Anti-infliximab antibodies and low infliximab levels correlate with drug discontinuation in pediatric inflammatory bowel disease.

BACKGROUND: Infliximab (IFX) use is limited by loss of response often due to the development of anti-IFX antibodies and low drug levels. METHODS: We performed a single center prospective observational cohort study of pediatric and young adult subjects with inflammatory bowel disease (IBD) on IFX with over 3 years of follow-up. Infliximab levels (IFXL) and antibodies to infliximab (ATI) were measured throughout the study. Subjects were followed until IFX was discontinued. RESULTS: We enrolled 219 subjects with IBD (184: Crohn's disease; 33: Ulcerative colitis; and 2 Indeterminant colitis; 84 female, median age 14.4 years, 37% on concomitant immunomodulator). Nine hundred and nineteen serum samples (mean 4.2 ± 2.1 per patient) were tested for IFXL and ATI. During the study, 31 (14%) subjects discontinued IFX. Sixty patients had ATI. Twenty-two of those 60 patients with ATI discontinued IFX; 14 of 31 patients who discontinued IFX had detectable ATI at study onset. The combination of ATI and IFXL < 5 µg/mL at study entry was associated with the highest risk of drug discontinuation (hazard ratios [HR] ATI 4.27 [p < 0.001] and IFXL < 5 µg/mL [HR]: 3.2 p = 0.001). Patients with IFXL 5-10 µg/mL had the lowest rate of discontinuation (6%). IFX dose escalation eliminated ATI in 21 of 60 subjects. CONCLUSIONS: ATI is a strong predictor of needing to stop IFX use and inversely correlates with IFXL. Detection of ATI during therapeutic drug monitoring postinduction but also periodically during maintenance therapy identifies individuals who may benefit from IFX dose escalation and/or the addition of an immunomodulator, as these interventions may reduce or eliminate ATI.

Subcutaneous Infliximab in Refractory Crohn's Disease Patients: A Possible Biobetter?

Background: A subcutaneous formulation of infliximab (IFX-SC) approved to treat patients with inflammatory bowel disease may offer improved efficacy versus intravenous infliximab. Methods: Patients with refractory Crohn's disease (CD, n = 32) previously treated unsuccessfully with at least 2 biologics were treated with IFX-SC and followed from baseline at Week 0 (W0) to Week 30 (W30). The study's primary endpoint was the treatment's persistence at W30, while secondary goals included the analysis of serum infliximab trough levels (TL IFX), dynamics of anti-IFX antibodies (ATIs), and clinical, serum and fecal markers of CD activity during IFX-SC treatment. Results: Midterm treatment persistence with the continuation of treatment after W30 was 53%. TL IFX median values showed rapid, significant upward dynamics and exceeded 15.5 µg/mL at W30, whereas median ATI levels significantly declined. Among ATI-negative patients at W0 (n = 15), only one showed IFX immunogenicity with newly developed ATIs at W30. Among ATI-positive patients at W0, ATI seroconversion from ATI-positive to ATI-negative status was observed in 10 of 17 patients (58.8%). Patients who had continued IFX-SC treatment at W30 showed significant decreases in C-reactive protein (P = .0341), fecal calprotectin (P = .0002), and Harvey-Bradshaw index (P = .0029) since W0. Conclusions: Patients with refractory CD previously treated with at least 2 biologics exhibited clinically relevant improvement with IFX-SC, which showed less immunogenic potential than IFX-IV and highly stable TL IFX.

Free antibodies-to-infliximab are biomarker for predicting the effect of dose intensification in pediatric Crohn's disease patients with secondary loss of response.

