Infliximab and adalimumab drug levels in Crohn's disease: contrasting associations with disease activity and influencing factors

Evaluation of infliximab-induced genotoxicity and possible action on BCL-2 and P53 genes

Although the last pandemic created an urgency for development of vaccines, there was a continuous and concerted effort to search for therapeutic medications among existing drugs with different indications. One of the medications of interest that underwent this change was infliximab (IFM). This drug is used as an anti-inflammatory, predominantly in patients with Crohn 's disease, colitis ulcerative, and rheumatoid arthritis. In addition to these patients, individuals infected with Coronavirus Disease (COVID-19) were administered this chimeric monoclonal antibody (IMF) to act as an immunomodulator for patients in the absence of comprehensive research. Consequently, the present study aimed to examine the genotoxic effects attributed to IFM treatment employing different assays in vivo using mouse Mus musculus. Therefore, IFM was found to induce genotoxic effects as evidenced by the comet assay but did not demonstrate genotoxic potential utilizing mouse bone marrow MN test. The results of evaluating the expression of the P53 and BCL-2 genes using RT-qPCR showed stimulation of expression of these genes at 24 hr followed by a decline at 48 hr. Although the comet assay provided positive results, it is noteworthy that based upon negative findings in the micronucleus test, the data did not demonstrate significant changes in the genetic material that might affect the therapeutic use of IFM. The stimulation of expression of P53 and BCL-2 genes at 24 hr followed by a decline at 48 hr suggest a transient, if any, effect on genetic material. However, there is still a need for more research to more comprehensively understand the genotoxic profile of this medication.

6-Thioguanine nucleotide levels are associated with infliximab but not adalimumab levels in inflammatory bowel disease patients on combination therapy

BACKGROUND

Thiopurine co-therapy with anti-tumour necrosis factor-alpha (anti-TNFα) agents is associated with higher anti-TNFα drug levels and reduced immunogenicity in inflammatory bowel disease (IBD).

AIMS

We aimed to evaluate the association between 6-thioguanine nucleotide (6-TGN) and anti-TNFα levels and the optimal 6-TGN threshold level associated with higher anti-TNFα levels in combination therapy.

METHODS

We performed a retrospective cross-sectional multicentre study of patients with IBD on combination anti-TNFα and thiopurine maintenance therapy between January 2015 and August 2021. Primary outcomes were infliximab and adalimumab levels. Secondary outcomes were antibodies to infliximab (ATI) or adalimumab (ATA). Univariable and multivariable linear regression were performed to identify variables associated with anti-TNFα levels. Receiver operator characteristic curves were used to define the optimal 6-TGN cut-off levels associated with therapeutic anti-TNFα levels.

RESULTS

The study included 743 paired 6-TGN and anti-TNFα levels (640 infliximab and 103 adalimumab). 6-TGN levels were associated with infliximab levels, but not adalimumab levels, on univariable and multivariable regression. The optimal 6-TGN cut-off associated with therapeutic infliximab levels (≥5 mcg/mL) was 261 pmol/8 × 108 red blood cell (RBC) (area under the curve (AUC) = 0.57) for standard infliximab dosing and 227.5 pmol/8 × 108 RBC (AUC = 0.58) for escalated dosing. For therapeutic adalimumab levels (≥7.5 mcg/mL), the 6-TGN cut-off was 218.5 pmol/8 × 108 RBC (AUC = 0.59) for standard adalimumab dosing and 237.5 pmol/8 × 108 RBC (AUC = 0.63) for escalated dosing.

CONCLUSION

6-TGN levels were weakly associated with infliximab but not adalimumab levels in combination therapy. 6-TGN levels in the lower end of the therapeutic range (230-260 pmol/8 × 108 RBC) may be adequate to maintain higher infliximab levels, particularly with escalated infliximab dosing.

What are the benefits of therapeutic drug monitoring in the optimization of adalimumab therapy? a systematic review and meta-analysis up to 2022

Aims

Persistent uncertainties exist surrounding the therapeutic drug monitoring (TDM) of adalimumab in clinical settings. To address these issues, we conducted a systematic review to assess the current evidence regarding the benefits of TDM for adalimumab.

Methods

PubMed, EMBASE, and Cochrane Databases were searched from inception to October 2022. The trials regarding to the list three key questions were considered: 1) Could routine proactive TDM assist in improving outcomes in patients receiving adalimumab? 2) Could reactive TDM assist in guiding subsequent treatment strategies for patients with treatment failure to adalimumab? 3) Could TDM assist in informing dose reduction or discontinuation in patients with low disease activity or in remission treated with adalimumab? Two reviewers independently selected the studies and extracted the data. Meta-analysis was performed to calculate the relative risk (RR) and 95% confidence interval (CI).

Results

A total of 9 studies was included in this review. For proactive TDM, meta-analysis indicated that proactive TDM (n = 163/257, 63.42%) showed no significant superiority over reactive TDM and/or conventional management (n = 336/606, 55.44%) in achieving and/or maintaining clinical remission by random effects model (RR: 1.24, 95% CI 0.98-1.58, I 2 = 73%). There were three studies that supporting the reactive TDM, low drug levels in the absence of anti-drug antibodies (ADA) strongly indicate the need for dose intensification, and infliximab is a feasible choice for patients with low drug levels and ADA positivity. While swapping to another class should be considered in patients with adequate drug levels. In addition, TDM can help clinicians optimize dosing schedules and prevent overtreatment in patients who have achieved low disease activity and sufficient drug concentrations, with no predictive value for successful adalimumab discontinuation.

Conclusion

Current evidence suggests that proactive TDM is numerically but not statistically significant superiority over reactive TDM and/or conventional management. Reactive TDM can aid in understanding treatment failure and developing subsequent therapy. For patients reaching low disease activity and remission, TDM can help successful dose reduction, while it cannot inform the successful drug discontinuation. However, existing trials are limited, and more well-designed trials are necessary to clarify the role of TDM in adalimumab treatment.

Development and validation of a novel therapeutic drug monitoring-based nomogram for prediction of primary endoscopic response to anti-TNF therapy in active Crohn's disease

Background

Anti-tumor necrosis factor (TNF) monoclonal antibodies, especially infliximab (IFX) and adalimumab (ADA), are considered the first-line treatment for active Crohn's disease (CD). However, the predictive role of therapeutic drug monitoring (TDM) of serum anti-TNF in monitoring the treatment of inflammatory bowel disease (IBD) remains controversial.

Objectives

To explore the correlation between serum anti-TNF levels and early endoscopic response in active CD using a TDM-based nomogram.

Design

Cross-sectional study.

Methods

The simplified endoscopic activity score for CD (SES-CD), Crohn's disease activity index (CDAI), laboratory parameters, and the serum trough levels of IFX and ADA were assessed.

Results

The trough levels of IFX or ADA were significantly higher in patients with endoscopic response compared to non-responders in the development cohort (p < 0.001). The IFX and ADA levels showed a weak but significantly negative correlation with SES-CD (p < 0.001), CDAI (p < 0.001), and C-reactive protein (CRP) (p < 0.001) at week 14 post-IFX therapy in the development cohort. Furthermore, the receiver operating characteristic curve revealed that an optimal level of IFX (4.80 μg/mL) and ADA (8.80 μg/mL) exhibited the best performance in predicting endoscopic response. Concomitantly, we developed a novel nomogram prediction model based on the results of multivariate logistic regression analysis, which consisted of CRP, albumin (Alb), and anti-TNF trough levels at week 14. The nomogram showed significant discrimination and calibration for both IFX and ADA in the development cohort and performed well in the external validation cohort.

Conclusion

This study demonstrates a robust association between serum concentrations of IFX, ADA, Alb, and CRP and primary endoscopic response in active CD patients. Importantly, the TDM- and laboratory marker-based nomogram may be used to evaluate the primary endoscopic response to anti-TNF therapy, especially for optimizing treatment strategies and switching therapy in CD patients.

The perceived waning of biologics in severe asthma

BACKGROUND

Biologics are highly effective in severe asthma and used at fixed dosing intervals. However, in clinical practice, dosing intervals are sometimes shortened if patients perceive a decreased biologic effect before the next administration. The occurrence and clinical relevance of this perceived waning of biological effect is unknown.

OBJECTIVE

To explore (1) the frequency, severity and conditions, (2) associated symptoms and (3) relationship with clinical characteristics of the patient-perceived waning effect of biologics before the next administration.

METHODS

Severe asthma patients receiving biological treatment ≥4 months were included. Based on 17 semi-structured patient interviews, we developed a questionnaire focusing on the waning effect of biologics before the next administration, which was distributed among 129 patients. Clinical characteristics, including asthma control (ACQ) and quality of life (AQLQ) scores, were collected from patient files.

RESULTS

65/101 patients who completed the questionnaire reported a waning of biological effect, graded as severe (median (IQR) 6.5 (5-7.5) on a 0-10 BORG-scale). Waning manifested in a broad spectrum of symptoms. Patients reporting waning had higher ACQ and lower AQLQ scores versus those without (p < 0.05) and higher BORG-scores were associated with higher exacerbation rate (ρ = 0.309, p = 0.013). A third of all patients were in favor of extending or shortening their dosing interval.

CONCLUSION

Two-thirds of severe asthma patients report waning of biologic effect at the end of the dosing interval, which is associated with poorer asthma control and quality of life. The diversity in observed waning of effect opens the way for research into more individualized dosing of biologics.

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.

