HLADQA1*05 genotype predicts anti-drug antibody formation and loss of response during infliximab therapy for inflammatory bowel disease

Ancestral Diversity in Pharmacogenomics Affects Treatment for Hispanic/Latine Populations With Inflammatory Bowel Disease

BACKGROUND AND AIMS

The prevalence of inflammatory bowel disease among Hispanic/Latine communities is increasing. Pharmacogenomic studies reveal genetic markers that influence treatment decisions. The aim of our study was to examine the frequency and impact of genetic polymorphisms on thiopurine-associated leukopenia (NUDT15, TPMT) and anti-tumor necrosis factor (TNF) immunogenicity (HLA-DQA1∗05) in a cohort of Hispanic patients of diverse ancestral backgrounds.

METHODS

We performed a multicenter, retrospective cohort study comprising 2225 Hispanic participants. We measured the frequency of variation affecting drug response in NUDT15, TPMT, and HLA-DQA1∗05; their ancestral origin (European, African, or Amerindian); and the rate of development of myelosuppression and immunogenicity to thiopurines and anti-TNFs, in exposed patients.

RESULTS

NUDT15 and TPMT variants were rare, except for rs116855232 in NUDT15, which was common only in alleles of Amerindian origin. All NUDT15 variant alleles were inherited on an Amerindian haplotype, and among the Amerindian allele subset, the variant frequency of NUDT15∗4 (rs147390019) was a remarkable 23% in patients with leukopenia but only 3% in patients without leukopenia. HLA-DQA1∗05 and its European tagging variant rs2097432 were common in alleles from all ancestral origins and demonstrated association with immunogenicity to anti-TNFs. However, rs2097432 was only correlated with HLA-DQA1∗05 in the European allele subset.

CONCLUSIONS

These findings indicate that NUDT15 testing should become standard clinical practice before prescribing thiopurines in individuals with Amerindian/Alaska Native ancestry, including Hispanic individuals. Additionally, rs2097432 should not be used as a surrogate for HLA-DQA1∗05 testing for diverse populations. Ultimately, incorporating ancestry in personalized therapeutic approaches is important for treatment of Hispanic patients with inflammatory bowel disease.

HLA DQA1*05 and Risk of Antitumor Necrosis Factor Treatment Failure and Anti-Drug Antibody Development in Children With Crohn's Disease

INTRODUCTION

Human leukocyte antigen (HLA) DQA1*05 has been associated with the development of anti-drug antibodies (ADA) to tumor necrosis factor antagonists (anti-TNFα) and treatment failure among adults with Crohn's disease (CD). However, findings from other studies have been inconsistent with limited pediatric data.

METHODS

We analyzed banked serum from patients with CD aged <21 years enrolled in clinical outcomes of Methotrexate Binary Therapy in practice, a multicenter, prospective randomized trial of anti-TNFα monotherapy vs combination with methotrexate. The primary outcome was a composite of factors indicative of treatment failure. The secondary outcome was ADA development.

RESULTS

A trend toward increased treatment failure among HLA DQA1*05-positive participants was not significant (hazard ratio 1.58, 95% confidence interval [CI] 0.95-2.62; P = 0.08). After stratification by HLA DQA1*05 and by methotrexate vs placebo, patients who were HLA DQA1*05 negative and assigned to methotrexate experienced less treatment failures than HLA DQA1*05-positive patients on placebo (hazard ratio 0.31, 95% CI 0.13-0.70; P = 0.005). A trend toward increased ADA development among HLA DQA1*05-positive participants was not significant (odds ratio 1.96, 95% CI 0.90-4.31, P = 0.09). After further stratification, HLA DQA1*05-negative participants assigned to methotrexate were less likely to develop ADA relative to HLA DQA1*05-positive patients on placebo (odds ratio 0.12, 95% CI 0.03-0.55; P = 0.008).

DISCUSSION

In a randomized trial of children with CD initiating anti-TNFα, 40% were HLA DQ-A1*05 positive, which was associated with a trend toward increased risk of both treatment failure and ADA. These risks were mitigated, but not eliminated, by adding oral methotrexate. HLA DQ-A1*05 is an important biomarker for prognosis and risk stratification.

HLA-DQA1*05 Allele Carriage and Anti-TNF Therapy Persistence in Inflammatory Bowel Disease

INTRODUCTION

Carriage of the HLA-DQA1*05 allele is associated with development of antidrug antibodies (ADAs) to antitumor necrosis factor (anti-TNF) therapy in patients with Crohn's disease. However, ADA is not uniformly associated with treatment failure. We aimed to determine the impact of carriage of HLA-DQA1*05 allele on outcome of biologic therapy evaluated by drug persistence.

METHODS

A multicenter, retrospective study of 877 patients with inflammatory bowel disease (IBD) treated with anti-TNF therapy with HLA-DQA1*05 genotypes were generated by imputation from whole genome sequence using the HIBAG package, in R. Primary end point was anti-TNF therapy persistence, (time to therapy failure), segregated by HLA-DQA1*05 allele genotype and development of a risk score to predict anti-TNF therapy failure, incorporating HLA-DQA1*05 allele genotype status (LORisk score).

RESULTS

In all, 877 patients receiving anti-TNF therapy were included in our study; 543 (62%) had no copy, 281 (32%) one copy, and 53 (6%) 2 copies of HLA-DQA1*05 allele. Mean time to anti-TNF therapy failure in patients with 2 copies of HLA-DQA1*05 allele was significantly shorter compared with patients with 0 or 1 copy at 700 days' follow-up: 418 vs 541 vs 513 days, respectively (P = .012). Factors independently associated with time to anti-TNF therapy failure included carriage of HLA-DQA1*05 allele (hazard ratio [HR], 1.2, P = .02; female gender HR, 1.6, P < .001; UC phenotype HR, 1.4, P = .009; and anti-TNF therapy type [infliximab], HR, 1.5, P = .002). The LORisk score was significantly associated with shorter time to anti-TNF therapy failure (P < .001).

CONCLUSIONS

Carriage of 2 HLA-DQA1*05 alleles is associated with less favorable outcomes for patients receiving anti-TNF therapy with shorter time to therapy failure. HLA-DQA1*05 genotype status in conjunction with clinical factors may aid in therapy selection in patients with IBD.

Genetic polymorphisms impacting clinical pharmacology of drugs used to treat inflammatory bowel disease: a precursor to multi-omics approach to precision medicine

INTRODUCTION

Inflammatory bowel diseases (IBDs), comprised of ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory diseases of the gastrointestinal tract. Clinicians and patients must vigilantly manage these complex diseases over the course of the patient's lifetime to mitigate risks of the disease, surgical complications, progression to neoplasia, and complications from medical or surgical therapies. Over the past several decades, the armamentarium of IBD therapeutics has expanded; now with biologics and advanced small molecules complementing conventional drugs such as aminosalicylates, corticosteroids and thiopurines. Significant attention has been paid to the potential of precision medicine to assist clinicians in tailoring therapeutics based on patients' genetic signatures to maximize therapeutic benefit while minimizing adverse effects.

AREAS COVERED

In this paper, we review the published literature on genetic polymorphisms relevant to each class of IBD therapeutics.

EXPERT OPINION

Finally, we envision a paradigm shift in IBD research toward an omics-based network analysis approach. Through global collaboration, organization and goal setting, we predict the next decade of IBD research will revolutionize existing disease frameworks by developing precise molecular diagnoses, validated biomarkers, predictive models and novel molecularly targeted therapeutics.

Pharmacogenetics in Response to Biological Agents in Inflammatory Bowel Disease: A Systematic Review

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders influenced by microbial, environmental, genetic, and immune factors. The introduction of biological agents has transformed IBD therapy, improving symptoms, reducing complications, and enhancing patients' quality of life. However, approximately 30% of patients exhibit primary non-response, and 50% experience a loss of response over time. Genetic and non-genetic factors contribute to variability in treatment outcomes. This systematic review aims to thoroughly analyze and assess existing studies exploring the relationships between genetic variations and individual responses to biologic drugs, in order to identify genetic markers that are predictive of treatment efficacy, risk of adverse effects, or drug toxicity, thereby informing clinical practice and guiding future research. PubMed and EMBASE papers were reviewed by three independent reviewers according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] guidelines. Of the 883 records screened, 99 met the inclusion criteria. The findings of this review represent an initial step toward personalized medicine in IBD, with the potential to improve clinical outcomes in biological therapy.

Targeted Therapies: The Role of Monoclonal Antibodies in Disease Management

Monoclonal antibodies (mAbs) are a key class of biotherapeutic medicines used to treat a wide range of diseases, such as cancer, infectious diseases, autoimmune disorders, cardiovascular diseases, and hemophilia. They can be engineered for greater effectiveness and specific applications while maintaining their structural elements for immune targeting. Traditional immunoglobulin treatments have limited therapeutic uses and various adverse effects. That makes mAbs show rapid growth in the pharmaceutical market, with over 250 mAbs in clinical studies. Although mAbs offer higher specificity, they are less effective against complex antigens. They have become essential in treating diseases with limited medical options, providing innovative solutions that improve patients' quality of life through increasing survival rates, shortening the length of stay in hospitals with an improved treatment outcome, and reducing side effects. This review outlines the mechanisms, applications, and advancements of mAbs, highlighting their transformative role in modern medicine and their potential to shape future therapeutic interventions.

