspect and might be used in everyday clinical practice.

P531 A model-based tool for guiding infliximab induction dosing to maximise long-term deep remission in children with inflammatory bowel diseases

Abstract Background Adequate infliximab (IFX) concentrations during induction treatment are predictive for deep remission (corticosteroid-free clinical and endoscopic remission) at six months in children with Crohn’s disease (CD) and ulcerative colitis (UC).1 Under standard IFX induction dosing, children often have low IFX trough concentrations.2 Model-informed precision dosing (MIPD) is advocated as a promising IFX dosing strategy. We aimed to develop and validate an MIPD framework for guiding paediatric IFX induction treatment. Methods Data from 31 children (4-18 years, 15-76 kg, 20:11 CD:UC) receiving standard IFX induction dosing (5 mg/kg at week [w]0, w2, and w6) were repurposed.1 Eight paediatric population pharmacokinetic models were evaluated (six 2-compartment models and two 1-compartment models). Modelling and simulation were used to identify exposure targets, an optimal sampling strategy, and to develop a multi-model prediction algorithm for implementation into an MIPD software tool.3 A role for IFX clearance monitoring was evaluated. Results A total of 251 IFX concentrations were available (6-10 samples per patient). One patient had undetectable IFX concentrations at w6 and w12 but had no measurable antibodies to IFX (ATI). At six months after start of the IFX treatment, 58% (18/31) of patients achieved deep remission. The measured IFX concentration at w12 was the best predictor and classifier for deep remission. A 7.5 mg/L IFX concentration target at w12 was associated with a 64% probability of deep remission at six months (Figure 1). With standard dosing, less than 80% of simulated children &amp;lt;40 kg attained this target (Figure 2). Immunomodulator combo-therapy only subtly improved probability of target attainment. Presence of ATI lowered the target attainment considerably. The w12 target was most accurately and precisely achieved by implementing MIPD at w6 using the w6 IFX concentration. The multi-model algorithm outperformed single models when optimising the w6 dose based on combined w2 and w4 concentrations. MIPD using only the w2 concentration resulted in biased and imprecise predictions. The predictive performance of the MIPD multi-model algorithm was robust to misspecification of ATI status. IFX clearances at w6 and w12 were predictive for deep remission (P=0.02) (Figure 3). An IFX module was added to the TDMx software tool to facilitate MIPD and clearance monitoring (https://tdmx.shinyapps.io/Infliximab_paediatric/). Conclusion A freely available, interactive, multi-model MIPD software tool is provided to facilitate IFX induction dosing and improve deep remission rates in children with CD and UC. 1van Hoeve et al. J Pediatr 2022. 2van Rheenen et al. J Crohns Colitis 2020. 3Kantasiripitak et al. CPT:PSP 2022.

P149 Novel capillary blood point-of-care test for adalimumab and infliximab trough levels: Effects of abnormal blood conditions on the test result

