Serious safety events in rituximab-treated multiple sclerosis and related disorders.

INTRODUCTION: Studies investigating rates and risk factors for serious safety events (SSEs) during rituximab treatment of multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD), and related disorders are limited.

METHODS: Rituximab-treated patients with MS, NMOSD, or related disorders at the Rocky Mountain and New York University MS Care Centers were included. The follow-up period was defined as the time from the initial dose of rituximab up to 12 months of last dose of rituximab or ocrelizumab (in patients who switched). Clinician-reported and laboratory data were retrospectively collected from electronic medical records.

RESULTS: One-thousand patients were included comprising 907 MS, 77 NMOSD, and 16 related disorders. Patients had a mean follow-up of 31.1 months and a mean cumulative rituximab dose of 4012 mg. Of the 169 patients who switched to ocrelizumab, the mean ocrelizumab dose was 1141 mg. Crude incidence rate per 1000 person-years (PY) for lymphopenia was 19.2, neutropenia 5.6, and hypogammaglobulinemia 17.8. Infections resulting in either hospitalization, IV antibiotics, or using antibiotics ≥14 days occurred at a rate of 38.6/1000 PY. Risk factors for infection were duration of therapy, male gender, increased disability, prior exposure to immunosuppression/chemotherapy, lymphopenia, and hypogammaglobulinemia. Particularly, wheelchair-bound patients had 8.56-fold increased odds of infections. Crude incidence rates of malignant cancer were 3.5, new autoimmune disease 2.3, thromboembolic event 3.1, and mortality of 5.4 per 1000 PY.

INTERPRETATION: Rates of SSEs in patients with MS, NMOSD, and related disorders were low. Through properly assessing risk:benefit of B-cell depleting therapy in neuroinflammatory disorders and continual monitoring, clinicians may decrease the risk of serious infections.