Copy Number Variation in Asthma: An Integrative Review

Asthma is a complex disease with varied clinical manifestations resulting from the interaction between environmental and genetic factors. While chronic airway inflammation and hyperresponsiveness are central features, the etiology of asthma is multifaceted, leading to a diversity of phenotypes and endotypes. Although most research into the genetics of asthma focused on the analysis of single nucleotide polymorphisms (SNPs), studies highlight the importance of structural variations, such as copy number variations (CNVs), in the inheritance of complex characteristics, but their role has not yet been fully elucidated in asthma. In this context, an integrative review was conducted to identify the genes and pathways involved, the location, size, and classes of CNVs, as well as their contribution to asthma risk, severity, control, and response to treatment. As a result of the review, 16 articles were analyzed, from different types of observational studies, such as case-control, cohort studies and genotyped-proband or trios design, that have been carried out in populations from different countries, ethnicities, and ages. Chromosomes 12 and 17 were the most studied in three publications each. CNVs located on 12 chromosomes were associated with asthma, the majority being found on chromosome 6p and 17q, of the deletion type, encompassing 30 different coding-protein genes and one pseudogene region. Six genes with CNVs were identified as significant expression quantitative locus (eQTLs) with mean expression in asthma-related tissues, such as the lung and whole blood. The phenotypic variability of asthma may hinder the clinical application of these findings, but the research shows the importance of investigating these genetic variations as possible biomarkers in asthma patients.

Immunogenicity of Therapeutic Antibodies Used for Inflammatory Bowel Disease: Treatment and Clinical Considerations

The introduction of tumor necrosis factor inhibitors has led to a paradigm shift in the management of inflammatory bowel disease (IBD). The subsequent introduction of both anti-integrins and cytokine blockers has since expanded the biologic armamentarium. However, immunogenicity, defined as the production of anti-drug antibodies (ADAs) to the prescribed biopharmaceutical, means a significant fraction of patients exposed to biologic agents will experience a secondary loss of response to one or more of the drugs. In clinical settings, immunogenicity may be caused by several factors, both patient related (e.g., underlying chronic disease, systemic immune burden, including previous biologic therapy failure, and [epi]genetic background) and treatment related (e.g., dose and administration regimens, drug physical structure, photostability, temperature, and agitation). Here, we outline these elements in detail to enhance biopharmaceutical delivery and therapy for patients with IBD. Moreover, concurrent immunomodulator medication may reduce the risks of ADA generation, especially when using the chimeric drug infliximab. Summarizing the latest developments and knowledge in the field, this review aims to provide strategies to prevent ADA production and information on managing non-responsiveness or loss of response to biologics. Better understanding of the molecular mechanisms underlying the formation of ADAs and the critical factors influencing the immunogenicity of biopharmaceuticals may lead to improved health outcomes in the IBD community that may benefit both the individual patient and society through lower healthcare expenses.

Does HLA-DQA1*05 carriage have a greater impact on the outcome of infliximab therapy for isolated small-bowel Crohn's disease?

Carriage of HLA-DQA1*05 is thought to increase the formation of anti-tumour necrosis factor alpha (TNF-α) antibodies, reducing the drug efficacy in Crohn's disease (CD) patients. However, little data are currently available for small-bowel Crohn's disease (SB-CD). A specific assessment of the impact of HLA-DQA1*05 on the clinical response to treatment with infliximab (IFX), a TNF-α antagonists, in SB-CD patients is necessary. We conducted a single-center retrospective study that included 106 SB-CD patients treated with IFX. The serum samples were collected for antibodies to infliximab (ATI) testing and HLA-DQA1*05 genotyping. Double-balloon enteroscopy (DBE) was performed following the IFX treatment, with endoscopic outcomes evaluated using the partial simple endoscopic score for CD (pSES-CD), whereas the clinical response was assessed with the Crohn's disease activity index (CDAI). Multivariate logistic regression and multivariate COX regression analyses were employed to analyze the correlation of the HLA-DQA1*05 genotypes with other clinical variables. In this study, 30.2% of SB-CD patients carried the HLA-DQA1*05 allele, which significantly increased their risk of ATI generation (odds ratio [OR] = 2.337, p = .043), but it was not associated with the clinical response to IFX and drug persistence (OR = 2.356, p = .145; OR = 0.457, p = .249). The endoscopic remission rates were 40.6% (13/32) and 55.4% (41/74) in HLA-DQA1*05 carriers and non-carriers, respectively. HLA-DQA1*05 was not associated with endoscopic remission (OR = 0.684, p = .414). The HLA-DQA1*05 variant is identified as a significant risk factor of ATI formation in Chinese patients with SB-CD, but is not associated with the clinical response of IFX treatment and endoscopic remission of SB lesions.

HLA-DQA1*05 Not Associated With Ustekinumab Loss of Response and Antidrug Antibodies in Ulcerative Colitis and Crohn's Disease Patients

It is unknown if inflammatory bowel disease patients carrying the HLA-DQA1*05 allele have a greater risk of immunogenicity to ustekinumab. We observed that ustekinumab-treated patients carrying the allele did not have increased immunogenicity or reduced efficacy/serum ustekinumab concentrations vs noncarriers

Carriage of the HLA-DQA1⋆05 haplotype is associated with a higher risk of infratherapeutic drug concentration and higher immunogenicity in patients undergoing treatment with anti-TNF for inflammatory bowel disease

Background

The success of anti-tumor necrosis factor (TNF) drug strategies in the treatment of inflammatory bowel disease (IBD) is altered by the development of anti-drug antibodies that reduce their efficacy. Studies have shown that the HLA-DQA1⋆05 allele increases the risk of immunogenicity to anti-TNF drugs approximately twofold.

Objective

Analyze whether the presence of the HLA-DQA1⋆05 allele is associated with the development of immunogenicity and to evaluate the disease response to anti-TNF drugs (infliximab (IFX) and adalimumab (ADA)), according to the presence of this allele.

Design

This is an observational retrospective cohort study, single center, to determine the impact of HLA-DQA1⋆05 on disease activity in patients with IBD at the Hospital Universitario Virgen Macarena.

Methods

In total, 200 IBD patients were included: 109 treated with IFX and 91 with ADA. Data were collected using the computerized medical records from the DIRAYA program of the Servicio Andaluz de Salud. Response-defined as improvement-and remission-defined as the disappearance of symptoms and analytical/endoscopic signs-were assessed using activity indices (partial Mayo, Harvey-Bradshaw) in all patients. Anti-TNF drug levels were also determined, as well as the presence or absence of anti-IFX and anti-ADA antibodies. The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology statement.

Results

The HLA-DQA1⋆05 haplotype was present in 70 (35%) patients, including 39 (36%) treated with IFX and 31 (34%) with ADA. The risk of withdrawal, intensification, as well as antibody development, was higher in patients carrying the allele and on treatment with IFX or ADA.

Conclusion

In our study, we demonstrated that there is an increased risk of immunogenicity in patients carrying the HLA-DQA1⋆05 genotype, which would support the idea of screening for this genetic variant before starting anti-TNF therapy, as its prevalence is high in the general population and increases the risk of treatment discontinuation due to loss of response.

Real-World Experience of the Association of HLADQA1*05 Allele With Loss of Response to Anti-TNF Inhibitors

Background

Antitumor necrosis factor (anti-TNF) biologics have revolutionized the treatment of inflammatory bowel disease (IBD). Previously, studies have shown an association between the HLADQA1*05 allele and the development of antibodies and were predictive of loss of response. We sought to investigate the rate of the HLADQA1*05 allele in patients with IBD at a New England center and its association with antibody development and discontinuation of anti-TNF therapy.

Methods

A single center retrospective cohort study with patients on anti-TNF inhibitor therapy being followed at our IBD clinic who had testing performed for the HLADQA1*05 allele were identified and separated into 2 different groups: HLADQA1*05 positive (HLA carriers) or HLADQA1*05 negative (HLA noncarriers). Persistence of remaining on anti-TNF therapy, measurement of drug/antibody levels, and need for dose escalation were collected and stratified amongst the 2 groups.

Results

The prevalence of the HLADQA1*05 allele among all IBD patients followed was 53%. We identified 67 IBD patients being treated with anti-TNF medications, 46 (69%) patients with Crohn's disease and 21 (31%) with ulcerative colitis. Most of the HLA carriers (85%) and HLA noncarriers (92%) remained on anti-TNF therapy at the end of the study period. Thirty-six (84%) patients had therapeutic drug monitoring performed during maintenance therapy. Three patients in the HLA carrier group had meaningful antidrug antibody levels necessitating cessation of therapy compared to one patient in the HLA noncarrier group (P = .61). Only 3 (13%) of HLA carriers and 4 (21%) of HLA noncarriers were on combination therapy with an immunomodulator. 65% of HLA carriers required dose escalation compared to 50% of HLA noncarriers (P = .70).

