Therapeutic drug monitoring (TDM) for dose modification of biologics has the potential to improve patient outcomes. The US Food and Drug Administration (FDA) and the American Association of Pharmaceutical Scientists (AAPS) hosted the first US-based public workshop on TDM of biologics with contributions from a broad array of interested parties including healthcare providers, clinical pharmacologists, test developers, bioanalysis and immunogenicity scientists, health economics and outcomes research (HEOR) experts and regulators. The key insight was that despite a body of evidence to support TDM in certain therapeutic areas, there remain substantial challenges to widespread clinical implementation. There is a lack of consensus regarding the integration of TDM in clinical guidelines, and a lack of consensus on the cost-effectiveness of TDM; both factors contribute to the difficulty that healthcare providers face in obtaining reimbursement for TDM (both coverage of testing itself, and coverage of potential dosing modifications). The HEOR experts outlined alternative routes to obtaining reimbursement and suggested advocating for changes in coverage policies to promote TDM use in the clinic. Reaching alignment across policy makers, patients and advocacy groups, payers, and healthcare providers, on specific treatment settings where TDM will be clearly beneficial, was identified as an important step to advancing TDM implementation for the benefit of patients.

The emergence of tumor necrosis factor inhibitors (anti-TNF) has considerably changed the management of inflammatory bowel disease (IBD) in patients who do not respond to traditional therapies. This study assesses the prevalence of anti-TNF drug levels (DLs) and antibodies (ATAbs) in patients with IBD in Saudi Arabia and explores their associations with IBD type and prior anti-TNF failure.

This cross-sectional study included patients aged 14-75 years diagnosed with Crohn's disease (CD) or ulcerative colitis (UC), treated with anti-TNF medications at King Fahad Medical City over January 2016 to December 2022. Data were analyzed using descriptive statistics, Mann-Whitney U test, Kruskal-Wallis test, Pearson's Chi-squared test, and multinomial logistic regression.

Among 392 patients with IBD (median age, 31 years), 75.8% were diagnosed with CD and 24.2% with UC. Anti-TNF levels were subtherapeutic in 27.0% patients, therapeutic in 21.5%, and supratherapeutic in 51.5%. ATAbs were negative in 73.1% patients, weakly positive in 9.8%, and positive in 17.1%. Subtherapeutic anti-TNF levels were significantly associated with positive ATAbs ( P < 0.001). Prior anti-TNF therapy failure was observed in 37.2% cases, with 15.3% showing immunogenicity. No significant demographic differences were noted across ATAbs groups.

We highlight the prevalence of subtherapeutic and supratherapeutic anti-TNF levels among patients with IBD in Saudi Arabia and their association with ATAbs. The findings underscore the importance of monitoring anti-TNF DLs and ATAbs to optimize treatment outcomes in IBD management. Future research should focus on the longitudinal impact of these factors and explore genetic predictors of treatment response.

Background: Although it is generally believed that infliximab dose optimization in patients with inflammatory bowel disease with low serum infliximab concentration at trough results in increased treatment persistence, empirical data to support this notion are lacking. This study evaluated the association of infliximab therapeutic drug monitoring (TDM) and TDM-associated dose optimization with persistence in real-world practice. Methods: Data from adults with Crohn's disease (CD) or ulcerative colitis (UC) who participated in a national patient support program (PSP) in Canada were analyzed. Participants who had a first TDM evaluation (with a recorded infliximab trough concentration) in the maintenance phase of treatment were assessed (excluding those who underwent prior dose optimization). Persistence was evaluated using time-dependent Cox proportional hazards models. Results: In the overall population of patients with CD or UC, TDM was not associated with longer persistence (n = 13,203). In patients with no prior dose optimization (n = 2729) who had a serum infliximab concentration of < 3 μg/mL, dose optimization within 9 weeks of TDM was associated with significantly longer persistence (HR: 0.36; 95% CI: 0.26, 0.50 for CD [n = 711] and HR: 0.30, 95% CI: 0.21, 0.43 for UC [n = 501]). Sensitivity analyses yielded similar results when using a threshold concentration of < 5 μg/mL. In an analysis excluding patients who received no further treatment after TDM, the association between dose optimization and longer persistence was not confirmed in patients with CD, and mostly confirmed in patients with UC at a threshold concentration of < 3 μg/mL. Conclusion: TDM-associated dose optimization in patients with UC with low serum infliximab concentrations was associated with longer persistence. This association was not confirmed in patients with CD. This study demonstrated that real-world data from a PSP-generated cohort can be evaluated to inform clinical practice and that this approach may be complementary to other types of cohort studies.

Background: Over the past decade, TNF inhibitors such as Infliximab and Adalimumab have become central to Inflammatory Bowel Diseases treatment, greatly enhancing patient outcomes. However, immunogenicity-where anti-drug antibodies diminish effectiveness-remains an issue, often requiring dose changes or combination therapies. Pharmacogenomics is increasingly applied in IBD to personalise treatment, especially since genetic factors like the HLA-DQA1*05 variant heighten the immunogenicity risk with IFX. This study aims to examine the relationship between the HLA-DQA1*05 variant and response loss or antibody development in patients regularly monitored on IFX or ADA. Methods: Sixty-five paediatric IBD patients were enrolled, with therapeutic drug monitoring (TDM) of IFX and ADA, conducted using immunoenzymatic assays. The presence of the HLA-DQA1*05 T>C allele variant was also tested using a Biomole HLA-DQA1 Real-time PCR kit. Results: The HLA-DQA1*05 rs2097432 T>C allele was present in 54% of patients on IFX and 69% of those on ADA. No statistically significant differences were found between HLA carriers and non-carriers across any of the three analysed groups: IFX, ADA and the overall anti-TNFα. Conclusions: Our study suggests that the HLA-DQA1*05 allele does not increase the risk of secondary loss of response to anti-TNF therapy, likely because most patients were on a combination of anti-TNF agents and immunomodulators, which can lower anti-drug antibody production. Testing for HLA-DQA105 can aid in personalising treatment and optimising therapy to minimise immunogenicity risks.

In children, ulcerative colitis (UC) is often more severe and extensive than in adults and hospitalization for acute exacerbations occurs in around a quarter of subjects. There is a need for effective drugs, which could avoid or reduce the use of corticosteroids which, especially in children, are burdened by a number of severe side effects. The introduction in therapy of monoclonal antibodies has completely changed the therapeutic scenario and the prognosis of the disease.

In this review, the use of the monoclonal antibodies directed against tumor necrosis factor (TNF)α or other inflammatory targets for the treatment of pediatric UC will be discussed. A search of the literature was done using the keywords 'pediatric,' 'ulcerative colitis,' 'inflammatory bowel disease,' 'monoclonal antibodies;' 'infliximab,' 'adalimumab,' 'golimumab,' vedolizumab," 'ustekinumab' and 'risankizumab.'

