Infliximab Drug Levels Research Articles

PTU-065 Four-Way Comparison of Elisa Methods Available for the Measurement of Infliximab and Anti-Infliximab Antibody in IBD Patients

Introduction Commercial assays are now widely available and in routine use for the therapeutic drug monitoring of Infliximab (IFX) and anti-Infliximab antibody (ADAb). Although results generated using these assays are used to guide clinical decision making, there is no standardisation and data assessing the comparability between these assays is lacking. Methods A prospective evaluation of IFX drug levels and ADAb was performed using our standard ELISA assay; LISA TRACKER (Theradiag) and also Promonitor (Proteomika), IDKmonitor (Immundiagnostik) and RIDASCREEN IFX (R-Biopharm AG / KU Leuven) ELISA assays. 105 samples from 102 IBD patients were analysed for IFX, free ADAb (LT/PRO) and total ADAb (ID) automated on eRobot and Grifols Triturus analysers. LT, PRO and RS kits were provided at no cost.Method comparisons were performed using difference plots and Passing Bablok analysis. Results A summary of IFX drug level comparison data is shown in the image below. The distribution of bias between methods was variable (-6.7% to +87.8%) with PRO and ID showing scattered, bimodal distributions of %bias. A consistent, proportional relationship was observed between LT and RS results. Free ADAb were detected in 4/105 (3.8%) samples using LT and 3/105 using PRO. All patients with detectable free ADAb had undetectable IFX drug levels. Conversely, total ADAb were detected in 23/105 (21.9%) samples but IFX drug levels were sub-therapeutic ( 2.0 ug/mL) in the majority of cases (13/23). Conclusion These results show that there is significant variation in IFX drug levels obtained when using different CE marked ELISA assays and as such, results are not directly comparable. Although the clinical utility of measuring total ADAb is yet to be established, a significant proportion of patients tested will be positive for total ADAb irrespective of therapeutic IFX drug levels. In the absence of assay standardisation and external quality assurance, laboratory providers and clinicians should ensure that assays currently in routine use are fit for purpose. Disclosure of Interest None Declared

PWE-017 Prospective Evaluation of The Safety and Efficacy of Switching Stable Patients with Inflammatory Bowel Disease from Remicade™ to Biosimilar Infliximab (IFX)

Introduction Biosimilar IFX (CT-P13; RemsimaTM/InflectraTM) became available in the UK in February 2015 offering significant savings to the NHS. Efficacy and safety data in inflammatory bowel disease (IBD) is limited. From May 2015 IBD patients at the Royal Devon and Exeter NHSFT were switched from RemicadeTM to Biosimilar IFX. We reviewed efficacy and safety data during this switch. Methods Treatment was evaluated in IBD patients who met the following criteria: i) RemicadeTM treatment for greater than 6 months prior to switch ii) minimum follow-up data of 6 months following switch. Disease activity scores (Harvey-Bradshaw Index for Crohn’s disease [CD] and Simple Colitis Score for ulcerative colitis [UC]), CRP, drug levels and total anti-drug antibody levels were collected immediately prior to biosimilar switch and then every 16 weeks. All adverse events were recorded. Results 104 patients (54 male) met the inclusion criteria with a mean age of 43 years (range 17–71). 73 had CD, 29 had UC and 2 had IBD-unclassified. The median duration of RemicadeTM therapy prior to switch was 1137 days (95% confidence interval = 933–1290). Missing cases were excluded on a variable by variable basis. There was no significant difference in CRP (median pre-switch = 2, post-switch = 2, P = 0.81) or disease activity score (median pre-switch = 1, post-switch = 1, P = 0.44) after switching from RemicadeTM to Biosimilar IFX. 85% were in remission before compared with 81% six months following switch (P = 0.51). There was no difference in the number of people with detectable total anti-drug antibody levels (pre-switch = 29, post-switch = 27, P = 0.88) but a fall in drug levels was noted after switching (median pre-switch =5.4, post-switch = 2.8, P = 0.01). 41% had significant anti-drug antibodies pre-switch compared to 36% at 6 months post switch (P = 0.50). 11% of patients had positive anti-drug antibodies with undetectable drug levels pre-switch compared to 7% at 6 months (P = 0.35). 4 patients had adverse events within eight months of switching to biosimilar IFX; 2 minor infusion reactions and 2 anti-TNF induced skin disease. 19 patients stopped within six months of switching; 6 electively, 9 due to loss of response and 4 for other reasons. Conclusion This uncontrolled data suggests biosimilar IFX is safe and effective with no significant change observed in CRP, disease severity index and drug antibody levels six months after switch. The fall in IFX drug level after switch warrants further investigation. Disclosure of Interest K. Bennett: None Declared, G. Heap Grant/research support from: Hospira, Knapp, Abbvie, MSD, S. Hawkins: None Declared, T. Ahmad Grant/research support from: Hospira, Knapp, Abbvie, MSD