Background: Immunogenicity to antitumor necrosis factor alpha agents, such as infliximab (IFX), may lead to therapeutic failure. Objectives: This study evaluated the relationship between free and total antibodies-to-infliximab (ATIs), trough levels (TLs) of IFX, and the response to dose intensification. Design: We performed a prospective, observational study including pediatric patients with Crohn's disease (CD) receiving IFX maintenance therapy without dose intensification. Methods: We compared clinical and laboratory outcomes according to the presence of free and total ATIs. Factors associated with response to IFX dose intensification were investigated by analyzing IFX TLs and free and total ATIs. Results: Of the 98 patients, 9 patients had detectable free ATIs and 38 patients had total ATIs. Patients with free ATIs had significantly lower TLs (0.7 versus 5.1 µg/mL, p < 0.001) than patients without free ATIs. However, there was no difference in the IFX TLs according to the presence of total ATIs (p = 0.2523). Analysis of the 38 samples with total ATIs showed that response to dose intensification was significantly lower in patients with free ATIs than those without free ATIs (22.2% versus 65.5%, p < 0.001). In addition, free ATIs were the only factor with poor response to dose intensification [odds ratio (OR): 14.15, 95% confidence interval (CI): 1.31-151.97, p = 0.0140]. According to the receiver operating characteristic analysis, the optimal cutoff level indicating non-response to IFX dose intensification was 30.0 AU/mL for free ATIs concentration (area under curve, 0.792; 95% CI: 0.590-0.942; sensitivity, 60.0%; specificity, 96.7%; p = 0.0241). Conclusion: Free ATIs, but not total ATIs, have a negative impact on the course of CD. Free ATIs are potential reliable biomarker for predicting the effect of dose intensification in patients with loss of response to IFX. Future studies based on serial and proactive therapeutic drug monitoring are required in the future.

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.

Comparison of three commercially available ELISA assays for anti-infliximab antibodies.

Three commercially available assays for the measurement of antibodies to infliximab (ATI) are approved for clinical use in Australia: Promonitor anti-infliximab (Grifols), Lisa Tracker anti-infliximab (Theradiag) and Ridascreen anti-IFX (R-Biopharm). All are bridging ELISA assays. Measurement of ATI has been incorporated into treatment algorithms for assessing loss of response to infliximab in patients with inflammatory bowel disease, but results obtained by the three ATI assays have not been systematically compared. We performed a series of experiments to allow comparison of results between the assays. Forty-two patient samples known to be positive for ATI by the Lisa Tracker assay were run on the Promonitor assay in singlicate, of which 26 were run on the Ridascreen assay in duplicate, according to the manufacturers' instructions. The Spearman correlation coefficient for all three pairwise assay comparisons was 0.95. Results were not numerically comparable between the assays. The coefficient of variation (CV) was 2.3% for the Lisa Tracker assay, 7.6% for the Promonitor assay and 7.4% for the Ridascreen assay. The presence of infliximab interfered with all three assays in a dose dependent manner. The cut-point for loss of response to infliximab dose intensification, previously demonstrated to be 200 ng/mL on the Lisa Tracker assay, is equivalent to approximately 60 ng/mL on the Ridascreen assay and between 22.9 and 41 AU/mL on the Promonitor assay. All three assays are suitable for clinical use.

Clinical efficacy of infliximab level and anti-infliximab antibody measurement in patients with inflammatory bowel disease: An audit.

BACKGROUND AND AIMS: Infliximab (IFX) monitoring has been proposed for effective therapeutic management of inflammatory bowel disease (IBD). There is no data on infliximab levels and its antibody measurement in Indian patients. We assessed the clinical efficacy of IFX level and antibodies to infliximab (ATI) monitoring in IBD patients. METHODS: Infliximab trough level and antibody testing was done in 50 and 30 IBD patients, respectively using commercially available enzyme-linked immunosorbent assay (ELISA) kits. The levels were correlated with the disease status, albumin, and C-reactive protein (CRP) levels. The clinical efficacy of level-based change in patient management was evaluated. RESULTS: Of 50 patients, IFX levels were therapeutic in 8, sub-therapeutic in 40, and supra-therapeutic in 2. High ATI titer was present in 8/30 patients. The IFX level did not correlate with the dose of 5 or 10 mg/kg. Based on IFX level and ATI estimation, management was changed in 35 patients: increase in dose in 7, decrease in dosing interval in 17, increase in interval in 2, surgery in 2, change in biologic in 5, and cessation of IFX in 2 patients. Therapy modification based on IFX level improved the clinical response in 25 patients, of whom 5 are in remission at a median duration of 2 years. CONCLUSION: Most (80%) of the IBD patients had subtherapeutic IFX levels while high ATI titers were found in 27% of the patients. There was no correlation between infliximab dose and drug levels. Therapy modification based on drug level benefitted the majority. Our results suggest that measurement of IFX level assists in attaining therapeutic levels and improves clinical response.

