Clinical implications of variations in anti-infliximab antibody levels in patients with inflammatory bowel disease

Reactive Immunomodulator Addition to Infliximab Monotherapy Restores Clinical Response in Inflammatory Bowel Disease: A Meta-Analysis

BACKGROUND AND AIMS

Patients with inflammatory bowel disease (IBD) receiving infliximab (IFX) commonly experience immunogenic loss of response (LOR) by formation of anti-drug antibodies (ADAs). An immunomodulator (IMM) used in combination with initial IFX induction is known to reduce ADA development and improve clinical outcomes. We aimed to assess the impact of reactively adding an IMM to patients on IFX monotherapy.

METHODS

We conducted a retrospective cohort study and systematic review with meta-analysis of patients with IBD demonstrating immunologic LOR, with or without clinical LOR, that had an IMM (azathioprine, 6-mercaptopurine, or methotrexate) reactively added (reactive combination therapy; rCT) to combat elevated ADAs and raise IFX level. Data were extracted for pooled effect size estimation using random-effects models, and ADA and IFX trough levels were compared pre- and post-IMM initiation.

RESULTS

We identified 6 patients who received rCT due to rising ADA titers and low IFX levels. Median ADA titer decreased from 506 ng/mL (interquartile range (IQR) [416-750]) to 76.5 ng/mL (IQR [25.8-232]), an 85% decrease (p = 0.031). Median IFX trough increased from 0.4 µg/mL (IQR [0.4-0.48]) to 8.25 µg/mL (IQR [3.7-9.6]), a 20.6-fold increase (p = 0.038). Meta-analysis pooled effect size of 7 studies with 89 patients showed an 87% ADA titer reduction [95% confidence interval (CI) = 72-94%], 6.7-fold increased IFX trough (95% CI = 2.4-18.7), and 76% clinical remission rescue rate (95% CI = 59-93%).

CONCLUSIONS

These results suggest rCT is a valid rescue strategy in patients with immunogenic LOR to IFX to reduce ADA titers, restore therapeutic IFX levels, and recapture clinical remission of IBD.

Outcomes of Infliximab-Treated inflammatory bowel disease patients undergoing therapeutic drug monitoring with two different assays

OBJECTIVES

There are multiple assays for infliximab (IFX) drug level (IFX-DL) and antibody to infliximab (ATI) measurement. The aims of this study are to examine the correlation and outcomes of IFX-DL and ATI in inflammatory bowel disease (IBD) patients, simultaneously measured with different methods in different institutions.

DESIGN AND METHODS

Residual samples of IFX-treated IBD patients undergoing drug monitoring for IFX-DL and ATI, both measured by ECLIA (Esoterix Laboratories) were used to simultaneously quantify IFX-DL via LC-MS/MS and ATI via an in-house ECLIA (ih-ECLIA) (Mayo Clinic Laboratories). Comparisons of IFX-DL and ATI detection between the assays from different institutions were performed, along with a comparison between the assays by association of IFX-DL and ATI obtained by each method with clinical remission, endoscopic healing (EH) and normal serum C-reactive protein (CRP ≤ 8 mg/L).

RESULTS

A total of 151 patients were included (median age, 32 years (range, 12-84); 45.7% female). The median IFX-DL was 7 mcg/mL (IQR: 1.3, 19.4) and 6 mcg/mL (IQR: 0.9, 20) via LC-MS/MS and ECLIA, respectively (Spearman correlation coefficient r = 0.97). ATI was detected in 13/142 (9.2%) via ih-ECLIA of whom 100% had IFX-DL < 5 mcg/mL by LC-MS/MS. ATI was positive in 39/151 (25.8%) via ECLIA, and 84.6% of positives had IFX-DL < 5 mcg/mL by ECLIA. Compared to ECLIA, the frequency of ATI detection via ih-ECLIA was lower in patients in clinical remission (7.3% vs 36.6%; p = 0.0005), those with normal CRP (5.9% vs. 20.0%; p = 0.0005), and in patients with EH (5.3% vs 18.4%; p = 0.03).

CONCLUSIONS

IFX-DL was comparable between LC-MS/MS and ECLIA assays. Rate of ATI detection via ih-ECLIA was lower than ECLIA, which was more aligned with favorable clinical outcomes.

Past, Present and (Foreseeable) Future of Biological Anti-TNF Alpha Therapy

Due to the key role of tumor necrosis factor-alpha (TNF-α) in the pathogenesis of immunoinflammatory diseases, TNF-α inhibitors have been successfully developed and used in the clinical treatment of autoimmune disorders. Currently, five anti-TNF-α drugs have been approved: infliximab, adalimumab, golimumab, certolizumab pegol and etanercept. Anti-TNF-α biosimilars are also available for clinical use. Here, we will review the historical development as well as the present and potential future applications of anti-TNF-α therapies, which have led to major improvements for patients with several autoimmune diseases, such as rheumatoid arthritis (RA), ankylosing spondylitis (AS), Crohn's disease (CD), ulcerative colitis (UC), psoriasis (PS) and chronic endogenous uveitis. Other therapeutic areas are under evaluation, including viral infections, e.g., COVID-19, as well as chronic neuropsychiatric disorders and certain forms of cancer. The search for biomarkers able to predict responsiveness to anti-TNF-α drugs is also discussed.

A Systematic Review on the interest of Drug Tolerant assay in the monitoring of Inflammatory Bowel Disease

Many patients with inflammatory bowel disease (IBD) are treated with anti-tumor necrosis factor (TNF) therapies, of which infliximab (IFX) is most commonly used. Loss of response (LOR) to anti-TNF therapy due to immunogenic failure accounts for 20% of subsequent medical intervention and is defined, using a drug sensitive assay, as low or undetectable concentration of drug with high titers of anti-drug antibodies (ADAb). We performed a systematic review to investigate the use of a drug tolerant assay during both induction and maintenance to monitor patients treated with anti-TNFs. After the search on PubMed, 90 publications were reviewed. Most ADAb detection methods are drug sensitive, cannot detect ADAb in the presence of drug, and therefore cannot be used close to drug administration, when the drug concentration is too high. To overcome this major limitation, several drug-tolerant techniques have been developed and will be discussed in this review. Using drug-tolerant assays ADAb against infliximab (IFX) or adalimumab (ADM) can be detected during induction and predict primary non-response or LOR. Drug sensitive assays do not allow detection of ADAb during the induction phase as IFX or ADM concentration is typically high.

Retrospective Database Analysis: Dose Escalation and Adherence in Patients Initiating Biologics for Ulcerative Colitis

BACKGROUND

Biologic therapies are often used in patients with ulcerative colitis (UC) who are nonresponsive to conventional treatments. However, nonresponse or loss of response to biologics often occurs, leading to dose escalation, combination therapy, and/or treatment switching. We investigated real-world treatment patterns of biologic therapies among patients with UC in the USA.

METHODS

This study analyzed data from the IBM® MarketScan® Commercial and Medicare Supplemental Databases (medical/pharmacy claims for >250 million patients in the USA) to identify patients with UC initiating a biologic therapy (adalimumab, infliximab, golimumab, or vedolizumab) with 12 months of follow-up post-initiation. Key measures were patient baseline characteristics, dose escalation (average maintenance dose >20% higher than label), adherence (proportion of days covered), and ulcerative colitis-related healthcare costs in the 12 months following biologic therapy initiation.