Conclusions

The prevalence of the HLADQA1*05 allele was 53% in our New England IBD patient population, similar to what has previously been reported in European studies. The majority of patients remained on anti-TNF therapy at the end of the study period despite carrier status. While there was a trend toward increased need for dose escalation among HLA carriers, this was not statistically significant. Future studies are needed to determine if the presence of the HLADQA1*05 allele leads to antibody development against anti-TNF inhibitors and treatment failure in patients with IBD.

Impact of HLA-DQA1*05 Genotype in Immunogenicity and Failure to Treatment with Tumour Necrosis Factor-alpha Antagonists in Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND

HLA-DQA1*05 carriage has been associated with an increased risk of immunogenicity in patients with immune-mediated inflammatory diseases treated with tumour necrosis factor-alpha [TNF-a] antagonists. Results have shown an inconsistent association with a loss of response [LOR] in patients with inflammatory bowel disease [IBD], which could be modified when using proactive optimisation and association with immunomodulatory drugs.

AIMS

To define the association of HLA-DQA1*05 on anti-drug antibody development and loss of response [LOR] to anti-TNF-a in IBD.

METHODS

We searched MEDLINE, EMBASE, and SCOPUS, for the period up to August 2023, to identify studies reporting the risk of immunogenicity and/or LOR in IBD patients with HLA-DQA1*05 genotype.

RESULTS

A total of 24 studies comprising 12 papers, 11 abstracts and one research letter, with a total of 5727 IBD patients, were included. In a meta-analysis of 10 studies [2984 patients; 41.9% with HLA-DQA1*05 genotype], HLA-DQA1*05 carriers had higher risk of immunogenicity compared with non-carriers (risk ratio, 1.54; 95% confidence interval [CI], 1.23 - 1.94; I2 = 62%) [low certainty evidence]. Lack of therapeutic drug monitoring [TDM] increased immunogenicity in the presence of risk human leukocyte antigen [HLA] [risk ratio 1.97; 95% CI, 1.35 - 2.88; I2 = 66%], whereas proactive TDM revoked this association [very low certainty of evidence]. A meta-analysis of six studies [765 patients] found that risk for secondary LOR was higher among HLA-DQA1*05 carriers [hazard ratio 2.21; 95% CI, 1.69 - 2.88; I2 = 0%] [very low certainty evidence], although definition and time to assessment varied widely among studies.

CONCLUSION

HLA-DQA1*05 carriage may be associated with an increased risk of immunogenicity and secondary LOR in IBD patients treated with TNF-a antagonists.

Implementation of pharmacogenomics: Where are we now?

Pharmacogenomics (PGx), examining the effect of genetic variation on interpatient variation in drug disposition and response, has been widely studied for several decades. However, as cost, as well as turnaround time associated with PGx testing, has significantly improved, the use of PGx in the clinical setting has been gaining momentum. Nevertheless, challenges have emerged in the broader clinical implementation of PGx. In this review, we will outline current models of PGx delivery and methodologies of evaluation, and discuss clinically relevant PGx tests and associated medications. Additionally, we will describe our approach for the broad implementation of pre-emptive DPYD genotyping in patients taking fluoropyrimidines in Ontario, Canada, as an example of clinically actionable PGx testing with sufficient clinical evidence of patient benefit that can become a new standard of patient care. We will highlight challenges associated with PGx testing, including a lack of diversity in PGx studies as well as general limitations that impact the broad adoption of PGx testing. Lastly, we examine the future of PGx, discussing new clinical targets, methodologies and analysis approaches.

HLA-DQA1*05 correlates with increased risk of anti-drug antibody development and reduced response to infliximab in Chinese patients with Crohn's disease

Background

The efficacy of anti-TNF therapy in Crohn's disease (CD), such as infliximab, is often compromised by the development of anti-drug antibodies (ADAs). The genetic variation HLA-DQA1*05 has been linked to the immunogenicity of biologics, influencing ADA formation. This study investigates the correlation between HLA-DQA1*05 and ADA formation in CD patients treated with infliximab in a Chinese Han population and assesses clinical outcomes.

Methods

In this retrospective cohort study, 345 infliximab-exposed CD patients were genotyped for HLADQ A1*05A > G (rs2097432). We evaluated the risk of ADA development, loss of infliximab response, adverse events, and treatment discontinuation among variant and wild-type allele individuals.

Results

A higher percentage of patients with ADAs formation was observed in HLA-DQA1*05 G variant carriers compared with HLA-DQA1*05 wild-type carriers (58.5% vs 42.9%, P = 0.004). HLA-DQA1*05 carriage significantly increased the risk of ADAs development (adjusted hazard ratio = 1.65, 95% CI 1.18-2.30, P = 0.003) and was associated with a greater likelihood of infliximab response loss (adjusted HR = 2.55, 95% CI 1.78-3.68, P < 0.0001) and treatment discontinuation (adjusted HR = 2.21, 95% CI 1.59-3.06, P < 0.0001). Interestingly, combined therapy with immunomodulators increased the risk of response loss in HLA-DQA1*05 variant carriers.

Conclusions

HLA-DQA1*05 significantly predicts ADAs formation and impacts treatment outcomes in infliximab-treated CD patients. Pre-treatment screening for this genetic factor could therefore be instrumental in personalizing anti-TNF therapy strategies for these patients.

Intestinal mRNA expression profiles associated with mucosal healing in ustekinumab-treated Crohn's disease patients: bioinformatics analysis and prospective cohort validation

BACKGROUND

Variations exist in the response of patients with Crohn's disease (CD) to ustekinumab (UST) treatment, but the underlying cause remains unknown. Our objective was to investigate the involvement of immune cells and identify potential biomarkers that could predict the response to interleukin (IL) 12/23 inhibitors in patients with CD.

METHODS

The GSE207022 dataset, which consisted of 54 non-responders and 9 responders to UST in a CD cohort, was analyzed. Differentially expressed genes (DEGs) were identified and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Least absolute shrinkage and selection operator (LASSO) regression was used to screen the most powerful hub genes. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive performances of these genes. Single-sample Gene Set Enrichment Analysis (ssGSEA) was used to estimate the proportions of immune cell types. These significantly altered genes were subjected to cluster analysis into immune cell-related infiltration. To validate the reliability of the candidates, patients prescribed UST as a first-line biologic in a prospective cohort were included as an independent validation dataset.

RESULTS

A total of 99 DEGs were identified in the integrated dataset. GO and KEGG analyses revealed significant enrichment of immune response pathways in patients with CD. Thirteen genes (SOCS3, CD55, KDM5D, IGFBP5, LCN2, SLC15A1, XPNPEP2, HLA-DQA2, HMGCS2, DDX3Y, ITGB2, CDKN2B and HLA-DQA1), which were primarily associated with the response versus nonresponse patients, were identified and included in the LASSO analysis. These genes accurately predicted treatment response, with an area under the curve (AUC) of 0.938. T helper cell type 1 (Th1) cell polarization was comparatively strong in nonresponse individuals. Positive connections were observed between Th1 cells and the LCN2 and KDM5D genes. Furthermore, we employed an independent validation dataset and early experimental verification to validate the LCN2 and KDM5D genes as effective predictive markers.

CONCLUSIONS

Th1 cell polarization is an important cause of nonresponse to UST therapy in patients with CD. LCN2 and KDM5D can be used as predictive markers to effectively identify nonresponse patients.

TRIAL REGISTRATION

Trial registration number: NCT05542459; Date of registration: 2022-09-14; URL: https://www.

CLINICALTRIALS

gov .

HLA-DQA1*05 Was Not Associated With Primary Nonresponse or Loss of Response to First Anti-TNF in Real-World Inflammatory Bowel Disease Patients

BACKGROUND

We lack predictors of response to biologics in the management of patients with inflammatory bowel disease (IBD). A recent study has shown a significant association between HLA-DQA1*05 carriers and the development of loss of response to anti-tumor necrosis factor (TNF) mediated by immunogenicity.

METHODS

Retrospective single-center cohort study including IBD patients who had received anti-TNF therapy as a first biologic and whose HLA-DQA1*05 had been determined. Primary nonresponse and secondary failure (assessed by survival analysis) have been evaluated as well as safety outcomes.

RESULTS

A total of 199 IBD patients (161 [81%] with Crohn's disease and 38 [19%] with ulcerative colitis) were included. A total of 42.4% were HLA-DQA1*05 carriers and 60% received combination therapy at the start of anti-TNF treatment. Median follow-up was 24 (interquartile range, 11-66) months. No statistically significant differences were found in primary nonresponse to anti-TNF (89.3% vs 87.8%; P = .825), depending on HLA carriers and noncarriers. No differences in secondary loss of response according to HLA variant in any of the analyses performed (full cohort, according to IBD or anti-TNF type) were observed. Again, no differences were observed in patients treated with combination therapy. In terms of safety, no significant differences were found in the rate of infusion reactions or serious adverse events.

CONCLUSION

In our real-life cohort of IBD patients treated for the first time with anti-TNF, being an HLA-DQA1*05 carrier did not act as a predictor of response failure, either primary or secondary. The safety of anti-TNF treatment has also not been influenced by the variant.