Association between genetic variants and development of antibodies to infliximab: A cross-sectional study in Chinese patients with Crohn's disease

Aims: Genetic variants increase the susceptibility to anti-drug antibodies (ADA) in response to anti-TNF therapy in chronic inflammatory diseases. However, little is known about genetic variants in Chinese populations. This study aimed to identify genetic variants contributing to the risk of the development of antibodies to infliximab (ATI) in Chinese patients with Crohn's disease (CD). Methods: CD patients (n = 104) treated with infliximab (IFX) during the maintenance therapy were enrolled in this cross-sectional study. ATI was assessed by an in-house developed drug-tolerant ELISA method. ATI titers of 1:20 and ≥1:60 were considered a low titer and a high titer, respectively. Thirteen types of single nucleotide polymorphisms (SNPs) within 13 genes involved in the immune process, the susceptibility to chronic inflammatory diseases, cytokines and apoptosis pathways were investigated. Results: The median trough levels of infliximab (TLI) in patients with clinical remission (CR) were higher than those in patients without CR (3.80 vs. 1.50 μg/mL, p < .001). The median TLI in patients with high-titer ATI was significantly lower than that in ATI-negative patients (1.15 vs. 4.48 μg/mL, p < .001) or those with low-titer ATI (1.15 vs. 2.95 μg/mL, p = .03). The HLA-DQA1*05 rs2097432 GG and GA genotypes were more frequent in patients with ATI (GG and AG vs. AA, 27/38 = 71.05% vs. 29/66 = 43.94%, OR 2.94, 95% CI 1.19-7.30, p = .02). Patients carrying the CC and AC genotypes of rs396991 in FCGR3A were associated with a higher frequency of ATI formation (CC and AC vs. AA, 37/57 = 64.91% vs. 19/47 = 40.43%, OR 2.94, 95% CI 1.24-6.96, p = .01). According to the number of variants in rs2097432 and rs393991, patients with two variants had a higher proportion of producing ATI (two variants vs. no variant, 17/21 = 80.95% vs. 9/30 = 30.00%, OR 9.92, 95% CI 2.59-37.87, p = .001; single variant vs. no variant, 30/53 = 56.60% vs. 9/30 = 30.00%, OR 3.04, 95% CI 1.18-7.88, p = .02). No association was found between other SNPs and ATI production. Conclusion: Rs2097432 in HLA-DQA1*05 and rs396991 in FCGR3A are associated with ATI production in Chinese patients with CD. A pharmacogenomic strategy could help with the clinical management of CD.

[Association between drug trough concentration and disease outcome before infliximab maintenance treatment in children with Crohn's disease]

OBJECTIVES

To study the association between infliximab trough level (IFX-TL) prior to maintenance treatment and disease outcome in children with Crohn's disease (CD).

METHODS

A retrospective analysis was performed on 35 children with CD who received induction therapy with infliximab (IFX) and the measurement of IFX-TL before maintenance treatment from August 2018 to November 2021. Clinical data and laboratory markers at baseline and before maintenance treatment were collected, and the association between outcome and IFX-TL was analyzed.

RESULTS

The clinical remission group, endoscopic remission group, and combined remission group had a significantly higher IFX-TL level than the corresponding non-remission groups (P<0.05), and there was no significant difference in the IFX-TL level between the biological remission and non-biological remission groups (P>0.05). The receiver operating characteristic (ROC) curve showed that IFX-TL had an area under the ROC curve of 0.959 (95%CI: 0.894-1) in predicting clinical remission, with a sensitivity of 90% and a specificity of 100% at the optimal cutoff value of 2.3 µg/mL (P<0.001).

CONCLUSIONS

Among children with CD receiving infliximab induction therapy, the children achieving clinical and endoscopic remission before maintenance treatment tend to have a higher level of IFX-TL. IFX-TL has a certain predictive value for clinical remission.

Updates in therapeutic drug monitoring in inflammatory bowel disease

Biologics and immunomodulators (IMM) are generally considered the most effective therapies for the treatment of ulcerative colitis and Crohn's disease. However, despite the efficacy of these therapies, many patients either have a primary lack of response or a secondary loss of response to these medications. Therapeutic drug monitoring (TDM) is a systematic approach to managing such patients. In this review, we summarize the latest data on TDM, including reactive and proactive TDM, in patients with inflammatory bowel disease on biologics and/or IMM.

Incidence of and Risk Factors for Paradoxical Psoriasis or Psoriasiform Lesions in Inflammatory Bowel Disease Patients Receiving Anti-TNF Therapy: Systematic Review With Meta-Analysis

Background

Paradoxical psoriasis or psoriasiform lesions induced by anti-tumor necrosis factor (anti-TNF) therapies receive increasing attention worldwide. However, no comprehensive meta-analysis investigating the incidence estimates and risk factors for anti-TNF-induced psoriasis is currently available. We aimed to precisely quantify its incidence as well as risk factors in patients with inflammatory bowel disease (IBD).

Methods

This study was registered on PROSPERO database under review registration number CRD42021233695. The electronic databases PubMed, EMBASE, and the Cochrane library were comprehensively searched for observational studies published as full-length papers in English and reporting the incidence and/or predictors for psoriasis or psoriasiform lesions in IBD patients. A random-effects meta-analysis was performed to calculate the pooled incidence. Pooled odds ratio (OR) and 95% confidence interval for potential predictors were combined using a fixed-effects or random-effects model.

Results

In total, 30 articles comprising 24,547 IBD patients treated by anti-TNF were finally included. The overall pooled incidence of psoriasis and/or psoriasiform lesions following anti-TNF therapy was 6.0% (5.0–7.0%; I² = 93.9%), with 6.9% (5.1–8.7%; I² = 92.4%) for psoriasiform lesions and 4.6% (3.6–5.6%; I² = 93.9%) for psoriasis. Multivariable meta-regression analysis indicated regions and populations that significantly contributed to the heterogeneity. A statistically higher risk for psoriasis or psoriasiform lesions during anti-TNF therapy was observed in female patients (OR 1.46, 1.23–1.73), those who are at a younger age at anti-TNF initiation (OR 1.03, 1.00–1.05), smokers (OR 1.97, 1.56–2.48), ileocolonic Crohn’s disease patients (OR 1.48, 1.03–2.13), and those who are using adalimumab or certolizumab (vs. infliximab) (OR: 1.48 and 2.87 respectively).

Conclusions

The incidence of psoriasis or psoriasiform lesions was not uncommon in IBD patients following anti-TNF therapy. Female, younger age, smoker, ileocolonic Crohn’s disease, and the types of anti-TNF were significantly associated with such risk. These findings may help gastroenterologists to make more individualized decisions and understand the mechanisms of this paradoxical phenomenon.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=233695, identifier CRD42021233695.

Deep learning vs conventional learning algorithms for clinical prediction in Crohn's disease: A proof-of-concept study

BACKGROUND

Traditional methods of developing predictive models in inflammatory bowel diseases (IBD) rely on using statistical regression approaches to deriving clinical scores such as the Crohn's disease (CD) activity index. However, traditional approaches are unable to take advantage of more complex data structures such as repeated measurements. Deep learning methods have the potential ability to automatically find and learn complex, hidden relationships between predictive markers and outcomes, but their application to clinical prediction in CD and IBD has not been explored previously.

AIM

To determine and compare the utility of deep learning with conventional algorithms in predicting response to anti-tumor necrosis factor (anti-TNF) therapy in CD.

METHODS

This was a retrospective single-center cohort study of all CD patients who commenced anti-TNF therapy (either adalimumab or infliximab) from January 1, 2010 to December 31, 2015. Remission was defined as a C-reactive protein (CRP) < 5 mg/L at 12 mo after anti-TNF commencement. Three supervised learning algorithms were compared: (1) A conventional statistical learning algorithm using multivariable logistic regression on baseline data only; (2) A deep learning algorithm using a feed-forward artificial neural network on baseline data only; and (3) A deep learning algorithm using a recurrent neural network on repeated data. Predictive performance was assessed using area under the receiver operator characteristic curve (AUC) after 10× repeated 5-fold cross-validation.

RESULTS

A total of 146 patients were included (median age 36 years, 48% male). Concomitant therapy at anti-TNF commencement included thiopurines (68%), methotrexate (18%), corticosteroids (44%) and aminosalicylates (33%). After 12 mo, 64% had CRP < 5 mg/L. The conventional learning algorithm selected the following baseline variables for the predictive model: Complex disease behavior, albumin, monocytes, lymphocytes, mean corpuscular hemoglobin concentration and gamma-glutamyl transferase, and had a cross-validated AUC of 0.659, 95% confidence interval (CI): 0.562-0.756. A feed-forward artificial neural network using only baseline data demonstrated an AUC of 0.710 (95%CI: 0.622-0.799; P = 0.25 vs conventional). A recurrent neural network using repeated biomarker measurements demonstrated significantly higher AUC compared to the conventional algorithm (0.754, 95%CI: 0.674-0.834; P = 0.036).

CONCLUSION

Deep learning methods are feasible and have the potential for stronger predictive performance compared to conventional model building methods when applied to predicting remission after anti-TNF therapy in CD.