RESULTS

Of 2,331 patients included in the study (adalimumab [N = 1,291], infliximab [N = 810], golimumab [N = 127], and vedolizumab [N = 103]), 28.1% used concomitant immunosuppressant therapy within 12 months post-initiation. Overall, 23.6% (adalimumab), 34.8% (infliximab), 9.9% (golimumab), and 39.2% (vedolizumab) of patients dose escalated within 12 months. Patients who dose escalated incurred USD 20,106 higher total UC-related healthcare costs over 12 months than those who did not. Adherence (covariate-adjusted proportion of days covered) ranged from 0.63 to 0.73, and 39.3% of patients discontinued within 12 months (median treatment duration = 112 days).

CONCLUSION

Dose escalation was common, and incurred higher costs, in patients with UC initiating biologic therapies. Suboptimal adherence and/or discontinuation within 12 months of initiation occurred frequently, highlighting the challenges in managing these patients.

Anti-infliximab antibodies and clinical response in noninfectious uveitis and scleritis patients treated with infliximab: A retrospective review

Purpose

To investigate the clinical response to infliximab in ocular inflammation patients who develop anti-infliximab antibodies (AIA) vs. those patients who do not develop AIA.

Observations

A retrospective review was performed of patients treated with infliximab for noninfectious uveitis (NIU) or scleritis. Clinical response was determined as a composite clinical endpoint and classified as complete, partial, or absent. Nine of 32 infliximab-treated patients (28%) were found to develop AIA. Among the AIA-positive patients, clinical response was complete in 7 patients (78%) and partial in 2 patients (22%). Among the AIA-negative patients, clinical response was complete in 15 patients (65%), partial in 6 patients (26%) and absent in 2 patients (9%). Serum infliximab levels tended to decrease with appearance of AIA but rarely became undetectable.

Conclusions and Importance

In this pilot study, AIA-positive patients did not have diminished clinical response to infliximab when compared with AIA-negative patients. There was a high rate of complete clinical response to infliximab in this group of NIU and scleritis patients. Approximately a quarter of patients developed AIA. AIA-positive patients did not have diminished rates of clinical response when compared with AIA-negative patients. This suggests that routine AIA monitoring may not be clinically useful, although validation of this finding in larger cohorts is necessary.

Differential Serum-intestinal Dynamics of Infliximab and Adalimumab in Inflammatory Bowel Disease Patients

BACKGROUND AND AIMS

Therapeutic drug monitoring is used to guide anti-tumour necrosis factor [TNF] therapy. However, the associations between serum drug levels [SDL], TNF-bound, and free anti-TNF in the target tissue are incompletely defined. We aimed to assess the interactions between these parameters in inflammatory bowel disease [IBD] patients.

METHODS: ENZYME-LINKED IMMUNOSORBENT

assays [ELISA assays] were used to detect free drug and TNF-drug complexes in intestinal tissues. Concurrent SDL, anti-drug antibodies [ADA], pharmacotherapy, clinical response, endoscopic appearance, and histological severity were determined. Comparisons between anti-TNFs and paired inflamed/non-inflamed tissue were performed. Variables were correlated and potential interactions detected using multivariate analysis.

RESULTS

A total of 95 biopsies taken from 49 anti-TNF treated IBD patients [26 receiving infliximab and 23 adalimumab] were studied. Free drug levels were higher in inflamed compared with non-inflamed paired specimens. Tissue free-drug and TNF-drug complexes levels were higher in adalimumab-treated patients. In adalimumab-treated patients, SDL were correlated with free drug, but not TNF-drug complex levels, in both inflamed and non-inflamed segments. In infliximab-treated patients, higher SDL were associated with the presence of tissue free drug in both inflamed and non-inflamed segments, whereas TNF-drug complexes were mostly detected in non-inflamed but not in inflamed tissue. In the presence of ADA, neither free drug nor TNF-infliximab complexes were measured in the tissue. Tissue levels did not correlate well with clinical, endoscopic, or histological scores.

CONCLUSIONS

SDL correlated with tissue free drug levels; however, different dynamics were observed for TNF-drug complex levels. Infliximab and adalimumab tissue drug dynamics differ. Better understanding of these interactions may allow future therapeutic optimisation.

The Impact of Intermediate Antidrug Antibodies to Infliximab and Adalimumab on Clinical Outcomes in Patients with Crohn’s Disease or Ulcerative Colitis

Background: The anti-TNF drugs adalimumab (ADA) and infliximab (IFX) are effective treatments for inflammatory bowel disease (IBD). However, 40% of patients lose response, often due to the development of antibodies-to-ADA (ATA) and antibodies-to-IFX (ATI). While low ATA/ATI titres (<200 ng/mL) are associated with better outcomes and high ATA/ATI titres (>1,000 ng/mL) are associated with poorer outcomes, the significance of intermediate ATA/ATI titres (200–999 ng/mL) is not well understood. This study aims to investigate the impact of intermediate ATA/ATI titres on outcomes in patients with IBD. Methods: A retrospective chart review of 376 patients with IBD was conducted. The primary clinical outcome was persistence on anti-TNF therapy for 1 year after the measurement of ATA/ATI titres. The participants consisted of patients with IBD treated with IFX or ADA at the University of Maryland Medical Center’s Inflammatory Bowel Disease Program between October 2016 and October 2019. Results: Out of 322 patients with low titres, 271 persisted on their original anti-TNF, compared with nine out the 15 patients with intermediate titres (p=0.026) and one out the 10 patients with high titres (p<0.0001). The odds ratio of persistence when comparing intermediate titres to low titres was 0.26 (0.09–0.80), and when comparing high titres to low titres was 0.02 (0.00–0.14). Conclusion: Patients with intermediate titres were more likely to lose response to anti-TNF drugs and require a change in anti-TNF therapy than patients with low titres. Although the sample size of patients with intermediate titres was small, providers should consider dose optimisation of anti-TNF drugs, with or without the addition of an immunosuppressant, when intermediate titres are present.

Association of polymorphisms in promoter region of TNF-α -238 and -308 with clinical outcomes in patients with immune-mediated inflammatory diseases on anti-TNF therapy

The hypothesis of the study was that polymorphisms in promoter regions -238 and -308 of TNF-α could be associated with different clinical outcomes in inflammatory bowel diseases (IBD) and immune-mediated rheumatic diseases (IMRD). The aim was to examine the possible association of both polymorphisms with concentration of C-reactive protein (CRP) and fecal calprotectin (fCAL), onset of the remission and development of the ADA in patients on therapy with anti-TNF inhibitors. The prospective study was done in patients with IBD and IMRD on infliximab (IFX) or adalimumab (ADM). Patients were genotyped for TNF-α -238 and -308 polymorphisms. The concentration of CRP, fCAL, IFX or ADM and antibodies to drugs were measured according to manufacturer's instructions and followed-up for 6 or 12 months. Out of all patients (N = 112), number of patients in remission did not differ according to genotypes (for IBD patients P = 0.509 vs 0.223; for IMRD patients P = 0.541 vs 0.132 for TNF-α -238 and -308, respectively). Initial CRP concentration was higher in IBD patients with TNF-α -308 GG than GA/AA genotypes in patients who failed to achieve remission [11.8 (4.4-39.6) vs 3.1 (1.5-6.5), P = 0.033]. In IBD patients with remission, fCAL concentration after at least 6 months of therapy was higher in TNF-α-308 GG than in GA genotype [52 (25-552) vs 20 (20-20) µg/g, P = 0.041]. Our results showed the association of TNF-α -308 GG genotype with a higher concentration of CRP and fecal calprotectin in patients with inflammatory bowel diseases on IFX or ADM therapy. Clinical remission and development of antibodies to anti-TNF drugs were not associated with TNF-α -238 and -308 polymorphisms.

