# A large-scale comparison of clinical outcomes to IBD therapies in White and South Asian ethnicities

## TL;DR

This study compares how well IBD treatments work in White and South Asian patients, finding similar treatment responses but higher risks of certain side effects in South Asians.

## Contribution

The study provides new evidence on ethnic differences in IBD treatment safety but not efficacy, using a large UK cohort.

## Key findings

- No significant ethnic differences in treatment response to 5-ASAs, thiopurines, or anti-TNFs in IBD patients.
- South Asian patients had higher risks of pancreatitis, leucopenia with thiopurines, and renal dysfunction with anti-TNFs.
- Baseline phenotypic differences were observed, including more perianal disease in South Asian Crohn's patients.

## Abstract

While ethnic differences in IBD phenotype are recognised, the comparative efficacy and safety of common IBD therapies across ethnically diverse populations remain uncertain. This multicentre cohort study aimed to compare the efficacy and safety of these therapies between White (WH) and South Asian (SA) IBD cohorts.

Demographic, phenotypic and outcome data from the UK IBD BioResource were utilised (BioResource inception date: 1st January 2016; data lock for analysis: 12th May 2023). The primary outcome was treatment response (defined as treatment persistence free of discontinuation or failure) to 5-aminosalicylates (5-ASAs), thiopurines and anti-TNFs. The secondary outcome was the occurrence of treatment-related adverse events (AEs). Ethnic differences in treatment response were evaluated using propensity score weighting and Cox proportional hazards regression. AE occurrence was assessed through logistic regression analysis.

In total, 26,530 patients were included [51.2% females; median age at diagnosis 30 years (IQR 21–43); 96.1% WH, 3.9% SA]. SA were diagnosed at a younger age, began treatment younger than WH, and demonstrated baseline phenotypic differences including more perianal disease in CD. However, no significant differences in treatment response between WH and SA were identified in either CD (reference group WH; thiopurines, HR 0.82 (95% CI 0.53–1.27), p = 0.37; anti-TNFs, HR 1.07 (95% CI 0.34–3.37), p = 0.91] or UC [thiopurines, HR 0.98 (95% CI 0.95–1.02), p = 0.36; anti-TNFs, HR 0.98 (95% CI 0.92–1.04), p = 0.54]. SA were at significantly increased risk of pancreatitis [HR 2.34 (95% CI 1.37–3.75), p = 0.001] and leucopenia [HR 1.76 (95% CI 1.02–2.84), p = 0.03] with thiopurines, and renal dysfunction with anti-TNFs [HR 4.75 (95% CI 1.55–12.07), p = 0.002].

Treatment efficacy in similar WH and SA IBD patients recruited to the UK IBD BioResource is unaffected by ethnicity but patients from SA ethnic backgrounds are at increased risk of developing pancreatitis and leucopenia with thiopurines, and renal dysfunction with anti-TNFs. These findings highlight the importance of comprehensive risk assessment and counselling by clinicians, and emphasise the importance of improving ethnic representation in IBD research.

Bowel Research UK; 10.13039/501100013342NIHR Imperial Biomedical Research Centre (BRC); 10.13039/501100018956NIHR Cambridge BRC.