A Comprehensive Literature Review and Expert Consensus Statement on Therapeutic Drug Monitoring of Biologics in Inflammatory Bowel Disease

Therapeutic drug monitoring (TDM) of biologics is a rapidly evolving field. We aimed to provide a consensus statement regarding the clinical utility of TDM for biologics in inflammatory bowel disease (IBD). A modified Delphi method was applied to develop consensus statements. A comprehensive literature review was performed regarding TDM of biologic therapies in IBD, and 45 statements were subsequently formulated on the potential application of TDM in IBD. The statements, along with literature, were then presented to a panel of 10 gastroenterologists with expertise in IBD and TDM who anonymously rated them on a scale of 1-10 (1 = strongly disagree and 10 = strongly agree). An expert consensus development meeting was held virtually to review, discuss, refine, and reformulate statements that did not meet criteria for agreement or that were ambiguous. During the meeting, additional statements were proposed. Panelists then confidentially revoted, and statements rated ≥7 by 80% or more of the participants were accepted. During the virtual meeting, 8 statements were reworded, 7 new statements were proposed, and 19 statements were rerated. Consensus was finally reached in 48/49 statements. The panel agreed that reactive TDM should be used for all biologics for both primary nonresponse and secondary loss of response. It was recommended that treatment discontinuation should not be considered for infliximab or adalimumab until a drug concentration of at least 10-15 μg/mL was achieved. Consensus was also achieved regarding the utility of proactive TDM for anti-tumor necrosis factor therapy. It was recommended to perform proactive TDM after induction and at least once during maintenance. Consensus was achieved in most cases regarding the utility of TDM of biologics in IBD, specifically for reactive and proactive TDM of anti-tumor necrosis factors.

Systematic review: efficacy of escalated maintenance anti-tumour necrosis factor therapy in Crohn's disease

BACKGROUND

Loss of response to anti-TNF agents is a common clinical problem. Dose escalation may be effective for reestablishing clinical response in Crohn's disease (CD).

AIMS

To perform a systematic review assessing the efficacy of escalated maintenance anti-TNF therapy in CD.

METHODS

EMBASE, MEDLINE, Web of Science, and CENTRAL databases were searched for English language publications through to April 25, 2021. Full-text articles evaluating escalated maintenance treatment (infliximab or adalimumab) in adult CD patients were included.

RESULTS

A total of 4733 records were identified, and 68 articles met eligibility criteria. Rates of clinical response (33%-100%) and remission (15%-83%) after empiric dose escalation for loss of response to standard anti-TNF therapy were high but varied across studies. Dose intensification strategies (doubling the dose versus shortening the therapeutic interval) were similarly efficacious. Dose-escalated patients tended to have higher serum drug levels compared to those on standard dosing. An exposure-response relationship following dose escalation was found in a number of observational studies. Randomised controlled trials comparing therapeutic drug monitoring (TDM) to empiric treatment intensification have failed to reach their primary end-points. Strategies including Bayesian dashboard-dosing and early treatment escalation targeting biomarker normalisation were found to be associated with improved long-term outcomes.

CONCLUSIONS

Empiric escalation of maintenance anti-TNF therapy can recapture clinical response in a majority of patients with secondary loss of response to standard maintenance doses. Proactive optimisation of maintenance dosing might prolong time to loss of response in some patients.

No Difference of Adalimumab Pharmacokinetics When Dosed at 40 mg Every Week or 80 mg Every Other Week in IBD Patients in Clinical Remission After Adalimumab Dose Intensification

INTRODUCTION

The pharmacokinetic equivalence of dose intensification with adalimumab (ADA) 80 mg every other week (EOW) compared to weekly 40 mg has only been supported by modeling systems.

AIM OF THE STUDY

To compare the trough levels of ADA (TLA) and the occurrence of anti-ADA antibodies (AAA) between these two treatment regimens.

PATIENTS AND METHODS

This was a prospective study including all consecutive patients with inflammatory bowel disease (IBD) who had reached a longstanding and deep remission under treatment with ADA 40 mg once a week. In these patients, the ADA regimen was changed from 40 mg/week to 80 mg EOW. TLA and AAA levels using a drug-tolerant assay were monitored before and ten weeks after from the change in the ADA regimen and the results compared by a Wilcoxon paired test.

RESULTS

Sixty-two patients (60% CD, mean age 35 years) were included. Before and ten weeks after the changes of ADA regimen, the median TLA were (6.9 µg/mL versus 7.0 µg/mL, respectively; P = 0.34) and the AAA levels (3.4 µg/ml-eq versus 3.0 µg/ml-eq, respectively; P = 0.25.) were quite similar. Likewise, quartiles of TLA (Kendall test r = 0.91; P < 0.001) and AAA (r = 0.78; P < 0.001) did not differ before and after ADA regimen. When stratifying all the patients into 4 groups based on drug/antibody levels (immunogenic, subtherapeutic, therapeutic, or supratherapeutic), no patient needed for returning to the previous weekly regimen. In terms of acceptability, more than 60% of patients preferred an injection EOW compared once a week.

CONCLUSIONS

In IBD patients who achieved a deep clinical remission under ADA 40 mg once a week, the pharmacokinetic of ADA was similar when ADA regimen was changed to 80 mg EOW. Given the patient's preference for the latter regimen, a modification of injection regimen should be systematically proposed.

Development of a Simple, Serum Biomarker-based Model Predictive of the Need for Early Biologic Therapy in Crohn's Disease

BACKGROUND

Early or first-line treatment with biologics, as opposed to conventional immunomodulators, is not always necessary to achieve remission in Crohn's disease [CD] and may not be cost-effective. This study aimed to develop a simple model to predict the need for early biologic therapy, in order to risk-stratify CD patients and guide initial treatment selection.

METHODS

A model-building study using supervised statistical learning methods was conducted using a retrospective cohort across two tertiary centres. All biologic-naïve CD patients who commenced an immunomodulator between January 1, 2004 and December 31, 2016, were included. A predictive score was derived using Cox regression modelling of immunomodulator failure, and was internally validated using bootstrap resampling.

RESULTS

Of 410 patients [median age 37 years, 47% male, median disease duration 4.7 years], 229 [56%] experienced immunomodulator failure [39 required surgery, 24 experienced a new stricture, 44 experienced a new fistula/abscess, 122 required biologic escalation] with a median time to failure of 16 months. Independent predictors of treatment failure included raised C-reactive protein [CRP], low albumin, complex disease behaviour, younger age, and baseline steroids. Highest CRP and lowest albumin measured within the 3 months preceding immunomodulator initiation outperformed baseline measurements. After model selection, only highest CRP and lowest albumin remained and the resultant Crohn's Immunomodulator CRP-Albumin [CICA] index demonstrated robust optimism-corrected discriminative performance at 12, 24, and 36 months (area under the curve [AUC] 0.84, 0.83, 0.81, respectively).

CONCLUSIONS

The derived CICA index based on simple, widely available markers is feasible, internally valid, and has a high utility in predicting immunomodulator failure. This requires external, prospective validation.

Infliximab, Immunomodulators and Treatment Failures in Paediatric and Adolescent Patients with Crohn's Disease: a Nationwide Cohort Study

BACKGROUND AND AIMS

In paediatric patients with Crohn's disease, the role of combination therapy, infliximab plus immunomodulators [thiopurine or methotrexate], is debated and data are sparse. We examined whether infliximab plus immunomodulators, compared to infliximab therapy alone, reduces the risk of treatment failure measured by intestinal surgery or switching type of anti-tumour necrosis factor [TNF] α agent within 24 months.

DESIGN

Using Danish registries, we identified patients with Crohn's disease, aged ≤ 20 years at the time of the first infliximab treatment, and retrieved data on their co-medications. We used Cox regression models to examine surgery or switching type of anti-TNFα agent from January 1, 2003 to December 31, 2015.

RESULTS

We included 581 patients. The 2-year cumulative percentage of surgery was 8.5% among patients receiving combination therapy and 14.5% in those receiving infliximab alone. The adjusted 2-year hazard ratio [HR] of surgeries was 0.53 (95% confidence interval [CI] 0.32-0.88) in patients receiving combination therapy, compared to patients receiving infliximab alone. When examining a switch of anti-TNFα we included 536 patients. Within 2 years, 18.3% experienced a switch among patients receiving combination therapy and 24.8% in patients treated with infliximab alone, corresponding to an adjusted HR of 0.66 [95% CI 0.45-0.97] in patients receiving combination therapy.

CONCLUSIONS

The HR of intestinal surgeries and the risk of a switch to another anti-TNFα was reduced in paediatric and adolescent patients receiving combination therapy, compared to patients receiving only infliximab. These results suggest a benefit for infliximab therapy combined with immunomodulators, but these need to be confirmed in data with additional clinical information.

Is There a Role for Therapeutic Drug Monitoring in Patients with Hidradenitis Suppurativa on Tumor Necrosis Factor-α Inhibitors?

Tumor necrosis factor-α inhibitors, adalimumab and infliximab, are at the forefront of biologic therapy for the management of moderate-to-severe hidradenitis suppurativa, with adalimumab as currently the only approved medication for this condition. In treating patients, primary or secondary lack of response (also termed suboptimal response) is a major burden for both patients and healthcare systems and is a challenge with biologics in part owing to the development of anti-drug antibodies following treatment. To overcome this, therapeutic drug monitoring may be conducted proactively or reactively to a patient's suboptimal response guided by measurements of trough serum drug concentrations and levels of anti-drug antibodies. While strong evidence to support the utility of therapeutic drug monitoring exists in patients with inflammatory bowel disease, current information is limited in the context of hidradenitis suppurativa. We sought to summarize the available evidence and to present the role of therapeutic drug monitoring and other dose optimization strategies in improving clinical response in patients with hidradenitis suppurativa treated with tumor necrosis factor-α inhibitors.