Dynamics of serum concentrations of antibodies to infliximab: a new approach for predicting secondary loss of response in inflammatory bowel diseases

BACKGROUND

Antibodies to infliximab (ATI) in serum are associated with secondary loss of response (LOR) to infliximab (IFX) therapy in patients with inflammatory bowel disease (IBD). However, feasible ATI-related predictors of therapy success are lacking and knowledge about individual ATI dynamics is limited. Therefore, this study analyzed whether ATI dynamics are able to predict LOR to IFX therapy and compared their predictive power with known predictors of LOR to IFX.

METHODS

This was a retrospective study of patients with Crohn's disease (CD) or ulcerative colitis (UC) on IFX maintenance therapy and proactive IFX and immunogenicity monitoring in an outpatient clinic in Germany. Slopes of ATI (S _ATI) and IFX levels (dynamic parameters) and medians of ATI, IFX, C-reactive protein, and fecal calprotectin (static parameters) were calculated over a defined period of time after ATI emergence. Dynamic and static parameters were analyzed for associations with end points infliximab discontinuation due to secondary LOR and total IFX discontinuation.

RESULTS

In all, 500 visits from 38 IBD patients (28 CD, 10 UC) with a median IFX maintenance duration of 68.2 weeks were evaluated. Grouping by S _ATI (ATI-N = ATI nondetectable, ATI- ↓  = negative S _ATI, ATI- ↑  = positive S _ATI) yielded significant differences for outcomes LOR (p = 0.004) and total IFX discontinuation (p = 0.01). Patients in the ATI-↓ group survived significantly longer LOR-free compared with the ATI-↑ group (p = 0.02). Cox regression confirmed S _ATI to be a significant risk factor for LOR (p = 0.002). An S _ATI cut-off of approximately 2.0 AU mL^-1 week^-1 was determined to predict LOR with 83.3% sensitivity and 93.8% specificity.

CONCLUSION

The ATI slope-based index S _ATI is a new feasible diagnostic predictor of LOR in IBD patients. S _ATI may facilitate quick therapeutic decisions after ATI emerge.

Impact of Switching on Pharmacokinetics of Therapeutic Biologics and Interchangeability Assessment-A Simulation Study

The risk in terms of safety or diminished efficacy of switching between an originator biological product and a proposed interchangeable product is an important consideration for interchangeability evaluation in the regulatory framework. This simulation study evaluated the impact of several switching study design scenarios on the pharmacokinetic (PK) assessment between a virtual originator biological product and a virtual proposed interchangeable product. Our results show that (1) at least 3 switches are needed to optimize the detection of potential PK differences, (2) the initial incidence of antidrug antibodies after treatment with the reference product in the lead-in period is a significant covariate affecting the PK results, and (3) the area under the concentration-time curve is more sensitive than peak concentration in assessing the impact of switching on PK similarity. Our simulation work illustrates that a range of factors should be carefully considered when designing a switching study for the assessment of interchangeability between 2 biological products.

Drug Levels Associated with Optimal Discrimination Between Remission and Non-Remission and Comparison of Antibody Assays During First Year of Stable Infliximab Maintenance Therapy in Inflammatory Bowel Disease

BACKGROUND

In order to implement therapeutic drug monitoring (TDM)-based strategies for infliximab (IFX) in inflammatory bowel disease (IBD), the authors assessed IFX levels for optimal discrimination between remission and non-remission and compared assays for anti-IFX antibodies (Abs).

METHODS

The retrospective cohort comprised 163 bionaïve patients with IBD who received stable IFX maintenance therapy (5 mg/kg every 8 weeks [q8w]) for one year. The clinical and biochemical remission status was assessed at all infusions (weeks 14-22-30-38-46-54), and IFX and anti-IFX Abs were estimated using a time-resolved fluorometric assay (n=690; 88% of infusions). Samples positive for anti-IFX Abs or IFX levels <limit of detection (LOD; n=102) were analyzed by two binding assays (ELISA) and functional reporter gene assay/drug-tolerant enzyme immunoassay (RGA/EIA).

RESULTS

At all assessed time points, IFX levels were more than double in patients presenting clinical or biochemical remission. An IFX concentration of 4.5 µg/mL was associated with clinical remission during the entire first year of therapy (sensitivity 54% [49-59], specificity 73% [67-78], AUCROC 0.65 [0.60-0.69], p<0.0001); these values were comparable with biochemical remission. Exploratory assessments for endoscopic remission (n=131) were performed at the discretion of the treating physician. Anti-IFX Abs were associated with undetectable IFX and treatment failure (OR 2.9 [1.4-6.0], p<0.01), irrespective of persistency or transiency. All performed assays detected anti-IFX Abs in [SWUNG DASH]2/3 of samples. Binding assays demonstrated a higher sensitivity to anti-IFX Abs.

CONCLUSION

IFX at [SWUNG DASH]5 µg/mL was associated with clinical and biochemical remission during the first year of maintenance therapy. During this phase of therapy, standard binding assays are appropriate for TDM.

Clinical Relevance of Anti-TNF Antibody Trough Levels and Anti-Drug Antibodies in Treating Inflammatory Bowel Disease Patients

Background and Aims

The majority of patients treated with anti-tumor necrosis factor (TNF) therapy develop anti-drug antibodies (ADAs), which might result in loss of treatment efficacy. Strict guidelines on measuring trough levels (TLs) and ADA in clinical routine do not exist. To provide real-world data, we took advantage of our tertiary inflammatory bowel disease (IBD) center patient cohort and determined indicators for therapeutic drug monitoring (TDM) and actual consequences in patient care.

Methods

We retrospectively collected clinical data of 104 IBD patients treated with infliximab or adalimumab in our IBD clinic. Patients with TL and ADA measurements between June 2015 and February 2018 were included.

Results

The main reason for determining TL was increased clinical disease. Subtherapeutic TLs were found in 33 patients, therapeutic TLs in 33 patients, and supratherapeutic TLs in 38 patients. Adjustments in anti-TNF therapy occurred more frequently (p = 0.01) in patients with subtherapeutic TL (24 of 33 patients; 73%) as compared to patients with therapeutic and supratherapeutic TLs (26 of 71 patients; 37%). No correlation could be found between TL and disease activity (p = 0.16). Presence of ADA was found in 16 patients, correlated with the development of infusion reactions (OR: 10.6, RR: 5.4, CI: 2.9-38.6), and was associated with subtherapeutic TL in 15 patients (93.8%). Treatment adaptations were based on TL and/or ADA presence in 36 of 63 patients.

Conclusions

TDM showed significant treatment adaptations in patients with subtherapeutic TL. Conversely, in patients with therapeutic and supratherapeutic TLs, reasons for adaptations were based on considerations other than TL, such as clinical disease activity. Further studies should focus on decision-making in patients presenting with supratherapeutic TL in remission.

Monocytes from infliximab-resistant patients with Crohn's disease exhibit a disordered cytokine profile

Crohn's disease (CD) is a chronic inflammatory disorder characterized by immune response dysregulation. Tumor necrosis factor-α (TNFα) is a key cytokine in the pathogenesis of CD, as indicated by the efficacy of anti-TNF-α therapy with infliximab (IFX). However, approximately 30-40% of CD patients fail to respond to IFX with still unclear underlying mechanisms. This study compares the inflammatory phenotype of monocytes from CD patients, who respond or non-respond to IFX. Under basal conditions, the mRNA for the cytokines TNFα, IL-23, IL-1β and the chemokines CXCL8/IL-8, CCL5/RANTES and CCL2/MCP-1 was up-regulated in monocytes from non-responders than responders. The expression of the same cytokines and CCL2/MCP-1 was higher in non-responders also upon LPS treatment. Moreover, higher secretion of TNFα, IL-1β, IFNγ and IL-2 proteins occurred in the supernatants of LPS-treated non-responders cells. Resistance to IFX in CD may result from a transcriptional dysregulation of circulating monocytes, leading to hyperactivation of pro-inflammatory pathways. Monocytes' cytokine profile may thus represent a predictive marker of response to IFX. Monocytes were isolated from blood samples of 19 CD patients (11 responders, 8 non-responders) and incubated with or without LPS. Cytokine profiles were assessed by RT-qPCR and, in the supernatants, by ELISA assay.