Abstract Background Patients suffering from inflammatory bowel disease can be treated with the biologics adalimumab (ADL) or infliximab (IFX). Previous studies demonstrated the usefulness of therapeutic drug monitoring (TDM) to adjust the patient’s biologic concentration individually. Commercially available rapid assays support laboratories in the fast and easy detection of ADL and IFX concentrations but the assays’ dependency on serum as analyte matrix is a general hindrance for TDM, as serum preparation from whole blood is time-consuming and requires laboratory equipment. Patients and clinicians would thus benefit from rapid point-of-care (POC) and easy to use assays that are independent of laboratory equipment. The objective of this project was to expand existing serum lateral flow assays for the analysis of ADL or IFX in capillary blood and investigate potential interactions resulting from the blood matrix. Methods ADL and IFX lateral flow serum kits were optimized in such a way that both, capillary blood and EDTA whole blood can be used as analyte matrix by using disposable capillaries for blood collection and for its transfer into dropper bottles that are prefilled with chase buffer. To measure ADL or IFX levels with a POC lateral flow test cassette reader (BÜHLMANN Quantum Blue® Reader) the mixture is then applied on an ADL or IFX lateral flow test cassette. Matrix agreement studies were performed to compare spiked EDTA whole blood and capillary blood samples with serum as reference. Additionally, spiked EDTA whole blood samples were treated to obtain three abnormal blood conditions: Icteric, hemolytic and lipemic blood. Bias in results exceeding 30% relative difference to the untreated sample was considered as an interference. Results Spiked blood samples showed good agreement with reference serum samples. A bias of less than 15% at the clinical decision points for ADL (5 µg/mL and 12 µg/mL) and IFX (3 µg/mL and 7 µg/mL) was revealed. Observed relative differences between all tested abnormal blood conditions ranged between -20% and +26% for IFX and -16% and +5% for ADL. Conclusion Two POC assays for the determination of ADL or IFX in capillary blood or EDTA whole blood samples were successfully developed and can be used by healthcare professionals with time to results of only 15 minutes and without the need for additional laboratory equipment. No systematic interferences were detected with treated EDTA whole blood samples, which could appear when using blood as analyte matrix. The excellent agreement to serum trough levels shows that the POC adalimumab/infliximab capillary blood assays are ideal for therapeutic drug monitoring analysis at a clinician’s office or an infusion site.

P701 A time-to-event model relating infliximab trough concentrations to the risk of relapse after extending the infusion interval

Abstract Background Extending the infliximab infusion interval has been attempted in patients with Crohn’s disease (CD) and ulcerative colitis (UC) who sustained treatment response following an earlier interval shortening. We aimed to identify predictors of sustained remission after infliximab interval extension. Methods: Data from 30 adult patients (17 CD, 13 UC), who underwent infliximab interval extension following earlier interval shortening, were collected from a single-centre database search. All patients were in steroid-free clinical (two-item patient-reported outcome [PRO2] ≤1 [UC] and ≤8 [CD]) and biological (C-reactive protein [CRP] &amp;lt;5 mg/L or faecal calprotectin [FC] &amp;lt;250 mg/kg) remission at interval extension. Time-to-relapse was modelled using a time-to-event (TTE) model with loss of steroid-free clinical and biological remission being the event of interest (NONMEM7.5). Various hazard functions were explored, and disease type, time-varying infliximab concentrations and infliximab clearance were investigated as predictors of the relapse hazard risk. The infliximab clearance was calculated using weighted averaging of the estimates of 18 population pharmacokinetics models.1 Results In total, 37% of patients (n=11) remained relapse-free until one year after infliximab interval extension (Figure 1). A time-constant (exponential) hazard model proved best to describe the relapse data of patients with CD (Figure 2, Table 1). The Gompertz hazard model best described the data of patients with UC, with the relapse hazard risk increasing over time. Patients with CD had an overall higher relapse hazard risk than patients with UC. For patients with UC, the infliximab trough concentration was negatively related to the relapse hazard risk and was included in the model using a sigmoidal inhibitory Emax function. Also, in patients with UC, a higher infliximab clearance was associated with an increase in the relapse risk. The infliximab clearance was also a predictor of the relapse hazard risk, but its effect could not be precisely estimated. Conclusion Patients with CD had a higher relapse risk than patients with UC. Only in patients with UC, the hazard risk increased with time, but this risk was lower when the infliximab trough concentration increased. No exposure-response relationship was observed in patients with CD. Results of this exploratory analysis should be interpreted with care and prospective confirmation is awaited (MODIFI study; NCT04982172).2 1Kantasiripitak W. et al. CPT PSP. 2022 2Sheiner LB. et al. CPT. 1997

A Model-Based Tool for Guiding Infliximab Induction Dosing to Maximize Long-term Deep Remission in Children with Inflammatory Bowel Diseases.