Therapeutic Drug Monitoring for Current and Investigational Inflammatory Bowel Disease Treatments

This article reviews therapeutic drug monitoring (TDM) use for current inflammatory bowel disease (IBD) treatments. IBD comprises Crohn's disease and ulcerative colitis-chronic gastrointestinal inflammatory disorders. Treatment options for moderate to severe IBD include thiopurines; methotrexate; biologic agents targeting tumor necrosis factor, α4β7 integrin or interleukins 12 and 23; and Janus kinase inhibitors. TDM is recommended to guide treatment decisions for some of these agents. Published literature concerning TDM for IBD treatments was reviewed. S.D.L., R.S., and E.V.L. drew on their clinical experiences. Polymorphisms resulting in altered enzymatic activity inactivating thiopurine metabolites can lead to myelotoxicity and hepatotoxicity. Increased elimination of biologic agents can result from immunogenicity or higher disease activity, leading to low drug concentration and consequent nonresponse or loss of response. TDM may aid treatment and dose decisions for individual patients, based on monitoring metabolite levels for thiopurines, or serum drug trough concentration and antidrug antibody levels for biologic agents. Challenges remain around TDM implementation in IBD, including the lack of uniform assay methods and guidance for interpreting results. The Janus kinase inhibitor tofacitinib is not impacted by enzyme polymorphisms or disease activity, and is not expected to stimulate the formation of neutralizing antidrug antibodies. TDM is associated with implementation challenges, despite the recommendation of its use for guiding many IBD treatments. Newer small molecules with less susceptibility to patient variability factors may fulfill the unmet need of treatment options that do not require TDM, although further study is required to confirm this.

The shining DIAMOND for evidence-based treatment strategies for Crohn's disease

Anti-tumor necrosis factor (TNF)-α antibodies are effective therapeutic agents to treat inflammatory bowel disease (IBD). In the biologic era, the development of immunogenicity has been a critical issue for secondary loss of response. The superiority of anti-TNF therapy in combination with immunomodulators (IMs) is well-established for infliximab (IFX) but less evident for adalimumab (ADA). To clarify the contribution of thiopurines to ADA-treated patients with Crohn's disease (CD), the deep remission of immunomodulator and adalimumab combination therapy for Crohn's disease (DIAMOND) studies provided the first randomized comparison of efficacy between ADA monotherapy and ADA with thiopurine. The results of the DIAMOND and DIAMOND2 studies revealed the appropriate ADA therapeutic strategy for immunosuppressant-naïve patients with active CD based on therapeutic drug monitoring, endoscopic findings and clinical issues regarding the use of thiopurines.

Bayes-based dosing of infliximab in inflammatory bowel diseases: Short-term efficacy

AIMS

Therapeutic drug monitoring of infliximab can guide clinical decisions in patients with loss of response and in those who can benefit from a de-intensification. The aim of this study was to determine the impact of therapeutic drug monitoring combined with Bayesian forecasting methodology on clinical response in a real-world dataset of patients suffering from inflammatory bowel disease.

METHODS

We performed a single-centre prospective study with one-group pre-test/post-test design in 108 adult inflammatory bowel disease patients treated with model-based dosing of infliximab maintenance treatment. We recorded clinical activity scores (Harvey-Bradshaw index and partial Mayo) and inflammatory biomarkers per patient.

RESULTS

The initial infliximab regimen was maintained in 49 (45.4%) patients and was adjusted in 59 (54.6%) patients (34 treatment intensifications, 9 de-intensifications and 16 treatment discontinuations or therapy replacements). The median time from intervention to index measurement was 126 (103-160) days. The overall proportion of patients in clinical remission increased from 65.7% to 80.4% (P < .0001) and the median infliximab trough concentrations increased from 3.21 (0.99-5.45) to 5.13 mg/L (3.57-6.53) (P < .0001). In the intensified group, the remission rate increased from 35.3% to 61.8% (P = .001) and the percentage of patients in clinical remission or with mild symptoms increased from 76.5% to 94.1%. In the de-intensification cohort, no patients experienced an increase in the Harvey-Bradshaw index or partial Mayo scores, and all patients maintained an infliximab trough concentration of >5 mg/L.

CONCLUSION

In our cohort of inflammatory bowel disease patients, Bayes-based optimized dosing improved the short-term efficacy of infliximab treatment.

Review article: determination of the therapeutic range for therapeutic drug monitoring of adalimumab and infliximab in patients with inflammatory bowel disease

BACKGROUND

Clinical application of therapeutic drug monitoring (TDM) to optimise anti-TNF therapies in patients with IBD depends upon target ranges.

AIMS

To review methodology used to determine therapeutic ranges and critically compare and contrast its application to infliximab and adalimumab.

METHODS

A systematic review was performed, and relevant literature was summarised and critically examined.

RESULTS

Upper limits of the therapeutic range are determined by toxicity, a plateau response and cost. Lower limits are determined by optimal concentration on the target of action in vitro and/or in vivo, or by correlation of drug levels with clinical efficacy using area-under-receiver-operator-curve (AUROC) analysis. In 43 studies, there were huge variations in time at which infliximab and adalimumab levels were measured, the end-points used (clinical remission to mucosal healing), the clinical setting (active disease vs maintenance phase) and the reason for TDM (proactive vs reactive). In the maintenance phase for infliximab, lower trough limits 2.8-5.7 µg/mL are reported depending upon end-points used, with consistent AUROC 0.68-0.77. Adalimumab TDM targets are even less consistent with a lower limit 5.9-11.8 µg/mL (AUROC 0.66-0.83) in some studies, but no cut-off can be identified that is significantly associated with outcome in others, related to inherent pharmacokinetic and pharmacodynamic differences, and heterogeneity of study design.

CONCLUSIONS

Evidence for exposure-response relationship is stronger for infliximab than adalimumab. Due to heterogeneity in settings for drug level measurements, therapeutic ranges vary. These factors need to be taken into account when interpreting the evidence and extending this to therapeutic strategies for IBD patients.

Comparison of Adalimumab Serum Drug Levels When Delivered by Pen Versus Syringe in Patients With Inflammatory Bowel Disease. An International, Multicentre Cohort Analysis

BACKGROUND

Adalimumab is administered via a pre-filled syringe or spring-loaded pen. In a previous study in Crohn's disease, higher drug levels were observed in syringe users. The aim of this study was to evaluate the impact of delivery device on adalimumab drug levels in patients with Crohn's disease.

METHODS

Consecutive Crohn's disease patients treated with maintenance adalimumab [40 mg fortnightly] were recruited from five centres. The first recorded drug level with matched clinical and biochemical markers of disease activity was compared between pen and syringe users.

RESULTS

Of 218 patients, 64% used pen, with a median faecal calprotectin 110 μg/g and serum C-reactive protein 4 mg/L. In comparison to pen, syringe users had higher albumin [39 vs 42 g/L; p = 0.016], lower Harvey-Bradshaw Index [2 vs 1; p = 0.017], and higher rates of concomitant immunomodulation [54% vs 71%; p = 0.014]. Drug levels were equivalent between pen and syringe users [median 5.3 vs 5.2 μg/ml; p = 0.584], even after controlling for disease activity and immunomodulation. Syringe users at Alfred Health had higher drug levels than pen [6.1 vs 4.5 μg/ml; p = 0.039]; a greater proportion achieved therapeutic levels [75% vs 44%; p = 0.045]. A higher proportion of pen users from Saint-Étienne had therapeutic levels [79% vs 42%; p = 0.027], yet no significant difference in drug levels [7.9 vs 4.5 μg/ml; p = 0.119].

CONCLUSIONS

Delivery device does not appear to significantly affect adalimumab drug levels. Given differences between study sites, studies evaluating administration education and technique are warranted.

Distinct Cutoff Values of Adalimumab Trough Levels Are Associated With Different Therapeutic Outcomes in Patients With Inflammatory Bowel Disease

Background and Aims

We aimed to evaluate the relationship of serum adalimumab trough levels (ATL) with disease activity of inflammatory bowel disease (IBD) patients in a large, well-characterized referral center-based cohort.

Methods

We compared serum ATL between those with clinical, biochemical, or endoscopic/radiologic disease activity and those without.

Results

A total of 236 patients with IBD were included. Higher cutoff levels were associated with endoscopic and/or radiologic responses (cutoff value: 5.3 mcg/mL, P = 0.003) compared with improvement in C-reactive protein (cutoff value: 4.3 mcg/mL, P = 0.031).

Conclusions

Higher cutoff ATL was associated with endoscopic and/or radiologic response.

Determination of lower cut-off levels of adalimumab associated with biochemical remission in Crohn's disease

Background and Aim

Adalimumab is administered and dosed using a standardized treatment regimen. Although therapeutic drug monitoring (TDM) may help optimize treatment efficacy, the lower cut‐off concentration of adalimumab needed to retain disease remission has not been established. This cross‐sectional study of patients with Crohn's disease on stable medication aimed to determine a lower therapeutic drug concentration threshold of adalimumab associated with biochemical disease remission.

Methods

C‐reactive protein (CRP) and fecal calprotectin were used as established markers and albumin as an explorative marker of disease activity. Time since introduction, treatment interval, drug dosage, serum drug concentration and antidrug antibodies, disease duration, age, and sex were recorded.