Immunogenicity-unwanted immune responses to biological drugs - can we predict them?

INTRODUCTION

Biological agents (BAs) target molecules involved in disease mechanisms and have modified the natural history of several immune-mediated disorders. All BAs are immunogenic, resulting in the formation of antidrug antibodies (ADAs), which can neutralize drug activity leading to loss of response and potential relapse, or serious adverse events such as infusion hypersensitivity reactions. The production of ADAs is the result of a specific adaptive immune response in which T and B cells are involved.

AREAS COVERED

Factors conditioning the immunogenicity of BAs, including drug-, treatment- and patient-related factors are currently the subject of many studies. Among them, a lot of attention is dedicated to define the impact of BAs structure, the effect of targeting (soluble or membrane) molecules, the impact of interruption of therapy as well as the role of genetic (HLA and non-HLA) predisposing factors and disease activity.

EXPERT OPINION

Knowledge of factors capable of influencing the immunogenicity of BAs may help to understand, in a predictive manner and at the single patient level, the presence of risk factors influencing the production of ADAs and their impact on clinical outcomes.

Immunogenicity of TNF-Inhibitors

Tumor necrosis factor inhibitors (TNFi) have significantly improved treatment outcome of rheumatic diseases since their incorporation into treatment protocols two decades ago. Nevertheless, a substantial fraction of patients experiences either primary or secondary failure to TNFi due to ineffectiveness of the drug or adverse reactions. Secondary failure and adverse events can be related to the development of anti-drug antibodies (ADA). The earliest studies that reported ADA toward TNFi mainly used drug-sensitive assays. Retrospectively, we recognize this has led to an underestimation of the amount of ADA produced due to drug interference. Drug-tolerant ADA assays also detect ADA in the presence of drug, which has contributed to the currently reported higher incidence of ADA development. Comprehension and awareness of the assay format used for ADA detection is thus essential to interpret ADA measurements correctly. In addition, a concurrent drug level measurement is informative as it may provide insight in the extent of underestimation of ADA levels and improves understanding the clinical consequences of ADA formation. The clinical effects are dependent on the ratio between the amount of drug that is neutralized by ADA and the amount of unbound drug. Pharmacokinetic modeling might be useful in this context. The ADA response generally gives rise to high affinity IgG antibodies, but this response will differ between patients. Some patients will not reach the phase of affinity maturation while others generate an enduring high titer high affinity IgG response. This response can be transient in some patients, indicating a mechanism of tolerance induction or B-cell anergy. In this review several different aspects of the ADA response toward TNFi will be discussed. It will highlight the ADA assays, characteristics and regulation of the ADA response, impact of immunogenicity on the pharmacokinetics of TNFi, clinical implications of ADA formation, and possible mitigation strategies.

Infliximab-Tumor Necrosis Factor Complexes Elicit Formation of Anti-Drug Antibodies

BACKGROUND & AIMS

Some patients develop anti-drug antibodies (ADAs), which reduce the efficacy of infliximab, a monoclonal antibody against tumor necrosis factor (TNF), in the treatment of immune-mediated diseases, including inflammatory bowel diseases. ADAs arise inconsistently, and it is not clear what factors determine their formation. We investigated features of the immune system, the infliximab antibody, and its complex with TNF that might contribute to ADA generation.

METHODS

C57BL/6 mice were given injections of infliximab and recombinant human TNF or infliximab F(ab')₂ fragments. Blood samples were collected every 2-3 days for 2 weeks and weekly thereafter for up to 6 weeks; infliximab-TNF complexes and ADAs were measured by enzyme-linked immunosorbent assay (ELISA). Intestinal biopsy and blood samples were obtained from patients having endoscopy who had received infliximab therapy for inflammatory bowel diseases; infliximab-TNF complexes were measured with ELISA. Infliximab-specific plasma cells were detected in patient tissue samples by using mass cytometry. We studied activation of innate immune cells in peripheral blood mononuclear cells (PBMCs) from healthy donors incubated with infliximab or infliximab-TNF complexes; toll-like receptors (TLRs) were blocked with antibodies, endocytosis was blocked with the inhibitor PitStop2, and cytokine expression was measured by real-time polymerase chain reaction and ELISAs. Uptake of infliximab and infliximab-TNF complexes by THP-1 cells was measured with confocal microscopy.

RESULTS

Mice given increasing doses of infliximab produced increasing levels of ADAs. Blood samples from mice given injections of human TNF and infliximab contained infliximab-TNF complexes; complex formation was associated with ADA formation with an area under the curve of 0.944 (95% confidence interval, 0.851-1.000; P = .003). Intestinal tissues from patients, but not blood samples, contained infliximab-TNF complexes and infliximab-specific plasma cells. Incubation of PBMCs with infliximab-TNF complexes resulted in a 4.74-fold increase in level of interleukin (IL) 1β (IL1B) messenger RNA (P for comparison = .005), increased IL1B protein secretion, and a 2.69-fold increase in the expression of TNF messenger RNA (P for comparison = 0.013) compared with control PBMCs. Infliximab reduced only IL1B and TNF expression. Antibodies against TLR2 or TLR4 did not block the increases in IL1B or TNF expression, but endocytosis was required. THP-1 cells endocytosed higher levels of infliximab-TNF complexes than infliximab alone.

CONCLUSIONS

In mice, we found ADA formation to increase with dose of infliximab given and concentration of infliximab-TNF complexes detected in blood. Based on studies of human intestinal tissues and blood samples, we propose that infliximab-TNF complexes formed in the intestine are endocytosed by and activate innate immune cells, which increase expression of IL1B and TNF and production of antibodies against the drug complex. It is therefore important to optimize the infliximab dose to a level that is effective but does not activate an innate immune response against the drug-TNF complex.

Wide variation in the use and understanding of therapeutic drug monitoring for anti-TNF agents in inflammatory bowel disease: an inexact science?

BACKGROUND

We aimed to understand the way in which therapeutic drug monitoring (TDM) is used, understood and interpreted for anti-TNF agents in IBD.

RESEARCH DESIGN AND METHODS

We designed an 18-question survey that included 5 TDM-based clinical scenarios, for which the 'most appropriate' responses were based on the BRIDGe groups 'Anti-TNF Optimizer'. This resource combines TDM evidence with expert consensus.

RESULTS

We received 110 complete responses: 50 (45%) consultants, 30 (27%) trainees, 25 (23%) IBD nurse specialists and 5 (5%) gastroenterology pharmacists. Over half (61, 55%) only carry out TDM in non-response. The remainder use TDM routinely, including during stable maintenance therapy for patients in remission. Lower therapeutic thresholds used were variable. Most (82, 75%) were unsure whether their laboratory uses a drug-tolerant or drug-sensitive antidrug antibody assay and few (15, 14%) understand the difference. Consultants, high-frequency users (> 3requests/month) and clinicians with larger anti-TNF cohorts (> 100) were significantly more likely to select the 'most appropriate' answer to at least 1 of the 5 TDM-based clinical scenarios.

CONCLUSIONS

There exists marked heterogeneity in the practical use, understanding and interpretation of biologic TDM. Biologic decision-making, informed by TDM, should involve consultation with experienced clinicians who are frequent TDM users, ideally, as part of a multidisciplinary, biologics-focused IBD meeting.

