What is the background to this research?
Axial spondyloarthritis (axSpA) is a long-term inflammatory condition mainly affecting the spine and joints, but it can also cause inflammation elsewhere in the body — including the bowel, where it may lead to inflammatory bowel disease (IBD) such as Crohn’s disease or ulcerative colitis. Treatments known as biologic therapies, particularly anti-TNF drugs, are widely used for axSpA. Some reports have suggested that one such drug, etanercept, might be linked to an increased risk of developing IBD, but the evidence has been inconsistent.
What did we seek to find out?
We wanted to determine whether people with axSpA treated with biologic drugs have a higher risk of developing IBD compared with those receiving other treatments. We also wanted to know whether the risk differs between specific biologic drugs, especially etanercept compared with other anti-TNF agents.
What did we do?
We used data from the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS), which follows people with axSpA, across the UK. We compared the number of new cases of IBD among those taking biologic drugs with those who were not. We also carried out a systematic review and meta-analysis, a method that combines results from many previous studies, to assess whether similar findings were reported by other studies including those conducted in other countries, including both clinical trials and observational studies.
What did we find?
In the BSRBR-AS, people treated with biologic drugs were more likely to develop IBD than those not receiving these treatments. However, etanercept was not linked to a higher risk than other anti-TNF drugs. When all studies were combined, observational research showed a clear excess risk of IBD in people treated with biologics, but randomised controlled trials (which have shorter follow-up and stricter inclusion criteria) showed little or no difference.
Why does this research matter?
This study provides the most comprehensive evidence to date on IBD risk in people with axSpA treated with biologic therapies. The overall risk was small, but it helps clinicians and patients make more informed treatment decisions, particularly when choosing between different biologic drug options. The findings also highlight that long-term, real-world data can reveal effects that may not appear in short clinical trials.
Who funded this study?
The BSRBR-AS study is funded by the British Society for Rheumatology, which received funding from Pfizer, AbbVie, and UCB (pharmaceutical companies that make biologic therapies). These companies have no role in deciding what topics to study or how to analyse the data.
Where can I read more?
You can read the full research paper here.