To examine the effects of ocrelizumab on serum lymphocyte subsets and immunoglobulins in a real-world setting

Ocrelizumab is a recently approved monoclonal antibody targeting B-lymphocytes for treatment of relapsing and primary progressive multiple sclerosis (MS). 

Retrospective chart review and longitudinal analysis of laboratory and clinical data including serum lymphocyte subsets and immunoglobulins in MS patients treated with ocrelizumab at our center.

In this analysis 113 patients were included:  55 males, 58 females, mean age 45.1 years; 73.4% with relapsing remitting and 26.6% with progressive MS. Most patients were on prior disease modifying therapy (85.8%) whereas 14.2% were treatment-naïve. 

After the first dose of ocrelizumab, all patients had a significant reduction of mean ALC and CD3 (24.4% and 11.8% respectively, p < 0.0001) and increase in mean CD4/CD8 ratio by 13.5% (p<0.0001). Treatment-naïve patients demonstrated a notable reduction in mean ALC, CD3, CD4, and CD8 counts (40.1% p=0.02, 26.4% p=0.03, 15.8% p= 0.02, 51.8% p=0.03 respectively).  Patients switching from natalizumab demonstrated a significant reduction in mean ALC and CD4 (48.6%, p<0.0001, 25.2% p = 0.006 respectively). Those switching from fingolimod showed a significant increase in mean CD3, CD4, CD8, and CD4/8 ratio (51.1% p = 0.002, 48.9% p=0.001, 25.6% p=0.012, 45.5% p=0.0001 respectively). 

Baseline IgG and IgM levels were abnormally low in 8.1% and 15.6% of cohort. Followed for up to 12 months, low IgG levels were found in 19.8% and low IgM in 28.9% of patients. A total of 38 infections but no opportunistic infections were reported. No relationship between infection and Ig status was observed.

Beyond the expected B-cell depletion, effects on both T-lymphocytes subset and immunoglobulins levels were observed in MS patients treated with ocrelizumab. While the clinical significance is undetermined, data may suggest the importance of clinical vigilance in those treated with ocrelizumab.