The use of monoclonal antibodies has greatly increased in recent years in pediatric UC, both in patients who did not respond to conventional therapies, and, more often, as initial therapy. Thanks to therapeutic drug monitoring and to the availability of biologics with different targets, therapy has become more targeted and personalized, with a significant improvement in response, in quality of life, and with a good safety profile.

Several studies associate the presence of higher serum concentrations of infliximab (IFX) with fistula healing in perianal Crohn's disease (CD). This study aimed to evaluate serum IFX concentrations in patients with perianal fistulizing CD (PFCD) in the presence or absence of general, clinical, and radiological activities.

This was a cross-sectional study in patients with PFCD during maintenance treatment with IFX from two centers. Serum IFX concentrations were measured before their next infusion and anal fistulas were evaluated by clinical examination and magnetic resonance imaging (MRI), whenever possible, performed 90 days before or after serum collection. According to clinical scores, radiological activity, and disease markers, patients were classified as in remission or active disease. Mean serum IFX concentrations were compared between the groups.

Thirty-eight patients with PFCD were included. Demographic characteristics were similar in patients with remission or active disease. The overall mean serum IFX concentration of the entire sample (n = 38) was 5.21 ± 4.75 μg/mL (median 3.63; IQR 1.44-8.82). Serum IFX levels were 6.25 ± 5.34 μg/mL (median 3.62; IQR 1.95-11.03) in the 23 (60.5%) patients in remission and 3.63 ± 3.24 μg/mL (median 3.63; IQR 1.32-6.43; p = 0.226) in the 15 (39 .5%) who presented active disease. When evaluating general, clinical, and radiological activity of PFCD, and deep remission in isolation, no statistical difference between the groups was observed (p = 0.226, p = 0.418, p = 0.126, and p = 0.232, respectively). The 13 (34.2%) patients with an optimized dose of IFX had significantly higher serum concentrations than the remaining 25 (65.8%) with a standard dose: 8.33 ± 4.41 μg/mL (median 8.36; IQR 3.82-11.20) vs. 3.59 ± 4.13 μg/mL (median 1.97; IQR 1.18-3.85) -p = 0.002. Patients in remission and with an optimized IFX dose had significantly higher serum IFX concentrations than those with a standard dose (p = 0.006), whereas no significant difference was observed among those with active disease (p = 0.083).

There were no differences in IFX serum concentrations in patients with clinical or radiological active PFCD as compared with those in remission. Patients with an optimized IFX dose had significantly higher serum concentrations than those with a standard dose. Patients in remission and with an optimized IFX dose had significantly higher serum concentrations than those with a standard dose.

Hypersensitivity reactions (HSR) to the administration of infliximab (IFX) in Inflammatory Bowel Diseases (IBD) patients are not rare and usually lead to drug discontinuation. We report data on safety and effectiveness of desensitization to IFX in patients with previous HSR.

We conducted a retrospective monocentric observational study. Patients for whom a desensitization protocol to IFX was realized after a previous HSR were included. Anti-drug antibodies (ADA) and IFX trough levels at both inclusion and six months after desensitization were collected. Clinical outcomes, including recurrence of HSR were evaluated.

From 2005 to 2020, 27 patients (Crohn's Disease: 26 (96%) were included). Desensitization after HSR was performed after a median time of 10.4 months (2.9-33.1). Nineteen (70%) patients received immunosuppressants at time of desensitization. Eight (30%) patients presented HSR at first (n = 2), second (n = 4) or third (n = 2) IFX perfusion after desensitization. None led to intensive care unit transfer or death. Thirteen (48%) had clinical response at 6 months and 8 (29%) were still under IFX treatment two years after desensitization. IFX trough levels and ADA were available for 14 patients at time of desensitization. Most patients (12 out of 14) had ADA at a high level. At 6 months, among the 7 patients with long term response to IFX, 4 presented a decrease of ADA titers and 2 had a significant trough level of IFX.

IFX desensitization in patients with IBD is a safe therapeutic alternative and represents a potential option for patients refractory to multiple biologics.What is already known? Hypersensitivity reactions to the administration of infliximab is frequent. Occurrence of hypersensitivity reaction, either immediate or delayed, usually leads to permanent drug discontinuation.What is new here? Infliximab desensitization is well tolerated with no hypersensitivity reaction recurrence in 70% of patients. Clinical success at 6 months was of 48% and around a third of patients remained under infliximab therapy two years after desensitization. Antidrug antibodies decreased and infliximab trough levels increased in these patients showing the impact of desensitization on immunogenicity.How can this study help patient care? Infliximab desensitization represents a potential option for patients refractory to multiple biologics who presented hypersensitivity reaction to the drug.

Precision-dosing models forecast infliximab doses to achieve targeted trough concentrations in patients with inflammatory bowel disease (IBD). These models have shown to reduce nonresponse and improve patient outcomes. We compared infliximab doses determined by iDOSE precision dosing with standard dosing, and the associated drug costs, in patients with IBD. In this retrospective study, patients with IBD treated with infliximab every 8 weeks at 5 mg/kg were included. An infliximab dose was named dose X if 3 previous infliximab doses, laboratory values including trough infliximab concentrations, and the patient's weight were recorded. The actual dose X was compared to an iDOSE-predicted dose X. Net drug use and costs were evaluated. A total of 174 patients-56% men; median age, 36 (interquartile range, 29-47) years; 135 with Crohn disease; and 31 with ulcerative colitis-were included, with 417 dose X recordings. Median prior infliximab therapy was 2 (0-4) years. Comparing actual dose X with predicted dose X, 52% and 32% of doses were subtherapeutic when aiming for trough concentrations of 5-10 and 3-7 μg/mL, respectively. Treatment costs increased by 102% and 29% for the 2 trough ranges, respectively. On multivariate regression analysis, subtherapeutic infliximab concentrations were associated with ulcerative colitis compared with Crohn disease (odds ratio, 9.81; 95% confidence interval, 1.28-75.40; P = .028) and predose X infliximab trough concentration [odds ratio, 0.07; 95% confidence interval, 0.03-0.15; P < .001]. Over half of maintenance infliximab drug doses were too low to achieve infliximab blood concentrations of 5 μg/mL or greater. While applying precision dosing may improve patient outcomes, drug costs could be considerably greater.

Methotrexate (MTX) combination therapy with biological agents has gained increasing interest. Here, we assessed the efficacy and tolerability of the MTX combination therapy in patients with Crohn's disease (CD).

We performed a multicenter observational study with 185 patients with CD with MTX and biologics combination therapy; the patients were recruited from three IBD Clinics in Korea. We evaluated the outcomes of the MTX combination therapy and examined the predictive factors of clinical and endoscopic remission.