Results

The study included 101 patients who were divided into “active disease” and “remission” groups for inflammatory markers based on cut‐off levels of 5 mg/L for CRP and 50 mg/kg for fecal calprotectin. Cut‐off levels for albumin of 36.5 and 41.5 g/L were also added as further indicatives of remission. Receiver operating characteristic analysis found optimal thresholds for adalimumab associated with remission at 6.8–7.0 mg/L for the combination of CRP and fecal calprotectin and when combining CRP, fecal calprotectin, and albumin.

Conclusions

In patients with Crohn's disease, serum adalimumab of at least 6.8 mg/L was associated with biochemical disease remission based on CRP and fecal calprotectin, supporting the use of TDM to ensure disease control. Albumin should be further tested in this setting.

Proactive Therapeutic Drug Monitoring of Adalimumab Is Associated With Better Long-term Outcomes Compared With Standard of Care in Patients With Inflammatory Bowel Disease

BACKGROUND AND AIMS

Therapeutic drug monitoring [TDM] has proven to be effective for optimising anti-tumour necrosis factor [TNF] therapy in inflammatory bowel disease [IBD]. Nevertheless, the majority of data refer to infliximab and reactive testing or association studies. We aimed to compare the long-term outcome of patients with IBD who received at least one proactive TDM of adalimumab, with standard of care, defined as empirical dose escalation and/or reactive TDM.

METHODS

This was a multicentre retrospective cohort study. Patients on maintenance adalimumab therapy from June 2006 to December 2015 were eligible. We analysed time to treatment failure from start of adalimumab until the end of follow-up [July 2016]. Treatment failure was defined as drug discontinuation for secondary loss of response or serious adverse event or need for IBD-related surgery. Serum adalimumab concentrations and antibodies to adalimumab were measured using the Prometheus homogeneous mobility shift assay.

RESULTS

A total of 382 patients with IBD [Crohn's disease, n = 311, 81%] were included and received either at least one proactive TDM [n = 53] or standard of care [empirical dose escalation, n = 279; reactive TDM, n = 50]. Patients were followed for a median of 3.1 years [interquartile range, 1.4-4.8 years]. Multiple Cox regression analyses showed that at least one proactive TDM was independently associated with a reduced risk for treatment failure (hazard ratio [HR]: 0.4; 95% confidence interval [CI]: 0.2-0.9; p = 0.022).

CONCLUSIONS

This multicentre, retrospective cohort study reflecting real-life clinical practice provides the first evidence that proactive TDM of adalimumab may be associated with a lower risk of treatment failure compared with standard of care in patients with IBD.

Appropriate Therapeutic Drug Monitoring of Biologic Agents for Patients With Inflammatory Bowel Diseases

BACKGROUND & AIMS

Therapeutic drug monitoring (TDM) is widely available for biologic therapies in patients with inflammatory bowel disease (IBD). We reviewed current data and provided expert opinion regarding the clinical utility of TDM for biologic therapies in IBD.

METHODS

We used a modified Delphi method to establish consensus. A comprehensive literature review was performed regarding the use of TDM of biologic therapy in IBD and presented to international IBD specialists. Subsequently, 28 statements on the application of TDM in clinical practice were rated on a scale of 1 to 10 (1 = strongly disagree and 10 = strongly agree) by each of the panellists. Statements were accepted if 80% or more of the participants agreed with a score ≥7. The remaining statements were discussed and revised based on the available evidence followed by a second round of voting.

RESULTS

The panel agreed on 24 (86%) statements. For anti-tumor necrosis factor (anti-TNF) therapies, proactive TDM was found to be appropriate after induction and at least once during maintenance therapy, but this was not the case for the other biologics. Reactive TDM was appropriate for all agents both for primary non-response and secondary loss of response. The panellists also agreed on several statements regarding TDM and appropriate drug and anti-drug antibody (ADA) concentration thresholds for biologics in specific clinical scenarios.

CONCLUSION

Consensus was achieved towards the utility of TDM of biologics in IBD, particularly anti-TNF therapies. More data are needed especially on non-anti-TNF biologics to further define optimal drug concentration and ADA thresholds as these can vary depending on the therapeutic outcomes assessed.

Actual Anti-TNF Trough Levels Relate to Serum IL-10 in Drug-Responding Patients With Crohn's Disease

BACKGROUND

Patients with Crohn's disease (CD) responding to anti-tumor necrosis factor (anti-TNF) show great variability in serum drug levels, even within the therapeutic range. We aimed at exploring the role of inflammatory, genetic, and bacterial variables in relation to anti-TNF through levels in CD patients.

METHODS

Consecutive CD patients receiving stable doses of infliximab or adalimumab were included. Clinical and analytical parameters were recorded. Cytokine response, bacterial DNA translocation, and several immune-related genes' genotypes were evaluated, along with serum through anti-TNF drug levels. A linear regression analysis controlled by weight and drug regimen was performed.

RESULTS

One hundred nineteen patients were initially considered. Five patients on infliximab and 2 on adalimumab showed antidrug antibodies in serum and were excluded. One hundred twelve patients were finally included (62 on infliximab, 50 on adalimumab). Fourteen patients on infliximab and 15 on adalimumab (22.6% vs 30%, P = 0.37) were receiving an intensified drug regimen. C-reactive protein (CRP), fecal calprotectin, Crohn's Disease Activity Index, leukocyte count, and albumin levels in plasma were not significantly associated with infliximab or adalimumab levels in the multivariate analysis. Serum interleukin-10 (IL-10) levels were directly related to infliximab (Beta = 0.097, P < 0.0001) and adalimumab levels (Beta = 0.069, P = 0.0241). The best multivariate regression model explaining the variability of serum infliximab and adalimumab levels included IL-10. Predicted drug levels by this model robustly fitted with actual drug levels (R2 = 0.841 for infliximab, R2 = 0.733 for adalimumab).

CONCLUSION

Serum IL-10 is significantly related to serum anti-TNF levels in CD patients, showing how the disposition of anti-TNF drugs is significantly influenced by the degree of immunological activation.

Therapeutic drug monitoring in inflammatory bowel disease: for every patient and every drug?

PURPOSE OF REVIEW

The current review provides an updated overview on the role of therapeutic drug monitoring (TDM) of biological therapies in inflammatory bowel disease (IBD). We examine the data behind TDM for the antitumor necrosis factor agents, vedolizumab and ustekinumab, in patients with IBD. In addition, we discuss reactive vs. proactive TDM.

RECENT FINDINGS

There is a positive correlation between biologic drug concentrations and favorable therapeutic outcomes in IBD, although the majority of data refer to antitumor necrosis factor therapy. Reactive TDM has rationalized the management of patients with IBD with loss of response to biological therapy. Moreover, reactive TDM of infliximab has been proven to be more cost-effective when compared with empiric dose optimization. Preliminary data suggest that proactive TDM of infliximab and adalimumab applied in patients with clinical response/remission is associated with better therapeutic outcomes compared with standard of care (empiric treatment and/or reactive TDM).

SUMMARY

For all biologics in IBD, there is a positive correlation between drug concentrations and favorable therapeutic outcomes. Reactive TDM is the new standard of care for optimizing biologic therapies in IBD, whereas recent data suggest an important role of proactive TDM for optimizing antitumor necrosis factor therapy in IBD.

Higher Adalimumab Drug Levels During Maintenance Therapy for Crohn's Disease Are Associated With Biologic Remission

BACKGROUND

Adalimumab is an established treatment for Crohn's disease. Limited data are available regarding the relationship between adalimumab drug levels and serum/fecal markers of gut inflammation. We therefore aimed to characterize the relationship between adalimumab levels and biologic remission during maintenance therapy.

METHODS

A single-center prospective cross-sectional study was undertaken on Crohn's disease patients who had received adalimumab therapy for a minimum of 12 weeks after induction. Data on clinical activity (Harvey-Bradshaw Index), C-reactive protein (CRP), adalimumab drug and antibody levels, and fecal calprotectin were collected. Biologic remission was defined as a CRP <5 mg/L and fecal calprotectin <250 µg/g. Adalimumab drug and antibody levels were processed using the Immundiagnostik monitor enzyme-linked immunosorbent assay.

RESULTS

One hundred fifty-two patients had drug and antibody samples matched with CRP and fecal calprotectin. Patients in biologic remission had significantly higher adalimumab levels compared with others (12.0 µg/mL vs 8.0 µg/mL, P < 0.0001). Receiver operating characteristic curve analysis demonstrated an optimal adalimumab level of >8.5 µg/mL (sensitivity, 82.2%; specificity, 55.7%; likelihood ratio, 1.9) for predicting biologic remission. Multivariable logistic regression revealed that adalimumab levels >8.5 µg/mL were independently associated with biologic remission (odds ratio, 5.27; 95% confidence interval, 2.43-11.44; P < 0.0001).

CONCLUSIONS

Higher adalimumab levels are associated with biologic remission. An optimal level of >8.5 µg/mL was identified.

Key insights from therapeutic drug monitoring in Crohn's disease patients

INTRODUCTION

The incidence and prevalence of Crohn's disease are increasing causing a significant disease burden. Therapeutic drug monitoring (TDM) is advocated as a promising tool for personalized or individual-tailored therapy strategies and has been welcomed as a new means to improve current therapy strategies. Nevertheless, pharmacokinetic-based TDM has limitations, and straightforward target concentrations for most therapies are lacking. Areas covered: In the following concise review of literature, key insights of TDM in thiopurine, methotrexate, anti-TNF, vedolizumab and ustekinumab therapy for Crohn's disease are being described. Expert opinion: Therapeutic drug monitoring may, up till now, be helpful to adjust thiopurine and infliximab therapy, primarily in a reactive setting, in case of inefficacy and of occurrence of adverse event. With this restricted application, the goal of individualized therapy based on TDM has not yet been achieved.

