ABSTRACT
Introduction Disruption to clinical services, triggered by the COVID-19 pandemic, led to extended intervals between ocrelizumab treatments for some patients. Objectives To assess the rates of developing low immunoglobulin levels and timing of CD19+ B-cell count repopulation in a real-world clinical population. To assess for evidence of clinical or radiological MS disease activity with extended interval dosing of ocrelizumab. Methods We audited 712 patients given ocrelizumab by our seven clinical services. All monitoring of immunoglobulin levels and CD19+ cell counts were recorded. Disease activity was defined as on treatment clinical relapse, radiological activity, and EDSS progression. Results Low immunoglobulin levels developed in 102 patients, the odds ratio for developing hypogam- maglobulinaemia comparing extended to standard interval dosing was 0.42 (CI 0.22-0.81). Disease activity included 20 participants with clinical relapses and 72 with new MRI lesions. There was no evidence of excess clinical or radiological disease activity on switching to extended interval dosing. 38 had EDSS progression, giving an odds ratio comparing extended to standard interval dosing of 0.77 (CI 0.38-1.56). Conclusions This real-world data of extended interval dosing of ocrelizumab indicates lower rates of hypogammaglobulinaemia and no detrimental effect on short-term treatment efficacy.