MTX was administered orally to 62.7% of patients; the mean dose was 15.5 mg per week, and the mean treatment duration was 36 months. Of the 169 patients treated with MTX combination therapy for over 6 months, the steroid-free clinical remission rates were 34.3%, 26.0%, 29.8%, and 32.7% at 4, 12, 18, and 24 months, respectively. Previous thiopurine use was a significant negatively associated independent factor (p < 0.001), and a higher dose of MTX (≥ 15 mg/week) was a positively associated independent factor of steroid-free clinical remission (p = 0.035). Ninety-six patients underwent follow-up endoscopy after 28 months, and 36 (37.5%) achieved endoscopic remission. Longer disease duration (p = 0.006), ileocolonic type of Montreal location (p = 0.036), and baseline C-reactive protein (CRP) level of more than 5 mg/L (p = 0.035) were significant negatively associated independent factors and a higher dose of MTX (≥ 15 mg/week) was a positively associated independent factor of endoscopic remission (p = 0.037).

MTX combination therapy with biologics was effective and tolerable in patients with CD.

The efficacy and safety of anti-tumor necrosis factor-α (TNF-α) monoclonal antibody therapy [adalimumab (ADA) and infliximab (IFX)] with therapeutic drug monitoring (TDM), which has been proposed for inflammatory bowel disease (IBD) patients, are still controversial.

To determine the efficacy and safety of anti-TNF-α monoclonal antibody therapy with proactive TDM in patients with IBD and to determine which subtype of IBD patients is most suitable for proactive TDM interventions.

As of July 2023, we searched for randomized controlled trials (RCTs) and observational studies in PubMed, Embase, and the Cochrane Library to compare anti-TNF-α monoclonal antibody therapy with proactive TDM with therapy with reactive TDM or empiric therapy. Pairwise and network meta-analyses were used to determine the IBD patient subtype that achieved clinical remission and to determine the need for surgery.

This systematic review and meta-analysis yielded 13 studies after exclusion, and the baseline indicators were balanced. We found a significant increase in the number of patients who achieved clinical remission in the ADA [odds ratio (OR) = 1.416, 95% confidence interval (CI): 1.196-1.676] and RCT (OR = 1.393, 95%CI: 1.182-1.641) subgroups and a significant decrease in the number of patients who needed surgery in the proactive vs reactive (OR = 0.237, 95%CI: 0.101-0.558) and IFX + ADA (OR = 0.137, 95%CI: 0.032-0.588) subgroups, and the overall risk of adverse events was reduced (OR = 0.579, 95%CI: 0.391-0.858) according to the pairwise meta-analysis. Moreover, the network meta-analysis results suggested that patients with IBD treated with ADA (OR = 1.39, 95%CI: 1.19-1.63) were more likely to undergo TDM, especially in comparison with patients with reactive TDM (OR = 1.38, 95%CI: 1.07-1.77).

Proactive TDM is more suitable for IBD patients treated with ADA and has obvious advantages over reactive TDM. We recommend proactive TDM in IBD patients who are treated with ADA.

The pharmacokinetics and pharmacodynamics of biosimilar infliximab (IFX-BioS) in pediatric inflammatory bowel disease (IBD) are poorly investigated. The aim of this study was to investigate factors predicting IFX-BioS trough levels (TLs).

IBD children with an indication to start IFX-BioS were included in this prospective observational study (January 2021-June 2022). TLs were measured at the 4th and 6th infusions and correlated with several covariates.

A total of 110 TLs in 55 children were included. The multivariate linear regression model at the 4th infusion found a positive correlation between TLs and age at diagnosis (B:1.950, 95% CI: [0.019, 3.882], p = 0.048) and IFX-BioS dose/kg (B:1.962, 95% CI: [0.238, 3.687], p = 0.029), and a negative correlation with clinical scores (B:-0.401, 95% CI: [-0.738, -0.064], p = 0.023). At the 6th infusion, female gender (B:6.887, 95% CI: [0.861, 12.913], p = 0.029), hemoglobin (B:1.853, 95% CI: [0.501, 3.204], p = 0.011), and IFX-BioS dose/kg (B:1.792, 95% CI: [0.979, 2.605], p < 0.001) were found to be positively correlated to TLs. No association between combined clinical and biochemical remission and TLs was found.

This study discovered some predictors for IFX-BioS TLs in IBD children. Knowledge of predictive factors could help physicians choose the best dosing regimen.

Infliximab (IFX) use is limited by loss of response often due to the development of anti-IFX antibodies and low drug levels.

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.

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.

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.

Background: Inflammatory bowel disease (IBD), encompassing ulcerative colitis and Crohn's disease, necessitates long-term medical therapy to manage symptoms and prevent complications. Therapeutic drug monitoring (TDM) has emerged as a strategy to optimize treatment efficacy, particularly with anti-tumour necrosis factor (anti-TNF) alpha drugs. This review explores the role of TDM for non-anti-TNF advanced therapies in IBD, focusing on vedolizumab, ustekinumab, tofacitinib, upadacitinib, risankizumab and ozanimod. Methods: The literature search, conducted through OVID (Medline) and PubMed, delves into proactive versus reactive TDM, timing of monitoring and methods for measuring drug levels and anti-drug antibodies. Results: While ustekinumab and vedolizumab exhibit exposure-response relationships, consensus on target levels and the role of TDM adjustments remains elusive. Limited data on risankizumab suggest a dose-dependent response, while for small molecule therapies (janus kinase inhibitors and ozanimod), the absence of real-world data and commercially available TDM tools pose challenges. Conclusion: At present, with the available data, there is a limited role for TDM in non-anti-TNF biologic and small-molecule therapies. This review underscores the need for further research to delineate the utility of TDM in guiding treatment decisions for these agents.

Therapeutic drug monitoring of infliximab (IFX) is important to optimise treatment of inflammatory bowel disease (IBD). A recent IBD consensus statement recommends targeting trough serum concentrations of >3 μg/mL, higher than our local recommendation of >1 μg/mL. We therefore investigated the relationship between IFX trough concentrations and C reactive protein (CRP), faecal calprotectin (FCP), clinical outcomes and anti-IFX antibody (AB) development as well as the influence of concomitant thiopurine treatment.

Observational data, prospectively collected in a cohort of adult patients with IBD newly initiated on IFX at a single centre.

IFX concentrations >3 μg/mL were associated with a greater reduction in CRP (% change from baseline) and lower FCP; mean (SD) 47 (33.8) % vs 102.3 (136.9) % and 233.9 (505.1) μg/g vs 416.3 (613.5) μg/g, respectively. Lower IFX concentrations were observed in patients who developed AB than those who did not, mean (range) 6.2 (1.1-10) μg/mL vs 0.9 (0.4-4.9) μg/mL, respectively, and also in patients who stopped/switched therapy compared with those who continued, 2.4 (2.9) μg/mL vs 6.5 (2.8) μg/mL; p=0.0002. Patients taking a concomitant thiopurine were found to have higher IFX concentrations; mean (range) 6.4 (0.7-10) μg/mL vs 3.9 (0.4-10) μg/mL.

IFX concentrations are correlated with biomarkers, clinical response and AB development in patients with IBD. Concomitant thiopurine therapy appears to be associated with higher IFX concentrations and reduced likelihood of AB development.

