Reinitiating ocrelizumab with a full 600 mg dose after extended treatment interruption: No increased risk of infusion-related reactions

Background Infusion-related reactions (IRRs) are a common side-effect of ocrelizumab (OCR), with the highest risk occurring during treatment initiation. To minimize IRR risk, the first dose is split into two 300 mg infusions over two weeks. Subsequent doses are administered every six months as a 600 mg infusion. After treatment interruptions, some physicians restart with two separate 300 mg infusions due to concern about IRRs. This study evaluates IRR occurrence following a 600 mg infusion after extended treatment interruption. Methods This retrospective cohort study included all multiple sclerosis (MS) patients who received at least one 600 mg OCR infusion between June 2018 and January 2024 at Amsterdam UMC. Infusions were categorized by interval duration: normal (6 months), moderate (7–9 months) and long (>9 months). Logistic regression analyzed the IRR occurrence. Results 1438 infusions, in 275 patients, were analyzed. Neither the moderate interval group (306 infusions, OR = 0.914, p = 0.77) nor the long interval group (56 infusions, OR = 0.928, p = 0.575) had significantly higher odds of developing IRRs compared to the normal interval group. Conclusion Despite the retrospective design and smaller sample sizes in the moderate and long interval groups, our findings indicate that administering OCR as a single 600 mg infusion after a prolonged interval is safe regarding IRR occurrence.