Adequate infliximab concentrations during induction treatment are predictive for deep remission [corticosteroid-free clinical and endoscopic remission] at 6 months in children with inflammatory bowel diseases [IBD]. Under standard infliximab induction dosing, children often have low infliximab trough concentrations. Model-informed precision dosing [MIPD; i.e. model-based therapeutic drug monitoring] is advocated as a promising infliximab dosing strategy. We aimed to develop and validate an MIPD framework for guiding paediatric infliximab induction treatment. Data from 31 children with IBD [4-18 years] receiving standard infliximab induction dosing (5 mg/kg at week [w]0, w2 and w6) were repurposed. Eight paediatric population pharmacokinetic models were evaluated. Modelling and simulation were used to identify exposure targets, identify an optimal sampling strategy, and develop a multi-model prediction algorithm for implementation into an MIPD software tool. A role for infliximab clearance monitoring was evaluated. A 7.5 mg/L infliximab concentration target at w12 was associated with 64% probability of deep remission at 6 months. With standard dosing, less than 80% of simulated children <40 kg attained this target. The w12 target was most accurately and precisely achieved by implementing MIPD at w6 using the w6 infliximab concentration [rapid assay required]. The multi-model algorithm outperformed single models when optimizing the w6 dose based on both w2 and w4 concentrations. MIPD using only the w2 concentration resulted in biased and imprecise predictions. Infliximab clearances at w6 and w12 were predictive for deep remission. A freely available, multi-model MIPD tool facilitates infliximab induction dosing and improves deep remission rates in children with IBD.

Combination Therapy With Immunomodulators Improves the Pharmacokinetics of Infliximab But Not Vedolizumab or Ustekinumab

Background and AimsThe aim of this study was to assess how 6-thioguanine nucleotide (6-TGN) levels and use of oral methotrexate relate to the pharmacokinetics of biologics. MethodsThis was a prospective cohort study including patients with inflammatory bowel diseases on maintenance doses of infliximab, vedolizumab, or ustekinumab on monotherapy or combination with a thiopurine or oral methotrexate. We collected 6-TGN concentrations, biomarker levels, and clinical and endoscopic disease activity. The primary outcomes were infliximab, vedolizumab, and ustekinumab concentrations as well as anti-drug antibodies (ADAs). ResultsA total of 369 patients were recruited (113 infliximab, 133 vedolizumab, and 123 ustekinumab). Patients with 6-TGN levels ≥146 pmol per 8 × 108 red blood cells (RBCs), and those receiving combination therapy with thiopurine or oral methotrexate had significantly higher infliximab concentrations when compared with monotherapy (median levels of 17.4 μg/mL on thiopurine with 6-TGN ≥146 pmol per 8 × 108 RBCs, 17.1 on methotrexate, and 3.9 on infliximab monotherapy; P = .001 for both comparisons). However, there was no association between the use of immunomodulators and 6-TGN concentrations with vedolizumab (median levels of 8.8 on thiopurine with 6-TGN ≥152 pmol per 8 × 108 RBCs, 6.8 on methotrexate, and 10.5 on vedolizumab monotherapy; P > .05 for both comparisons) or ustekinumab median concentrations (median levels of 5.0 on thiopurine with 6-TGN ≥154 pmol per 8 × 108 RBCs, 5.2 on methotrexate and 7.0 on ustekinumab monotherapy; P > .05 for both comparisons). Fourteen (12%) patients had anti-infliximab antibodies, while 1 patient had ADAs in each of the other drug cohorts. ConclusionsAchieving higher 6-TGN levels or the use of methotrexate improved the pharmacokinetics of infliximab. Conversely, these data do not support the use of combination therapy to augment pharmacokinetics with vedolizumab or ustekinumab.

