Utilisation of anti-TNF levels in a UK tertiary IBD centre

Prevalence and clinical implications of anti-drug antibody formation and serum drug levels among patients with IBD receiving anti-TNF therapy: A cross-sectional study

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Increased Induction Infliximab Clearance Predicts Early Antidrug Antibody Detection

Treatment of patients with biologics such as infliximab may trigger development of antidrug antibodies, which are associated with faster drug clearance, reduced treatment efficacy, and increased risk of infusion‐related reactions. The aim of this study was to identify predictors of baseline infliximab clearance and early antidrug antibody formation. Pharmacokinetic and pharmacokinetic/pharmacodynamic models for infliximab were developed using 21 178 observations from 859 patients from the PLANETRA (ClinicalTrials.gov identifier: NCT01217086) and PLANETAS (NCT01220518) studies in rheumatoid arthritis and ankylosing spondylitis, respectively, to address the specified aims. Infliximab pharmacokinetics were well described by a 2‐compartment model with linear mean estimated baseline clearance of 0.26 L/day. Alongside increased body weight, serum C‐reactive protein, and antidrug antibody concentrations and decreased serum albumin, elevated serum glucose levels predicted higher clearance. In patients with rheumatoid arthritis, baseline infliximab clearance and body weight were the only identified predictors of early antidrug antibody detection. The odds ratio for antidrug antibody detection for each 0.1 L/day increase in baseline infliximab clearance was 1.78 (95% confidence interval, 1.50–2.12); for each 10‐kg increase in body weight, this was 1.19 (1.06–1.33). Here we describe increased serum glucose levels as a novel independent predictor of baseline infliximab clearance. Estimates of baseline infliximab clearance should be incorporated to guide dosing modifications and/or antidrug antibody prophylaxis in clinical practice.

Wide variation in the use and understanding of therapeutic drug monitoring for anti-TNF agents in inflammatory bowel disease: an inexact science?

BACKGROUND

We aimed to understand the way in which therapeutic drug monitoring (TDM) is used, understood and interpreted for anti-TNF agents in IBD.

RESEARCH DESIGN AND METHODS

We designed an 18-question survey that included 5 TDM-based clinical scenarios, for which the 'most appropriate' responses were based on the BRIDGe groups 'Anti-TNF Optimizer'. This resource combines TDM evidence with expert consensus.

RESULTS

We received 110 complete responses: 50 (45%) consultants, 30 (27%) trainees, 25 (23%) IBD nurse specialists and 5 (5%) gastroenterology pharmacists. Over half (61, 55%) only carry out TDM in non-response. The remainder use TDM routinely, including during stable maintenance therapy for patients in remission. Lower therapeutic thresholds used were variable. Most (82, 75%) were unsure whether their laboratory uses a drug-tolerant or drug-sensitive antidrug antibody assay and few (15, 14%) understand the difference. Consultants, high-frequency users (> 3requests/month) and clinicians with larger anti-TNF cohorts (> 100) were significantly more likely to select the 'most appropriate' answer to at least 1 of the 5 TDM-based clinical scenarios.

CONCLUSIONS

There exists marked heterogeneity in the practical use, understanding and interpretation of biologic TDM. Biologic decision-making, informed by TDM, should involve consultation with experienced clinicians who are frequent TDM users, ideally, as part of a multidisciplinary, biologics-focused IBD meeting.

ABBREVIATIONS

TDM: therapeutic drug monitoring; CNS: clinical nurse specialist; ELISA: enzyme-linked immunosorbent assay; RIA: radioimmunoassays; HMSA: homogenous mobility shift assays; BSG: British Society of Gastroenterology.