Therapeutic drug monitoring (TDM) of tumor necrosis factor-α (TNFα)-inhibitors adalimumab and infliximab is important to establish optimal drug dose and maximize treatment efficacy. Currently, TDM is primarily performed with ELISA techniques in clinical laboratories, resulting in a long sample-to-result workflow. Point-of-care (POC) detection of these therapeutic antibodies could significantly decrease turnaround times and allow for user-friendly home-testing. Here, we adapted the recently developed bioluminescent dRAPPID (dimeric Ratiometric Plug-and-Play Immunodiagnostics) sensor platform to allow POC TDM of infliximab and adalimumab. We applied the two best performing dRAPPID sensors, with limit-of-detections of 1 pM and 17 pM, to measure the infliximab and adalimumab levels in 49 and 40 patient serum samples, respectively. The analytical performance of dRAPPID was benchmarked with commercial ELISAs and yielded Pearson's correlation coefficients of 0.93 and 0.94 for infliximab and adalimumab, respectively. Furthermore, a dedicated bioluminescence reader was fabricated and used as a readout device for the TDM dRAPPID sensors. Subsequently, infliximab and adalimumab patient serum samples were measured with the TDM dRAPPID sensors and bioluminescence reader, yielding Pearson's correlation coefficients of 0.97 and 0.86 for infliximab and adalimumab, respectively, and small proportional differences with ELISA (slope was 0.97 ± 0.09 and 0.96 ± 0.20, respectively). The adalimumab and infliximab dRAPPID sensors, in combination with the dedicated bioluminescence reader, allow for ease-of-use TDM with a fast turnaround time and show potential for POC TDM outside of clinical laboratories.

In patients with inflammatory bowel diseases (IBDs), high visceral adipose tissue (VAT) burden is associated with a lower response to infliximab, potentially through alterations in volume distribution and/or clearance. Differences in VAT may also explain the heterogeneity in target trough levels of infliximab associated with favorable outcomes. The aim of this study was to assess whether VAT burden may be associated with infliximab cutoffs associated with efficacy in patients with IBD.

We conducted a prospective cross-sectional study of patients with IBD receiving maintenance infliximab therapy. We measured baseline body composition parameters (Lunar iDXA), disease activity, trough levels of infliximab, and biomarkers. The primary outcome was steroid-free deep remission. The secondary outcome was endoscopic remission within 8 weeks of infliximab level measurement.

Overall, 142 patients were enrolled. The optimal trough levels of infliximab cutoffs associated with steroid-free deep remission and endoscopic remission were 3.9 mcg/mL (Youden Index [J]: 0.52) for patients in the lowest 2 VAT % quartiles (<1.2%) while optimal infliximab level cutoffs associated with steroid-free deep remission for those patients in the highest 2 VAT % quartiles was 15.3 mcg/mL (J: 0.63). In a multivariable analysis, only VAT % and infliximab level remained independently associated with steroid-free deep remission (odds ratio per % of VAT: 0.3 [95% confidence interval: 0.17-0.64], P < 0.001 and odds ratio per μg/mL: 1.11 [95% confidence interval: 1.05-1.19], P < 0.001).

The results may suggest that patients with higher visceral adipose tissue burden may benefit from achieving higher infliximab levels to achieve remission.

Infliximab and its anti-drug antibody (ADA) serum concentrations exhibit a strong correlation with clinical response and loss of response. The use of therapeutic drug monitoring to measure the concentration of infliximab and ADA can facilitate clinical decision-making, helping patients attain optimal therapeutic effects. However, there are still limitations to the existing infliximab and its ADA detection methods. Therefore, this study aimed to develop and validate enzyme-linked immunosorbent assay (ELISA)-based methods for measuring infliximab and its ADA levels in human plasma according to the general recommendations for immunoassays. Free infliximab is bound by recombinant TNF-α and detected using HRP-labeled anti-human antibody. The ADA is captured by on-plate-coated infliximab and recognized by biotin-labeled infliximab. Two bridging ELISA assays were developed and after assay optimization and validation, these assays have been applied in ten patients with inflammatory bowel disease (IBD). In infliximab detection assay, a standard curve ranging from 0.10 μg/mL to 8.0 μg/mL with great precision and accuracy has been established. Drug tolerance of the ADA assay was that 100 ng/mL ADA could tolerate at least 5.0 μg/mL infliximab in the plasma using a commercially available monoclonal anti-infliximab antibody as the positive control. The ADA screening and confirmatory assays achieved a sensitivity of 36.74 ng/mL and 37.15 ng/mL, respectively. All other assay characteristics met the requirements. The mean concentration of infliximab in eight patients with IBD was 7.88 (1.87-21.1) μg/mL, and the ADA levels were all negative. Moreover, the concentrations of infliximab in the remaining two patients were below the LLOQ and the ADAs were positive. Thus, accurate and sensitive ELISA methods have been developed and validated for the detection of infliximab and its ADA concentrations and have been successfully applied to clinical therapeutic drug monitoring.

Background: Inflammatory Bowel Disease (IBD) impacts millions worldwide, presenting a major challenge to healthcare providers and patients. The advent of biologic therapies has enhanced the prognosis, but many patients exhibit primary or secondary non-response, underscoring the need for rigorous monitoring and therapy optimization to improve outcomes. Objective: This narrative review seeks to understand the role of therapeutic drug monitoring (TDM) in optimizing treatment for IBD patients, especially for those on combination therapies of biologics and immunomodulators. Methods: A comprehensive synthesis of the current literature was undertaken, focusing on the application, benefits, limitations, and future directions of TDM in patients receiving a combination of biologic therapies and immunomodulators. Results: While biological therapies have improved outcomes, rigorous monitoring and therapy optimization are needed. TDM has emerged as a pivotal strategy, enhancing outcomes cost-effectively while reducing adverse events. While most data pertain to monotherapies, TDM's applicability also extends to combination therapy. Conclusion: TDM plays a crucial role in the treatment optimization of IBD patients on combination therapies. Further research is needed to fully understand its potential and limitations in the broader context of IBD management.

The combination of antitumor necrosis factor-alpha (TNF-α) agents with immunomodulators (IMMs) is a common treatment for pediatric Crohn's disease (CD). Although methotrexate (MTX) can be a first-line medication as an IMM, most clinicians in real-life practice, especially in South Korea, are more familiar with thiopurines. This study aimed to compare the efficacy and immunogenicity of MTX and azathioprine (AZA) as concurrent therapies for pediatric CD.

In this pilot study, 29 newly diagnosed pediatric patients with moderate-to-severe CD were randomized to receive either MTX (n = 15) (15 mg/body surface area (BSA) per week) or oral AZA (n = 14) (0.5 mg/kg per day) in combination with Infliximab (IFX). The primary outcomes were the proportion of patients in endoscopic, biochemical, and transmural remission after 14 and 54 weeks of IFX therapy. The trough levels (TLs) of IFX and anti-drug antibody (ADA) levels were also compared.