A Real-World Evaluation of the Long-Term Safety and Efficacy of Infliximab in the Treatment Moderate-to-Severe Psoriasis.

INTRODUCTION: Psoriasis is a chronic immune-mediated inflammatory skin disease that occurs in 2.5-3.5% of the general population. Infliximab (INF), a TNF-α inhibitor biologic agent, is a long-standing efficacious treatment for psoriasis; however, not all patients sustain a long-term response (LTR) because of a number of factors including antibody production. There is a paucity of studies assessing infliximab efficacy over a period ≥ 5 years. METHODS: A retrospective cohort chart review of our clinic patients who had undergone ≥ 5 years of treatment with infliximab for chronic plaque psoriasis was performed. The following variables were recorded and analyzed with the Fisher exact test: age, sex, body mass index ([BMI]; normal weight [NW], overweight [OW], obese [OB]), changes in infliximab strength (dose or frequency), concomitant systemic therapy, and side effects. Clinical improvement was assessed by comparing the total body surface area (tBSA) affected by psoriasis before and after treatment. RESULTS: There was a significant difference in likelihood of achieving LTR between the NW, OW and OB groups (p = 0.044). Non-normal-weight patients (OW + OB) were significantly more likely to achieve and sustain LTR than NW patients (OR 9.07, p = 0.020). There were no other significant associations for the other evaluated variables. LIMITATIONS: Patients who began treatment with infliximab before 2009 (prior to the use of the clinic's electronic medical record) were excluded. The Psoriasis Area and Severity Index (PASI) was not available for this study. CONCLUSION: Surprisingly, patients who are overweight or obese are more likely to obtain long-term clinical benefit in their psoriasis symptoms with infliximab therapy than patients who are normal weight.

Efficacy of Granulocyte and Monocyte Adsorptive Apheresis in Patients With Inflammatory Bowel Disease Showing Lost Response to Infliximab.

BACKGROUND AND AIMS: In inflammatory bowel disease [IBD] patients, antibody-to-infliximab [ATI] generation is responsible for loss of response [LOR] and infusion reaction [IR] to infliximab. An immuno-therapeutic approach is considered an option to overcome LOR. Granulocyte/monocyte adsorptive apheresis [GMA] using an Adacolumn has been shown to have clinical efficacy together with immunomodulatory effects in IBD patients. METHODS: We developed an ATI-CAI assay utilizing a C1q immobilized plate and applied it to measure ATI in patients who were receiving infliximab, including 56 with sustained response, 76 with LOR and six with IR. Furthermore, 14 patients with LOR and two with paradoxical skin reactions who received infliximab + GMA combination therapy were analysed. RESULTS: Fourteen patients with LOR, seven with Crohn's disease and seven with ulcerative colitis, showed significantly improved clinical indices [p = 0.0009], and decreased ATI [p = 0.0171] and interleukin-6 [p = 0.0537] levels at week 8 following initiation of infliximab + GMA therapy. Nine patients who received combination therapy achieved remission, which was maintained to week 24 with infliximab alone. Additionally, cutaneous lesions in two patients with IR were improved. ATI-CAI assay efficiency was not influenced by infliximab concentration during the test. Pre- and post-infliximab infusion ATI levels were not different. Patients with ATI greater than the 0.153 µg/mL cut-off value were likely to experience LOR [odds ratio 3.0]. CONCLUSIONS: Patients who received infliximab + GMA therapy appeared to regain clinical response to infliximab by a decrease in ATI level. Furthermore, the concentration of infliximab in the test did not influence ATI measurement, but was associated with clinical response.

