Disease-modifying drugs for multiple sclerosis and infection risk: a cohort study

Abstract

Objective: Little is known about disease-modifying treatments (DMTs) for multiple sclerosis (MS) and infection risk in clinical practice. We examined the association between DMTs and infection-related medical encounters.

Methods: Using population-based administrative data from British Columbia, Canada, we identified MS cases and followed them from their first demyelinating event (1996-2013) until emigration, death or study end (December 2013). Associations between DMT exposure (by DMT generation or class) and infection-related physician or hospital claims were assessed using recurrent time-to-events models, adjusted for age, sex, socioeconomic status, index year and comorbidity count. Results were reported as adjusted HRs (aHRs).

Results: Of 6793 MS cases, followed for 8.5 years (mean), 1716 (25.3%) were DMT exposed. Relative to no DMT, exposure to any first-generation DMT (beta-interferon or glatiramer acetate) was not associated with infection-related physician claims (aHR: 0.96; 95% CI 0.89 to 1.02), nor was exposure to these drug classes when assessed separately. Exposure to any second-generation DMT (oral DMT or natalizumab) was associated with an increased hazard of an infection-related physician claim (aHR: 1.47; 95% CI 1.16 to 1.85); when assessed individually, the association was significant for natalizumab (aHR: 1.59; 95% CI 1.19 to 2.11) but not the oral DMTs (aHR: 1.17; 95% CI 0.88 to 1.56). While no DMTs were associated with infection-related hospital claims, these hospitalisations were also uncommon.

Conclusion: Exposure to first-generation DMTs was not associated with an altered infection risk. However, exposure to the second-generation DMTs was, with natalizumab associated with a 59% increased risk of an infection-related physician claim. Continued pharmacovigilance is warranted, including an investigation of the DMT-associated infection burden on patient outcomes.