P616. Early infliximab drug levels predict perianal fistula response to treatment

P616. Early infliximab drug levels predict perianal fistula response to treatment

PWE-038 Utility of measuring infliximab drug levels and anti-drug antibodies in clinical practice: a large ibd referral centre experience

<h3>Introduction</h3> The development of infliximab (IFX) drug level and anti-drug antibody (ADA) testing has allowed a personalised approach to IFX use in inflammatory bowel disease (IBD). We present our 2-year experience at a tertiary IBD centre. <h3>Method</h3> All IFX drug and ADA levels measured in patients managed at the Guy’s and St. Thomas’ IBD centre were reviewed. Indications for carrying out drug levels, subsequent changes in management and long-term outcomes were evaluated. <h3>Results</h3> 330 levels were measured in 199 patients from May 2012 to October 2014. Median IFX levels were 4.1 (range 0- &gt;8 µg/ml). 109 (33%) levels were sub therapeutic (≤2.0 µg/ml), of which 61 patients were symptomatic. This resulted in a change in management in 44 (72%) of those patients. ADA were detected in 22 tests (7%) from 19 patients. 12 patients were switched to adalimumab of which 11 continue (median 11 months follow-up) and 1 was a primary non-responder. 4 patients continued on IFX but were optimised on thiopurines, only 1 of which had a subsequent improvement in disease activity. 1 patient stopped anti-TNF therapy due to demyelination, and 2 discontinued anti-TNF to take part in clinical trials. 121 levels (37%) were measured in patients with loss of response (LOR) of whom 50 (41%) had sub therapeutic levels (&lt;2.0 µg/ml). 27 patients, all with no detectable antibodies, underwent dose escalation. 32 levels (10%) were measured at week 14 after standard induction of IFX resulting in 3 patients being switched to adalimumab (Ada) due to significant antibody detection (&gt;200 U/ml) and 1 patient having their dose increased to 10 mg/kg due to borderline levels (2.0 µg/ml) along with poor clinical response. 97 levels (29%) were measured as part of annual reassessment resulting in only 8 changes in management. 1 patient with levels &gt;8 µg/ml had a de-escalation from 10 to 5 mg/kg and 3 had their dose increased due to low levels. As a result of inactive disease, 4 out of the 81 patients with therapeutic IFX levels were able to be withdrawn. The remaining levels were measured after a change in dose of IFX (17%) or for consideration of: withdrawal of concomitant immunosuppression (1%), dose reduction (3%) and withdrawal from IFX (3%). <h3>Conclusion</h3> IFX drug and antibody level testing is being increasingly used in clinical practice. The benefits seem greatest in patients with LOR although our understanding of their utility in other circumstances is increasing. <h3>Disclosure of interest</h3> E. Johnston: None Declared, B. Warner: None Declared, J. Digby-Bell: None Declared, N. Unsworth: None Declared, S. Anderson: None Declared, J. Sanderson: None Declared, Z. Arkir: None Declared, P. Irving Speaker Bureau of: MSD, Abbvie and Takeda.

PTU-077 Association between crohn’s disease activity and therapeutic drug monitoring of thiopurines and infliximab comparing free and total antidrug antibody measurement: Abstract PTU-077 Table 1