S725 linical Utility of Precision-Guided Dosing Tool for Infliximab During Maintenance Therapy of Inflammatory Bowel Disease

Introduction: A precision-guided dosing tool that uses Bayesian data assimilation was developed to forecast Infliximab (IFX) exposure. Our objective was to establish the utility of the tool in clinical decision making during IFX maintenance therapy when used reactively, to address inadequate disease control that results from suboptimal exposure, and proactively, to sustain exposure commensurate with disease remission in inflammatory bowel disease (IBD). Methods: Blood specimens were collected, anytime beyond 20 days after a prior infusion in a prospective study (EMPOWER). Pharmacokinetic (PK) testing was conducted at Prometheus Laboratories (San Diego, CA). Serum IFX, antibodies to IFX (ATI) and albumin concentrations were all imputed with dosing regimen and weight in a Bayesian data assimilation tool to produce individualized PK profiles that forecasted IFX concentration and time to trough concentration below pre-specified thresholds (e.g., < 10 µg/mL). Forecasted exposure at various dosing regimens was also provided. Physician’s global assessment of disease activity was collected with the decision to change IFX dosing that resulted from PK test results. Statistical analysis consisted of Mann-Whitney and Fisher Exact test as appropriate. Results: A total of 111 patients were assessed by 21 physicians. A change in IFX dose regimen was initiated in 51 patients (46%). Inadequate exposure and forecasted IFX levels below 10 µg/mL associated with dose intensification (76%, median IFX 6.3 µg/mL) (p< 0.01), with lower remission rate (23.5%) achieved in that group as compared to two other groups having better disease control and PK profiles (p< 0.001) (Table). Forecasted IFX levels below 10 µg/mL were associated with 4-fold higher likelihood of active disease (OR=4.1; 95%CI: 1.7-9.4) as compared to IFX levels above 10 µg/mL (p< 0.01). Time to trough below 10µg/mL was shorter in active disease (median: 46 days, IQR: 32-59) than in remission (median 57 days, IQR: 48-69) (p< 0.001). As presented in Figure, dose intensification using a 5 mg/kg every 4 weeks dosing regimen forecasted 2.3-fold higher IFX levels as compared to a 10 mg/kg every 8 weeks dosing regimen (median of 17.1 vs 7.4 µg/mL, respectively) (p< 0.001). Similar results were observed among patients presenting with disease remission. Conclusion: Our study suggests that the precision-guided dosing tool provides clinical utility and helps with dose adjustments in both interval changes as well as dose intensification.Figure 1.: Forecasted IFX Exposure at various dose and interdose intervals, given the individual PK parameters Table 1. - Patient Characteristics (n=111), by treatment intervention based on test results Variable IFX Dose RegimenReductionN=17 IFX Dose RegimenContinuationN=60 IFX Dose RegimenIntensificationN=34 OverallPopulationN=111 Patient Characteristics Age (years) 16 (14-19) 32 (18-45) 32 (17-46) 26 (16-44) Female (%, n/N) 44.1% (7/17) 43.3% (26/60) 44.1% (15/34) 43.2% (48/111) CD/UC/Indeterminate 13/3/1 36/15/8 22/9/3 71/27/12 Weight (Kg) 64 (43-76) 71 (61-92) 69 (61-92) 70 (60-84) Dose mg/Kg 10.0 (9.0-10.4) 8.2 (5.0-10.0) 5.5 (5.0-10.0) 8.0 (5.1-10.0) Interdose interval (weeks) 6 (5-8) 8 (6-8) 8 (6-8) 8 (6-8) PGA Remission Status, remission (%, n/N) 70.6% (12/17) 41.7% (25/60) 23.5% (8/34) 40.5% (45/111) Clinical PK Measurements Measured IFX levels (µg/mL) 23.3 (17.2-28.5) 12.9 (7.2-20.6) 8.0 (5.2-14.7) 12.5 (7.2-20.9) ATI status (%, n/N) 0% (0/17) 10.0% (6/60) 11.8% (4/34) 9.0% (10/111) Albumin (g/dL) 4.1 (4.0-4.3) 4.0 (3.6-4.2) 3.9 (3.7-4.2) 4.0 (3.7-4.2) Clearance (L/day) 0.19 (0.15-0.22) 0.27 (0.20-0.33) 0.28 (0.22-0.35) 0.25 (0.19-0.31) Time to Trough < 10 µg/mL (weeks) 11 (10-12) 7 (6-9) 6 (4-7) 7 (6-9) Forecasted Trough (µg/mL) 26.2 (20.1-34.5) 12.7 (8.6-17.6) 6.3 (3.1-9.4) 11.6 (6.5-19.5) Forecasted Trough < 10 µg/mL 0% (0/17) 31.7% (19/60) 76.5% (26/34) 40.5% (45/111)

