Tolerability and Safety of Switching from Rituximab to Ocrelizumab: Evaluating Factors Associated with Infusion Related Reactions

BACKGROUND: Ocrelizumab and rituximab are frequently used treatments for multiple sclerosis (MS). Data on switching from rituximab to ocrelizumab is limited. OBJECTIVES: To assess the frequency, severity, and factors of infusion related reactions (IRRs) in patients with MS who switch from rituximab to ocrelizumab, compared to those who stay on rituximab. METHODS: Prospective study on MS patients aged 18–65, on rituximab for at least 2 cycles, who either switched to ocrelizumab (switch group) or stayed on rituximab (comparator group) (n = 100 each). Participants were followed for IRRs, safety, and tolerability over 12 months. RESULTS: The proportion of IRRs in patients who continue on rituximab (14%) were similar to those who switched to ocrelizumab on Day 1 (14%; p = 1.000) and Week 24 (12%; p = 0.647) but higher than at Day 15 (4%; 0.005). The risk of IRRs for the switch group was associated with the presence of B cells (CD19 and/or CD20 counts ≥1%) increasing by 5.01 (1.49, 16.82) times on Day 1 (p = 0.007). Antidrug antibodies to ocrelizumab were not associated with IRRs. No other safety concerns were identified in switching to ocrelizumab. CONCLUSION: IRRs are similar between both groups, which suggests that it is safe to switch from rituximab to ocrelizumab.