Among the 29 patients, there were no significant differences in the biochemical (p = 1.0 at week 14, p = 0.45 at week 54), endoscopic (p = 0.968 at week 14, p = 0.05 at week 54), or transmural (p = 0.103 at week 54) remission rates between the two medications during the concurrent therapy. Additionally, the trends in the IFX trough and ADA levels over time during the treatments were similar for both medications, with no significant differences (p = 0.686, p = 0.389, respectively).

The MTX showed comparable efficacy to the AZA in pediatric CD patients with moderate-to-severe disease. This effectively maintained adequate IFX levels and reduced ADA production. Therefore, although additional large-scale clinical trials are needed, this study demonstrated that either MTX or AZA can be selected as IMMs in the concurrent treatment of pediatric CD, depending on individual medical institutions' circumstances.

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.

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).

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).

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.

We aimed to compare trough infliximab levels and the development of antidrug antibody (ADA) for 1 year between Crohn's disease (CD) and ulcerative colitis (UC) patients who were biologic-naive, and to evaluate their impact on clinical outcomes.

This was a prospective, multicenter, observational study. Biologic-naive patients with moderate to severe CD or UC who started CT-P13, an infliximab biosimilar, therapy were enrolled. Trough drug and ADA levels were measured periodically for 1 year after CT-P13 initiation.

A total of 267 patients who received CT-P13 treatment were included (CD 168, UC 99). The rates of clinical remission (72% vs. 32.3%, P <0.001) at week 54 were significantly higher in CD than in UC. The median trough drug level (μg/mL) was significantly higher in CD than in UC up to week 14 (week 2, 18.7 vs. 14.7, P <0.001; week 6, 12.5 vs. 8.6, P <0.001; week 14, 3.4 vs. 2.5, P =0.001). The median ADA level (AU/mL) was significantly lower in CD than in UC at week 2 (6.3 vs. 6.5, P =0.046), week 30 (7.9 vs. 11.8, P =0.007), and week 54 (9.3 vs. 12.3, P =0.032). Development of ADA at week 2 [adjusted odds ratio (aOR)=0.15, P =0.026], initial C-reactive protein level (aOR=0.87, P =0.032), and CD over UC (aOR=1.92, P <0.001) were independent predictors of clinical remission at week 54.

Infliximab shows more favorable pharmacokinetics, including high drug trough and low ADA levels, in CD than in UC, which might result in better clinical outcomes for 1-year infliximab treatment in CD patients.

There are no prospective, head-to-head, controlled trials comparing the efficacy and safety of Infliximab (IFX) and Vedolizumab (VDZ) for the treatment of moderate-to-severe ulcerative colitis (UC), while only a few real-life retrospective studies have been published so far. We assessed the efficacy of IFX vs. VDZ in two cohorts of biologic-naïve outpatients with moderate-to-severe UC or mild, but refractory, disease. Data were extracted from patients' files and reviewed. The duration of follow-up (FU) was 52 weeks. The primary endpoint was the clinical remission (CR) at the end of FU. Secondary endpoints were: drug persistency, time to obtain CR, clinical response at the end of the induction phase (IP), steroid-free CR (compared to patients who used steroids at baseline) at the end of FU, need for drug optimization, adverse events (AEs), and normalization of C-reactive protein (CRP). We also analyzed the causes of dropping out (primary non-response), or secondary loss of response (immunogenic or not), for each group. We enrolled 82 patients (50 IFX and 32 VDZ) who met the inclusion criteria. At the end of FU, CR was obtained in 32% of the patients on IFX and 75% on VDZ (p = 0.0003). Drug persistency was superior for VDZ compared to IFX (78% vs. 52%, p = 0.033). Clinical response at the end of induction was reached in 54% and in 81% in the IFX and VDZ group, respectively (p = 0.014). Steroid-free clinical remission at the end of FU was 62% and 94% in the IFX vs. VDZ group, respectively (p = 0.036). The need for drug optimization was higher for VDZ than for IFX (28% vs. 57%, p = 0.009), while the time to obtain CR, the incidence of AEs, mean duration of FU, and rate of CRP normalization at the end of IP were comparable between the two groups. There was a prevalence of patients dropping out because of primary non-response in IFX group (p = 0.027), while the incidence of secondary loss of response was similar in the two groups. At the multivariate analysis, CRP and Partial Mayo Score (PMS) at T0 did not correlate with CR at the end of FU in both groups. In this retrospective, real world data study in biologic-naïve patients, VDZ was superior to IFX in CR, clinical response rate at the end of IP, drug persistency, steroid-free remission, and need for optimization at the end of FU.

Among prematurely born infants and newborns with chronic conditions, a respiratory syncytial virus (RSV) infection may cause (re-)admission and later respiratory complications. Therapeutic protection is possible with monthly injections of a specific monoclonal antibody, palivizumab, during RSV season. Standard care is giving up to five injections in clinic-based settings. Immunization at home could be an alternative to standard care for vulnerable infants to reduce the number of revisits and associated risk of RSV infection. The aim of this randomized pilot trial was to evaluate safety aspects and explore parents' preferences of home versus hospital immunization with palivizumab during one RSV season. Immediate adverse events (AEs) were observed and registered by a pediatric specialist nurse. Late-onset AEs were reported by parents. Parents' perceptions were collected through a questionnaire and analyzed using content analysis. The study population consisted of 43 infants in 38 families. No immediate AEs occurred. Three late-onset AEs were reported in two infants in the intervention group. Three categories emerged in the content analysis: (1) protect and watch over the infant, (2) optimal health and well-being for the whole family, and (3) avoid suffering for the infant. The study results show that home immunization with palivizumab is feasible if safety aspects are considered and that parental involvement in the choice of place for immunization after a neonatal intensive care experience can be important.

Inflammatory bowel diseases (IBD) encompass two main entities including ulcerative colitis and Crohn's disease. Although having a common global pathophysiological mechanism, IBD patients are characterized by a significant interindividual heterogeneity and may differ by their disease type, disease locations, disease behaviours, disease manifestations, disease course as well as treatment needs. Indeed, although the therapeutic armamentarium for these diseases has expanded rapidly in recent years, a proportion of patients remains with a suboptimal response to medical treatment due to primary non-response, secondary loss of response or intolerance to currently available drugs. Identifying, prior to treatment initiation, which patients are likely to respond to a specific drug would improve the disease management, avoid unnecessary side effects and reduce the healthcare expenses. Precision medicine classifies individuals into subpopulations according to clinical and molecular characteristics with the objective to tailor preventative and therapeutic interventions to the characteristics of each patient. Interventions would thus be performed only on those who will benefit, sparing side effects and expense for those who will not. This review aims to summarize clinical factors, biomarkers (genetic, transcriptomic, proteomic, metabolic, radiomic or from the microbiota) and tools that could predict disease progression to guide towards a step-up or top-down strategy. Predictive factors of response or non-response to treatment will then be reviewed, followed by a discussion about the optimal dose of drug required for patients. The time at which these treatments should be administered (or rather can be stopped in case of a deep remission or in the aftermath of a surgery) will also be addressed. IBD remain biologically complex, with multifactorial etiopathology, clinical heterogeneity as well as temporal and therapeutic variabilities, which makes precision medicine especially challenging in this area. Although applied for many years in oncology, it remains an unmet medical need in IBD.