ABBREVIATIONS

TDM: therapeutic drug monitoring; CNS: clinical nurse specialist; ELISA: enzyme-linked immunosorbent assay; RIA: radioimmunoassays; HMSA: homogenous mobility shift assays; BSG: British Society of Gastroenterology.

Evaluation of Rapid vs Standard Infliximab Infusions in the Pediatric Population

BACKGROUND

Rapid 1-hour infliximab infusions have been safely implemented in adults, but studies of these rapid infusions in pediatric patients are limited. This study's primary objective was to determine the safety of 1-hour infliximab infusions compared with standard 2- to 3-hour infusions in children with inflammatory bowel disease and other autoimmune disorders.

METHODS

We conducted an institutional review board-approved prospective study using an unmatched historical control group at a freestanding children's hospital comparing rapid vs standard infusion rates of infliximab and the use of premedications and immunomodulatory agents on the frequency of early and delayed infusion reactions.

RESULTS

There were 50 subjects with 540 total standard (2- to 3-hour) infusions in the retrospective group and 66 subjects with 545 total rapid (1-hour) infusions assessed in the prospective group. Although the prospective group received a significantly higher infliximab dose, was significantly less likely to receive premedication, and was significantly more likely to receive another immunomodulatory agent, only 2 instances of potential infusion reactions occurred in the 545 rapid infusions (0.36%; 95% confidence interval [CI], 0.22%-11.01%; 3% of patients) administered in the prospective group compared with 1 documented infusion reaction (0.19%; 95% CI, 0.0%-11.47%; 2% of patients) in the retrospective group (odds ratio, 0.65; 95% CI, 0.01-12.93; P = 0.99).

CONCLUSIONS

This study suggests that rapid infusion of infliximab over 1 hour is not associated with an increased risk of infusion reactions when compared with standard 2- to 3-hour infusions and can be safely used in children with no previous reaction to standard infusions to treat inflammatory bowel disease and other autoimmune diseases.

Infliximab trough levels and persistent vs transient antibodies measured early after induction predict long-term clinical remission in patients with inflammatory bowel disease

BACKGROUND

The use of therapeutic drug monitoring has been proposed as a useful tool in the management of patients with loss of response to biological therapy in patients with inflammatory bowel disease.

AIMS

To evaluate whether early, post-induction anti-tumor necrosis factor trough levels and the presence of different types of anti-drug antibodies may impact long-term clinical remission in patients with inflammatory bowel disease.

METHODS

We prospectively assessed anti-tumor necrosis factor trough levels and both persistent and transient anti-drug antibodies. The Harvey-Bradshaw Index and the partial Mayo score were evaluated at each visit or in case of relapse.

RESULTS

At week 14, median infliximab trough levels were significantly lower in patients who experienced loss of response at week 48 as compared to patients in stable remission (1.3mcg/mL [range 0-10.2mcg/mL] vs. 10.1mcg/mL[range 0-42.8mcg/mL], P<0.0004). ROC curve identified an infliximab trough levels of 6.2mcg/mL as the cut-off value with the highest accuracy (c-index=0.864) for loss of response at week 48. At week 14 we observed a correlation between anti-drug antibodies concentration and infliximab trough levels (r_s=-0.513, P=0.04).

CONCLUSIONS

The results highlight the usefulness of assessing early biological TL in order to predict patients' long-term outcome.

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

OBJECTIVE

To evaluate the clinical relevance of antidrug antibodies (ADAs) measured using a drug-tolerant assay in a post hoc analysis of the Trough Concentration (TC) Adapted Infliximab Treatment (TAXIT) randomised controlled trial.

DESIGN

ADA in serum samples (n=221) of 76 patients enrolled in TAXIT, who presented with an infliximab TC <3 µg/mL at screening, were reanalysed after optimisation and at the end of the study using a drug-tolerant ADA assay. Patients underwent dose escalation to achieve therapeutic TCs between 3 µg/mL and 7 µg/mL prior to randomisation. Patients were grouped into quartiles (Q1-4) according to ADA concentration at screening.

RESULTS

Using a drug-tolerant assay, the immunogenicity detection rate increased from 21% (drug-sensitive assay) to 63% at screening, from 0% to 51% after optimisation and from 3% to 42% at the end of TAXIT. Patients in ADA Q4 required a higher cumulative infliximab dose (2390 (880-2998) mg) to achieve target TCs, resulting in a higher drug cost (€10 712 (4120-13 596)) compared with ADA-negative patients (€2060 (1648-3296)) and patients in ADA Q1/Q2 (€2060 (1648-4120)/€2060 (1751-3296), p<0.001). However, all but one patient belonging to ADA Q4 were also ADA-positive using a drug-sensitive assay.

CONCLUSIONS

Upon dose intensification, low concentration ADAs, not detectable using a drug-sensitive assay, disappear in more than half of the patients over time and are clinically non-relevant. In contrast, high concentration ADAs which are typically also detected in a drug-sensitive assay, persist over time and necessitate a higher cumulative dose and drug cost. In the latter group, proactive drug switching may be more cost-efficient.

CLINICAL TRIALS REGISTER

2011-002061-38; Post-results.

Immunogenicity of biologics in inflammatory bowel disease

Crohn's disease and ulcerative colitis are chronic inflammatory disorders of the gastrointestinal tract. Treatment options include biologic therapies; however, a proportion of patients lose response to biologics, partly due to the formation of anti-drug antibodies (ADAbs). Concomitant immunosuppressive agents reduce the development of ADAbs. This review article aims to assess the immunogenicity of biologic therapies and their clinical implications. A comprehensive literature search was conducted for articles published January 2009 to August 2015 reporting immunogenicity to adalimumab (ADM), certolizumab pegol (CZP), golimumab, infliximab (IFX), ustekinumab, and vedolizumab in inflammatory bowel disease (IBD). Eligible articles were reviewed and quality assessed by independent reviewers. Overall, 122 publications reporting 114 studies were assessed. ADAbs were reported for all agents, but the percentage of patients developing ADAbs was extremely variable, with the highest (65.3%) being for IFX administration to patients with IBD. ADAb presence was frequently associated with a reduction in primary efficacy and a loss of response, and, for IFX, an increase in adverse events (AEs). Lower serum levels of ADM, CZP and IFX were seen in ADAbs-positive rather than ADAbs-negative patients; pharmacokinetic data were unavailable for other therapies. Little information was available regarding the timing of ADAb development; studies reported their detection from as early as 10-14 days up to months after treatment initiation. Biologic therapies carry an intrinsic risk of immunogenicity, although reported rates of ADAbs vary considerably. The clinical implications of immunogenicity are a concern for effective treatment; further research, particularly into the more recently approved biologics, is required.

Review article: consensus statements on therapeutic drug monitoring of anti-tumour necrosis factor therapy in inflammatory bowel diseases

BACKGROUND

Therapeutic drug monitoring (TDM) in inflammatory bowel disease (IBD) patients receiving anti-tumour necrosis factor (TNF) agents can help optimise outcomes. Consensus statements based on current evidence will help the development of treatment guidelines.

AIM

To develop evidence-based consensus statements for TDM-guided anti-TNF therapy in IBD.

METHODS

A committee of 25 Australian and international experts was assembled. The initial draft statements were produced following a systematic literature search. A modified Delphi technique was used with 3 iterations. Statements were modified according to anonymous voting and feedback at each iteration. Statements with 80% agreement without or with minor reservation were accepted.

RESULTS

22/24 statements met criteria for consensus. For anti-TNF agents, TDM should be performed upon treatment failure, following successful induction, when contemplating a drug holiday and periodically in clinical remission only when results would change management. To achieve clinical remission in luminal IBD, infliximab and adalimumab trough concentrations in the range of 3-8 and 5-12 μg/mL, respectively, were deemed appropriate. The range may differ for different disease phenotypes or treatment endpoints-such as fistulising disease or to achieve mucosal healing. In treatment failure, TDM may identify mechanisms to guide subsequent decision-making. In stable clinical response, TDM-guided dosing may avoid future relapse. Data indicate drug-tolerant anti-drug antibody assays do not offer an advantage over drug-sensitive assays. Further data are required prior to recommending TDM for non-anti-TNF biological agents.