Best Practice for Therapeutic Drug Monitoring of Infliximab: Position Statement from the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

BACKGROUND

Infliximab, an anti-tumor necrosis factor monoclonal antibody, has revolutionized the pharmacological management of immune-mediated inflammatory diseases (IMIDs). This position statement critically reviews and examines existing data on therapeutic drug monitoring (TDM) of infliximab in patients with IMIDs. It provides a practical guide on implementing TDM in current clinical practices and outlines priority areas for future research.

METHODS

The endorsing TDM of Biologics and Pharmacometrics Committees of the International Association of TDM and Clinical Toxicology collaborated to create this position statement.

RESULTS

Accumulating data support the evidence for TDM of infliximab in the treatment of inflammatory bowel diseases, with limited investigation in other IMIDs. A universal approach to TDM may not fully realize the benefits of improving therapeutic outcomes. Patients at risk for increased infliximab clearance, particularly with a proactive strategy, stand to gain the most from TDM. Personalized exposure targets based on therapeutic goals, patient phenotype, and infliximab administration route are recommended. Rapid assays and home sampling strategies offer flexibility for point-of-care TDM. Ongoing studies on model-informed precision dosing in inflammatory bowel disease will help assess the additional value of precision dosing software tools. Patient education and empowerment, and electronic health record-integrated TDM solutions will facilitate routine TDM implementation. Although optimization of therapeutic effectiveness is a primary focus, the cost-reducing potential of TDM also merits consideration.

CONCLUSIONS

Successful implementation of TDM for infliximab necessitates interdisciplinary collaboration among clinicians, hospital pharmacists, and (quantitative) clinical pharmacologists to ensure an efficient research trajectory.

Mechanisms and management of loss of response to anti-TNF therapy for patients with Crohn's disease: 3-year data from the prospective, multicentre PANTS cohort study

BACKGROUND

We sought to report the effectiveness of infliximab and adalimumab over the first 3 years of treatment and to define the factors that predict anti-TNF treatment failure and the strategies that prevent or mitigate loss of response.

METHODS

Personalised Anti-TNF therapy in Crohn's disease (PANTS) is a UK-wide, multicentre, prospective observational cohort study reporting the rates of effectiveness of infliximab and adalimumab in anti-TNF-naive patients with active luminal Crohn's disease aged 6 years and older. At the end of the first year, sites were invited to enrol participants still receiving study drug into the 2-year PANTS-extension study. We estimated rates of remission across the whole cohort at the end of years 1, 2, and 3 of the study using a modified survival technique with permutation testing. Multivariable regression and survival analyses were used to identify factors associated with loss of response in patients who had initially responded to anti-TNF therapy and with immunogenicity. Loss of response was defined in patients who initially responded to anti-TNF therapy at the end of induction and who subsequently developed symptomatic activity that warranted an escalation of steroid, immunomodulatory, or anti-TNF therapy, resectional surgery, or exit from study due to treatment failure. This study was registered with ClinicalTrials.gov, NCT03088449, and is now complete.

FINDINGS

Between March 19, 2014, and Sept 21, 2017, 389 (41%) of 955 patients treated with infliximab and 209 (32%) of 655 treated with adalimumab in the PANTS study entered the PANTS-extension study (median age 32·5 years [IQR 22·1-46·8], 307 [51%] of 598 were female, and 291 [49%] were male). The estimated proportion of patients in remission at the end of years 1, 2, and 3 were, for infliximab 40·2% (95% CI 36·7-43·7), 34·4% (29·9-39·0), and 34·7% (29·8-39·5), and for adalimumab 35·9% (95% CI 31·2-40·5), 32·9% (26·8-39·2), and 28·9% (21·9-36·3), respectively. Optimal drug concentrations at week 14 to predict remission at any later timepoints were 6·1-10·0 mg/L for infliximab and 10·1-12·0 mg/L for adalimumab. After excluding patients who had primary non-response, the estimated proportions of patients who had loss of response by years 1, 2, and 3 were, for infliximab 34·4% (95% CI 30·4-38·2), 54·5% (49·4-59·0), and 60·0% (54·1-65·2), and for adalimumab 32·1% (26·7-37·1), 47·2% (40·2-53·4), and 68·4% (50·9-79·7), respectively. In multivariable analysis, loss of response at year 2 and 3 for patients treated with infliximab and adalimumab was predicted by low anti-TNF drug concentrations at week 14 (infliximab: hazard ratio [HR] for each ten-fold increase in drug concentration 0·45 [95% CI 0·30-0·67], adalimumab: 0·39 [0·22-0·70]). For patients treated with infliximab, loss of response was also associated with female sex (vs male sex; HR 1·47 [95% CI 1·11-1·95]), obesity (vs not obese 1·62 [1·08-2·42]), baseline white cell count (1·06 [1·02-1·11) per 1 × 109 increase in cells per L), and thiopurine dose quartile. Among patients treated with adalimumab, carriage of the HLA-DQA1*05 risk variant was associated with loss of response (HR 1·95 [95% CI 1·17-3·25]). By the end of year 3, the estimated proportion of patients who developed anti-drug antibodies associated with undetectable drug concentrations was 44·0% (95% CI 38·1-49·4) among patients treated with infliximab and 20·3% (13·8-26·2) among those treated with adalimumab. The development of anti-drug antibodies associated with undetectable drug concentrations was significantly associated with treatment without concomitant immunomodulator use for both groups (HR for immunomodulator use: infliximab 0·40 [95% CI 0·31-0·52], adalimumab 0·42 [95% CI 0·24-0·75]), and with carriage of HLA-DQA1*05 risk variant for infliximab (HR for carriage of risk variant: infliximab 1·46 [1·13-1·88]) but not for adalimumab (HR 1·60 [0·92-2·77]). Concomitant use of an immunomodulator before or on the day of starting infliximab was associated with increased time without the development of anti-drug antibodies associated with undetectable drug concentrations compared with use of infliximab alone (HR 2·87 [95% CI 2·20-3·74]) or introduction of an immunomodulator after anti-TNF initiation (1·70 [1·11-2·59]). In years 2 and 3, 16 (4%) of 389 patients treated with infliximab and 11 (5%) of 209 treated with adalimumab had adverse events leading to treatment withdrawal. Nine (2%) patients treated with infliximab and two (1%) of those treated with adalimumab had serious infections in years 2 and 3.

INTERPRETATION

Only around a third of patients with active luminal Crohn's disease treated with an anti-TNF drug were in remission at the end of 3 years of treatment. Low drug concentrations at the end of the induction period predict loss of response by year 3 of treatment, suggesting higher drug concentrations during the first year of treatment, particularly during induction, might lead to better long-term outcomes. Anti-drug antibodies associated with undetectable drug concentrations of infliximab, but not adalimumab, can be predicted by carriage of HLA-DQA1*05 and mitigated by concomitant immunomodulator use for both drugs.

FUNDING

Guts UK, Crohn's and Colitis UK, Cure Crohn's Colitis, AbbVie, Merck Sharp and Dohme, Napp Pharmaceuticals, Pfizer, and Celltrion Healthcare.

Therapeutic drug monitoring in inflammatory bowel diseases. Position statement of the Spanish Working Group on Crohn's Disease and Ulcerative Colitis

The treatment of inflammatory bowel disease has undergone a significant transformation following the introduction of biologic drugs. Thanks to these drugs, treatment goals have evolved from clinical response and remission to more ambitious objectives, such as endoscopic or radiologic remission. However, even though biologics are highly effective, a significant percentage of patients will not achieve an initial response or may lose it over time. We know that there is a direct relationship between the trough concentrations of the biologic and its therapeutic efficacy, with more demanding therapeutic goals requiring higher drug levels, and inadequate exposure being common. Therapeutic drug monitoring of biologic medications, along with pharmacokinetic models, provides us with the possibility of offering a personalized approach to treatment for patients with IBD. Over the past few years, relevant information has accumulated regarding its utility during or after induction, as well as in the maintenance of biologic treatment, in reactive or proactive strategies, and prior to withdrawal or treatment de-escalation. The aim of this document is to establish recommendations regarding the utility of therapeutic drug monitoring of biologics in patients with inflammatory bowel disease, in different clinical practice scenarios, and to identify areas where its utility is evident, promising, or controversial.

Cellular and Molecular Determinants of Biologic Drugs Resistance and Therapeutic Failure in Inflammatory Bowel Disease

The advent of biologic drugs has revolutionized the treatment of Inflammatory Bowel Disease, increasing rates of response and mucosal healing in comparison to conventional therapies by allowing the treatment of corticosteroid-refractory cases and reducing corticosteroid-related side effects. However, biologic therapies (anti-TNFα inhibitors, anti-α4β7 integrin and anti-IL12/23) are still burdened by rates of response that hover around 40% (in biologic-naïve patients) or lower (for biologic-experienced patients). Moreover, knowledge of the mechanisms underlying drug resistance or loss of response is still scarce. Several cellular and molecular determinants are implied in therapeutic failure; genetic predispositions, in the form of single nucleotide polymorphisms in the sequence of cytokines or Human Leukocyte Antigen, or an altered expression of cytokines and other molecules involved in the inflammation cascade, play the most important role. Accessory mechanisms include gut microbiota dysregulation. In this narrative review of the current and most recent literature, we shed light on the mentioned determinants of therapeutic failure in order to pave the way for a more personalized approach that could help avoid unnecessary treatments and toxicities.