A considerable proportion of Crohn's disease patients that undergo ileocecal resection (ICR) have failed anti-tumor necrosis factor (TNF) therapy preoperatively. This study aimed to assess the effectiveness of retreatment of anti-TNF therapy in patients with postoperative recurrence.

A real-world cohort study was performed on Crohn's disease patients who underwent primary ICR after anti-TNF therapy failure, and who were retreated with anti-TNF therapy for postoperative symptomatic Crohn's disease. The primary outcome was treatment failure (the need for (re)introduction of corticosteroids, immunosuppressants, or biologicals or the need for re-resection). Sub-analyses were performed on the nature of preoperative anti-TNF failure (primary non-response, secondary loss of response, intolerance), indication for ICR (refractory, stricturing, penetrating disease), combination therapy with immunomodulators, retreatment with the same anti-TNF agent and preoperative exposure to 1 vs. >1 anti-TNF agents.

In total, 66 of 364 patients retreated with anti-TNF therapy following ICR. Cumulative rates of treatment failure at 1 and 2 years were 28% and 47%. Treatment failure rate at 2 years was significantly lower in patients receiving combination therapy as compared to anti-TNF monotherapy (30% vs. 49%, P = 0.02). No difference in treatment failure was found with regards to the nature of preoperative anti-TNF failure (P = 0.76), indication for ICR (P = 0.88) switch of anti-TNF agent (P = 0.55) agent, and preoperative exposure to 1 vs. >1 anti-TNF agents (P = 0.88).

Retreatment with anti-TNF therapy for postoperative Crohn's disease recurrence is a valid strategy after preoperative failure. Combination therapy is associated with a lower rate of treatment failure.

Crohn's disease (CD) and ulcerative colitis (UC) are chronic diseases that result from the deregulation of the mucosal immune system of the gastrointestinal tract. The use of biological therapies, including infliximab (IFX), is one of the strategies to treat both CD and UC. The IFX treatment is monitored by complementary tests, namely: fecal calprotectin (FC); C-reactive protein (CRP); and endoscopic and cross-sectional imaging. Besides, serum IFX evaluation and antibody detection are also used.

To evaluate trough levels (TL) and antibodies in a population with inflammatory bowel (IBD) disease undergoing treatment with IFX, and the factors that might impact the treatment effectiveness.

Retrospective, cross-sectional study with patients with IBD that were assessed for TL and antibody (ATI) levels in a southern Brazilian hospital, from June 2014 to July 2016.

The study assessed 55 patients (52.7% female) submitted to serum IFX and antibody evaluations (95 blood samples, 55 first test; 30 second test, and 10 as third testing. Forty-five (47.3%) cases were diagnosed with CD (81.8%), and ten with UC (18.2%). Serum levels were adequate in 30 samples (31.57%), subtherapeutic in 41 (43.15%), and supratherapeutic in 24 (25.26%). IFX dosages were optimized for 40 patients (42.10%), maintained for 31 (32.63%), and discontinued for 7 (7.60%). The intervals between infusions were shortened in 17.85% of the cases. In 55 tests (55.79%), the therapeutic approach was exclusively defined according to IFX and/or serum antibody levels. The assessment of patients one year later indicated that: the approach was maintained with IFX for thirty-eight patients (69.09%); the class of biological agent was changed for eight (14.54%); changes using the same class of biological agent occurred for two patients (3.63%); the medication was discontinued and not replaced for three patients (5.45%), and four patients (7.27%) were lost to follow-up.

There were no differences in TL between groups with or without immunosuppressants, serum albumin (ALB), erythrocyte sedimentation rate (ESR), FC, CRP, and endoscopic and imaging examinations. Current therapeutic approach could be maintained for almost 70% of patients. Thus, serum and antibody levels are a useful tool in the follow-up of patients undergoing maintenance therapy and after treatment induction in patients with inflammatory bowel disease.

Adrenomedullin is a bioactive peptide with many pleiotropic effects, including mucosal healing and immunomodulation. Adrenomedullin has shown beneficial effects in rodent models of inflammatory bowel disease and, more importantly, in clinical trials including patients with ulcerative colitis. We performed a successive clinical trial to investigate the efficacy and safety of adrenomedullin in patients with Crohn's disease (CD).

This was a multicenter, double-blind, placebo-controlled phase 2a trial that evaluated 24 patients with biologic-resistant CD in Japan. Patients were randomly assigned to three groups and were given an infusion of 10 or 15 ng/kg/min of adrenomedullin or placebo for 8 h per day for 7 days. The primary endpoint was the change in the CD activity index (CDAI) at 8 weeks. The main secondary endpoints included changes in CDAI from week 4 to week 24.

No differences in the primary or secondary endpoints were observed between the three groups by the 8th week. Changes in CDAI in the placebo group gradually decreased and disappeared at 24 weeks, but those in the adrenomedullin-treated groups (10 or 15 ng/kg/min group) remained at steady levels for 24 weeks. Therefore, a significant difference was observed between the placebo and adrenomedullin-treated groups at 24 weeks (P = 0.043) in the mixed-effects model. We noted mild adverse events caused by the vasodilatory effect of adrenomedullin.

In this trial, we observed a long-lasting (24 weeks) decrease in CDAI in the adrenomedullin-treated groups. Adrenomedullin might be beneficial for biologic-resistant CD, but further research is needed.

Accelerated infliximab (IFX) induction is often based on clinical parameters as opposed to pharmacokinetics (PK). We aimed to investigate the impact of dashboard-guided optimized induction dosing on IFX durability and immunogenicity in a real-world inflammatory bowel disease (IBD) setting.

Pediatric and adult IBD patients were enrolled in a prospective single arm intervention trial. Cumulative data from each infusion (INF), weight, albumin, C-reactive protein, IFX dose, IFX trough level, and antidrug antibody presence were used to inform subsequent INF dosing. Forecasts driven by adaptive Bayesian modeling were generated to maintain trough levels for the third (INF3) and fourth (INF4) infusions of 17 μg/mL and 10 μg/mL, respectively. The primary outcome was proportion of patients prescribed accelerated dosing (AD) intervals by INF3 (<22 days) or INF4 (<49 days). Secondary outcomes included week 52 clinical and PK outcomes. Multivariate analyses and Kaplan-Meier curves compared outcomes based on adherence to dashboard forecasts.

Of the 180 per-protocol population, AD was forecast for 41% (INF3) and 69% (INF4) of patients with median intervals of 17 (INF3) and 39 (INF4) days. Baseline age >18 years, albumin >3.5 g/L, and 10-mg/kg dose were independently associated with lower rates of AD by INF4. Nonadherence with the INF4 forecast (n = 39) was an independent predictor of antidrug antibody (P < .0001) and IFX discontinuation (P = .0006). A total of 119 of 123 patients on IFX at week 52 were in steroid-free remission.

