Anti-drug antibodies against anti-TNF in patients with inflammatory bowel disease: an evaluation of possible strategies.

OBJECTIVE: Immunogenicity against anti-TNF antibodies usually leads to loss of response. We aimed to evaluate the efficacy of clinical strategies to improve clinical remission and pharmacokinetics upon detection of anti-drug antibodies (ADA). METHODS: Inflammatory bowel disease (IBD) patients with ADA against infliximab or adalimumab were identified through a single centre database search covering 2004-2022. Criteria for successful intervention upon ADA detection (baseline) were clinical remission after 1 year without further change in strategy. RESULTS: Two-hundred-and-fifty-five IBD patients (206 Crohn's disease) were identified. At baseline, median ADA level was 77 AU/ml; 50.2% of patients were in clinical remission. Implemented strategies were: (1) 81/255 (32%) conservative management, (2) 102/255 (40%) anti-TNF optimisation, (3) 72/255 (28%) switch within or out of class. Switching was the most successful strategy for clinical remission (from 19% at baseline to 69% at 1 year, p < 0.001). Patients that continued the same dose anti-TNF or discontinued biological therapy were often in clinical remission, but deteriorated significantly (-22.7%, p = 0.004). Anti-TNF dose intensification with immunomodulator optimisation was the fastest (median 3.0 months, p = 0.009) and most effective (65% ADA suppression, p < 0.001) strategy to suppress ADA compared to solely anti-TNF or immunomodulator optimisation. CONCLUSIONS: Switching therapy, within or out of class, is the most successful strategy to regain and maintain clinical remission upon immunogenicity. When switching to another anti-TNF, concomitant immunomodulatory therapy should be started or continued to prevent repeated immunogenic loss of response. Anti-TNF dose escalation with concomitant immunomodulator optimisation is the fastest and most effective strategy to suppress ADA.

Immunogenicity against anti-TNF antibodies is associated with loss of response in patients with inflammatory bowel diseases and remains a clinical challenge. We investigated potential therapeutic strategies in a retrospective patient cohort focusing on clinical efficacy and pharmacokinetics.

Anti-Drug Antibody Formation Against Biologic Agents in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis.

BACKGROUND AND AIMS: Immunogenicity with formation of anti-drug antibodies (ADA) to biologics is an important reason for treatment failure in inflammatory bowel disease (IBD). Our aim was to assess the rate of ADA, the effect of combination therapy with immunomodulators on ADA and the influence of ADA on efficacy and safety of biologics for IBD treatment. METHODS: MEDLINE, Embase and Cochrane Central Register of Controlled Trials (CENTRAL) were searched from inception to April 2020 for trials of biologics that assessed immunogenicity. The overall certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluations (GRADE). The primary outcome was rate of ADA. Secondary outcomes included efficacy and safety outcomes among patients with detectable versus undetectable ADA. For dichotomous outcomes, pooled risk ratios (RR) and 95% confidence intervals (CI) were calculated. RESULTS: Data from 68 studies were analyzed and 33 studies (5850 patients) were included in the meta-analysis. Pooled ADA rates for biologic monotherapy were 28.0% for infliximab, 7.5% for adalimumab, 3.8% for golimumab, 10.9% for certolizumab, 6.2% for ustekinumab and 16.0% for natalizumab. Pooled ADA rates were 8.4% for vedolizumab and 5.0% for etrolizumab for combo- and monotherapy combined. In all biologics, ADA rates were underestimated by use of drug-sensitive ADA assays and higher dose and/or frequency. ADA rate was significantly reduced in patients treated with combination therapy for infliximab (RR 0.52; 95% CI 0.44-0.62), adalimumab (RR 0.31; 95% CI 0.14-0.69), golimumab (RR 0.29; 95% CI 0.10-0.83), certolizumab pegol (RR 0.30; 95% CI 0.14-0.67) and natalizumab (RR 0.20; 95% CI 0.11-0. 39). ADA to infliximab were associated with lower clinical response rates (RR 0.75; 95% CI 0.61-0.91) and higher rates of infusion reactions (RR 2.36; 95% CI 1.85-3.01). CONCLUSIONS: Differences in analytical methods to detect ADA hamper comparison of true ADA rates across biologics in IBD. Use of combination therapy with immunomodulators appeared to reduce ADA positivity for most biologics. For infliximab, ADA were associated with reduced drug efficacy and increased adverse events.