Serum Levels of Infliximab and Anti-Infliximab Antibodies in Brazilian Patients with Crohn's Disease

OBJECTIVES

The aim of this study was to evaluate the quantitative serum level of infliximab (IFX) as well as the detection of anti-infliximab antibodies (ATIs) in patients with Crohn's disease (CD).

METHOD

Forty patients with CD under treatment at a tertiary center in southeastern Brazil were evaluated. Their use of infliximab was continuous and regular. We analyzed and compared the differences in the IFX and ATI levels between the patients with active CD (CDA) and those with CD in remission (CDR).

RESULTS

There was no difference in the IFX level between the CDA and CDR groups (p>0.05). Eighty percent of all patients had IFX levels above the therapeutic concentration (6-10 μg/mL). Two (9%) of the 22 patients with active disease and four (22.2%) of the 18 patients in remission had undetectable levels of IFX. Four (66.6%) of the six patients with undetectable levels of IFX had positive ATI levels; three of these patients were in remission, and one had active disease. In addition, the other two patients with undetectable levels of IFX presented ATI levels close to positivity (2.7 and 2.8 AU/ml). None of the patients with therapeutic or supratherapeutic IFX levels had positive ATI levels.

CONCLUSIONS

The undetectable levels of IFX correlated with the detection of ATIs, which was independent of disease activity. Immunogenicity was not the main factor for the loss of response to IFX in our study, and the majority of patients in both groups (CDA and CDR) had supratherapeutic levels of IFX.

Positive acceleration adaptive training attenuates gastric ischemia-reperfusion injury through COX-2 and PGE2 expression

The mechanism involved in the effects of positive acceleration adaptive training (PAAT) on gastric ischemia-reperfusion injury (GI-RI) has not been fully characterized. The aim of the present study was to investigate the effects of PAAT in attenuating GI-RI in a rat model. The inflammatory factor and caspase-3 levels were measured using ELISA kits. A western blot assay was used to analyze tumor necrosis factor-α (TNF)-α, tumor necrosis factor receptor 1 (TNFR1), tumor necrosis factor-related apoptosis inducing ligand (TRAIL), death receptor (DR) 4, DR5, cyclooxygenase (COX)-2, COX-1 and prostaglandin E2 (PGE2) protein expression levels. It was revealed that PAAT could alleviate GI-RI and inflammatory factor levels in a rat model. PAAT suppressed TNF-α and TNFR1 protein expression levels, inhibited TRAIL, DR4, DR5, COX-2 and PGE2 protein expression levels; however, it did not have an effect on COX-1 protein expression in the model of GI-RI. The data indicated that the effects of PAAT attenuated GI-RI through the downregulation of COX-2 and PGE2 expression.

Optimised infliximab monotherapy is as effective as optimised combination therapy, but is associated with higher drug consumption in inflammatory bowel disease

BACKGROUND

Combination treatment with azathioprine for 6-12 months is the preferred strategy for starting infliximab due to improved pharmacokinetics. However, optimised infliximab monotherapy with proactive dose escalations in case of low trough levels is a safer but under-studied alternative.

AIM

To compare the clinical success and infliximab consumption of combination vs optimised monotherapy strategies.

METHODS

We studied the clinical success and infliximab consumption of both strategies in 149 patients (94 Crohn's disease; 55 ulcerative colitis) starting infliximab and undergoing intensive drug monitoring assisted treatment optimisation.

RESULTS

The drug retention rates were similar for optimised monotherapy and combination treatment after induction (96% vs 97%, P = 0.73), after the first year (90% vs 83%, P = 0.23) and at the end of follow-up (74% vs 75%, P = 0.968). Similarly, no differences were observed for steroid use at year 1 (5% vs 14%, P = 0.08) or mucosal healing at the end of follow-up (64% vs 67%, P = 0.8). Higher infliximab consumption (7.6 mg/kg q8 weeks [interquartile range (IQR): 5.9-10.3] vs 6.4 mg/kg q8 weeks [IQR: 5.2-8.0], P = 0.019) combined with lower trough levels (1.7 µg/mL [IQR: 0.3-6.6] vs 5.0 µg/mL [2.5-8.7], P = 0.012) resulted in almost 3-fold higher drug-to-trough ratio (3.9 vs 1.5) in monotherapy compared to combination strategy at year 1. At the end of follow-up, when azathioprine had been discontinued for a median of 14 [IQR: 3-33] months, these differences disappeared.

CONCLUSIONS

In this study, optimised infliximab monotherapy was as clinically effective as combination therapy but was associated with significantly higher infliximab consumption. The infliximab-sparing effect disappeared after azathioprine withdrawal.

Serum vitamin D but not zinc levels are associated with different disease activity status in patients with inflammatory bowel disease

The incidence of inflammatory bowel disease (IBD) is increasing and the pathogenesis is still not completely understood. Micronutrients like vitamin D [25 (OH)D] and zinc play an important role in enzyme activities and the immune system. As the 25 (OH)D-receptor has been shown to be downregulated in patients with IBD, 25 (OH)D may emerge as a predictive marker for disease improvement. Studies on relationship of both micronutrients in IBD patients are lacking.We retrospectively evaluated serum levels of 25(OH)D and zinc together with baseline characteristics of 232 IBD patients. Uni- and multivariate analyses were performed for association between serum levels of 25(OH)D and zinc with clinical and deep remission (CR and DR).155 Crohn's disease (CD) and 77 ulcerative colitis (UC) patients were included. 54% (n = 125) and 6% (n = 14) of IBD patients showed deficient serum 25(OH)D levels below 20 ng/mL and zinc levels below 7 μmol/L. Serum 25(OH)D levels were significantly higher in IBD patients with CR (P = .02) and DR (P < .001) but not serum zinc levels, respectively. Serum 25(OH)D levels (P = .008), anti-tumor-necrosis-factor-α-trough-concentration (anti-TNF-α-TC) (P = .02) and CRP level (P = .02) were independently associated with CR in CD patients. Serum 25(OH)D threshold of 19 ng/mL discriminated CD patients with or without CR, having an area under the receiver operating curve analysis (AUROC) of 0.77 [95%-confidence interval (CI): 0.68-0.85]. In multivariate analysis serum 25(OH)D levels (P = .04) and anti-TNF-α-TC (P = .04) were associated with DR in CD patients. Serum 25(OH)D threshold of 26 ng/mL discriminated CD patients with or without DR, having an AUROC of 0.75 (95%-CI: 0.68-0.83).Serum 25(OH)D (P = .04) and fecal calprotectin levels (P = .04) were independently correlated with CR in UC patients. Serum 25(OH)D threshold of 32 ng/mL discriminated UC patients in CR with an AUROC of 0.83 (95%-CI: 0.71-0.95). Zinc levels did not correlate with disease activity status in CD or UC patients either.In conclusion, beside CRP and fecal calprotectin, serum 25(OH)D levels, but not serum zinc levels, may be an additional useful and noninvasive marker for characterizing different disease activity status of IBD patients. Measurement of serum 25(OH)D in IBD patients may be warranted. 25(OH)D supplementation in deficient IBD patients is recommended.

New steps in infliximab therapeutic drug monitoring in patients with inflammatory bowel diseases

AIMS

Therapeutic drug monitoring (TDM) of infliximab (IFX) appears to be beneficial for patients with inflammatory bowel disease (IBD). However, the recommended target concentrations depend partly on the method used to quantify IFX. Since we recently developed a liquid chromatography-tandem mass spectrometry method to quantify IFX, we aimed to determine IFX trough concentrations (Cmin) associated with biological remission.

METHODS

We retrospectively measured IFX Cmin in sera from 55 patients with IBD, on IFX maintenance therapy, and for whom demographic, biological and clinical data were collected from medical records. A threshold of IFX Cmin associated with biological remission (defined by C-reactive protein < 5 mg l-1 and faecal calprotectin <150 μg g-1 ) was determined using receiver operating characteristics analysis.

RESULTS

IFX Cmin ranged from <1 mg l-1 to 57.2 mg l-1 . IFX Cmin were higher (P = 0.038) in patients with biological remission and a cut-off of IFX Cmin set to 6.2 mg l-1 was associated with biological remission (sensitivity = 0.75, 95% confidence interval 0.58-0.75; specificity = 0.61, 95% confidence interval 0.39-0.83).

CONCLUSION

Liquid chromatography-tandem mass spectrometry measurement of IFX Cmin and the determination of a new threshold of IFX Cmin associated with biological remission are new steps towards IFX treatment personalization in patients with IBD.

Infliximab in inflammatory bowel disease

Anti-tumor necrosis factor (TNF) therapy has revolutionized the medical treatment of the inflammatory bowel diseases (IBD), Crohn’s disease (CD), and ulcerative colitis. Twenty years ago, infliximab became the first anti-TNF agent approved for IBD. Data from randomized controlled trials, large observational cohort studies, postmarketing registries, and meta-analyses show that infliximab is a very effective treatment for moderate to severe IBD with a good safety profile. Infliximab has been also used to treat pouchitis following an ileal pouch–anal anastomosis (IPAA) after restorative proctocolectomy and to prevent postoperative recurrence following an ileocolonic resection for CD with good results. Nevertheless, up to 30% of patients show no clinical benefit following induction and up to 50% lose response over time. Both these unwanted outcomes can be largely explained by inadequate drug concentrations and frequently by the development of antibodies to infliximab. Loss of response can be managed efficiently and often prevented by applying therapeutic drug monitoring. Recently, the first biosimilars of infliximab have been approved and are utilized in clinical practice with comparable efficacy and safety with the originator. This review will mainly focus on the efficacy of infliximab in IBD.