<h3>Introduction</h3> Therapeutic drug monitoring (TDM) of infliximab (IFX) is useful in patients with Crohn’s disease (CD). Therapeutic cut-offs to predict active disease and the influence of thiopurines on drug levels (DL) according to 6-thioguanine nucleotide (TGN) are not defined. There is limited data on the utility of free anti-drug antibodies (ADAb) against total ADAb. We assessed the utility of TDM of IFX in CD using a commercially available ELISA and investigated the influence of TGNs on DL and free/total ADAb. <h3>Method</h3> Prospective evaluation of trough DL and ADAb using Lisa-Tracker, ((LT), Theradiag, France) and Immundiagnostik ELISA, ((IM), Germany) in 79 CD patients (male = 40) between January and May 2014. Only free ADAb is detected with LT assay, whereas IM assay measures total ADAb (semiquantitative). Total ADAb results were calculated using the cut off control. Results of TDM were assessed with respect to faecal calprotectin (FC), C-reactive protein (CRP) and clinical activity (Harvey Bradshaw Index, (HBI) &lt;5 remission). The relationship between TGN and DL/ADAb was also assessed. LT kits were provided by Theradiag. <h3>Results</h3> Higher DL were observed amongst patients in remission (HBI &lt;5 DL 4.7 vs 1.7 μg/mL (p = 0.01), CRP &lt;5 mg/L DL 5 vs 2.5 μg/mL (p = 0.007), FC &lt;250 μg/g DL 5.6 vs 2.9 μg/mL (p = 0.001), FC &lt;59 μg/g DL 5.8 vs 3.3 μg/mL (p = &lt;0.001)). ROC curve analysis including thresholds to detect active disease are shown in Table 1. ADAb were detected in 3 (4%) patients using LT vs 19 (24%) using IM assay. All patients with ADAb with LT had undetectable DL and had active disease on FC59. Total ADAb with IM assay did not correlate with outcomes. Concomitant immunomodulation use was associated with absence of ADAb using IM assay (p = 0.03), however a therapeutic TGN (&gt;245 pmol/8 × 10⁸) was not associated with ADAb (p = 0.5). TGN quartile analysis did not identify a value associated with DL (p &gt; 0.5), nor was a therapeutic TGN associated with higher DL (p = 0.7). <h3>Conclusion</h3> IFX DL were inversely related to disease activity. A cut-off of 3.0–5.7 μg/mL was associated with active disease depending on the definition used. The presence of free ADAb was associated with active inflammation, whereas the presence of total ADAb was not. There was no relationship between TGN and DL or ADAb, although most patients were adequately dosed. This study highlights the limitations and utility of TDM in IBD. <h3>Disclosure of interest</h3> B. Warner: None Declared, M. Ward: None Declared, E. Johnston: None Declared, P. Irving Speaker Bureau of: AbbVie, MSD, Takeda, Warner Chilcott, Shire, Ferring and Tillotts Pharma.

Tu1279 Biomarkers Predict Lack of Response to Anti-TNF in Moderate to Severe Ulcerative Colitis

Background The optimal target anti-TNF drug level that correlates with control of intestinal inflammation in IBD patients is still poorly defined. We aimed to define infliximab and adalimuamb serum levels that distinguish patients with mucosal healing (MH) from those with ongoing inflammation. Methods We conducted a retrospective study of 135 IBD (107 Crohn's disease, CD, 28 ulcerative colitis, UC) patients treated with infliximab (n=75) or adalimumab (n=60) maintenance therapy, who underwent lower endoscopy at a tertiary medical center. Infliximab/adalimumab drug levels were measured in temporal relation to endoscopy, and correlated with inflammatory markers (CRP) and with endoscopic evaluation of disease activity (SES-CD and MAYO scores for CD and UC respectively). Results Median drug levels (DL) were significantly higher in patients withMH vs. patients with endoscopically active disease, for both infliximab and adalimumab therapy (4.3 vs. 1.15 μg/ml, p=0.0002, 6.2 vs. 3.1 μg/ml, p=0.044, respectively). Patients whose CRP normalized under treatment, similarly had higher median DL than those who did not (4 vs. 2 μg/ml, p=0.022 for infliximab, 5.7 vs. 2.2 μg/ml, p=0.015 for adalimumab, respectively). Infliximab DL above 5.8 μg/ml (AUC=0.75, p<0.0001) and adalimumab levels above 7.4 μg/ml (AUC=0.68, p= 0.03) had 85% specificity for achieving MH. Incremental gain analysis demonstrated that 50% of patients achieved MH when infliximab serum levels were above 4μg/ml and 75% reached MH with levels above 8μg/ml, whereas for adalimumab 50 and 75% of patients achieved MH when DL were above 7.5 and 10mcg/ml, respectively. Higher anti-TNF levels (infliximab DL above 8μg/ml or adalimumab DL above 10mcg/ml) were associated with only a negligible incremental increase of MH percentage.Conclusions Infliximab and adalimumab serum levels were significantly associated with MH. Infliximab DL above 5.8μg/ml and adalimumab DL above 7.4μg/ml had 85% specificity for MH, whereas increasing infliximab DL above 8μg/ml or adalimumab DL above 10mcg/ml conferred little additional endoscopic benefit.

