Risk of Inflammatory Bowel Disease After Anti-CD20 Treatment in Multiple Sclerosis

Importance: Anti-CD20 biologics are widely used as disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS), but recent reports have raised concerns about an increased risk of inflammatory bowel disease (IBD) during treatment. This study aimed to assess treatment-associated IBD risk in individuals with RRMS.

Objective

To compare the risk of new-onset IBD across different therapies for RRMS and relative to the general population. Design, setting, and participants: This was a population-based cohort study conducted in Sweden. Through the Swedish MS register, initiations of rituximab, natalizumab, dimethyl fumarate, and fingolimod were identified between January 1, 2011, and December 31, 2023, in individuals with RRMS aged 18 to 55 years with at least 10 years of lookback time (5 years for dispensed drugs) and no evidence of previous IBD. These initiations were matched with general population comparator episodes selected from the Swedish population. Exposures: Rituximab, comparator DMTs (natalizumab, dimethyl fumarate, fingolimod), or general population comparator. Main outcomes and measures: New-onset IBD, defined as 2 or more records on separate dates with the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, codes K50 (Crohn disease), K51 (ulcerative colitis), and/or K52.3 (indeterminate colitis).