A Narrative Review of Cytokine Networks: Pathophysiological and Therapeutic Implications for Inflammatory Bowel Disease Pathogenesis

Inflammatory bowel disease (IBD) is a lifelong inflammatory immune mediated disorder, encompassing Crohn's disease (CD) and ulcerative colitis (UC); however, the cause and specific pathogenesis of IBD is yet incompletely understood. Multiple cytokines produced by different immune cell types results in complex functional networks that constitute a highly regulated messaging network of signaling pathways. Applying biological mechanisms underlying IBD at the single omic level, technologies and genetic engineering enable the quantification of the pattern of released cytokines and new insights into the cytokine landscape of IBD. We focus on the existing literature dealing with the biology of pro- or anti-inflammatory cytokines and interactions that facilitate cell-based modulation of the immune system for IBD inflammation. We summarize the main roles of substantial cytokines in IBD related to homeostatic tissue functions and the remodeling of cytokine networks in IBD, which may be specifically valuable for successful cytokine-targeted therapies via marketed products. Cytokines and their receptors are validated targets for multiple therapeutic areas, we review the current strategies for therapeutic intervention and developing cytokine-targeted therapies. New biologics have shown efficacy in the last few decades for the management of IBD; unfortunately, many patients are nonresponsive or develop therapy resistance over time, creating a need for novel therapeutics. Thus, the treatment options for IBD beyond the immune-modifying anti-TNF agents or combination therapies are expanding rapidly. Further studies are needed to fully understand the immune response, networks of cytokines, and the direct pathogenetic relevance regarding individually tailored, safe and efficient targeted-biotherapeutics.

Precision medicine in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an incurable disease characterized by remission-relapse cycles throughout its course. Both Crohn's disease (CD) and ulcerative colitis (UC), the two main forms of IBD, exhibit tendency to develop complications and substantial heterogeneity in terms of frequency and severity of relapse, thus posing great challenges to the clinical management for IBD. Current treatment strategies are effective in different ways in induction and maintenance therapies for IBD. Recent advances in studies of genetics, pharmacogenetics, proteomics and microbiome provide a strong driving force for identifying molecular markers of prognosis and treatment response, which should help clinicians manage IBD patients more effectively, and then, improve clinical outcomes and reduce treatment costs of patients. In this review, we summarize and discuss precision medicine in IBD, focusing on predictive markers of disease course and treatment response, and monitoring indices during therapeutic drug monitoring.

Treatment Strategies in Inflammatory Bowel Diseases

BACKGROUND

The prevalence of inflammatory bowel disease (IBD) is rising globally. In Germany, these conditions affect 0.7% of the population, or approximately 600 000 patients. Treatment strategies have become more diversified as a result of an improved understanding of disease pathogenesis. It remains unclear how the currently available drugs should best be used in each individual patient.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, with special attention to phase III and IV trials and to the German and European guidelines on the treatment of IBD.

RESULTS

An improved understanding of the immunological mechanisms of disease underlies the current treatment strategies in patients with IBD. For those with a complex clinical course, monoclonal antibodies against pro-inflammatory cytokines (TNF, IL-12/IL-23, IL-23) and cell adhesion molecules (α4β7) are of established therapeutic value, along with "small molecules" such as JAK inhibitors and sphingosine-1-phosphate receptor modulators. The numerous studies that have been performed, only a few of which have been head-to-head comparison trials, and the (network) meta-analyses that have been published to date do not imply that any single one of these drugs can be considered the universal, primary treatment for all patients with IBD. In this review, we discuss the available substances and certain important differential-therapeutic aspects of the treatment of IBD.

CONCLUSION

The treatment of a patient with IBD must take his or her prior treatment(s) and comorbidities into account, along with individual patient characteristics and treatment goals. Rational decision-making is required on the basis of the mechanism of action and the side-effect profile of the various drugs that are now available for use.

The HLA-DQA1*05 genotype does not influence the clinical response to ustekinumab and vedolizumab

BACKGROUND

the success of strategies with earlier anti-TNF drugs for the treatment of inflammatory bowel disease (IBD) have been shadowed by the development of anti-drug antibodies that reduce their effectiveness. The HLA-DQA1*05 allele has been shown to increase the risk of immunogenicity to anti-TNF drugs by approximately two-fold. The negative impact of this allele has not been fully investigated for newer biotherapies.

OBJECTIVE

whether the presence of the HLA-DQA1*05 allele is associated with a reduction of response to ustekinumab and vedolizumab was investigated.

MATERIAL AND METHODS

the impact of HLA-DQA1*05 on disease activity in 93 patients with IBD, treated with ustekinumab (n = 39) or vedolizumab (n = 54) was investigated in a retrospective cohort study. Treatment response and remission was assessed at 6 and 12 months for ustekinumab, and up to 18 and 24 months for vedolizumab, using Harvey-Bradshaw index (Crohn's disease) and Mayo score (ulcerative colitis).

RESULTS

the HLA-DQA1*05 allele was found in 35.9 % and 38.9 % of patients treated with ustekinumab and vedolizumab, respectively. Clinical response was not affected by the presence of the HLA-DQA1*05 allele for both treatment groups.

CONCLUSIONS

in contrast to anti-TNF drugs, HLA-DQA1*05 presence does not correlate with the decreased response to ustekinumab or vedolizumab.

HLA-DQA1*05 and upstream variants of PPARGC1B are associated with infliximab persistence in Japanese Crohn's disease patients

Recently, the HLA-DQA1*05 (rs2097432) genetic variation has been reported to be linked to early infliximab (IFX) treatment failure in the Caucasian Crohn's disease (CD) population, but that evidence is scarce in the Asian population. This study aimed to investigate the relationship between rs2097432 and the cumulative discontinuation-free time of IFX (IFX persistence) in 189 Japanese biologics-naive CD patients. We also performed a genome-wide association study (GWAS) to discover novel genetic predictors for IFX persistence. The C allele of rs2097432 significantly increased the risk of early discontinuation of IFX [Hazard ratio (HR) = 2.23 and P-value = 0.026]. In GWAS, one locus tagged by rs73277969, located upstream of PPARGC1B which attenuates macrophage-mediated inflammation, reached genome-wide significance (HR = 6.04 and P-value = 7.93E-9). Pathway analysis suggested association of signaling by PDGF and FCGR activation signaling with IFX persistence (P-value = 8.56E-5 and 5.80E-4, respectively).

Biological treatment interruption in inflammatory bowel disease: Motivation and predictive factors

BACKGROUND

Loss-of-response and adverse events (AE) to biologics have been linked to HLA-DQA1*05 allele. However, the clinical factors or biologic used may influence treatment duration. Our objective was to evaluate the influence of clinical and therapeutic factors, along with HLA, in biological treatment discontinuation.

METHODS

A retrospective study of consecutive IBD patients treated with biologics between 2007 and 2011 was performed. Main outcome was treatment discontinuation due to primary non-response (PNR), secondary loss of response (SLR) or AE. HLA-DQA1 genotyping was done in all patients. Regression analyses were used to assess risk factors of treatment discontinuation.

RESULTS

One hundred fifty patients (61% male) with 312 biologic treatments were included. 147 (47%) were discontinued with a cumulative probability of 30%, 41% and 56% at 1, 2 and 5 years. The use of infliximab (p=0.006) and articular manifestations (p<0.05) were associated with treatment discontinuation. Considering cause of withdrawal, Ulcerative Colitis (UC) had a higher proportion of PNR (HR=4.99; 95% CI=1.71-14.63; p=0.003), SLR was higher if biologics had been indicated due to disease flare (HR=2.32; 95% CI=1.05-5.09; p=0.037) while AE were greater with infliximab (HR=2.46; 95% CI=1.48-4.08; p<0.001) or spondylitis (HR=2.46; 95% CI=1.78-6.89; p<0.001). According to the biological drug, HLA-DQA1*05 with adalimumab showed more SLR in cases with Crohn's disease (HR=3.49; 95% CI=1.39-8,78; p=0.008) or without concomitant immunomodulator (HR=2.8; 95% CI=1.1-6.93; p=0.026).

CONCLUSIONS

HLA-DQ A1*05 was relevant in SLR of IBD patients treated with adalimumab without immunosupression. In patients treated with other biologics, clinical factors were more important for treatment interruption, mainly extensive UC or extraintestinal manifestations and having indicated the biologic for flare.

HLA-DQA1∗05 Genotype and Immunogenicity to Tumor Necrosis Factor-α Antagonists: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Identifying patients at high risk of immunogenicity is important when selecting tumor necrosis factor (TNF)-α antagonists in patients with immune-mediated inflammatory diseases (IMIDs). We evaluated the association HLA-DQA1∗05 genotype and risk of immunogenicity with TNF-α antagonists.

METHODS

Through a systematic review through July 14, 2022, we identified studies in patients with IMIDs treated with TNF-α antagonists, which reported the risk of immunogenicity and/or secondary loss of response in patients with HLA-DQA1∗05 variants. Primary outcome was risk of immunogenicity. We performed random effects meta-analysis and used GRADE to appraise certainty of evidence.

