Rituximab Associated with Elevated Risk of Inflammatory Bowel Disease in Individuals with Multiple Sclerosis: JAMA
Sweden: A cohort study has revealed that rituximab treatment in patients with multiple sclerosis (MS) is associated with an elevated risk of developing inflammatory bowel disease (IBD) compared to other modern MS therapies, even after adjusting for baseline patient characteristics. Consequently, healthcare providers and individuals with MS should account for potential IBD risks when selecting treatments and maintain heightened monitoring for gastrointestinal symptoms during anti-CD20 therapy.
Rituximab is an anti-CD20 biologic used as a disease-modifying treatment for MS. Although these therapies help control disease activity, concerns have emerged about a possible association between anti-CD20 treatment and new-onset IBD, which includes Crohn’s disease and ulcerative colitis.
To investigate this association, Sandra Kallin from the Department of Clinical Sciences, Karolinska Institutet Danderyd Hospital, Stockholm, Sweden, and colleagues conducted a population-based cohort study using Swedish MS registry data. The researchers examined treatment initiations between January 2011 and December 2023 among adults aged 18 to 55 years with relapsing-remitting multiple sclerosis (RRMS) and no previous evidence of IBD.
The analysis covered 13,748 treatment episodes involving 9,251 individuals. These included 6,481 rituximab episodes, 2,976 involving natalizumab, 2,767 involving dimethyl fumarate, and 1,524 involving fingolimod. Outcomes were also compared with 61,065 matched episodes from the general population. New-onset IBD was identified through repeated diagnostic records for Crohn’s disease, ulcerative colitis, or indeterminate colitis.
The findings, published in JAMA Neurology, revealed the following:
- Higher IBD incidence with rituximab: The incidence rate was 110 cases per 100,000 person-years among rituximab recipients, compared with 13 per 100,000 person-years among patients receiving the other three MS therapies and 41 per 100,000 person-years in the general population.
- Increased risk compared with other MS treatments: After adjustment for demographic and MS-related characteristics, the combined comparator therapies were associated with a 90% lower hazard of IBD than rituximab (hazard ratio, 0.10; 95% confidence interval, 0.04–0.22).
- Crohn’s disease predominated: Crohn’s disease accounted for 62% of IBD cases in the rituximab group, compared with 29% among the general population.
- Estimated number needed to harm: The researchers calculated that treating 131 patients with rituximab instead of the comparator therapies for five years would result in one additional IBD case, based on the adjusted estimate.
The researchers concluded that rituximab was associated with a higher risk of new-onset IBD than the other evaluated MS therapies. They recommended considering this potential risk during treatment selection, particularly for patients with a history of IBD, and remaining alert to gastrointestinal symptoms during anti-CD20 therapy.
However, the observational design cannot establish that rituximab directly causes IBD. Further research is needed to identify patients at greatest risk and determine whether targeted monitoring or treatment modifications could reduce this risk.
Reference:
Kallin S, Svenningsson A, Olén O, Hedin C, Lycke J, Alping P. Risk of Inflammatory Bowel Disease After Anti-CD20 Treatment in Multiple Sclerosis. JAMA Neurol. Published online October 22, 2026. doi:10.1001/jamaneurol.2026.3439
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