Development of a C1q-immobilized (Cim) assay to measure total antibodies to infliximab and its clinical relevance in patients with inflammatory bowel disease.

OBJECTIVE: Determination of antibodies to infliximab (ATI) is desirable for the management of patients with inflammatory bowel disease (IBD) who receive infliximab. Conventional ligand-binding ATI-assays detect only free-form of ATI, potentially increasing the proportion of patients with undetectable ATI, but with adequate trough infliximab (TRI) level who experience loss of response (LOR) to infliximab. We investigated this assertion using a novel ATI-Cim assay. METHODS: An ATI-Cim assay was developed by utilizing a C1q-immobilized plate, detecting free-form and ATI-infliximab complexes. Plasma ATI in 137 consecutive IBD patients, 56 with sustained clinical response (SCR), 76 with LOR and 5 with infusion reactions was measured. RESULTS: ATI levels reached a plateau following addition of up to 25 µg/mL infliximab to different concentrations of free-form ATI. ATI concentration did not significantly change during infliximab infusion (P = 0.4316). ATI concentration > 0.153 µg/mL was associated with LOR (odds ratio 3.0: 95%, confidence interval 1.5 to 6.1, P = 0.0029). The number of patients with undetectable ATI was higher in SCR than in LOR, 53.6% vs 22.4% (P = 0.0004). Patients with SCR and LOR were divided into 4 subgroups by combined cut-off ATI and TRI values. (A) ATI > 0.153 µg/mL and TRI ≤ 2 µg/mL; (B) ATI > 0.153 µg/mL and TRI > 2 µg/mL; (C) ATI ≤ 0.153 µg/mL and TRI ≤ 2 µg/mL; (D) ATI ≤ 0.153 µg/mL and TRI > 2 µg/mL. The frequency of LOR showed a decreasing trend from subgroup A to D, 80.8%, 64.1%, 55.2% and 36.8%, respectively (P = 0.0003). CONCLUSIONS: The measured ATI level appeared to define the patients' response to infliximab. Combining ATI and trough infliximab levels should help to understand the mechanism of LOR and make therapeutic algorithms.

An automated mass spectrometric blood test for therapeutic drug monitoring of infliximab.

Infliximab is a monoclonal antibody therapy used to treat several chronic immune-mediated diseases, including Crohn's disease, ulcerative colitis, and rheumatoid arthritis. Infliximab acts by binding to tumor necrosis factor and, thus, inhibiting the inflammatory cascade. While it is a highly effective therapy, a subset of patients on infliximab will develop a loss of response to therapy. In these circumstances, therapeutic drug monitoring of infliximab offers a rational approach to clinical decision making and is associated with improved outcomes. While infliximab has most commonly been measured by immunometric approaches, mass spectrometric approaches offer the opportunity to improve test accuracy and reduce test costs. Herein, we describe a simple, bottom-up high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) approach for quantitation of infliximab in serum. Method development included pre-digestion and digestion experiments to determine critical sample preparation steps, optimization of the workflow and selection of rapidly produced proteolytic peptide(s) for quantitation. The workflow was further improved by automating all sample preparation steps on a robotic liquid handler, facilitating implementation in routine clinical use. A method comparison was performed against a Health Canada and US Food and Drug Administration licensed enzyme-linked immunosorbent assay. Our LC-MS/MS assay accurately reported concentrations based on drug manufacturer targets and demonstrated no interference from endogenous antibodies to infliximab; immunoassay methods did not share these performance characteristics. This LC-MS/MS method provides a workflow amenable to implementation in a clinical laboratory and desired performance characteristics for guiding clinical decision making.

