Ocrelizumab is a B cell depleting anti-CD20 humanized monoclonal antibody approved for the treatment of MS patients. CD20 is not expressed on mature plasma cells and accordingly ocrelizumab does not have immediate effects on immunoglobulin levels. However, after Ocrelizumab some patients develop hypogammaglobinemia.

We performed a single center retrospective review of 168 patients with MS receiving Ocrelizumab between 03/2017 and 10/2018. Baseline characteristics of patients included in this study are available (Table 1). The incidence, severity and complications of hypogammaglobulinemia were investigated.

Median Ocrelizumab dose was 600 mg and total follow-up was 1731 patient-months. Baseline immunoglobulin levels were available in 21 patients. Of those, the proportion of patients with baseline IgG <6 g/L was 9%. At the time of this abstract, a total of 128 patients had follow up immunoglobulin levels. Following Ocrelizumab therapy, 11/128 patients (8.5%) developed IgG <6 g/L, of whom 0/128 (0%) had IgG <3 g/L. A total of 29 patients (17%) had any infections during the treatment period with ocrelizumab therapy. Of those, 19/117 (16%) with IgG ≥6 g/L versus 0/11 (0%) with IgG <6 g/L experienced a single infection (p=0.14), and 9/117 (7.6%) with IgG ≥6 g/L versus 1/11 (9%) with IgG <6 g/L experienced recurrent infections (p=0.88). There were no severe infections in our patient group. One patient received intravenous immunoglobulin replacement therapy.

A small proportion of patients receiving Ocrelizumab therapy developed hypogammaglobulinemia. Infections were common but were not associated with immunoglobulin levels.