RESULTS

On meta-analysis of 13 studies (3756 patients; median follow-up, 12 months; 41% with variants), HLA-DQA1∗05 variants were associated with 75% higher risk of immunogenicity compared with non-carriers (relative risk, 1.75; 95% confidence interval, 1.37-2.25) with considerable heterogeneity (I2 = 62%) (low certainty evidence). Positive and negative predictive values of HLA-DQA1∗05 variants for predicting immunogenicity were 30% and 80%, respectively. Proactive therapeutic drug monitoring, but not concomitant use of IMMs, IMIDs, and TNF-α antagonist-type, modified this association. Patients with HLA-DQA1∗05 variants experienced 2.2-fold higher risk of secondary loss of response (6 cohorts; relative risk, 2.24; 95% confidence interval, 1.67-3.00; I2 = 0%) (moderate certainty evidence).

CONCLUSION

Variants in HLA-DQA1∗05 are associated with an increased risk in immunogenicity and secondary loss of response in patients with IMIDs treated with TNF-α antagonists. However, the positive and negative predictive value is moderate, and decisions on concomitant use of IMMs to prevent immunogenicity should be individualized based on all factors that influence drug clearance.

Influence of HLADQA1*05 Genotype in Adults With Inflammatory Bowel Disease and Anti-TNF Treatment With Proactive Therapeutic Drug Monitoring: A Retrospective Cohort Study

BACKGROUND

Carriers of the human leucocyte antigen variant HLADQA1*05 (rs2097432) are at risk of developing antibodies against infliximab and adalimumab with reduced tumor necrosis factor (TNF) antagonist persistence. The impact of proactive therapeutic drug monitoring (PTDM) on this association has been barely assessed.

METHODS

We conducted a retrospective single-center cohort study including patients with inflammatory bowel disease starting anti-TNF therapy between January 2017 and March 2021. Proactive therapeutic drug monitoring was defined as periodic drug level measurement (≥2 determinations during the first year of treatment and ≥1/annual determination during the following years), regardless of clinical condition, followed by dose optimization. Variables associated with treatment persistence were assessed with multivariable Cox regression analysis.

RESULTS

A total of 112 patients were included, 52 (46.4%) HLA-DQA1*05 carriers, with a median follow-up of 73.9 (interquartile range, 35.4-133.1) weeks. Combination therapy with thiopurines was more frequent among HLA-DQA1*05 noncarriers (28 [46.7%] vs 12 [23.1%]; P = .01). Clinical remission rates at week 14 (77.9% vs 73.9%; P = .69) and 56 (73.2% vs 68.4%; P = .64) were similar between HLA-DQA1*05 noncarriers and carriers. Drug persistence was higher among HLA-DQA1*05 carriers (hazard ratio [HR], 0.32; 95% confidence interval, 0.14-0.71; P = .01). Multivariable Cox regression analysis identified systemic steroids at anti-TNF initiation (HR, 4; 95% confidence interval, 1.7-9.7) as a risk factor and HLA-DQA1*05 carriers (HR, 0.31; 95% confidence interval, 0.12-0.81) as a protective factor of treatment cessation.

CONCLUSION

In adult patients with PTDM, a positive HLA-DQA1*05 genotype does not associate a higher risk of treatment cessation nor worse clinical outcomes.

One year of experience with combined pharmacokinetic/pharmacogenetic monitoring of anti-TNF alpha agents: a retrospective study

Anti-tumor necrosis factor alpha (anti-TNFα) inhibitors are used extensively for the management of moderate to severe inflammatory bowel disease (IBD) in both adult and pediatric patients. Unfortunately, not all patients show an optimal response to induction therapy, while others lose their response over time for reasons yet poorly understood. We report on a pharmacokinetic/pharmacogenetic approach to monitor the therapy with anti-TNFα in a real-world cohort of seventy-nine pediatric patients affected by IBD that was analyzed retrospectively. We evaluated plasma concentrations of infliximab, adalimumab, and related anti-drug antibodies (ADAs), and single nucleotide polymorphisms (SNPs) in genes involved in immune processes and inflammation on the anti-TNFα response. We found a significant association between the SNP in TNFα promoter (-308G>A) and clinical remission without steroids in patients on infliximab therapy. Additionally, a potential connection between HLA-DQA1*05 genetic variant carriers and a higher risk of anti-TNFα immunogenicity emerged.

Predictors and optimal management of tumor necrosis factor antagonist nonresponse in inflammatory bowel disease: A literature review

Tumor necrosis factor-α (TNF-α) antagonists, the first biologics approved for treating patients with inflammatory bowel disease (IBD), are effective for the induction and maintenance of remission and significantly improving prognosis. However, up to one-third of treated patients show primary nonresponse (PNR) to anti-TNF-α therapies, and 23%-50% of IBD patients experience loss of response (LOR) to these biologics during subsequent treatment. There is still no recognized predictor for evaluating the efficacy of anti-TNF drugs. This review summarizes the existing predictors of PNR and LOR to anti-TNF in IBD patients. Most predictors remain controversial, and only previous surgical history, disease manifestations, drug concentrations, antidrug antibodies, serum albumin, some biologic markers, and some genetic markers may be potentially predictive. In addition, we also discuss the next steps of treatment for patients with PNR or LOR to TNF antagonists. Therapeutic drug monitoring plays an important role in treatment selection. Dose escalation, combination therapy, switching to a different anti-TNF drug, or switching to a biologic with a different mechanism of action can be selected based on the concentration of the drug and/or antidrug antibodies.

Polymorphisms indicating risk of inflammatory bowel disease or antigenicity to anti-TNF drugs as biomarkers of response in children

Few genetic polymorphisms predict early response to anti-TNF drugs in inflammatory bowel disease (IBD), and even fewer have been identified in the pediatric population. However, it would be of considerable clinical interest to identify and validate genetic biomarkers of long-term response. Therefore, the aim of the study was to analyze the usefulness of biomarkers of response to anti-TNFs in pediatric IBD (pIBD) as long-term biomarkers and to find differences by type of IBD and type of anti-TNF drug. The study population comprised 340 children diagnosed with IBD who were treated with infliximab or adalimumab. Genotyping of 9 selected SNPs for their association with early response and/or immunogenicity to anti-TNFs was performed using real-time PCR. Variants C rs10508884 (CXCL12), A rs2241880 (ATG16L1), and T rs6100556 (PHACTR3) (p value 0.049; p value 0.03; p value 0.031) were associated with worse long-term response to anti-TNFs in pIBD. DNA variants specific to disease type and anti-TNF type were identified in the pediatric population. Genotyping of these genetic variants before initiation of anti-TNFs would enable, if validated in a prospective cohort, the identification of pediatric patients who are long-term responders to this therapy.

Pretreatment Vitamin D Concentrations Do Not Predict Therapeutic Outcome to Anti-TNF Therapies in Biologic-Naïve Patients With Active Luminal Crohn's Disease

Background and Aims

Vitamin D has a regulatory role in innate and adaptive immune processes. Previous studies have reported that low pretreatment vitamin D concentrations are associated with primary non-response (PNR) and non-remission to anti-TNF therapy. This study aimed to assess whether pretreatment 25-hydroxyvitamin D concentrations predicted PNR and non-remission to infliximab and adalimumab in patients with active luminal Crohn's disease.

Methods

25-Hydroxyvitamin D concentrations were measured in stored baseline samples from 659 infliximab- and 448 adalimumab-treated patients in the Personalised Anti-TNF Therapy in Crohn's disease (PANTS) study. Cut-offs for vitamin D were deficiency <25 nmol/L, insufficiency 25-50 nmol/L, and adequacy/sufficiency >50 nmol/L.

Results

About 17.1% (189/1107; 95% CI, 15.0-19.4) and 47.7% (528/1107; 95% CI, 44.8-50.6) of patients had vitamin D deficiency and insufficiency, respectively. 22.2% (246/1107) of patients were receiving vitamin D supplementation. Multivariable analysis confirmed that sampling during non-summer months, South Asian ethnicity, lower serum albumin concentrations, and non-treatment with vitamin D supplementation were independently associated with lower vitamin D concentrations. Pretreatment vitamin D status did not predict response or remission to anti-TNF therapy at week 14 (infliximab P_pnr = .89, adalimumab P_pnr = .18) or non-remission at week 54 (infliximab P = .13, adalimumab P = .58). Vitamin D deficiency was, however, associated with a longer time to immunogenicity in patients treated with infliximab, but not adalimumab.

Conclusions

Vitamin D deficiency is common in patients with active Crohn's disease. Unlike previous studies, pretreatment vitamin D concentration did not predict PNR to anti-TNF treatment at week 14 or nonremission at week 54.

Validation of a rapid HLA-DQA1*05 pharmacogenomics assay to identify at-risk resistance to anti-tumor necrosis factor therapy among patients with inflammatory bowel disease

OBJECTIVES

The HLA-DQA1*05 variant (rs2097432) is associated with increased risk of immunogenicity to tumor necrosis factor antagonists, with subsequent resistance to therapy in patients with inflammatory bowel disease. Identification of these patients would optimize personalized therapeutic selection.