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

BACKGROUND: The aim of this study was to evaluate reliability of four different assays for measuring infliximab trough levels and antibodies to infliximab (ATI). METHODS: In this non-interventional, cross-sectional study including IBD patients, infliximab levels and ATI were measured using four different assays: Lisa-Tracker, Promonitor, Q-Inflixi and Sanquin. Reliability and agreement for infliximab levels was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plots. Qualitative agreement for infliximab (based on a pre-established target window of trough levels between 3 µg/ml and 7 µg/ml) and for ATI were estimated by Cohen's kappa. RESULTS: Serum samples of 84 IBD patients were evaluated for infliximab using the four assays. Reliability was 'substantial' between Lisa-Tracker versus Promonitor and 'almost perfect' between the remaining assay pairs, with ICCs [95% confidence interval (CI)] ranging from 0.93 (0.70-0.97) for Lisa-Tracker versus Promonitor to 0.97 (0.95-0.98) for Q-Inflixi versus Sanquin. Bland-Altman plots showed significant bias between assays except Promonitor versus Q-Inflixi, which had excellent agreement. The greatest differences in mean infliximab were found between Promonitor versus Lisa-Tracker (-0.91 µg/ml) and Lisa-Tracker versus Q-Inflixi (0.69 µg/ml). Qualitative agreement for infliximab was 'almost perfect' for Promonitor versus Q-Inflixi (kappa 0.84) and Q-Inflixi versus Sanquin (kappa 0.81), and 'substantial' for the remaining pairs. More than 10% of patients who had infliximab levels within the target interval by Lisa-Tracker had suboptimal concentrations (<3 µg/ml) with Promonitor and Q-Inflixi. Furthermore, 11% of patients within the target interval by Q-Inflixi had supra-optimal levels (>7 µg/ml) by Lisa-Tracker. In the remaining paired comparisons, fewer than 5% of patients were placed in different subgroups. Qualitative agreement for ATI fluctuated between 'moderate' and 'almost perfect'. CONCLUSIONS: All four assays seem suitable for therapeutic drug monitoring of infliximab. Promonitor and Q-Inflixi had the best agreement, making those assays fully interchangeable. Systematic biases between Lisa-Tracker with Promonitor and Q-Inflixi suggest that these assays should not be interchanged during the follow up of an individual patient.

Trough level of infliximab is useful for assessing mucosal healing in Crohn's disease: a prospective cohort study.

BACKGROUND/AIMS: Decreased trough levels of infliximab (TLI) and antibodies to infliximab (ATI) are associated with loss of response (LOR) in Crohn's disease. Two prospective studies were conducted to determine whether TLI or ATI better correlates with LOR (Study 1), and whether TLI could become a predictor of mucosal healing (MH) (Study 2). METHODS: Study 1 was conducted in 108 patients, including those with LOR and remission to compare ATI and TLI in discriminating the 2 conditions based on receiver operating characteristic (ROC) curve analyses. Study 2 involved 35 patients who were evaluated endoscopically. RESULTS: In Study 1, there were no differences between the 2 assays in ROC curve analyses; the TLI cutoff value for LOR was 2.6 µg/mL (sensitivity, 70.9%; specificity, 79.2%), and the ATI cutoff value was 4.9 µg/mL (sensitivity, 65.5%; specificity, 67.9%). The AUROC (area under the ROC curve) of TLI was greater than that of ATI. AUROC was useful for discriminating between the 2 conditions. In Study 2, the TLI was significantly higher in the colonic MH group than in the non-MH group (2.7 µg/mL vs. 0.5 µg/mL, P=0.032). CONCLUSIONS: TLI is better than ATI for clinically diagnosing LOR, and a correlation was observed between TLI and colonic MH.

Long-Term Outcome of Infliximab Optimization for Overcoming Immunogenicity in Patients with Inflammatory Bowel Disease.