Efficacy of dashboard driven dosing of infliximab in inflammatory bowel disease patients; a randomized controlled trial.

OBJECTIVES: Loss of response (LOR) to infliximab (IFX) remains a challenge in the management of inflammatory bowel diseases (IBD). Proactive dosing strategies to achieve and maintain predefined IFX trough levels (TL) may prevent LOR. We aimed to investigate the efficacy of dashboard driven IFX dosing compared to standard dosing in a prospective trial in IBD patients. METHODS: In this multicentre 1:1 'PRECISION' trial, we randomized IBD patients in clinical remission (Harvey Bradshaw Index ≤4 for Crohn's disease (CD) or a partial Mayo score ≤2 for ulcerative colitis (UC)) receiving IFX maintenance treatment. The precision group (PG) received IFX dosing guided by a Bayesian pharmacokinetic model, aiming to achieve and maintain a TL of 3 µg/ml by treatment (de)escalation as indicated by the dashboard. Patients in the control group (CG) continued treatment without dose adaptations. The primary endpoint was the proportion of patients in sustained clinical remission after 1 year. RESULTS: Eighty patients were enrolled (66 CD, 14 UC), and the median [interquartile range] age was 37 years [27-51]). After one year, 28/32 (88%) of patients in the PG were in sustained clinical remission versus 25/39 (64%) in the CG (p = .017). PG patients had lower median faecal calprotectin levels after 1 year (p = .031), whereas no significant differences in median CRP levels were found. CONCLUSION: We demonstrated that the use of a Bayesian dashboard for IFX dosing in maintenance treatment for IBD reduced the incidence of LOR compared to standard dosing. Precision dosing also resulted in lower FCP levels. CLINICALTRIALS.GOV NUMBER: NCT02453776.

Tumor necrosis factor-mediated disposition of infliximab in ulcerative colitis patients.

Ulcerative Colitis (UC) is an inflammatory bowel disease typically affecting the colon. Patients with active UC have elevated tumor necrosis factor (TNF) concentrations in serum and colonic tissue. Infliximab is a monoclonal antibody directed against TNF and binds with high affinity. Target-mediated drug disposition (TMDD) is reported for monoclonal antibodies meaning that their pharmacokinetics are affected by high target affinity. Here, a TMDD model is proposed to describe the interaction between infliximab and TNF in UC patients. Data from 20 patients with moderate to severe UC was used. Patients received standard infliximab induction therapy (5 mg kg-1) at week 0, followed by infusions at week 2 and 6. IFX, anti-drug antibodies and TNF serum concentrations were measured at day 0 (1 h after infusion), 1, 4, 7, 11, 14, 18, 21, 28 and 42. A binding model, TMDD model, and a quasi-steady state (QSS) approximation were evaluated using nonlinear mixed effects modeling (NONMEM). A two-compartment model best described the concentration-time profiles of infliximab. Typical clearance of infliximab was 0.404 L day-1 and increased with the presence of anti-drug antibodies and with lower albumin concentrations. The TMDD-QSS model best described the pharmacokinetic and pharmacodynamics data. Estimate for TNF baseline (Bmax was 19.8 pg mL-1 and the dissociation constant (Kss) was 13.6 nM. This model could eventually be used to investigate the relationship between suppression of TNF and the response to IFX therapy.

Pharmacokinetics of golimumab in moderate to severe ulcerative colitis: the GO-KINETIC study.

Background: Golimumab (GLM) is approved for the treatment of moderate to severe ulcerative colitis (UC). Higher serum concentrations of anti-tumor necrosis factor (TNF) agents are associated with improved clinical and endoscopic outcomes. Correlations between GLM serum concentrations and clinical and endoscopic outcomes were investigated during induction and maintenance treatment. In addition, a population pharmacokinetic model was developed to identify factors associated with the pharmacokinetics of GLM in UC. Methods: A prospective observational trial (GO-KINETIC) was conducted in patients with moderate to severe UC receiving induction and maintenance treatment with GLM. Clinical and endoscopic outcomes were evaluated, fecal GLM concentrations were measured and pharmacokinetic data were analyzed. Results: A total of 20 patients were enrolled. At week 8 (after induction treatment), 12 out of 20 patients (60%) showed an endoscopic response (≥1 point reduction in endoscopic Mayo score). Patients with endoscopic response at week 8 had numerically higher median GLM serum concentrations at week 2 compared to endoscopic non-responders: 9.1 µg/ml [5.9-12.3] vs. 7.1 µg/mL [5.2-9.0]; p = .384, respectively. At week 52, 3/20 patients (15%) achieved endoscopic remission (endoscopic Mayo score ≤1) and continued GLM treatment. Population pharmacokinetic analysis showed an inverse association between albumin concentrations and GLM clearance. GLM concentrations were undetectable in fecal samples. Conclusions: After induction therapy, 60% of the patients showed endoscopic response. During maintenance therapy, about one third of patients discontinued GLM treatment because of loss of response. These patients might benefit from dose optimization.