Mucosal IL13RA2 expression predicts nonresponse to anti-TNF therapy in Crohn's disease

BACKGROUND

Ileocolonic expression of IL13RA2 has been identified as a predictive marker for nonresponsiveness to infliximab (IFX) in patients with Crohn's disease (CD).

AIM

To validate the IL13RA2 biomarker, study its anti-TNF specificity and get a better understanding of the underlying biology driving its expression.

METHODS

IL13RA2 mucosal expression was studied in a cohort of adalimumab and vedolizumab treated patients. To identify the upstream regulators of anti-TNF nonresponsiveness, weighted gene co-expression network analysis was applied on publicly available microarray data of IFX-treated patients. Selected serum proteins, including TNF, were measured prior to first IFX exposure and compared between healers and nonhealers.

RESULTS

Increased mucosal IL13RA2 expression prior to start of biological therapy was predictive for anti-TNF nonresponsiveness specifically (AUROC, area under the curve = 0.90, P < 0.001 in anti-TNF vs AUROC = 0.63, P = 0.30 in vedolizumab treated patients). In baseline biopsies, TNF-driven pathways were significantly enriched in future anti-TNF nonhealers (P = 5.0 × 10-34 ). We found an increased baseline mucosal TNF burden in nonhealers (P = 0.02), and TNF mRNA correlated significantly with IL13RA2 expression (ρ = 0.55, P = 0.02). Baseline serum TNF levels were significantly lower in nonhealers (P = 0.04), and correlated inversely with IFX serum induction levels (r = -0.45, P = 0.002 at week 6).

CONCLUSIONS

Increased mucosal IL13RA2 expression is associated with an increased mucosal TNF burden in CD patients. In view of its specificity for prediction of anti-TNF therapy resistance, mucosal IL13RA2 expression is a potential biomarker for therapy selection and/or for the need of increased anti-TNF drug dosing.

Maintenance Adalimumab Concentrations Are Associated with Biochemical, Endoscopic, and Histologic Remission in Inflammatory Bowel Disease

BACKGROUND

A treat-to-target therapeutic approach is emerging as the new standard of care for treating inflammatory bowel disease (IBD), Crohn's disease (CD), and ulcerative colitis (UC).

AIMS

We aimed to investigate the association of serum adalimumab concentrations during maintenance therapy with biochemical, endoscopic, and histologic remission in IBD.

METHODS

This retrospective multicenter study included consecutive IBD patients on adalimumab maintenance therapy who had a C-reactive protein (CRP) within 1 week and/or endoscopic evaluation within 12 weeks of therapeutic drug monitoring between July 2013 and December 2016. Biochemical remission was defined as a normal CRP (≤ 5 mg/L). Endoscopic remission was defined as the absence of any ulceration/erosion or a Rutgeerts score of ≤ i1 for patients with an ileocolonic resection for CD and a Mayo endoscopic score of ≤ 1 for UC. Histologic remission was defined as the absence of any sign of active inflammation. Adalimumab concentrations were measured using the homogeneous mobility shift assay.

RESULTS

Ninety-one CRP levels and 72 colonoscopies from 98 IBD patients [CD: n = 72 (73%)] were evaluated. Based on receiver operating characteristic analyses, we identified an adalimumab concentration threshold of 11.8, 12, and 12.2 μg/mL in CD and 10.5, 16.2, and 16.2 μg/mL in UC to stratify patients with or without biochemical, endoscopic, or histologic remission, respectively. Adalimumab concentrations ≥ 12 μg/mL (OR 8; 95% CI 2-31.9; p = 0.003) and ≥ 12.2 μg/mL (OR 9.6; 95% CI 1.7-56.1; p = 0.012) were independently associated with endoscopic and histologic remission in CD, respectively.

CONCLUSIONS

This study demonstrates that higher maintenance adalimumab concentrations are associated with objective therapeutic outcomes in IBD.

Association Between Serum Infliximab Trough Concentrations During Maintenance Therapy and Biochemical, Endoscopic, and Histologic Remission in Crohn's Disease

BACKGROUND AND AIM

Objective and more rigorous therapeutic outcomes are emerging as novel targets in Crohn's disease (CD). We investigated the association between maintenance serum infliximab trough concentrations and biochemical, endoscopic, or histologic remission in CD.

METHODS

This retrospective multicenter study involved consecutive CD patients treated with infliximab who had a serum C-reactive protein (CRP) measured within 1 week or endoscopic evaluation within 12 weeks of therapeutic drug monitoring between January 2010 and June 2016. Biochemical remission was defined as a normal CRP (≤5 mg/L). Endoscopic remission was defined as absence of any mucosal break (ulceration or erosion) or for patients with an ileocolonic resection, a Rutgeerts score of ≤i1. Histologic remission was defined as absence of active inflammation.

RESULTS

Seventy-one CRP levels and 96 colonoscopies from 110 CD patients were evaluated. Based on ROC analyses, infliximab concentration thresholds of 2.2, 9.7, and 9.8 μg/mL were found to be related with biochemical, endoscopic, and histologic remission, respectively. Multiple logistic regression analyses identified infliximab concentration ≥2.2 (OR 6.4; 95% CI, 1.5-27.1; P = 0.011), ≥9.7 (OR 3.6; 95% CI, 1.4-9; P = 0.006) and ≥9.8 μg/mL (OR 3.2; 95% CI, 1.3-7.9; P = 0.011) as variables independently associated with biochemical, endoscopic, and histologic remission, respectively.

CONCLUSIONS

This study showed that higher maintenance infliximab trough concentrations are associated with more favorable rates of biochemical, endoscopic, or histologic remission in CD patients and that infliximab concentrations may differ based on the treatment goal.

Interactions Between Thiopurine Metabolites, Adalimumab, and Antibodies Against Adalimumab in Previously Infliximab-Treated Patients with Inflammatory Bowel Disease

BACKGROUND

Interactions between thiopurines and infliximab presumably contribute to superior effect of infliximab-thiopurine combination therapy in patients with inflammatory bowel disease (IBD). We examined whether principal cytotoxic thiopurine metabolites influence adalimumab (ADL) and anti-ADL antibodies (Abs).

METHODS

Ninety-eight IBD patients previously treated with infliximab (96%) in whom trough ADL and anti-ADL Abs had been assessed as part of their clinical care were included. Thiopurine metabolites [6-thioguanine nucleotides (6-TGN) and methylated mercaptopurine metabolites (6-MeMP)] were determined at similar time points.

RESULTS

ADL-thiopurine combination therapy was not associated with reduced anti-ADL Ab positivity compared to ADL monotherapy: 8/31 (26%) versus 19/67 (28%), p = 1.00. Concentrations of thiopurine metabolites were similar in anti-ADL Ab-positive and negative patients (6-TGN median 109 pmol/8 × 10⁸ RBC vs. 112, p = 0.80; 6-MeMP 448 RBC vs. 720, p = 0.94). ADL trough levels did not differ between anti-ADL Ab-negative patients on ADL-thiopurine combination therapy and those on monotherapy (9.5 μg/mL vs. 7.6, p = 0.31). ADL levels were also comparable between patients on ADL mono- and combination therapy after stratification for 6-TGN/6-MeMP quartiles. There were no correlations between levels of 6-TGN and ADL (r_P = - 0.17, p = 0.45; r_S = - 0.38, p = 0.08), or 6-MeMP and ADL (r_P = - 0.23, p = 0.31; r_S = - 0.35, p = 0.11). Anti-ADL Ab positivity was associated with ADL treatment failure (OR 6 [2-20], p < 0.01). Higher trough ADL (9.6 μg/mL vs. 7.3, p < 0.05), but not concomitant thiopurine treatment, metabolite levels, or dosage, was associated with clinical remission.

CONCLUSION

Effectiveness of ADL therapy associated with circulating ADL levels and anti-ADL Ab formation. In this study, there appeared no direct interactions between thiopurine metabolites and ADL or anti-ADL Abs.

Prospective Observational Evaluation of Time-Dependency of Adalimumab Immunogenicity and Drug Concentrations: The POETIC Study

OBJECTIVES

Adalimumab is usually self-injected at home, making prospective serial-sampling studies challenging and scarce. This has led to a gap in knowledge about evolution of anti-adalimumab antibodies (AAAs) over time and its correlation with clinical and inflammatory outcomes.

METHODS

A program for home visits by physicians at induction, every 3 months and at event of relapse, was established prospectively for Crohn's disease (CD) patients. At each visit, patients' clinical scores were determined and sera were obtained for C-reactive protein, drug, and AAA levels. This cohort was compared to a parallel prospective cohort of infliximab-treated CD patients. In a subgroup of 29 patients, trough and in-between-trough levels were compared, to elucidate the importance of timing of sampling during the injection cycle.

