Study Flags Inflammatory Bowel Disease Signal for Rituximab in MS
A Swedish population-based cohort study found that rituximab was associated with a higher risk of inflammatory bowel disease in people with relapsing-remitting multiple sclerosis than comparator disease-modifying treatments. The crude IBD incidence was 110 per 100,000 person-years with rituximab, compared with 13 for comparator treatments and 41 in the general population. Even in the rituximab group, the cumulative incidence of IBD remained below 2% at 10 years.
The Swedish cohort tracked 9,251 adults with relapsing-remitting MS who began rituximab or one of three comparator drugs between 2011 and 2023, matching them to general-population episodes. New IBD required two separate records with relevant diagnostic codes; prior IBD was excluded.
Among 164 IBD cases, 40 occurred with rituximab, four with comparator treatments, and 120 in the general population. Crohn’s disease accounted for 62% of rituximab-associated cases versus 29% in the general population, and the adjusted hazard ratio for comparator drugs versus rituximab was 0.10.
The findings could influence how clinicians and patients with MS weigh rituximab against other disease-modifying therapies, especially where off-label use is common. Because absolute IBD risk remained low, the signal may prompt closer attention to gastrointestinal symptoms rather than broad avoidance. People with MS who rely on anti-CD20 treatment, and those with existing bowel concerns, may face more nuanced discussions about benefits, monitoring, and alternatives.