Development of Reliable, Valid and Responsive Scoring Systems for Endoscopy and Histology in Animal Models for Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Although several endoscopic and histopathologic indices are available for evaluating the severity of inflammation in mouse models of colitis, the reliability of these scoring instruments is unknown. Our aim was to evaluate the reliability of the individual items in the existing indices and develop new scoring systems by selection of the most reliable index items. METHODS: Two observers scored the histological slides [n = 224] and endoscopy videos [n = 201] from treated and untreated Interleukin[IL]-10 knock-out and T-cell transferred SCID mice. Intra-rater and inter-rater reliability for endoscopy and histology scores, and each individual item, were measured using intraclass correlation coefficients [ICCs]. The Mouse Colitis Histology Index [MCHI] and Mouse Colitis Endoscopy Index [MCEI] were developed using the most reliable items. Both were correlated to the colon density and to each other and were evaluated for their ability to detect changes in pathobiology. RESULTS: The intraclass correlation coefficients (ICCs) for inter-rater agreement (95% CIs) for the total histology and endoscopy scores were 0.90 [0.87-0.92] and 0.80 [0.76-0.84], respectively. The MCHI and MCEI were highly correlated with colon density, with a Spearman Rho = 0.81[0.75-0.85] and 0.73 [0.66-0.79], respectively, and with each other, Spearman Rho = 0.71 [0.63-0.77]. The MCHI and MCEI were able to distinguish between the experimental groups within the models, with pairwise differences between the treated and untreated groups being statistically significant [p < 0.001]. CONCLUSIONS: These histological and endoscopic indices are valid and reliable measures of intestinal inflammation in mice, and they are responsive to treatment effects in pre-clinical studies.

Benzimidazoles Promote Anti-TNF Mediated Induction of Regulatory Macrophages and Enhance Therapeutic Efficacy in a Murine Model.

BACKGROUND AND AIMS: Regulatory macrophages play a critical role in tissue repair, and we have previously shown that anti-tumour necrosis factor [TNF] antibodies induce these macrophages in vitro and in vivo in IBD patients. The induction of regulatory macrophages can be potentiated using the combination of anti-TNF and thiopurines, consistent with the enhanced efficacy of this combination therapy described in clinical trials. As thiopurines are unfortunately associated with significant side effects, we here aimed to identify alternatives for combination therapy with anti-TNF, using the macrophage induction model as a screening tool. METHODS: Mixed lymphocyte reactions were treated with anti-TNF and a library of 1600 drug compounds. Induction of CD14+CD206+ macrophages was analysed by flow cytometry. Positive hits were validated in vitro and in the T cell transfer model of colitis. RESULTS: Among the 98 compounds potentiating the induction of regulatory macrophages by anti-TNF were six benzimidazoles, including albendazole. Albendazole treatment in the presence of anti-TNF resulted in alterations in the tubulin skeleton and signalling though AMPK, which was required for the enhanced induction. Combination therapy also increased expression levels of the immunoregulatory cytokine IL-10. In vivo, albendazole plus anti-TNF combination therapy was superior to monotherapy in a model of colitis, in terms of both induction of regulatory macrophages and improvement of clinical symptoms. CONCLUSIONS: Albendazole enhances the induction of regulatory macrophages by anti-TNF and potentiates clinical efficacy in murine colitis. Given its favourable safety profile, these data indicate that the repurposing of albendazole may be a novel option for anti-TNF combination therapy in IBD.

Infusion reactions during infliximab treatment are not associated with IgE anti-infliximab antibodies.