BACKGROUND: Preliminary data suggest that treatment optimization can reverse immunogenicity and regain response in patients with IBD and secondary loss of response (SLR) to anti-TNF therapy due to antidrug antibodies. However, data regarding the long-term outcome of these patients are scarce. AIMS: We aimed to investigate drug retention in IBD patients of whom infliximab was optimized to overcome immunogenicity and variables associated with drug retention. METHODS: This was a retrospective, multicenter study of consecutive IBD patients with antibodies to infliximab (ATI), based on either proactive or reactive therapeutic drug monitoring, who underwent infliximab optimization (increasing dose, shortening interval, adding an immunomodulator, or combination) to overcome immunogenicity from September 2012 to July 2015; they were followed through December 2015. ATI were analyzed using the drug-tolerant Prometheus homogeneous mobility shift assay. Drug retention was defined as no need for drug discontinuation due to SLR or serious adverse event. RESULTS: Our cohort consisted of 22 patients (Crohn's disease, n = 15). At the end of follow-up [median, (IQR): 17.3 (10.5-32.8) months] 77% (15/22) of patients were still on drug. Univariable Cox proportional hazards regression analysis identified first detectable ATI titer as the only variable associated with drug retention (HR: 0.89; 95% CI: 0.82-0.98, p = 0.016). Receiver-operating characteristic analysis identified an ATI titer < 8.8 U/mL associated with drug retention. CONCLUSIONS: In real-life clinical practice, optimization of infliximab therapy can prevent drug discontinuation in approximately 3/4 of patients with ATI, especially in those with low titers. Large prospective studies are needed to confirm these data.

Evaluation of Infliximab Therapy in Children with Crohn's Disease Using Trough Levels Predictors.

BACKGROUND: In adults, infliximab (IFX) levels correlate with disease activity, and antibodies to IFX (ATIs) predict treatment failure. We aimed to determine the association of IFX levels and ATIs with disease activity in a paediatric population. We prospectively collected blood, stool, and clinical data from 65 patients (age 10.5-15.1 years) with Crohn's disease (CD) before IFX administration, and measured IFX trough levels, ATIs, and faecal calprotectin levels (CPT). Samples were collected during maintenance therapy. We used multivariate analysis to identify the predictors of IFX levels. SUMMARY: Lower levels of IFX were associated with ATIs positivity (OR 0.027, 95% CI 0.009-0.077). Higher C-reactive protein (CRP) level, erythrocyte sedimentation rate, and CPT levels were found in patients with lower IFX levels. The optimal combination of sensitivity (0.5) and specificity (0.74) for disease activity was calculated for IFX levels ≥1.1 µg/mL using CRP level <5 mg/L as a marker of laboratory remission. In a model that used CPT ≤100 µg/g as the definition of remission, the optimal IFX trough level was 3.5 µg/mL. No independent association between remission and ATIs was found in our study population. However, we found an independentz association between IFX levels and serum albumin levels (OR 1.364, 95% CI 1.169-1.593), p < 0.001. Key Messages: The paediatric population was similar to adult populations in terms of the association between IFX and ATIs as well as between IFX and disease activity.

Trough level of infliximab is useful for assessing mucosal healing in Crohn's disease: a prospective cohort study

BACKGROUND/AIMS: Decreased trough levels of infliximab (TLI) and antibodies to infliximab (ATI) are associated with loss of response (LOR) in Crohn's disease. Two prospective studies were conducted to determine whether TLI or ATI better correlates with LOR (Study 1), and whether TLI could become a predictor of mucosal healing (MH) (Study 2). METHODS: Study 1 was conducted in 108 patients, including those with LOR and remission to compare ATI and TLI in discriminating the 2 conditions based on receiver operating characteristic (ROC) curve analyses. Study 2 involved 35 patients who were evaluated endoscopically. RESULTS: In Study 1, there were no differences between the 2 assays in ROC curve analyses; the TLI cutoff value for LOR was 2.6 µg/mL (sensitivity, 70.9%; specificity, 79.2%), and the ATI cutoff value was 4.9 µg/mL (sensitivity, 65.5%; specificity, 67.9%). The AUROC (area under the ROC curve) of TLI was greater than that of ATI. AUROC was useful for discriminating between the 2 conditions. In Study 2, the TLI was significantly higher in the colonic MH group than in the non-MH group (2.7 µg/mL vs. 0.5 µg/mL, P=0.032). CONCLUSIONS: TLI is better than ATI for clinically diagnosing LOR, and a correlation was observed between TLI and colonic MH.

Calprotectin and the Magnitude of Antibodies to Infliximab in Clinically-stable Ulcerative Colitis Patients are More Relevant Than Infliximab Trough Levels and Pharmacokinetics for Therapeutic Escalation.