CONCLUSION

Consensus statements support the role of TDM in optimising anti-TNF agents to treat IBD, especially in situations of treatment failure.

Assays for measurement of TNF antagonists in practice

Tumour necrosis factor (TNF) antagonist drug exposure is correlated with clinical, endoscopic and pathophysiological outcomes during induction and maintenance therapy. Measuring drug concentrations is therefore a useful tool when treating to target and optimising therapy. One of the main factors leading to suboptimal drug exposure is the formation of antidrug antibodies (ADAs), due to an immunogenic reaction of the immune system towards the non-self protein. The development of ADA does pose important concerns for drug efficacy and for safety as ADAs have been associated with acute infusion reactions, hypersensitivity reactions and serum sickness. Various assays exist to measure serum drug and ADA concentrations, either offered as a service in a specialised laboratory or commercially available as a kit. It is unclear how the performance of these assays relates to each other, until recently various comparative studies were carried out. The majority of these studies show that indeed a good correlation exists between the assays that measure drug, but that absolute concentrations can differ across tests. This is particularly relevant in clinical practice when a specific threshold or drug concentration range is targeted. For ADA assays, drug sensitivity or the ability of the assay to measure ADA in the presence of drug remains an important issue, especially for drugs with a higher dosing frequency. In addition, standardisation across ADA assays is difficult, making it hard to compare quantitative or semiquantitative (low/medium/high) results across assays and across studies.

Immunogenicity of Biologics in Chronic Inflammatory Diseases: A Systematic Review

OBJECTIVES

A systematic review was conducted to explore the immunogenicity of biologic agents across inflammatory diseases and its potential impact on efficacy/safety.

METHODS

Literature searches were conducted through November 2016 to identify controlled and observational studies of biologics/biosimilars administered for treatment of rheumatoid arthritis (RA), psoriatic arthritis (PsA), juvenile idiopathic arthritis (JIA), ankylosing spondylitis (AS), non-radiographic axial spondyloarthritis (nr-axSpA), psoriasis (Ps), Crohn's disease, and ulcerative colitis.

RESULTS

Of >21,000 screened publications, 443 were included. Anti-drug antibody (ADAb) rates varied widely among biologics across diseases (and are not directly comparable because of immunoassay heterogeneity); the highest overall rates were reported with infliximab (0-83%), adalimumab (0-54%), and infliximab biosimilar CT-P13 (21-52%), and the lowest with secukinumab (0-1%), ustekinumab (1-11%), etanercept (0-13%), and golimumab (0-19%). Most ADAbs were neutralizing, except those to abatacept and etanercept. ADAb+ versus ADAb- patients had lower rates of clinical response to adalimumab (RA, PsA, JIA, AS, Ps), golimumab (RA), infliximab (RA, PsA, AS, Ps), rituximab (RA), ustekinumab (Ps), and CT-P13 (RA, AS). Higher rates of infusion-related reactions were reported in infliximab- and CT-P13-treated ADAb+ patients. Background immunosuppressives/anti-proliferatives reduced biologic immunogenicity across diseases.

CONCLUSIONS

Based on reviewed reports, biologic/biosimilar immunogenicity differs among agents, with the highest rates observed with infliximab and adalimumab. As ADAb formation in biologic-/biosimilar-treated patients may increase the risk of lost response, the immunogenicity of these agents is an important (albeit not the only) consideration in the treatment decision-making process.

Effects of Transient and Persistent Anti-drug Antibodies to Certolizumab Pegol: Longitudinal Data from a 7-Year Study in Crohn's Disease

BACKGROUND

Anti-drug antibodies (ADAbs) may decrease the efficacy of biologics and increase the risk of adverse events. A single positive test may not preclude further treatment because of variations in assays used, test timing, and patient variables. We evaluated the longitudinal patterns of immunogenicity during 7 years of antitumor necrosis factor-alpha drug certolizumab pegol (CZP) treatment for moderate-to-severe Crohn's disease.

METHODS

PRECiSE 3 patients (n = 595) received open-label CZP 400 mg every 4 weeks up to 7 years. CZP-ADAb expression, plasma CZP concentration, Harvey-Bradshaw Index, C-reactive protein, and fecal calprotectin concentrations were measured multiple times. Longitudinal data, examined for CZP-ADAb positivity and categorized as transient (with temporary/no effect on CZP concentration), persistent, or negative, were correlated with clinical and biological variables.

RESULTS

Of the CZP-ADAb-positive patients, 40 (22.6%) had transient CZP-ADAbs and 94 (77.4%) had persistent CZP-ADAbs. Demographic characteristics were similar between groups. Median C-reactive protein and fecal calprotectin were higher (P < 0.05 at some visits) and plasma CZP concentrations were significantly lower (P < 0.0001 at all visits) in the persistent CZP-ADAb-positive group relative to the CZP-ADAb-negative group. Transient CZP-ADAb-positive and CZP-ADAb-negative patients had similar plasma CZP, C-reactive protein, and fecal calprotectin concentrations. Median Harvey-Bradshaw Index scores and rates of adverse events were similar among groups.

CONCLUSIONS

This analysis demonstrates that persistent CZP-ADAb has negative effects on drug levels and efficacy, whereas transient expression may not. Serial measurements may be needed to characterize ADAb positivity. www.clinicaltrials.gov, Number NCT00160524.

Magnitude of Increased Infliximab Clearance Imposed by Anti-infliximab Antibodies in Crohn's Disease Is Determined by Their Concentration

Antibodies (Abs) against infliximab (IFX) increase IFX clearance and can result in treatment failure and acute hypersensitivity reactions. However, interpretation of their clinical value is complicated by individual differences in Ab responses and methods used for quantification. The increase in IFX clearance imposed by anti-IFX Abs has generally been evaluated using a binary classification, i.e., positive or negative. This analysis aimed to investigate if anti-IFX Ab concentrations provide a more adequate prediction of alterations in clearance. Data originated from a clinical trial on Crohn's disease patients with IFX treatment failure. The trial was not originally designed for pharmacokinetic analysis. Therefore, published pharmacokinetic models were utilized as priors to enable covariate investigation. The impact of anti-IFX Abs on clearance was assessed using different mathematical relationships and exploiting information from two different quantification assays, measuring semi-quantitative "total" or "unbound neutralizing" concentrations of anti-IFX Ab, respectively. Inclusion of anti-IFX Ab status/concentration improved the model's performance for all investigated relationships. The anti-IFX Ab concentrations were superior to the binary classifications, indicating that the magnitude of increase in IFX clearance imposed by anti-IFX Abs closely relates to their concentration. Furthermore, total anti-IFX Ab concentrations appeared superior to the unbound neutralizing fraction in identifying high clearance individuals. Simulations showed that even at low concentrations, anti-IFX Abs lead to sub-therapeutic IFX concentrations, supporting a need of treatment interventions in all anti-IFX Ab positive patients. The developed model can serve as a basis for further investigations to refine treatment recommendations for patients with anti-IFX Abs.

Optimizing Treatment with TNF Inhibitors in Inflammatory Bowel Disease by Monitoring Drug Levels and Antidrug Antibodies

BACKGROUND

Biological tumor necrosis factor (TNF) inhibitors have revolutionized the treatment of inflammatory bowel disease and redefined treatment goals to include mucosal healing. Clinicians are faced with challenges such as inadequate responses, treatment failures, side effects, and high drug costs. The objective is to review optimization of anti-TNF therapy by use of personalized treatment strategies based on circulating drug levels and antidrug antibodies (Abs), i.e. therapeutic drug monitoring (TDM). Furthermore, to outline TDM-related pitfalls and their prevention.