OBJECTIVES: Controversy exists on the role of IgE antidrug antibodies (IgE-ADA) in infusion reactions (IR) on infliximab treatment, partly due to the lack of a positive control used for assay validation. We sought to (1) develop a robust assay to measure IgE-ADA, including a positive control, (2) determine the association between IgE-ADA and IR and (3) determine the incidence of IgE-ADA in infliximab treated patients. METHODS: A recombinant human IgE anti-infliximab monoclonal antibody was developed as standard and positive control. With this antibody, we set up a novel robust assay to measure IgE-ADA. IgE-ADA was determined in three retrospective cohorts (n=159) containing IR+ (n=37) and IR- (n=39), and longitudinal sera of 83 spondyloarthritis. RESULTS: IgE-ADA was found in 0/39 IR-, whereas 4/37 (11%) IR+ showed low levels (0.1-0.3 IU/mL, below the 0.35 IU/mL threshold associated with elevated risk of allergic symptoms). All patients who were IgE-ADA positive also had (very) high IgG-ADA levels. The incidence of IgE-ADA in patients with infliximab-treated spondyloarthritis was estimated at less than approximately 1%. CONCLUSIONS: IgE-ADA is rarely detected in infliximab-treated patients. Moreover, the absence of IgE-ADA in the majority of IR+ patients suggests that IgE-ADA is not associated with infusion reactions.

A Real-life Population Pharmacokinetic Study Reveals Factors Associated with Clearance and Immunogenicity of Infliximab in Inflammatory Bowel Disease.

BACKGROUND: Several factors influencing the pharmacokinetics of infliximab (IFX) in inflammatory bowel disease (IBD) have been identified. We studied the impact of patient, disease, and treatment characteristics on clearance and immunogenicity of IFX in a real-world patient-with-IBD cohort. METHODS: Serum concentrations of IFX and antibodies to IFX (ATIs) were measured in patients with IBD at a single center using an enzyme-linked immunosorbent assay and radioimmunoassay. Patient, disease, and treatment characteristics were retrospectively collected along with laboratory values. Pharmacokinetics and ATI titer were analyzed simultaneously by nonlinear mixed-effects modeling. RESULTS: Nine hundred ninety-seven IFX concentrations and 756 ATI measurements from 332 patients with IBD (253 Crohn's disease and 79 ulcerative colitis) were included. Mean (SD) IFX dose was 5.47 ± 1.33 mg/kg. ATIs were detected in 75/332 (23%) patients; insufficient exposure below an IFX trough level of 3 µg/mL was the most predictive factor of developing ATI and resulted in a 4-fold increased risk of ATI development. ATI titer was a better predictor of IFX clearance than ATI as a dichotomous parameter. ATI titers >30 AU/mL were consistently associated with undetectable IFX concentrations. IFX clearance was affected by body weight (40-149 kg) ranging from 0.27 to 0.53 L/d, serum albumin (2-5.4 g/dL) from 0.93 to 0.24 L/d, and titers of ATIs (0-53,000 AU/mL) from 0.36 L/d to 15.93 L/d (P < 0.001). Previously biologic-treated patients exhibited a higher clearance of IFX. CONCLUSIONS: IFX exposure below 3 µg/mL increases risk of ATIs. Identification of influential pharmacokinetics and ATI factors improves prediction of IFX levels, potentially allowing individualized dosing and cost reduction.

Performance of Common Disease Activity Markers as a Reflection of Inflammatory Burden in Ulcerative Colitis.