Su1206 Association Between Crohn's Disease Activity and Therapeutic Drug Monitoring of Thiopurines and Infliximab Comparing Free and Total Antidrug Antibody Measurement

Introduction Therapeutic drug monitoring (TDM) of infliximab (IFX) is useful in patients with Crohn’s disease (CD). Therapeutic cut-offs to predict active disease and the influence of thiopurines on drug levels (DL) according to 6-thioguanine nucleotide (TGN) are not defined. There is limited data on the utility of free anti-drug antibodies (ADAb) against total ADAb. We assessed the utility of TDM of IFX in CD using a commercially available ELISA and investigated the influence of TGNs on DL and free/total ADAb. Method Prospective evaluation of trough DL and ADAb using Lisa-Tracker, ((LT), Theradiag, France) and Immundiagnostik ELISA, ((IM), Germany) in 79 CD patients (male = 40) between January and May 2014. Only free ADAb is detected with LT assay, whereas IM assay measures total ADAb (semiquantitative). Total ADAb results were calculated using the cut off control. Results of TDM were assessed with respect to faecal calprotectin (FC), C-reactive protein (CRP) and clinical activity (Harvey Bradshaw Index, (HBI) Results Higher DL were observed amongst patients in remission (HBI 245 pmol/8 × 10 8 ) was not associated with ADAb (p = 0.5). TGN quartile analysis did not identify a value associated with DL (p > 0.5), nor was a therapeutic TGN associated with higher DL (p = 0.7). Conclusion IFX DL were inversely related to disease activity. A cut-off of 3.0–5.7 μg/mL was associated with active disease depending on the definition used. The presence of free ADAb was associated with active inflammation, whereas the presence of total ADAb was not. There was no relationship between TGN and DL or ADAb, although most patients were adequately dosed. This study highlights the limitations and utility of TDM in IBD. Disclosure of interest B. Warner: None Declared, M. Ward: None Declared, E. Johnston: None Declared, P. Irving Speaker Bureau of: AbbVie, MSD, Takeda, Warner Chilcott, Shire, Ferring and Tillotts Pharma.

Significance of low level infliximab in the absence of anti-infliximab antibodies.

To evaluate the prevalence of double negative (DN) sera and the mechanisms responsible for DN status. Sera of inflammatory bowel disease patients treated with infliximab (IFX) were tested for drug/antibodies to infliximab (ATI) trough levels and the proportion of DN results was compared between a commercially available double antigen ELISA (with labeled IFX as the detection antibody) and an anti-lambda ELISA (with anti-human lambda chain detection antibody). Repeat testing with lower than customary serum dilution (1:10) was performed. Patients with DN status were matched with IFX+/ATI- controls and were followed-up for subsequent development of non-transient ATI to investigate if DN status precedes ATI. Of 67 sera obtained at time of loss of response, only 6/67 (9%) were DN by anti-lambda ELISA compared to 27/67 (40%) with double antigen ELISA (P < 0.001, Fisher's Exact test). Of the latter 27 sera, 22% were also DN by anti-lambda ELISA, whereas 44% were actually IFX positive (IFX+ATI-), 30% were ATI positive (IFX-ATI+) and 4% were double positive (IFX+ATI+). Re-testing using a 1:10 dilution converted most DN results into IFX+ and /or ATI+ status. Patients with DN status had shorter survival free of non-transient ATI compared with matched controls (log rank test, P < 0.001). In 9/30 (30%) of these patients, non transient ATI occurred before and after the event at which the DN serum was obtained, supporting the view that a DN result may represent a particular time-point along the two curves of ATI titer rise and infliximab drug level decline. DN status may result from false negative detection of IFX or ATI by double antigen ELISA, suggesting a transitional state of low-level immunogenicity, rather than non-immunological clearance.