S824 Cost-Effectiveness of Precision-Guided Dosing in Adult Crohn’s Disease Patients Initiating Infliximab Maintenance Therapy

Introduction: Crohn’s disease (CD) patients that lose response to biologics experience reduced quality of life (QoL) and costly hospitalizations. Precision-guided dosing provides clinicians with a comprehensive pharmacokinetic (PK) profile that allows for the next biologic dose to be personalized. We analyzed the cost-effectiveness of infliximab (IFX) Precision-guided dosing relative to two IFX dose intensification strategies (DIS). Methods: We developed a hybrid (Markov and decision tree) model of CD patients who had a clinical response to IFX induction and entered IFX maintenance in “remission” or “mild symptoms” health states. The analysis took a US payer perspective, a time horizon of 2 years in the base case, and a cycle length of 4 weeks. There were 3 comparators for IFX dosing: Precision-guided dosing, dose intensification based on symptoms, inflammatory markers, and trough IFX concentration (DIS1), and IFX dose intensification based on symptoms alone (DIS2). Patients that failed IFX initiated ustekinumab (UST), followed by vedolizumab, and conventional therapy. Transition probabilities for IFX were estimated from real-world clinical PK data and interventional clinical trial (PMID: 34978325; 29317275) patient-level data. All other transition probabilities were derived from published randomized clinical trials and cost-effectiveness analyses. Utility values were sourced from previous health technology assessments. Direct costs included biologic acquisition and infusion, surgeries and procedures, conventional therapy, and lab testing. The primary outcomes were total discounted costs, total quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios (ICERs). The robustness of results was assessed via one-way sensitivity and scenario analyses. Results: Total costs and QALYs at 2 years are presented in Table. The ICERs of Precision-guided dosing relative to DIS1 and DIS2 were 171,810 and 127,990, respectively. One-way sensitivity analyses (Figure) demonstrated that the cost-effectiveness of Precision-guided dosing was most sensitive to the time between IFX doses. Precision-guided dosing had the lowest proportion of patients requiring a new biologic through 2 years (0.5% vs 2.4% and 27.7% for DIS1 and DIS2, respectively). Conclusion: Precision-guided dosing provides substantial clinical and QoL benefits for adult CD patients by maintaining clinical remission and avoiding IFX failure; it is cost-effective relative to other DISs at a WTP of $175,000/QALY.Figure 1.: Precision-guided Dosing ICER Relative to DIS2 † Varied by ±10% * Varied by ±5% CD: Crohn's disease, DIS: dose intensification strategy, ICER: incremental cost-effectiveness ratio, IFX: infliximab, M-S: moderate-severe, PMPM: per member per month, Rem: remission Table 1. - Base Case Results (2-year Horizon Discounted) DIS Total QALYs Total Costs ICER Relative to Precision-guided Dosing ICER Relative to DIS1 ICER Relative to DIS2 Incremental NMB vs DIS1 (WTP $150,000/QALY) Incremental NMB vs DIS1 (WTP $50,000/QALY) Incremental NMB vs DIS2 (WTP $150,000/QALY) Incremental NMB vs DIS2 (WTP $50,000/QALY) Precision-guided Dosing* 1.572 $50,753 - 171,810 127,990 -$765 -$4,274 $1,816 -$6,436 DIS1† 1.537 $44,725 171,810 - 95,581 - - $2,581 -$2,162 DIS2 ‡ 1.489 $40,191 127,990 95,581 - -$2,581 $2,162 - - DIS: dose intensification strategy, ICER: incremental cost-effectiveness ratio, NMB: net monetary benefit, QALY: quality-adjusted life year, WTP: willingness to pay.*Model informed precision dosing with homogenous mobility shift assay (Prometheus Laboratories).†Dose intensification based on a combination of symptoms, inflammatory markers and proactive therapeutic drug monitoring. Corresponds to cohorts 1 and 2 of the TAILORIX clinical trial.‡Dose intensification reactive on symptoms only. Corresponds to cohort 3 of the TAILORIX clinical trial.