BACKGROUND: The inflammatory burden influences therapeutic decisions in patients with ulcerative colitis (UC). We aimed to study which commonly used markers of disease activity correlate best with inflammatory burden in patients with UC using leukocyte scintigraphy (single-photon emission computed tomography [SPECT-CT]) as the gold standard. METHODS: Patients with different severity of UC underwent colonoscopy with biopsies and leukocyte SPECT-CT scintigraphy. Serum C-reactive protein (CRP), fecal calprotectin, and clinical questionnaires were collected. The maximum uptake of technetium-labeled leukocytes was calculated as a SPECT score for each colon segment and a summed activity score for 5 colonic segments combined. RESULTS: Thirty patients with UC were included; 14 of 30 (47%) had left-sided colitis, and 16 of 30 (53%) had pancolitis. One patient (3%) had inactive UC, 5 of 30 (17%) had mild, 11 of 30 (37%) had moderate, and 13 of 30 (43%) had severe disease activity based on the endoscopic Mayo score. The endoscopic Mayo score correlated better with the SPECT score than with the ulcerative colitis endoscopic index of severity (UCEIS) (r = 0.50; P < 0.01 and r = 0.32; P = 0.08, respectively). The Geboes UC histologic score correlated equally well as the Mayo score (r = 0.50; P < 0.01). We found a significant correlation between scintigraphy and fecal calprotectin (r = 0.44; P = 0.02) but not with serum CRP (r = 0.25; P = 0.18). Fecal calprotectin reflected inflammatory burden significantly better in left-sided colitis (r = 0.80; P = 0.001) than in pancolitis (r = 0.22; P = 0.41). CONCLUSIONS: The inflammatory burden in patients with UC, measured by SPECT-CT, is better reflected by the endoscopic Mayo score and the Geboes histologic score than by the UCEIS. Fecal calprotectin is a more accurate inflammatory marker than CRP, predominantly in patients with left-sided colitis. REGISTRATION: This study was approved by the Ethics Committee Review at October 22, 2012 and, in accordance with Dutch legislation, prospectively registered at the CCMO (Dutch central commission for human research) https://www.toetsingonline.nl with NL39801.018.12.

Pharmacokinetic Features and Presence of Antidrug Antibodies Associate With Response to Infliximab Induction Therapy in Patients With Moderate to Severe Ulcerative Colitis.

BACKGROUND & AIMS: The pharmacokinetics of infliximab during induction treatment for ulcerative colitis (UC) have not been studied. We investigated serum concentrations of infliximab and the early appearance of antibodies to infliximab (ATI) during induction treatment in patients with moderate-to-severe UC. METHODS: We performed a prospective analysis of 19 consecutive patients with moderate-severe UC (endoscopic Mayo ≥ 2) receiving induction therapy with infliximab (5 mg/kg at weeks 0, 2, and 6) at 2 centers in Amsterdam, The Netherlands, from July 2012 through March 2014. Serial serum and fecal samples were collected for 6 weeks and concentrations of infliximab, ATI, c-reactive protein (CRP), albumin, and fecal calprotectin were measured. Treatment success was defined as endoscopic response (≥ 1 point reduction in the endoscopic Mayo score) at week 8. RESULTS: Eleven patients (58%) had an endoscopic response. The median serum concentrations of infliximab at week 6 were 8.1 µg/mL in responders (interquartile range, 3.0-13.7 µg/mL) and 2.9 µg/mL in nonresponders (interquartile range, 0.01-5.8 µg/mL) (P = .03). ATIs were detected in 7 patients as early as day 18 (median, 28 d; interquartile range, 18-42 d). Six of the 8 nonresponders tested positive for ATIs vs 1 of 11 responders (P < .01; odds ratio, 30.0; 95% CI, 2.2-406.2). Patients with a baseline concentration of CRP greater than 50 mg/L had lower drug exposure from weeks 0 to 6 (587 mg/L/d in patients with high levels of CRP vs 1361 mg/L/day in patients with low CRP; P = .001). The median area under the curve for serum concentration of infliximab during induction therapy was 1230 mg/L/d in nonresponders vs 1352 mg/L/d in responders (P = .65). CONCLUSIONS: There is a significant difference in serum concentration of infliximab at week 6 of treatment between responders and nonresponders. Early development of ATIs during induction therapy reduces the serum concentration of infliximab and is associated with nonresponse to treatment. Patients with high baseline serum levels of CRP had lower serum concentrations of infliximab. CLINICAL TRIAL NUMBER: NL39626.018.12.

Serum Concentration of Anti-TNF Antibodies, Adverse Effects and Quality of Life in Patients with Inflammatory Bowel Disease in Remission on Maintenance Treatment.