The application of a PK dashboard during induction can optimize dosing early to improve IFX durability and immunogenicity.

The prevalence of immune-mediated diseases has increased in the past decades and despite the use of biological treatments all patients do not achieve remission. The aim of this study was to characterise the reasons for short interruptions during treatment with two commonly used TNF-inhibitors infliximab and adalimumab and to analyse the possible effects of the interruptions on immunisation and switching the treatment.

This case-control study was based on retrospective analyses of patient records and a questionnaire survey to clinicians. A total of 370 patients (194 immunised cases and 172 non-immunised controls, 4 excluded) were enrolled from eight hospitals around Finland. Eleven different diagnoses were represented, and the largest patient groups were those with inflammatory bowel or rheumatic diseases.

Treatment interruptions were associated with immunisation in patients using infliximab (p < .001) or adalimumab (p < .000001). Patients with treatment interruptions were more likely to have been treated with more than one biological agent compared to those without treatment interruptions. This was particularly prominent among patients with a rheumatic disease (p < .00001). The most frequent reason for a treatment interruption among the cases was an infection, whereas among the control patients it was remission. The median length of one interruption was one month (interquartile range 1-3 months).

Our results suggest that the interruptions of the treatment with TNF-inhibitors expose patients to immunisation and increase the need for drug switching. These findings stress the importance of careful judgement of the need for a short interruption in the biological treatment in clinical work, especially during non-severe infections.

Higher infliximab trough levels (TLs) correlate with better clinical, inflammatory, and endoscopic outcomes among inflammatory bowel disease (IBD) patients. Although standard scheduled infliximab therapy regimen consists of infusions at pre-defined time-points (weeks 0, 2, 6, and every 8 weeks), short-period deviations from therapeutic schedule are common in 'real life', but the pharmacokinetic impact of these deviations has not been explored. In this study, we aim to determine whether short-period deviations from infusion schedule affect infliximab-TL.

A retrospective analysis of all IBD patients receiving infliximab maintenance therapy every 8 weeks was conducted in a tertiary medical center. Patients with anti-drug antibodies, deliberate interval shortening and <3 sequential maintenance sera available were excluded. Associations between time since last infusion and TL were studied. Statistical analysis was performed using generalized estimating equations.

Out of over 10,000 sera, 2088 sera of 302 maintenance period stable infliximab-therapy-patients met inclusion criteria (median TL 4.1 μg/mL, interquartile range (IQR) 2.3-6.5 μg/mL). A delay beyond 3 days in infusion schedule (n > 59 days since last infusion) was found to significantly affect TL (mean difference in TL 0.9 μg/mL, 95% confidence interval (CI): 0.03-1.9 μg/mL, p < 0.04). Furthermore, among patients with delayed infusions, 80% had TL below 5 μg/mL, in comparison to 55% of patients who were not late (odds ratio (OR): 2.81, CI: 2.02-3.92, p < 0.0001).

Real-life delays of ⩽3 days from infusion protocol can probably be allowed. Delays >3 days culminate in measurable decrease of TL, although effect on clinical outcome is unclear. This needs to be taken into account when interpreting drug-level test results.

A total of 2088 sera of 302 maintenance period inflammatory bowel disease (IBD) patients treated with infliximab were analyzed, to assess effect of small deviations from infusion schedule on TLs. A significant decline in patients' trough level (TL) was noted as early as 3 days after scheduled infusion.

Infliximab dose escalation (DE) can be used in inflammatory bowel disease patient; however, the long-term benefit remains unclear, especially in those with antibodies to infliximab (ATI). The aim was to assess the effect of DE in patients with ATI on drug level, clinical response and ATI status.

All patients undergoing infliximab DE (a reduction in dose interval between infusions <8 weeks ± an increase in dose up to 10 mg/kg) at a referral centre between April 2016 and August 2019 were included.

Ninety-two patients were DE: 51 were men, 50 had CD and 63 were receiving immunosuppression. A total of 87 people received DE for a median of 44 weeks (range 4-176). Five stopped infliximab after 1 dose of DE: 2 for loss of response and 3 for infusion reaction. In patients with ATI ≤10 vs. >10 AU/mL, DE significantly increased drug levels: median infliximab levels of 1.4 and 0.9 at baseline, respectively, to 3.2 and 3.5 at week 24. After DE, 21/35 ATI-positive patients had a fall in ATI ≤10 AU/mL. At week 24 following DE 62/92 patients were in clinical remission. Duration of clinical remission was shorter in those with ATI >10 AU/mL (median 24 weeks, range 0-88) than in those with transient/ATI ≤10 AU/mL (median 36 weeks, range 0-126, P = 0.06).

A strategy of DE for selected patients receiving infliximab is associated with an increase in drug levels and reduced ATI positivity. This is associated with clinical remission in approximately 70% of patients at 6 months.

Antibodies to infliximab (ATI) are associated with secondary loss of response and increased risk for drug reactions. Limited studies have associated ATI with increased infliximab clearance.

We assessed the impact of ATI on infliximab clearance and loss of response in an inception paediatric Crohn's disease cohort with 1-year follow-up.

This multi-centre prospective cohort study collected peak and trough serum infliximab/ATI concentrations from 660 infusions (78 patients) during the first year of therapy. Clinicians were blinded to these research labs. The primary outcome was the difference in infliximab clearance between ATI-positive (ATI) and ATI-negative (no-ATI) patients. Secondary outcomes included pre-treatment predictors of ATI (including HLA-DQA1 genotyping). Clinical remission, loss of response and infliximab clearance were compared between pre-ATI, during ATI and following ATI resolution with MANOVA. Time to ATI was calculated by Cox proportional Hazards model.

ATI were detected in 68% (53/78) patients with a median concentration of 76 ng/mL (range 23-1828). Maximum ATI concentration was <200 ng/mL in 73.6% (39/53). Median clearance in ATI patients was higher (with higher clearance if loss of response), compared to no-ATI patients (P < 0.001). Neutrophil CD64 ratio >6 and starting dose <7.5 mg/kg independently predicted ATI in multivariable regression, while HLA-DQA1*05 presence did not. Dose adjustment resolved ATI in 37.5% (12/32) patients with concomitant infliximab concentration and clearance recovery. A maximum ATI level of ≤99 ng/mL predicted ATI resolution (area under the receiver operating curve 0.80 [95% CI 0.64-0.96]).

In this real-world cohort, ATI as low as 23 ng/mL impacted drug clearance. Our data suggest that dose optimisation for low-level ATI can improve infliximab clearance and prevent loss of response.