Cytokine Profile at Diagnosis Affecting Trough Concentration of Infliximab in Pediatric Crohn's Disease.

Background: This study aims to measure the concentration of cytokines produced during the inflammation process to investigate if there are any differences in response to treatment of pediatric Crohn’s disease and to determine if the initial tumor necrosis factor-alpha (TNF-α) level affected the trough concentration of infliximab (IFX). Methods: This study included 30 pediatric patients with moderate-to-severe Crohn’s disease. At the time of diagnosis, blood samples were collected for the measurement of cytokines (IL-6, TNF-α, IL-17A, and IL-10). Blood samples were extracted from patients who had begun IFX treatment to measure the IFX trough concentration immediately before the fourth dose administration. Results: All cytokines (TNF-α, IL-6, IL-10, and IL-17A) were significantly higher in patients who did not achieve clinical or biochemical remission than in those who did (p = 0.027, 0.006, 0.017, 0.032, respectively). TNF-α had a negative correlation with the IFX trough concentration (Pearson coefficient = −0.425, p = 0.034). The diagnostic capability of the initial TNF-α concentration to predict under the therapeutic IFX trough concentration, defined as less than 3 µg/mL, had an area under the receiver operating characteristic of 0.730 (p = 0.049). The TNF-α concentration was set at 27.6 pg/mL as the cutoff value. Conclusions: Measuring cytokines at the time of diagnosis can be used to predict the treatment response. Measuring the initial TNF-α concentration may help to predict the treatment response to IFX. When the initial TNF-α concentration is greater than 27.6 pg/mL, a higher dose of IFX may be more appropriate than routinely administering 5 mg/kg of IFX to maintain the therapeutic concentration.

Decreased Infliximab Concentrations in Patients With Inflammatory Bowel Disease Who Carry a Variable Number Tandem Repeat Polymorphism in the Neonatal Fc Receptor or Variant HLADQA1*05G>A Genotype.

Multiple variables contribute to variation in patient exposure and response to tumor necrosis factor alpha antagonist biologics such as infliximab. This study aimed to assess the association between maintenance-phase infliximab concentrations and genetic variation in HLADQA1*05G>A and fragment crystallisable (Fc) fragment of IgG receptor and transporter (FCGRT) among patients with inflammatory bowel disease. A cross-sectional study was carried out in participants with inflammatory bowel disease prescribed infliximab who were in the maintenance phase of treatment. Participants were genotyped for the presence of the FCGRT variable number tandem repeat (VNTR) and HLADQA1*05G>A (rs74291249). A point estimate of the infliximab trough concentration during the maintenance phase was determined using a standard enzyme-linked immunosorbent assay for each patient. Other variables associated with infliximab pharmacokinetics were collected. A total of 156 participants with inflammatory bowel disease were included from 2 tertiary care centers affiliated with Western University, London, Canada. Median infliximab trough concentrations were lower in participants who carried the FCGRT VNTR 2/3 or 2/2 (4.14 µg/mL; interquartile range [IQR], 6.48 µg/mL) vs wild type individuals (7.00 µg/mL; IQR, 7.66; P = .0027). Median infliximab trough concentrations were significantly lower in participants who were HLADQA1*05G>A variant carriers (4.73µg/mL; IQR, 4.79) vs wild type individuals (7.85µg/mL; IQR, 7.44; P = .0006). A significant decrease in infliximab trough concentrations was seen in individuals who were dual carriers of variant polymorphisms in HLADQA1*05G>A and FCGRT VNTR (no variants, 8.96µg/mL; IQR, 6.84 vs one variant, 4.96 µg/mL; IQR, 4.95 vs dual variants, 0.86µg/mL; IQR, 5.82). FCGRT VNTR and HLADQA1*05G>A are associated with lower maintenance-phase infliximab concentrations, particularly among patients who carry both variants.