BACKGROUND AND AIMS: High serum concentrations of infliximab [IFX] and adalimumab [ADA] may be associated with adverse effects in patients with inflammatory bowel disease [IBD]. We aimed to investigate whether high anti-tumour necrosis factor [TNF] trough levels [TLs] were associated with toxicity and impaired quality of life [QoL]. METHODS: We conducted a prospective cohort study in IBD patients in clinical and biochemical remission on IFX or ADA maintenance therapy. Trough serum concentrations and antidrug antibodies were measured in addition to biochemical markers of inflammation in serum and stool to confirm quiescent disease. QoL was assessed using the Inflammatory Bowel Disease Questionnaire and 36-item short form]. Side effects such as fatigue and arthralgia were measured with a visual analogue score [VAS]. Skin toxicity was reported with a European Organization for Research and Treatment of Cancer-derived score. RESULTS: In all, 252 IBD patients on maintenance anti-TNF therapy were screened, of whom 95 [73 with Crohn's disease, 22 with ulcerative colitis; 72 on IFX, 23 on ADA] were in clinical and biochemical remission and were included. Median TLs were 5.5 µg/ml and 6.6 µg/ml for IFX and ADA, respectively. Patients with anti-TNF TLs above median had lower IBDQ scores than patients with lower TLs [IBDQ 176 vs 187, p = 0.02], particularly regarding systemic symptoms and emotional status. A trend towards lower SF-36 and higher fatigue scores was observed in the higher anti-TNF TL group. Skin and arthralgia scores were not significantly different between the groups. CONCLUSIONS: IBD patients with higher anti-TNF serum concentrations had significantly lower disease-specific QoL. Fatigue, arthralgia, and skin lesions do not occur more often in these patients. These data are reassuring that high serum concentrations of anti-TNF antibodies are not toxic.

The association of infliximab trough levels with disease activity in pediatric inflammatory bowel disease.

OBJECTIVE: Low serum trough levels (TLs) of infliximab (IFX) and antibodies to IFX (ATIs) are associated with the loss of therapeutic response in adults with inflammatory bowel disease (IBD) receiving IFX. Until now, pediatric data are scarce. Therefore, we aimed to cross-sectionally investigate the association between ATIs and IFX TLs, and clinical and biochemical disease activity in children receiving IFX for IBD. MATERIAL AND METHODS: Children aged <18 years receiving IFX maintenance treatment for Crohn's disease (CD) or ulcerative colitis (UC) at three Dutch hospitals were included. Prior to two consecutive IFX infusions, IFX TLs and ATI levels were measured. Clinical disease activity was determined by Pediatric Crohn's Disease Activity Index (PCDAI) and Pediatric Ulcerative Colitis Activity Index (PUCAI), for CD and UC, respectively. Biochemical disease activity was assessed by serum C-reactive protein (CRP) and fecal calprotectin (FC). Clinical remission was defined as a PUCAI or PCDAI score of <10. Therapeutic range of IFX was considered 3-7 µg/ml. RESULTS: Thirty-nine patients were included (31 CD; 16 females). Median age was 15 years. Median IFX TL was 3.5 µg/ml [IQR 2-7]. Subtherapeutic and supratherapeutic TLs were found in 38% and 23% of children, respectively. ATIs were detected in four patients. A correlation was found between IFX TL and CRP [rs = -0.51; p < 0.01] and FC [rs = -0.49; p < 0.01]. However, when only clinical disease activity was considered, no difference in median TL was found between remission and active disease (resp. 3.5 µg/ml [IQR 2-5] and 2.3 µg/ml [IQR 0.3-4.6]; p = 0.2). CONCLUSIONS: IFX TLs are related to biochemical markers of disease activity. This could provide a rationale for monitoring TLs in children receiving IFX for IBD.

Loss of Infliximab Into Feces Is Associated With Lack of Response to Therapy in Patients With Severe Ulcerative Colitis.

BACKGROUND & AIMS: It is not clear why some patients with ulcerative colitis (UC) do not respond to treatment with anti-tumor necrosis factor (TNF) agents, such as infliximab. It could be that some patients have high level of inflammation, with large quantities of TNF to be neutralized by the drug. We investigated whether loss of anti-TNF agents through ulcerated intestinal mucosa reduces the efficacy of these drugs in patients with severe UC. METHODS: We collected fecal samples from 30 consecutive patients with moderate to severely active UC during the first 2 weeks of infliximab therapy at the University of Amsterdam hospital. Infliximab concentrations were measured in serum and supernatants of fecal samples using an enzyme-linked immunosorbent assay (Sanquin Biologicals Laboratory, Amsterdam, The Netherlands). Clinical and endoscopic responses were assessed 2 and 8 weeks and 3 months after treatment began. RESULTS: Infliximab was detected in 129 of 195 fecal samples (66%); the highest concentrations were measured in the first days after the first infusion. Patients that were clinical nonresponders at week 2 had significantly higher fecal concentrations of infliximab after the first day of treatment than patients with clinical responses (median concentration, 5.01 µg/mL in nonresponders vs 0.54 µg/mL in responders; P = .0047). We did not observe a correlation between fecal and serum concentrations of infliximab. CONCLUSIONS: Infliximab is lost into stools of patients with UC. High fecal concentrations of infliximab in the first days after therapy begins are associated with primary nonresponse. Additional studies are needed to determine how therapeutic antibodies are lost through the intestinal mucosa and how this process affects treatment response. Clinical trial ID: NL41310.018.12.