RESULTS

Ninety-eight CD patients starting adalimumab were prospectively followed (median follow-up 44 weeks) and 621 serum samples were analyzed. Thirty-three patients (32%) developed AAA; 18/33 (55%) of them as early as week 2, and 26/33 (79%) by week 14. Induction period AAAs were strongly associated with primary non-response (odds ratio (OR) = 5.4, 95% confidence interval (CI): 1.6-17.8, p = 0.005). As compared to antibodies-to-infliximab (ATI), AAA formation rate over time was significantly lower (p = 0.01) and AAA were much more specific-85% of AAA events were associated with loss-of-response compared with 58% rate for ATI (p = 0.01). In 29 patients sampled serially during an injection cycle, levels of drug and AAA seemed comparable between four time-points during a single cycle both in patients with or without AAA (n = 8, n = 21, respectively).

CONCLUSIONS

When followed prospectively and serially, AAAs are found to arise earlier than previously appreciated and their impact may be more pronounced for primary rather than secondary, non-response. Drug and AAA levels were similar both at trough and in-between injections, enabling to simplify therapeutic drug monitoring of adalimumab.

Therapeutic drug monitoring of vedolizumab in inflammatory bowel disease: current data and future directions

The introduction of vedolizumab, a lymphocyte adhesion inhibitor, has expanded the relatively limited therapeutic armamentarium available for Crohn's disease and ulcerative colitis. Despite its effectiveness, both primary nonresponse and secondary loss of response to vedolizumab do occur, as is observed with the use of anti-tumour necrosis factor (TNF) therapy. Further, in a proportion, onset of efficacy may be relatively slow. A large body of data support an exposure-response relationship with anti-TNF drug levels, which has led to therapeutic drug monitoring becoming incorporated into everyday clinical management. The influence of patient and disease factors on the pharmacokinetics of anti-TNF levels, including immunogenicity, has also been examined. The role of therapeutic drug monitoring with vedolizumab is less clear. This review summarizes the available evidence on the pharmacokinetics and pharmacodynamics of vedolizumab in inflammatory bowel disease and how drug levels, immunogenicity and other factors influence clinical outcomes. Vedolizumab clearance is increased with very high body weight and hypoalbuminaemia, but is not influenced by the addition of an immunomodulator. Immunogenicity is uncommon. α4β7 receptor saturation occurs at low serum vedolizumab drug levels, and measuring it alone is insufficient to predict clinical outcomes. Using quartile analysis of vedolizumab drug levels, there appears to be a modest exposure-response relationship during induction. Drug levels at week 6 of approximately >20 μg/ml have been shown to be associated with improved clinical outcomes, including subsequent mucosal healing rates during maintenance and avoiding the need to dose escalate due to lack of response. There are currently insufficient data to support the routine use of therapeutic drug monitoring during maintenance therapy. Further studies to elucidate the role of therapeutic drug monitoring of vedolizumab are needed.

Early vedolizumab trough levels predict mucosal healing in inflammatory bowel disease: a multicentre prospective observational study

BACKGROUND

The correlation between vedolizumab trough levels during induction therapy and mucosal healing remains unknown.

AIM

To compare early vedolizumab trough levels in patients with and without mucosal healing within the first year after treatment initiation.

METHODS

We prospectively collected vedolizumab trough levels in all inflammatory bowel disease patients at weeks 2, 6 and 14 of vedolizumab treatment in three French referral centres between 1 June 2014 and 31 March 2017. Results of every patient that underwent mucosal assessment by magnetic resonance imaging and/or endoscopy in the first year after treatment initiation were analysed.

RESULTS

Median vedolizumab trough levels in the overall population (n = 82) were 27 μg/mL (interquartile range, IQR 21.2-33.8 μg/mL) at week 2, 23 μg/mL (IQR 15-34.5 μg/mL) at week 6 and 10.7 μg/mL (IQR 4.6-20.4 μg/mL) at week 14. Only median vedolizumab trough levels at week 6 differed between patients with and without mucosal healing within the first year after treatment initiation (26.8 vs 15.1 μg/mL, P = 0.035). A cut-off trough level of 18 μg/mL at week 6 predicted mucosal healing within the first year after the start of vedolizumab with an area under the receiver operating curve of 0.735 (95% confidence interval 0.531-0.939). A vedolizumab trough level above 18 μg/mL at week 6 was the only independent variable associated with mucosal healing within the first year of treatment (odds ratio 15.7, 95% confidence interval 2.4-173.0, P = 0.01).

CONCLUSION

Early therapeutic drug monitoring might improve timely detection of vedolizumab-treated patients in need for an intensified dosing regimen.

Biological therapies in inflammatory bowel disease: Beyond anti-TNF therapies

The pharmacological management of inflammatory bowel disease (IBD) over the last two decades has transitioned from reliance on aminosalycilates, corticosteroids and immunomodulators to earlier treatment with anti-tumor necrosis factor (anti-TNF) therapy. Nevertheless, 20-30% of patients discontinue anti-TNF therapy for primary non-response and another 30-40% for losing response within one year of treatment. These undesirable therapeutic outcomes can be attributed to pharmacokinetic (anti-drug antibodies and/or low drug concentrations) or pharmacodynamic issues characterized by a non-TNF driven inflammation. The latter issues necessitate the use of medications with different mechanisms of action. Besides the biologics natalizumab, vedolizumab and ustekinumab that have already been approved for the treatment of IBD new non-anti-TNF therapies are currently under investigation including small molecule drugs against Janus kinase and sphingosine-1-phosphate receptors. This manuscript will review the medications that are in the later stages of development for the treatment of IBD and directed against immune targets other than TNF.

Infliximab trough concentrations during maintenance therapy are associated with endoscopic and histologic healing in ulcerative colitis

BACKGROUND

Endoscopic and histologic healing are emerging as new therapeutic goals in ulcerative colitis (UC), as these endpoints are associated with less relapse, hospitalization and colectomy.

AIM

To investigate the association of serum infliximab trough concentrations during maintenance therapy with endoscopic or histologic healing in UC.

METHODS

In this multi-center retrospective cohort study, we included consecutive patients with moderate-to-severe UC on infliximab maintenance therapy who had an endoscopic evaluation and underwent therapeutic drug monitoring within three months of the colonoscopy, between February 2008 and March 2016. Per event analysis was performed. Endoscopic healing was defined as Mayo endoscopic sub-score of ≤1. Histologic healing was defined as no or only focal mild active inflammation.

RESULTS

Seventy colonoscopies from 56 patients were evaluated. Infliximab trough concentrations (median [interquartile range]) were significantly higher in patients with endoscopic (11.3 [7.6-14.5] vs 6.3 [0-9.8] μg/mL, P < .001) or histologic (11.1 [6.7-14.5] vs 6.7 [0-9.9] μg/mL, P = .002) healing, respectively, compared to patients without healing. Receiver-operating characteristic analyses identified infliximab trough concentration thresholds of 7.5 (area under the curve [AUC]: 0.758) and 10.5 (AUC: 0.721) μg/mL to be associated with endoscopic and histologic healing, respectively. Multiple logistic regression analysis identified infliximab trough concentration ≥7.5 (P = .013; odds ratio [OR]: 4.3; 95% confidence intervals [CI]: 1.4-13.3) and ≥10.5 μg/mL (P = .013; OR: 3.8; 95% CI: 1.3-11) as independent factors associated with endoscopic and histologic healing, respectively.

CONCLUSIONS

This study demonstrated that infliximab trough concentrations during maintenance therapy are associated with endoscopic and histologic healing in patients with UC.

Early drug and anti-infliximab antibody levels for prediction of primary nonresponse to infliximab therapy

BACKGROUND

Primary nonresponse, defined as lack of clinical benefit during the induction phase, occurs in up to 30% of IBD patients treated with infliximab. The mechanisms underlying primary nonresponse have not yet been clearly defined.

AIM

To evaluate the association of early (week 2 and week 6) induction infliximab and anti-infliximab antibody levels with primary nonresponse.

METHODS

A retrospective observational case-control study of inflammatory bowel disease patients treated with infliximab and followed at Sheba Medical Center between 2009 and 2016 was performed. Pre-infusion infliximab and antibodies to infliximab (ATI) levels were measured by our previously described drug-tolerant ELISA assay.

RESULTS

Thirty-five primary nonresponders have been identified and matched with 105 primary responders (1:3 ratios). Both week 2 and week 6 infliximab levels were significantly lower among primary nonresponders compared to responders (week 2, 6: median level 7.2, 2.2 μg/mL vs 13.5, 9.5 μg/mL, P = .0019, P < .0001 respectively). Antibodies to infliximab appeared more frequently (either week 2 or 6, 68% vs 28% prevalence, P = .0004) and at higher levels in nonresponders compared to responders (week 2, 6: median ATI 7.3, 10.8 μg/mL-eq vs 3.8, 4.4 μg/mL-eq, P = .005, P = .008 respectively). Moreover, week 2 infliximab levels <6.8 μg/mL (AUC = 0.68, P = .002, sensitivity 50%, specificity 86%) and antibodies to infliximab levels >4.3 μg/mL-eq (AUC = 0.78, P = .0004, sensitivity 77%, specificity 71%) were predictive of primary nonresponse. Among the other clinical and demographic variables, higher baseline ulcerative colitis clinical score, infliximab monotherapy, prior adalimumab therapy and previous Crohn's disease-related surgeries were also associated with an increased risk of primary nonresponse.

CONCLUSIONS

Infliximab levels below 6.8 μg/mL and antibodies to infliximab levels above 4.3 μg/mL-eq before the second infusion are associated with primary nonresponse, especially among Crohn's disease patients.