Some patients with multiple sclerosis (MS) receiving ocrelizumab (OCR) report worsening symptoms toward the end of the 6-month infusion cycle ('wearing off'). The objective of our study was to comprehensively assess changes in symptom burden across 2 consecutive OCR infusion cycles.

SYMptom Burden on Ocrelizumab, a Longitudinal Study (SymBOLS; NCT04855617) was an investigator-initiated, 2-center study of patients with MS starting or receiving OCR. Patients' symptoms were assessed with NeuroQoL short forms, SymptoMScreen, and Work Productivity and Activity Impairment Questionnaire at the start-cycle, mid-cycle, and end-cycle time points in each of the 2 infusion cycles. Symptom scores at the 3 time points within each cycle were compared with repeated-measures ANOVA or the Friedman rank-sum test for non-normal variables. The proportions of patients with a meaningful symptomatic change from the start to the end of each infusion cycle were calculated, and patients whose symptoms improved, worsened, and stayed the same from the start to the end of the cycle were compared with respect to demographic and clinical characteristics.

One hundred three patients with MS provided longitudinal data for analyses (mean age [SD]: 46.7 [12.2] years, 68% female, 33% non-White, disease duration: 15.5 [5] years, 41% with the Extended Disability Status Scale score >3). On a group level, NeuroQoL and SymptoMScreen scores mostly remained stable or even improved slightly toward the end of each cycle. On an individual level, symptoms remained unchanged across either cycle for most patients, and meaningful symptom worsening from the start to the end of the cycle was no more common than improvement. Meaningful change in symptoms in both cycles was very rare and generally in the direction of improvement toward the end cycle. Despite the lack of evidence for symptom worsening with a longer time from infusion, 54% of patients endorsed feeling of "wearing off" at least sometimes, most commonly as an increase in fatigue.

Our prospective study failed to uncover evidence for the worsening of symptoms with a longer time from OCR infusion. These findings cast doubt on the existence of wearing off as a physiologic phenomenon in OCR-treated patients with MS. The perception of wearing off is likely the result of natural fluctuations in MS symptoms and attribution bias.