Commentary: detection of infliximab levels and anti‐infliximab antibodies

Clinicians treating inflammatory bowel disease frequently face the dilemma of loss of response to anti-TNF agents. Previous studies have demonstrated that poor clinical outcomes relate to a lack of circulating drug and the secondary development of antibodies to monoclonal antibodies including infliximab (ATI). 3 However, there is variability and a lack of standardisation in existing infliximab drug level and antidrug antibody assays. The nicely written manuscript by Vande Casteele et al., addresses these concerns by setting up a robust round robin experiment evaluating both serum samples and spiked control samples to compare three different European assays from the Netherlands, Belgium, and France. While the authors conclude that there was a good correlation of infliximab and ATI measurements between the assays, of concern, the commercially available Biomedical Diagnostics (BMD) kit from Paris, France, detected false positive infliximab levels in nearly a fifth of the samples. This has implications for the recently published retrospective study by Pariente et al. who utilised the BMD kit and concluded in contrast to existing literature and, perhaps incorrectly, that antibodies to infliximab may not predict response to intensification of infliximab therapy in patients with IBD. With the recent interest in therapeutic monitoring of anti-TNF therapy to optimise clinical outcomes for patients, there has been an explosion in the number and type of assays reported in the medical literature ranging from solid phase to fluid phase assays, different platforms, including radio-immunoassays and enzyme-linked immunosorbent assays, and differences in the antigenic targets e. g. double-antigen vs. antilambda chain assays. In the absence of a gold standard assay, most importantly, this article highlights the need for stringent assessment, standardisation and validation of any future assays before they become commercially available and used for clinical decision making.

Detection of Anti Infliximab Antibodies in Patients with Inflammatory Bowel Disease (IBD) in the Presence of Infliximab by Homogeneous Liquid Phase Anti Infliximab Mobility Shift Assay

Purpose: Trough levels (TL) as well as c-max levels have been positively associated with efficacy and negatively with immunogenicity of infliximab (IFX) in patients with IBD. Degradation of IFX is mainly determined by the presence of anti drug antibodies (ADA), increasing its clearance between 1.4 and 2.7 fold. With evidence accumulating in favour of the concept of therapeutic drug monitoring, standard enzyme linked immunosorbent assays (ELISA) for the detection of ADA reach their limits, as the presence of high IFX levels strongly interferes with the detection of ADA. Here we assess the perfomance of a new assay for the detection of ADA at midinfusion timepoints as compared to samples immediately prior to the next IFX infusion. Methods: 90 consecutive patients with established IBD (66 with Crohn's disease, 24 with Ulcerative Colitis) under maintenance therapy with IFX were asked to participate. Serum samples were acquired at half time between two infusions and immediately prior to the subsequent infusion. IFX drug levels were measured by ELISA (Immundiagnostik, Germany) and ADA were assessed by homogeneous liquid phase anti Infliximab mobility shift assay (HLPA) (Prometheus Labs Inc. CA) for all time points. Results: Patients were receiving a median dose of IFX of 5,51 mg/kg body-weight (4,08-10,94), yielding a median TL of 8.98 yg/ml IFX. Infliximab serum levels were significantly higher at mid infusion versus TL (p=0.000). ADA were detectable in 19 patients and 23 patients at mid infusion and trough timepoints, respectively. 17 patients were concordantly positive, 2 were positive soley at mid infusion and 6 at time of trough sampling. The agreement for the outcome positive ADA measured at week 4 versus week 8 yields a Cohen's kappa of 0,80, with a correlation of t=0,651 (p=0.001). ADA occurred most frequently in patients with non-detectable or very low TL (Table 1).Table: IFX trough levels and presence of ADAConclusion: With HLPA, it is feasible to detect ADA against IFX with excellent accordance not only at low levels of circulating infliximab but also earlier within an infusion interval, when IFX concentrations are high and interfering with conventional ELISAs. ADAs are preferrentially detected in patients with negative or low TLs. Disclosure: The work presented here was supported by Prometheus Labs Inc. who performed the mentioned analyses free of charge. This research was supported by an industry grant from Pormetheus Labs Inc.

P290 Infliximab drug levels in Crohn's disease responding to the treatment

P290 Infliximab drug levels in Crohn's disease responding to the treatment

Therapeutic infliximab drug level in a child born to a woman with ulcerative colitis treated until gestation week 31

A 26year old woman with ulcerative colitis was treated with regular infliximab (IFX) infusions until gestation week 31, and gave birth to a healthy child at gestation week 37. Maternal IFX trough level was relatively high during the course of pregnancy. In the infant, therapeutic level of IFX was detectable at week 16 after birth, but not at reassessment at week 28. Anti-IFX antibodies were consistently below the detection limit in the patient and in the child. This case illustrates that IFX is transferred through the placenta to the embryo, and may result in therapeutic drug levels in the newborn child despite IFX discontinuation in third trimester 6weeks prior to delivery. The half life of IFX appeared markedly longer in infants as compared to adults. The safety of IFX beyond the first trimester is unknown, and this case highlights the need for further investigations of maternal transfer of IFX as well as the risks associated with IFX administrations in the second and third trimester.