Few studies have demonstrated treatment strategies about the duration and cessation of medications in patients with Crohn's disease (CD). We investigated factors affecting clinical relapse after infliximab (IFX) or azathioprine (AZA) withdrawal in pediatric patients with CD on combination therapy. Pediatric patients with moderate-to-severe CD receiving combination therapy were analyzed retrospectively and factors associated with clinical relapse were investigated. Discontinuation of IFX or AZA was performed in patients who sustained clinical remission (CR) for at least two years and achieved deep remission. A total of 75 patients were included. Forty-four patients (58.7%) continued with combination therapy and 31 patients (41.3%) discontinued AZA or IFX (AZA withdrawal 10, IFX withdrawal 15, both withdrawal 6). Cox proportional-hazards regression and statistical internal validation identified three factors associated with clinical relapse: IFX cessation (hazard ratio; HR 2.982, P = 0.0081), IFX TLs during maintenance therapy (HR 0.581, P = 0.003), 6-thioguanine nucleotide (6-TGN) level (HR 0.978, P < 0.001). However, AZA cessation was not associated with clinical relapse (P = 0.9021). Even when applied in pediatric patients who met stringent criteria, IFX cessation increased the relapse risk. However, withdrawal of AZA could be contemplated in pediatric patients with CD who have sustained CR for at least 2 years and achieved deep remission.

To compare the timing of serum anti-drug antibodies in adult and pediatric age groups, males and females, treated for inflammatory bowel disease or arthritis with adalimumab or infliximab by retrospectively combining data collected during a 2-year therapeutic drug monitoring period.

Four hundred thirty sera were divided in groups collected at 0, 3, 6, 12, and 24 months (T0, T3, T6, T12, and T24) after initiation of therapy and assayed for drug and relative anti-drug antibodies levels. At each time point, the percentage of sera presenting anti-drug antibodies, as well as the drug concentrations, were calculated and correlated with patient age and sex.

Anti-drug antibodies were present in 31.5% of sera and were significantly higher in the pediatric age group than in the adult age group, through all time points. The percentages of sera showing anti-drug antibodies were significantly different as early as 3 months and were sera from pediatric female group. The percentages of sera showing anti-drug antibodies reached the highest value at 6 months in the pediatric age group and at 12 months in the adult age group.

Sera from pediatric had an earlier presence of anti-drug antibodies than adults. In particular, pediatric females sera showed the fastest anti-drug antibodies development.

We investigated relationships between induction ustekinumab levels and clinical and biochemical outcomes in Crohn's disease.

Following standard IV induction, ustekinumab levels were measured at week 2 (wk2) and week 6 (wk6). Ustekinumab levels were compared in patients receiving 260, 390 and 520 mg at induction. Crohn's disease activity index (CDAI), serum albumin, C-reactive protein (CRP) and fecal calprotectin (FCP) were measured at baseline and week 12 (wk12). Associations between ustekinumab levels and these parameters were assessed. Ustekinumab levels were compared between patients requiring dose intensification within one year of induction and those remaining on standard dosing.

Of 23 wk2 ustekinumab levels, 22(95.7%) were above the upper limit of quantification of the assay (25 µg/mL). Median wk6 ustekinumab level (n = 25) was 14.2 μg/mL [interquartile range (IQR), 9.6-20.1]. Median wk6 ustekinumab levels in patients receiving 260, 390 and 520 mg were 8.6, 16.3 and 25.0 µg/mL, respectively, P = 0.01. There were significant correlations between baseline albumin and wk6 ustekinumab levels; r = 0.644 [95% confidence interval (CI), 0.304-0.839], P < 0.001, and between baseline FCP and wk6 ustekinumab levels; r = -0.678 (95% CI, -0.873 to -0.296), P < 00.01. Median wk12 CDAI (n = 18), CRP (n = 22) and FCP (n = 13) were 78 (IQR, 52.5-152), 1.75 mg/L (IQR, 0.93-7.03) and 746 μg/g (IQR, 259-2100), respectively. There were significant correlations between wk6 ustekinumab levels and wk12 CDAI; r = -0.513 (95% CI, -0.796 to -0.046), P = 0.03; and between wk6 ustekinumab levels and wk12 CRP; r = -0.578 (95% CI, -0.808 to -0.194), P < 0.01. Wk6 ustekinumab levels were lower in patients undergoing subsequent dose intensification; 12.5 vs. 19.6 µg/mL, P = 0.04.

Wk6 ustekinumab levels are significantly associated with baseline Crohn's disease biomarkers and subsequent clinical and biochemical outcomes.

Infliximab is an efficacious therapy for inflammatory bowel disease and may play a role in management of some extraintestinal manifestations. While higher trough levels of infliximab are associated with higher rates of disease remission, the association between trough levels of infliximab and arthralgia activity characterised as an extraintestinal manifestation has yet to be defined.

We aimed to assess the association between serum trough levels of infliximab and peripheral arthralgia activity in patients with inflammatory bowel disease.

In this cross-sectional study, we identified patients with inflammatory bowel disease on infliximab therapy with known history of arthralgias attributed to an extraintestinal manifestation. Collected variables included disease phenotype, medications (such as thiopurines or methotrexate), Harvey Bradshaw Index, partial Mayo score, C reactive protein, trough levels of infliximab and anti-infliximab antibodies. The primary outcome was active patient-reported arthralgia.

Out of 267 patients included, 65 (24.4%) had active arthralgias at the time the trough level of infliximab was measured. No significant differences in trough levels were seen between those patients with and without arthralgias. Patients on combination therapy with methotrexate or thiopurines or those with detectable anti-infliximab antibodies were not more likely to have inactive arthralgias (OR 0.99, 95% CI 0.57 to 1.74, p=0.99 and OR 1.94, 95% CI 0.9 to 4.1, p=0.09, respectively).

This study suggests that although therapeutic drug monitoring of infliximab can have a role in the management of Crohn's disease and ulcerative colitis, it does not seem to be useful in managing arthralgias associated with inflammatory bowel disease.

Twenty-five years ago the field was revolutionized by the introduction of infliximab as the first hybrid anti-TNF-antibody. Subsequently, other humanized anti-TNFs were developed and marketed, followed by antibodies to new targets including integrins (vedolizumab) and interleukin 12/23 (ustekinumab). All these so-called biologicals were shown in registrational trials to induce remission superior to placebo but consistently were effective in only a minority of patients. Even though in most trials only the responders were selected to continue on the respective medication for maintenance, many experienced a secondary loss of response and only a minority of usually <25% of the initial cohort achieved long-term (1 year) remission. In 'real life studies', the outcome was somewhat better, probably due to proper selection of patients and open, mostly retrospective study designs. A clear benefit of biologicals is apparent in otherwise treatment refractory patients, in extraintestinal manifestations and in Crohn´s disease (CD) with fistulizing complications. Biologicals achieve mucosal healing (MH) more often than corticosteroids or thiopurines, and MH is associated with improved prognosis. However, this does not justify escalating treatment until MH is reached since controlled trials proving this point of 'treat to target' are lacking both in ulcerative colitis and CD. Surgical rates have decreased with increasing use of biologicals, but disease progression has not been proven to improve. With the exception of opportunistic infections, serious adverse events are rare. In conclusion, biologicals have changed the scene considerably and expanded our armamentarium, but there is also a marketing hype fostering expectations without evidence.