METHODS

Genomic DNA was extracted from 80 deidentified samples in an unselected patient population with an unknown rs2097432 genotype. Split sample analysis was performed using a reference laboratory. Primer probes for a TaqMan quantitative polymerase chain reaction (qPCR) assay (Thermo Fisher Scientific) were custom designed. Synthesized genomic-block fragments were used as controls. All qPCR reactions were performed using a TaqMan GTXpress Master Mix (Thermo Fisher Scientific) on the Applied Biosystems 7500 system under fast cycling conditions.

RESULTS

Of 80 samples, 50% were wild-type reference genotypes, 22.5% were heterozygous, and 27.5% were homozygous variant calls, comparable to population data. Split analysis samples between 2 independent laboratories were 100% concordant. The detection limit tested across genomic-block controls processed in duplicate was reproducible on sample input from 10 ng titrated down to 1.25 ng across 2 independent runs. Further, analytical specificity assessed with previous wild-type reference and homozygous variant DNA spiked into genomic-block controls produced appropriate heterozygous genotypes.

CONCLUSIONS

Here we present validation of a lab-developed test for a rapid HLA-DQA1*05 (rs2097432) pharmacogenomics assay targeting a hotspot identified by genome-wide association studies. Targeted genotyping employed here will allow for expeditious personalized therapeutic selection.

Single nucleotide polymorphisms in ADAM17, IL23R and SLCO1C1 genes protect against infliximab failure in adults with Crohn's disease

BACKGROUND

To predict primary failure of infliximab (IFX) therapy in Crohn's disease (CD) and to identify patients who maintain long-term effectiveness to IFX is currently not feasible. Some genetic variations are proposed as potential biomarkers.

AIM

We assessed a set of single nucleotide polymorphisms (SNPs) in genes related to the IFX mechanism of action and the presence of HLA-DQA1 * 05 allele on the primary response and long-term durability in CD patients.

METHODS

A multi-centre cross-sectional study of IFX-exposed adult patients with CD was undertaken. Treatment persistence and time to failure were co-primary endpoints. DNA from the 131 patients was genotyped. Association between SNPs and clinical variables with IFX persistence was assessed.

RESULTS

Failure to IFX was documented in 65 (49.6%) out of 131 patients. IFX persistence was associated either with carrying the TT genotype in ADAM17 rs10929587 (ORa=0.2; 95%CI=0.1-0.8; p = 0.021), or the CC genotype in SLCO1C1 rs3794271 (ORa=0.2; 95%CI=0.1-0.7; p = 0.008), according to multivariate logistic regression. In contrast, previous bowel resection increased the risk of IFX failure (ORa=2.8; 95%CI=1.1-7.3; p = 0.025). Cox regression analysis confirmed these findings and also identified IL23R rs10489629-TT (HRa 0.41; 95%CI=0.22-0.75; p = 0.004) and concomitant immunosuppressants (HRa 0.46; 95%CI=0.27-0.77; p = 0.003) as protection from IFX failure. However, no association between HLA-DQA1 * 05 allele and persistence of IFX therapy was found, with similar failure rates among carriers and non-carriers (52.8% vs. 47.4%, respectively; p = 0.544).

CONCLUSIONS

SNPs rs10929587-TT in ADAM17, rs10489629-TT in IL23R and rs3794271-CC in SLCO1C1, together with no previous bowel surgery and concomitant immunosuppression, were identified as protection from failure to IFX.

Decreased Infliximab Concentrations in Patients With Inflammatory Bowel Disease Who Carry a Variable Number Tandem Repeat Polymorphism in the Neonatal Fc Receptor or Variant HLADQA1*05G>A Genotype

BACKGROUND

Multiple variables contribute to variation in patient exposure and response to tumor necrosis factor alpha antagonist biologics such as infliximab. This study aimed to assess the association between maintenance-phase infliximab concentrations and genetic variation in HLADQA1*05G>A and fragment crystallisable (Fc) fragment of IgG receptor and transporter (FCGRT) among patients with inflammatory bowel disease.

METHODS

A cross-sectional study was carried out in participants with inflammatory bowel disease prescribed infliximab who were in the maintenance phase of treatment. Participants were genotyped for the presence of the FCGRT variable number tandem repeat (VNTR) and HLADQA1*05G>A (rs74291249). A point estimate of the infliximab trough concentration during the maintenance phase was determined using a standard enzyme-linked immunosorbent assay for each patient. Other variables associated with infliximab pharmacokinetics were collected.

RESULTS

A total of 156 participants with inflammatory bowel disease were included from 2 tertiary care centers affiliated with Western University, London, Canada. Median infliximab trough concentrations were lower in participants who carried the FCGRT VNTR 2/3 or 2/2 (4.14 µg/mL; interquartile range [IQR], 6.48 µg/mL) vs wild type individuals (7.00 µg/mL; IQR, 7.66; P = .0027). Median infliximab trough concentrations were significantly lower in participants who were HLADQA1*05G>A variant carriers (4.73µg/mL; IQR, 4.79) vs wild type individuals (7.85µg/mL; IQR, 7.44; P = .0006). A significant decrease in infliximab trough concentrations was seen in individuals who were dual carriers of variant polymorphisms in HLADQA1*05G>A and FCGRT VNTR (no variants, 8.96µg/mL; IQR, 6.84 vs one variant, 4.96 µg/mL; IQR, 4.95 vs dual variants, 0.86µg/mL; IQR, 5.82).

CONCLUSION

FCGRT VNTR and HLADQA1*05G>A are associated with lower maintenance-phase infliximab concentrations, particularly among patients who carry both variants.

HLA-DQ2 is associated with anti-drug antibody formation to infliximab in patients with immune-mediated inflammatory diseases

BACKGROUND

Immunogenicity to tumour necrosis factor inhibitors is a significant clinical problem leading to treatment failure and adverse events. The study aimed to assess human leukocyte antigen (HLA) associations with anti-drug antibody (ADAb) formation to infliximab.

METHODS

Immune-mediated inflammatory disease patients on infliximab therapy (n = 612) were included. Neutralising ADAb were assessed with a drug-sensitive assay. Next generation sequencing-based HLA typing was performed.

RESULTS

Overall, 147 (24%) patients developed ADAb. Conditional analyses indicated HLA-DQB1 (p = 1.4 × 10^-6 ) as a primary risk locus. Highest risk of ADAb was seen when carrying at least one of the HLA-DQ2 haplotypes; DQB1*02:01-DQA1*05:01 or DQB1*02:02-DQA1*02:01 (OR 3.18, 95% CI 2.15-4.69 and p = 5.9 × 10^-9 ). Results were consistent across diseases and when adjusting for concomitant immunomodulator. Computational predictions indicated that these HLA-DQ2 haplotypes bind to peptide motifs from infliximab light chain.

CONCLUSION

A genome-wide significant association between two HLA-DQ2 haplotypes and the risk of ADAb formation to infliximab was identified, suggesting that HLA-DQ2 testing may facilitate personalised treatment decisions.

Association between HLA DNA Variants and Long-Term Response to Anti-TNF Drugs in a Spanish Pediatric Inflammatory Bowel Disease Cohort

The genetic polymorphisms rs2395185 and rs2097432 in HLA genes have been associated with the response to anti-TNF treatment in inflammatory bowel disease (IBD). The aim was to analyze the association between these variants and the long-term response to anti-TNF drugs in pediatric IBD. We performed an observational, multicenter, ambispective study in which we selected 340 IBD patients under 18 years of age diagnosed with IBD and treated with anti-TNF drugs from a network of Spanish hospitals. Genotypes and failure of anti-TNF drugs were analyzed using Kaplan-Meier curves and Cox logistic regression. The homozygous G allele of rs2395185 and the C allele of rs2097432 were associated with impaired long-term response to anti-TNF drugs in children with IBD after 3 and 9 years of follow-up. Being a carrier of both polymorphisms increased the risk of anti-TNF failure. The SNP rs2395185 but not rs2097432 was associated with response to infliximab in adults with CD treated with infliximab but not in children after 3 or 9 years of follow-up. Conclusions: SNPs rs2395185 and rs2097432 were associated with a long-term response to anti-TNFs in IBD in Spanish children. Differences between adults and children were observed in patients diagnosed with CD and treated with infliximab.