Although infliximab (IFX) is an efficient therapy for ulcerative colitis (UC) patients, a considerably high rate of therapeutic failures still occurs. This study aimed at a better understanding of IFX pharmacokinetics and pharmacodynamics among clinically-asymptomatic UC patients. This was a multicentric and prospective study involving 65 UC patients in the maintenance phase of IFX therapy. There were no significant differences between patients with positive and negative clinical, endoscopic and histological outcomes concerning their IFX trough levels (TLs), area under the IFX concentration vs. time curve (AUC), clearance and antibodies to infliximab (ATI) levels. However, the need to undergo therapeutic escalation later in disease development was significantly associated with higher ATI levels (2.62µg/mL vs. 1.15µg/mL, p=0.028). Moreover, and after adjusting for disease severity, the HR (hazard ratio) for therapeutic escalation was significantly decreased for patients with an ATI concentration below 3µg/mL (HR=0.119, p=0.010), and increased for patients with fecal calprotectin (FC) level above 250µg/g (HR=9.309, p=0.018). In clinically-stable UC patients, IFX pharmacokinetic features cannot predict therapeutic response on a short-term basis. However, high levels of ATIs or FC may be indicative of a future therapeutic escalation.

Detection of adalimumab and antibodies to adalimumab using a homogeneous mobility shift assay.

OBJECTIVE: In 2013 a novel commercial test was launched (Anser 1 ADA test) for the assay of serum adalimumab (ADL) and antibodies to adalimumab (ATA). This study aims to understand clinical practice patterns used with ADL in a real-world cross-sectional population. METHODS: Wilcoxon rank sum test, and linear and logistic regression methods were applied in the statistical analysis to test hypotheses. The study design was observational and uncontrolled. RESULTS: Of a total of 14,239 tests conducted, 5509 had information available that pertained to reasons for ordering, of which disease monitoring (46.9%) was the most common. Median serum ADL level with standard maintenance dosing (40 mg, biweekly) was 8.8 µg/mL (n = 2901). A five-fold decrease in median serum ADL levels occurred with very low ATA titers (1.7-3 U/mL, p < .0001). Serum ADL levels decreased further with ATA >7 U/mL (p < .0001). A total of 16.5% of patients were ATA positive, of whom 61.9% had low ATA (1.7-7 U/mL); 87.9% of ATA-positive patients had serum ADL levels ≤4.4 µg/mL. Expression of inflammatory markers significantly increased with high ATA (>7 U/mL). An inverse relationship between ADL and ATA was observed (R2: 0.49), and 4.1 µg/mL was identified as a cut-off that may segregate ATA-positive patients. CONCLUSION: In this real-world cross-sectional population, serum ADL levels decreased with increasing ATA titers, with low ATA titers (≤7 U/mL) significantly reducing serum ADL compared to ATA-negative samples. Expression of inflammatory markers significantly increased at higher ATA titers (>7 U/mL). These findings highlight the clinical importance of monitoring patients for drug levels and anti-drug antibody titers.

Comparisons of Serum Infliximab and Antibodies-to-Infliximab Tests Used in Inflammatory Bowel Disease Clinical Trials of Remicade®.

Monitoring infliximab (IFX) concentrations and antibodies-to-IFX (ATI) titers during inflammatory bowel disease treatment may allow more informed decisions in assessing exposure/response and determining appropriate dosing. To aid in interpreting results from different commercial tests in the context of Janssen's published Remicade® results, the reliability of Janssen's IFX and ATI assays was compared with commercial assays from KU Leuven, Sanquin, Dynacare, and LabCorp. Test results were independently reported to Janssen. All assays were tested for specificity, selectivity, and precision. ATI assays were evaluated for sensitivity, drug interference, and potential interference of tumor necrosis factor-alpha (TNF-α). IFX assays were specific, accurate, and reproducible. Intra-class correlation of Janssen IFX assay results with those from KU Leuven, Sanquin, Dynacare, and LabCorp were 0.960, 0.895, 0.931, and 0.971, respectively. ATI titers >10 interfered with IFX assessment in all IFX assays, whereas TNF-α (≤50 ng/mL) did not interfere with IFX detection in any assay. ATI assays specifically and reproducibly detected ATI. Janssen, Sanquin, and LabCorp ATI methods were more resistant to IFX interference than Dynacare and KU Leuven, which were affected by IFX concentrations at ≥2 µg/mL. TNF-α (<5 ng/mL) did not interfere with ATI detection. Strong agreement was observed between Janssen's IFX and ATI assays and the diagnostic service provider assays. Our study results indicate that all four commercially available assays are suitable for therapeutic drug monitoring of IFX. The substantial agreement reported here between the comparator assays and the Janssen drug-tolerant assay provides support to clinicians in their use of these commercial assays, and for understanding their patients' IFX and ATI results relative to published data from clinical studies of Remicade.