Impact of disease location on fecal calprotectin levels in Crohn's disease.

OBJECTIVE: The correlation between the Simple Endoscopic Score for Crohn's Disease (SES-CD) and fecal calprotectin is well established in (ileo)colonic Crohn's disease (CD). However, for ileal CD, existing data are conflicting. The aim of this study is to evaluate the biomarker profile in CD patients with varying severity and location of mucosal ulceration. MATERIALS AND METHODS: An electronic patient database search identified CD patients in whom ileocolonoscopy, fecal calprotectin (CALPRO), serum C-reactive protein (CRP) and blood leukocyte counts (LEU) were measured within a 4-week interval without changes in medication. Ileocolonoscopies were scored for the presence of ulcers in each segment as defined by the SES-CD and the sum of segmental ulcer scores resulted in a partial SES-CD (pSES-CD). RESULTS: Fourty-four patients were identified, of whom 9/44 had ileal CD, 20/44 colonic and 15/44 ileocolonic CD based on the Montreal classification. In the total study population CALPRO correlated best with pSES-CD (r = 0.76, p < 0.0001), followed by LEU (r = 0.54, p = 0.0004) and CRP (r = 0.45, p = 0.0026). Patients with ileal CD had significantly lower CALPRO level than those with (ileo)colonic disease even in the presence of large and/or very large ulcers (mean ± SEM: 297 ± 81 µg/g vs. 1523 ± 97 µg/g, p < 0.0001). LEU was also significantly lower in the presence of large and/or very large ulcers in ileal CD compared to those with (ileo)colonic disease (mean ± SEM: 6.7 ± 0.9 × 10(9)/l vs. 10.6 ± 0.8 × 10(9)/l, p = 0.02). A similar trend was identified regarding CRP levels. CONCLUSIONS: Even in the presence of large or very large ulcers, patients with ileal Crohn's may not have markedly elevated fecal calprotectin levels.

Effects of infliximab retreatment after consecutive discontinuation of infliximab and adalimumab in refractory Crohn's disease.

BACKGROUND: Switches between anti-tumor necrosis factor agents in the treatment of Crohn's disease (CD) occur in case of treatment failure, intolerance, or patient preference. No data are currently available on the usefulness of a second infliximab treatment after earlier discontinuation and previous switch to an alternative anti-tumor necrosis factor agent. In this study, we evaluated the clinical benefit of infliximab retreatment in patients with CD after sequential use of both infliximab and adalimumab. METHODS: Twenty-nine patients with CD who had received earlier treatments with sequential infliximab and adalimumab and were then restarted on infliximab were retrieved from a multicenter registry designed for the follow-up of adalimumab treatment for CD. Short-term and sustained effects of infliximab retreatment were evaluated retrospectively by reviewing clinical records. Follow-up was 18 months for all patients. RESULTS: In 13/29 (45%) patients, infliximab was reintroduced at intensified dosing schedule (>5 mg/kg or <8 wk) for 23/29 (79%) of patients similar to the schedule who were on at time of previous discontinuation. During the second infliximab treatment course, dosing was further intensified in 11 out of 29 (38%) patients. After 18 months 18/29 (62%), patients were still on continued therapy of their second infliximab treatment. Infliximab was discontinued (after a median of 7 mo) in 11 out of 29 patients for loss of response (n = 7 [24%]), intolerance (n = 3 [10%]), or non-compliance (n = 1 [3%]). Use of induction schedule or concomitant immunomodulators were not significantly associated with treatment benefit. CONCLUSIONS: The majority of patients with CD benefit from a second treatment with infliximab after previous treatment with infliximab and adalimumab, which offer a meaningful therapeutic option in often highly refractory patients.