Association between genetic variants and development of antibodies to infliximab: A cross-sectional study in Chinese patients with Crohn's disease

Aims: Genetic variants increase the susceptibility to anti-drug antibodies (ADA) in response to anti-TNF therapy in chronic inflammatory diseases. However, little is known about genetic variants in Chinese populations. This study aimed to identify genetic variants contributing to the risk of the development of antibodies to infliximab (ATI) in Chinese patients with Crohn's disease (CD). Methods: CD patients (n = 104) treated with infliximab (IFX) during the maintenance therapy were enrolled in this cross-sectional study. ATI was assessed by an in-house developed drug-tolerant ELISA method. ATI titers of 1:20 and ≥1:60 were considered a low titer and a high titer, respectively. Thirteen types of single nucleotide polymorphisms (SNPs) within 13 genes involved in the immune process, the susceptibility to chronic inflammatory diseases, cytokines and apoptosis pathways were investigated. Results: The median trough levels of infliximab (TLI) in patients with clinical remission (CR) were higher than those in patients without CR (3.80 vs. 1.50 μg/mL, p < .001). The median TLI in patients with high-titer ATI was significantly lower than that in ATI-negative patients (1.15 vs. 4.48 μg/mL, p < .001) or those with low-titer ATI (1.15 vs. 2.95 μg/mL, p = .03). The HLA-DQA1*05 rs2097432 GG and GA genotypes were more frequent in patients with ATI (GG and AG vs. AA, 27/38 = 71.05% vs. 29/66 = 43.94%, OR 2.94, 95% CI 1.19-7.30, p = .02). Patients carrying the CC and AC genotypes of rs396991 in FCGR3A were associated with a higher frequency of ATI formation (CC and AC vs. AA, 37/57 = 64.91% vs. 19/47 = 40.43%, OR 2.94, 95% CI 1.24-6.96, p = .01). According to the number of variants in rs2097432 and rs393991, patients with two variants had a higher proportion of producing ATI (two variants vs. no variant, 17/21 = 80.95% vs. 9/30 = 30.00%, OR 9.92, 95% CI 2.59-37.87, p = .001; single variant vs. no variant, 30/53 = 56.60% vs. 9/30 = 30.00%, OR 3.04, 95% CI 1.18-7.88, p = .02). No association was found between other SNPs and ATI production. Conclusion: Rs2097432 in HLA-DQA1*05 and rs396991 in FCGR3A are associated with ATI production in Chinese patients with CD. A pharmacogenomic strategy could help with the clinical management of CD.

Therapeutic Drug Monitoring in Practice for Inflammatory Bowel Disease

PURPOSE OF REVIEW

To outline the development, rationale, and practical use of therapeutic drug monitoring in patients with inflammatory bowel disease.

RECENT FINDINGS

Therapeutic drug monitoring is traditionally discussed in terms of a proactive or reactive approach. However, these terms are not always consistently defined and can be confusing when translating research to clinical practice. Personalized approaches incorporating clinical context and precision medicine are emerging. Personalized therapeutic drug monitoring combines a structured and proactive strategy for monitoring biologic concentrations as well as identification of antidrug antibody development or subtherapeutic dosing in the setting of loss of response. Optimizing biologic therapy can improve outcomes and avoid loss of response. Why, when, and how we measure drug troughs and anti-drug antibodies is a moving target, though what is known is that the appropriate and evidence-based use of this practice prevents adverse events and improves outcomes in patients with inflammatory bowel disease.

Implications for sequencing of biologic therapy and choice of second anti-TNF in patients with inflammatory bowel disease: results from the IMmunogenicity to Second Anti-TNF therapy (IMSAT) therapeutic drug monitoring study

BACKGROUND

Anti-drug antibodies are associated with treatment failure to anti-TNF agents in patients with inflammatory bowel disease (IBD).

AIM

To assess whether immunogenicity to a patient's first anti-TNF agent would be associated with immunogenicity to the second, irrespective of drug sequence METHODS: We conducted a UK-wide, multicentre, retrospective cohort study to report rates of immunogenicity and treatment failure of second anti-TNF therapies in 1058 patients with IBD who underwent therapeutic drug monitoring for both infliximab and adalimumab. The primary outcome was immunogenicity to the second anti-TNF agent, defined at any timepoint as an anti-TNF antibody concentration ≥9 AU/ml for infliximab and ≥6 AU/ml for adalimumab.

RESULTS

In patients treated with infliximab and then adalimumab, those who developed antibodies to infliximab were more likely to develop antibodies to adalimumab, than patients who did not develop antibodies to infliximab (OR 1.99, 95%CI 1.27-3.20, p = 0.002). Similarly, in patients treated with adalimumab and then infliximab, immunogenicity to adalimumab was associated with subsequent immunogenicity to infliximab (OR 2.63, 95%CI 1.46-4.80, p < 0.001). For each 10-fold increase in anti-infliximab and anti-adalimumab antibody concentration, the odds of subsequently developing antibodies to adalimumab and infliximab increased by 1.73 (95% CI 1.38-2.17, p < 0.001) and 1.99 (95%CI 1.34-2.99, p < 0.001), respectively. Patients who developed immunogenicity with undetectable drug levels to infliximab were more likely to develop immunogenicity with undetectable drug levels to adalimumab (OR 2.37, 95% CI 1.39-4.19, p < 0.001). Commencing an immunomodulator at the time of switching to the second anti-TNF was associated with improved drug persistence in patients with immunogenic, but not pharmacodynamic failure.

CONCLUSION

Irrespective of drug sequence, immunogenicity to the first anti-TNF agent was associated with immunogenicity to the second, which was mitigated by the introduction of an immunomodulator in patients with immunogenic, but not pharmacodynamic treatment failure.

Immunogenicity of Monoclonal Antibodies and the Potential Use of HLA Haplotypes to Predict Vulnerable Patients

The use of monoclonal antibodies (mAbs) in the clinic has successfully expanded to treatment of cancer, viral infections, inflammations, and other indications. However, some of the classes of mAbs that are used in the clinic show the formation of anti-drug antibodies (ADAs) leading to loss of efficacy. This review describes ADA formation for the various mAbs, and its clinical effect. Lastly, this review considers the use of HLA-haplotypes as biomarkers to predict vulnerability of patients sensitive to formation of ADAs.

Alterations and Potential Applications of Gut Microbiota in Biological Therapy for Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, is a chronic immune-mediated inflammatory disorder of the gastrointestinal tract that is closely associated with dysbiosis of the intestinal microbiota. Currently, biologic agents are the mainstream therapies for IBD. With the increasing incidence of IBD, limitations of biologic agents have gradually emerged during treatment. Recent studies have indicated that gut microbiota is highly correlated with the efficacy of biologic agents. This review focuses on alterations in both the components and metabolites of gut microbiota during biological therapy for IBD, systematically summarises the specific gut microbiota closely related to the clinical efficacy, and compares current predictive models for the efficacy of biologics, further highlighting the predictive value of intestinal microbiota. Based on the mechanistic analysis of faecal microbiota transplantation (FMT) and biologic agents, a new therapeutic strategy, comprising a combination of FMT and biologics, has been proposed as a promising treatment for IBD with improved efficacy.

Therapeutic Drug Monitoring of Biologics in Crohn's Disease

Reactive therapeutic drug monitoring (TDM) is considered the standard of care for optimizing biologics in inflammatory bowel disease (IBD) including Crohn's disease (CD). Preliminary data show that proactive TDM is associated with positive outcomes in IBD and can be also used to efficiently guide therapeutic decisions in specific clinical scenarios. Higher biological drug concentrations are associated with favorable therapeutic outcomes in specific IBD populations or phenotypes including pediatric CD, perianal fistulizing CD, small bowel CD, and following an ileocolonic resection for CD. Future perspectives of TDM include the use of rapid testing, pharmacogenomics, and pharmacokinetic dashboards toward individualized therapy.

Anti-drug antibodies in the current management of cancer

Monoclonal antibodies (mAbs) have become one of the main therapeutic weapons in modern oncology, mainly as targeted therapies, and immune checkpoint inhibitors. The generation of anti-drug antibodies (ADAs) after their administration can alter their pharmacokinetic, pharmacodynamic, efficacy and safety profile causing infusion-related reactions. Several risk factors have been associated with ADAs development, notably host genetics and immune status, comorbidity, concomitant medications, mAbs molecular structure, dose and route of administration. ADAs are not usually tested on daily clinical practice, being their analysis generally placed in early stages of drug development. ELISA-type assay the most common method. ADAs detection can involve important implications for treatment strategies of cancer patients, guiding therapeutic adjustment. In oncology, some studies about ADAs synthesis related to targeted therapies and immune checkpoint inhibitors have been recently published. Several strategies are proposed to reduce mAbs immunogenicity, such as different schedules, routes of administration or even the use of immunosuppressants. Another question that arises in relation to ADAs generation is the need to measure the concentration levels of active drug to guide the administration schedule. In this review, we will discuss all the aspects that are currently under discussion in relation with ADAs in oncology.

Antibodies-to-infliximab accelerate clearance while dose intensification reverses immunogenicity and recaptures clinical response in paediatric Crohn's disease

BACKGROUND

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.

AIMS

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.

METHODS

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.

RESULTS

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]).

CONCLUSIONS

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.

Patients With Low Drug Levels or Antibodies to a Prior Anti-Tumor Necrosis Factor Are More Likely to Develop Antibodies to a Subsequent Anti-Tumor Necrosis Factor

Therapeutic drug monitoring (TDM) with measurement of serum drug and antidrug antibodies (ADAb) is used widely to confirm therapeutic exposure, rule out immunogenicity, and optimize treatment of biologics in patients with inflammatory bowel diseases.1 A recent genome-wide association study found the variant HLA-DQA1∗05 to increase the risk of development of antibodies against infliximab (IFX) and adalimumab (ADM) 2-fold, regardless of concomitant immunomodulator use.2,3 However, there is currently limited evidence showing whether patients who develop antibodies to 1 anti-tumor necrosis factor (TNF) are prone to develop antibodies to the subsequent anti-TNF. Our aim was to investigate the risk of subsequent antibody development in cases (with ADAb to prior anti-TNF) versus control subjects (without ADAb to prior anti-TNF) using a large cohort of patients with inflammatory bowel diseases who underwent TDM with a drug-tolerant assay.