METHODS

Literature review.

RESULTS

Circulating anti-TNF drug trough level is a marker for the pharmacokinetics (PK) of TNF inhibitors. Because of a number of factors, including antidrug antibodies, PK varies between and within patients across time leading to variable clinical outcomes. Differences in intestinal inflammatory phenotype influencing the pharmacodynamic (PD) responses to TNF inhibitors also affect treatment outcomes. As an alternative to handling anti-TNF-treated patients by empiric strategies, TDM identifies underlying PK and PD-related reasons for treatment failure and aids decision making to secure optimal clinical and economic outcomes. Although promising, evidence does not the support use of TDM to counteract treatment failure in quiescent disease. Use of TDM is challenged by methodological biases, difficulties related to differentiation between PK and PD problems, and temporal biases due to lack of chronology between changes in PK versus symptomatic and objective disease activity manifestations. Biases can be accommodated by knowledgeable interpretation of results obtained by validated assays with clinically established thresholds, and by repeated assessments over time using complimentary techniques.

CONCLUSIONS

TDM-guided anti-TNF therapy at treatment failure has been brought from bench to bedside.

The immunogenicity of biosimilar infliximab: can we extrapolate the data across indications?

Biopharmaceuticals or 'biologics' have revolutionized the treatment of many diseases. However, some patients generate an immune response to such drugs, potentially limiting clinical efficacy and safety. Infliximab (Remicade(®)) is a monoclonal antibody used to treat several immune-mediated inflammatory disorders. A biosimilar of infliximab, CT-P13 (Remsima(®), Inflectra(®)), has recently been approved in Europe for all indications in which infliximab is approved. Approval of CT-P13 was based in part on extrapolation of clinical trial data from two indications (rheumatoid arthritis and ankylosing spondylitis) to all other indications, including inflammatory bowel disease. This review discusses the validity of extrapolating immunogenicity data across indications - a process adopted by the EMA as part of their biosimilar approval process - with a focus on CT-P13.

Time Course and Clinical Implications of Development of Antibodies Against Adalimumab in Patients With Inflammatory Bowel Disease

BACKGROUND

Antibodies (Abs) against adalimumab (ADL) have been associated with low ADL levels and treatment failure.

AIM

To characterize the temporal characteristics of anti-ADL Ab appearance and possible disappearance, and determine the clinical significance on drug efficacy and disease course.

METHODS

Cohort study including inflammatory bowel disease patients in whom anti-ADL Abs had been assessed by radioimmunoassay (RIA) and, in case of disappearance, by enzyme immunoassay, and functional reporter gene assay.

RESULTS

Anti-ADL Abs were evaluated in 133 serum samples from 72 patients. Seventeen patients (24%) tested positive after median of 194 days, interquartile range of 66 to 361. The proportion with anti-ADL Abs was 22% after 1 year, and 32% from 21 months onwards. Anti-ADL Abs generally persisted at repeat assessments during continued ADL therapy (n=8). Disappearance of anti-ADL Abs during therapy (n=3) was presumably caused by methodological biases due to detection of nonfunctional nonpersistent anti-ADL Abs by RIA, or false-negative measurement at reassessment by RIA and reporter gene assay. Anti-ADL Abs appeared pharmacologically active as judged by a median ADL concentration below limit of detection versus 7.4 μg/mL in anti-ADL Ab-negative samples (P<0.0001). Anti-ADL Abs associated with loss of response (odds ratio estimated 67, P<0.0001), and shorter treatment duration (P<0.0001).

CONCLUSIONS

Abs against ADL appear in approximately one fourth of inflammatory bowel disease patients with decreasing frequency over time and usually within 1 year of therapy. Anti-ADL Abs generally persist during continued ADL therapy, and are associated with elimination of drug and treatment failure. Therefore, ADL cessation should be considered when anti-ADL Abs are detected and supported by clinical observations.

Practical Use of Infliximab Concentration Monitoring in Pediatric Crohn Disease

OBJECTIVES

Therapeutic drug monitoring (TDM) that guides infliximab (IFX) intensification strategies has been shown to improve IFX efficacy. We conducted a review to evaluate the utility of TDM in the assessment and subsequent management of IFX loss of response in our pediatric population with Crohn disease (CD).

METHODS

Single-center retrospective study of patients with CD receiving IFX that had TDM from December 2009 to September 2013. We defined subtherapeutic trough as a drug level below the detection limit of the Prometheus enzyme-linked immunoabsorbant assay and Anser reference values (1.4 and 1 μg/mL, respectively) or a mid-interval level <12 μg/mL.

RESULTS

One hundred ninety-one IFX concentration tests were performed on 72 patients with CD with loss of response to therapy as the primary indication (72%). 34% of all TDM were subtherapeutic. After initial TDM, 25 of the 72 patients received regimen intensification with 72% in clinical remission at 6 months. Including all of the TDM that resulted in IFX dose intensification, we found a significant improvement in 6-month remission rates whether intensification followed mid-interval (88% remission) or trough (56% remission) testing (P = 0.026). Antibody to infliximab was found in 14 patients with 5 occurring in the first year of therapy. Furthermore, 71% of patients with antibody to infliximab that were switched to an alternative anti-tumor necrosis factor achieved clinical remission at six months. In multivariable regression analysis, we found IFX dose (mg/kg), IFX dosing frequency (weeks), and the erythrocyte sedimentation rate at the previous infusion were significantly associated with the IFX concentration.

CONCLUSIONS

TDM in our pediatric population with CD led to informed clinical decisions and improved rates of clinical remission.

Development of a Recombinant Xenogeneic Tumor Necrosis Factor Alpha Protein Vaccine To Protect Mice from Experimental Colitis

Previous studies have highlighted the efficacy of tumor necrosis factor alpha (TNF-α) inhibitors, including monoclonal antibodies and soluble receptors, in the treatment and management of intestinal bowel disease (IBD). However, because of the immunogenicity of xenogeneic TNF-α inhibitors, antidrug antibodies (ADAs) can be triggered after repeated administration. An alternative way to target TNF-α is active immunization to elicit the production of high titers of neutralizing antibodies. In this study, we prepared a xenogeneic TNF-α protein vaccine and studied the protective effects in experimental colitis models. The xenogeneic TNF-α protein vaccine could overcome self-tolerance and induce TNF-α-specific neutralizing antibody. Moreover, the xenogeneic TNF-α protein vaccine could protect mice from acute and chronic colitis induced by dextran sodium sulfate (DSS). One possible explanation for this protective effect is the production of TNF-α-specific neutralizing antibody, which absorbed the biological activity of mouse TNF-α (mTNF-α) and failed to induce T lymphocyte apoptosis. In summary, use of the xenogeneic TNF-α protein vaccine may be a potent therapeutic strategy for IBD.

The relationship between infliximab concentrations, antibodies to infliximab and disease activity in Crohn's disease

OBJECTIVE

Although low infliximab trough concentrations and antibodies to infliximab (ATI) are associated with poor outcomes in patients with Crohn's disease (CD), the clinical relevance of ATI in patients with adequate infliximab concentrations is uncertain. We evaluated this question using an assay sensitive for identification of ATI in the presence of infliximab.

DESIGN

In an observational study, 1487 trough serum samples from 483 patients with CD who participated in four clinical studies of maintenance infliximab therapy were analysed using a fluid phase mobility shift assay. Infliximab and ATI concentrations most discriminant for remission, defined as a C-reactive protein concentration of ≤ 5 mg/L, were determined by receiver operating characteristic curves. A multivariable regression model evaluated these factors as independent predictors of remission.