Higher serum infliximab concentrations during induction predict short-term endoscopic response in patients with inflammatory bowel disease.

Measuring of serum infliximab (IFX) induction concentrations might reduce primary non-response rates in inflammatory bowel diseases (IBD), but optimal target concentrations are unclear. We investigated whether IFX induction concentrations predict short-term endoscopic response at week 12 or treatment persistence at week 52. Sixty-nine IBD patients (Crohn's disease, n=24; ulcerative colitis, n=45) received standard IFX induction of 5 mg/kg bodyweight at weeks 0, 2, and 6. Responders continued maintenance therapy and underwent follow-up until week 52 or treatment discontinuation. We measured IFX concentrations at weeks 2, 6, and 12, and evaluated treatment response around week 12 with endoscopy or with clinical scores and fecal calprotectin. Using the receiver operating characteristic analysis, we determined optimal IFX concentration thresholds associated with treatment response. We further compared IFX induction concentrations between patients persisting on IFX at week 52 and patients discontinuing treatment due to insufficient response. Responders (74%, 51 out of 69 patients) had significantly higher median IFX concentrations than non-responders at weeks 6 (25.06 vs. 19.68 µg/ml; P = 0.04) and 12 (18.03 vs. 10.02 µg/ml; P = 0.03), but not at week 2 (33.12 vs. 34.20 µg/ml; P = 0.97). Optimal IFX concentration thresholds for induction response were 21.33 and 5.13 µg/ml at weeks 6 and 12, respectively. Fifty-three patients continued IFX maintenance therapy until week 52. Induction concentrations failed to predict persistence on IFX therapy at week 52. Higher IFX induction concentrations predict endoscopic short-term response. However, induction concentrations failed to predict long-term persistence on IFX treatment.

Atomic Force Microscopy Application for the Measurement of Infliximab Concentration in Healthy Donors and Pediatric Patients with Inflammatory Bowel Disease.

The use of infliximab has completely changed the therapeutic landscape in inflammatory bowel disease. However, despite its proven efficacy to induce and maintain clinical remission, increasing evidence suggests that treatment failure may be associated with inadequate drug blood concentrations. The introduction of biosensors based on different nanostructured materials for the rapid quantification of drugs has been proposed for therapeutic drug monitoring. This study aimed to apply atomic force microscopy (AFM)-based nanoassay for the measurement of infliximab concentration in serum samples of healthy donors and pediatric IBD patients. This assay measured the height signal variation of a nanostructured gold surface covered with a self-assembled monolayer of alkanethiols. Inside this monolayer, we embedded the DNA conjugated with a tumor necrosis factor able to recognize the drug. The system was initially fine-tuned by testing known infliximab concentrations (0, 20, 30, 40, and 50 nM) in buffer and then spiking the same concentrations of infliximab into the sera of healthy donors, followed by testing pediatric IBD patients. A good correlation between height variation and drug concentration was found in the buffer in both healthy donors and pediatric IBD patients (p-value < 0.05), demonstrating the promising use of AFM nanoassay in TDM.

Quantification of infliximab and adalimumab in human plasma by aliquid chromatography tandem mass spectrometrykitand 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 inflammatorybowel disease. Methods & results: The mAbXmise method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was linear from 2 to 100μg/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 thein-house ELISA (-6.1 vs -1.8μg/ml, respectively). The mean bias between theLC-MS/MS assay and in-house ELISA was -1.2μg/ml for adalimumab (n=35). Conclusion: The LC-MS/MS method is a powerful alternative to immunoassays to monitor concentrations of infliximab and adalimumab.