Comparison of infliximab drug measurement across three commercially available ELISA kits.

The monitoring of infliximab drug levels aids in the management of several autoimmune diseases, notably inflammatory bowel disease. Several commercial kits are now available and approved by the Therapeutic Goods Administration (TGA) for the measurement of infliximab levels, but there have been limited verification or comparison studies to date. Finding an assay that most accurately measures infliximab is essential for optimal drug titration and patient management. We performed this study to compare the performance of the Grifols Promonitor, Theradiag Lisatracker and R-Biopharm Ridascreen enzyme linked immunosorbent assay (ELISA) kits. Preparations of serum containing known concentrations of infliximab were assayed using each kit, including in the presence of interference from anti-infliximab antibodies, autoantibodies and other biological agents. The Lisatracker kit provided the most accurate determination of infliximab drug levels, however it yielded false positive results at low concentrations of infliximab. The average coefficients of variation (CVs) for the kits were 8% for Lisatracker, 5% for Ridascreen and 11% for Grifols. Infliximab measurements across all kits were affected by interference from antibodies to infliximab (ATI). This study identified the Lisatracker kit as the most accurate in quantifying infliximab levels, although it was limited by false positive results at low concentrations of infliximab as well as interference from ATI. This has important implications for the monitoring and management of patients receiving infliximab therapy.

Infliximab Concentration Thresholds During Induction Therapy Are Associated With Short-term Mucosal Healing in Patients With Ulcerative Colitis.

BACKGROUND & AIMS: Mucosal healing is an independent predictor of sustained clinical remission in patients with ulcerative colitis (UC) treated with infliximab. We investigated whether infliximab concentrations during induction therapy are associated with short-term mucosal healing (STMH) in patients with UC. METHODS: We performed a retrospective, single-center analysis of data collected from a tertiary referral center from 101 patients with UC who received scheduled induction therapy with infliximab at weeks 0, 2, and 6 and had an endoscopic evaluation at baseline and after induction therapy. STMH was defined as Mayo endoscopic sub-score ≤1, assessed at weeks 10-14, with baseline sub-score ≥2. Infliximab concentrations were evaluated in serum samples collected at weeks 0, 2, 6, and 14 of infliximab therapy by using an enzyme-linked immunosorbent assay we developed. RESULTS: Fifty-four patients (53.4%) achieved STMH. Patients with STMH had a higher median infliximab concentration at weeks 2, 6, and 14 than patients without STMH. A receiver operating characteristic (ROC) analysis identified infliximab concentration thresholds of 28.3 (area under the ROC curve [AUROC], 0.638), 15 (AUROC, 0.688), and 2.1 µg/mL (AUROC, 0.781) that associated with STMH at weeks 2, 6, and 14, respectively. Multiple logistic regression analysis identified infliximab concentration ≥15 at week 6 (P = .025; odds ratio, 4.6; 95% confidence interval, 1.2-17.1) and ≥2.1 µg/mL at week 14 (P = .004; odds ratio, 5.6; 95% confidence interval, 1.7-18) as independent factors associated with STMH. CONCLUSIONS: In an analysis of data from real-life clinical practice, we associated infliximab concentrations during the induction therapy with STMH in patients with UC.