RESULTS

Based upon analysis of 1487 samples, 77.1% of patients had detectable and 22.9% had undetectable infliximab concentrations, of which 9.5% and 71.8%, respectively, were positive for ATI. An infliximab concentration of > 2.79 μg/mL (area under the curve (AUC) = 0.681; 95% CI 0.632 to 0.731) and ATI concentration of < 3.15 U/mL (AUC = 0.632; 95% CI 0.589 to 0.676) were associated with remission. Multivariable analysis showed that concentrations of both infliximab trough (OR 1.8; 95% CI 1.3 to 2.5; p < 0.001) and ATI (OR 0.57; 95% CI 0.39 to 0.81; p = 0.002) were independent predictors of remission.

CONCLUSIONS

The development of ATI increases the probability of active disease even at low concentrations and in the presence of a therapeutic concentration of drug during infliximab maintenance therapy. Evaluation of strategies to prevent ATI formation, including therapeutic drug monitoring with selective infliximab dose intensification, is needed.

Serum trough infliximab and anti-infliximab antibodies in a cohort of gastroenterology and rheumatology patients' infliximab therapeutic drug monitoring

BACKGROUND

Infliximab, a monoclonal antibody directed against tumour necrosis factor, is widely used in the treatment of chronic inflammatory conditions including Crohn's disease and rheumatoid arthritis. Its use is limited by development of anti-infliximab antibodies, which can lead to loss of therapeutic efficacy. Serum infliximab and anti-infliximab antibody measurements have recently become routinely available in the UK. The study aimed to assess the clinical utility of antibodies as an adjunct to trough infliximab.

METHODS

Serum trough infliximab was measured in 201 samples from 108 gastroenterology and rheumatology patients on maintenance infliximab therapy. Results were correlated with C-reactive protein concentrations. Total anti-infliximab antibodies were measured in 164 samples.

RESULTS

The median (25th-75th percentile) trough infliximab was 3.7 µg/mL (1.2-5.2 µg/mL) and 23% of samples had a concentration ≤1 µg/mL. A notable proportion had positive anti-infliximab antibodies: 84/164 (51%), which subdivided to 85% and 28% with infliximab ≤1 and >1 µg/mL, respectively.Serum C-reactive protein was found to be significantly higher where infliximab was ≤1 compared to >1 µg/mL (10 mg/L [<5-24 mg/L] vs. <5 mg/L [<5-8 mg/L], P < 0.01), although a strict correlation was not observed. The relationship between trough infliximab and C-reactive protein differed depending on antibody status and there was no association between C-reactive protein and the presence or absence of antibodies.

CONCLUSION

Our findings support measurement of anti-infliximab antibodies only in the context of low infliximab concentrations <1 µg/mL. A higher therapeutic cut-off may be relevant in patients with negative antibodies. Further work is indicated to investigate the clinical significance of positive antibodies with therapeutic infliximab concentrations.

Undetectable anti-TNF drug levels in patients with long-term remission predict successful drug withdrawal

BACKGROUND

Low drug levels are associated with emerging loss of response to anti-TNF. However, this may not be the case in patients with long-term remission.

AIM

To investigate the outcome of anti-TNF discontinuation in patients with long-term remission and incidental undetectable drug levels.

METHODS

A retrospective cohort study examining the duration of relapse-free survival in IBD patients in remission who discontinued infliximab or adalimumab having undetectable drug levels.

RESULTS

Forty eight patients who discontinued anti-TNF while in remission and had available drug levels were identified in two centres in France and Israel (infliximab-treated 35, adalimumab-13, Crohn's disease 30, ulcerative colitis 18, mean treatment duration of 22.7 ± 12.4 months). Endoscopy/MRE before stopping showed absence of active inflammation in 40/42 (95%) of evaluated patients, while inflammatory biomarkers (CRP and/or Calprotectin) were completely normal in only 31/48 (65%) of patients. During 12 months median follow-up, relapse occurred in 16/20 (80%) of patients who stopped anti-TNF while having measurable drug levels compared with 9/28 (32%) of patients who had undetectable drug levels (OR: 8.4, 95% CI: 2.2-32, P = 0.002). Relapse-free survival after anti-TNF cessation was significantly longer in patients with absent drug compared to those with detectable drug (P < 0.001, log rank test). On multivariate analysis, a patient's decision to stop therapy was weakly associated and abnormal inflammatory biomarkers and detectable drug levels were both strongly and independently associated with a higher risk of relapse after drug discontinuation.

CONCLUSION

Incidental finding of undetectable anti-TNF drug levels in patients with stable long-term deep remission may identify a subset of patients whose clinical remission is no longer dependent on anti-TNF treatment.

Therapeutic Drug Monitoring of Anti-tumor Necrosis Factor Agents in Patients with Inflammatory Bowel Diseases

Anti-tumor necrosis factor (TNF) agents have radically changed the treatment of inflammatory bowel diseases. Although a significant amount of patients respond to therapy, others experience only a partial response or do not benefit at all. Although, in some cases, the mechanistic action of the anti-TNF therapy may explain such findings, we have now learned that many patients may instead suffer from inadequate dosing and drug exposure. Such heterogeneity in how patients respond to therapy may be explained by multiple pharmacodynamic variables, such as factors that alter drug clearance, including the level of systemic inflammation, the presence of antidrug antibodies, and concomitant use of immunomodulators. Multiple studies have found that low-serum anti-TNF levels are associated with active disease and that adjusting the dose in these cases may offer a therapeutic benefit. In this review, we discuss the most recent evidence on therapeutic drug monitoring in patients with inflammatory bowel disease receiving anti-TNF biological therapies.

Combination of C-reactive protein, infliximab trough levels, and stable but not transient antibodies to infliximab are associated with loss of response to infliximab in inflammatory bowel disease

BACKGROUND

Antibodies to infliximab [ATI] and trough levels to infliximab [TRI] are associated with loss of response in inflammatory bowel diseases [IBD]. The best way to predict loss of response [LOR] to infliximab [IFX] is unknown.

METHODS

We conducted a prospective observational cohort study enrolling all IBD patients who were in clinical remission at Week 14 after IFX treatment initiation. TRI, ATI and C-reactive protein [CRP] level were measured at Week 22 [T1] and thereafter at every other IFX infusion. Loss of clinical response was defined by a flare requiring therapeutic change [IFX dose intensification, initiation of another drug class, and/or surgery].

RESULTS

A total of 93 patients [59 Crohn's disease, mean duration of follow-up 17.2 months] were included; 32 patients [34.4%] lost clinical response during follow-up. Cumulative probability of LOR was 50% at 20 months. Mean TRI at T1 was significantly lower in IBD patients with stable ATI as compared with those with transient ATI or without ATI [0.052, 3.34 ,and 4.29 µg/ml, respectively; p = 0.001 between no ATI vs stable ATI, and p = 0.005 between stable and transient ATI] [p = 0.0001]. Three independent factors were predictive of LOR after Cox proportional hazards modelling: TRI > 5.5 µg/ml (hazard ratio [HR]: 0.21; 95% confidence interval [CI]: 0.05-0.89;p = 0.034) at T1, CRP > 5mg/l [HR: 2.5; 95% CI: 1.16-5.26; p = 0.019] at T1, and stable ATI defined by two consecutive ATI > 20ng/ml [HR: 3.77; 95% CI: 1.45-10.0; p = 0.007]. Transient ATI did not influence LOR.

CONCLUSIONS

LOR can be predicted based on a combination of CRP, TRI and stable ATI with a high degree of accuracy.