Sergio Saldivar1, Mark Freedman1, Carolina Rush1, John Brooks1
1The Ottawa Hospital Research Institute
Objective:
To look for the incidence and clinical characteristics of patients receiving ocrelizumab who fail to lower their CD19 cell counts.
Background:
Ocrelizumab is a humanized anti-CD20 monoclonal antibody used in the treatment of multiple sclerosis (MS). Due to its mostly human origin, ocrelizumab is expected to induce few neutralizing antibodies (NAbs), but there is a small risk of this happening.
Ocrelizumab administration leads to a rapid and complete depletion of CD19 peripheral cells by 2 weeks and begins recovering after six months. Normal CD19 values despite infusions can indirectly correlate with the development of NAbs. High titers of NAbs can hinder the efficacy of MS treatments.
Design/Methods:
We conducted a retrospective study in which we searched our MS clinic database for all our patients who received at least one dose of ocrelizumab and had their CD19 population analyzed. Patients who were missing laboratory data or were receiving ocrelizumab infusions outside our clinic were excluded from the study.
After selecting the patients with normal CD19 counts, we obtained their demographic, clinical, laboratory and radiological data.
Results:
We found 305 patients who at one point received ocrelizumab in our database. After eliminating those who did not meet the inclusion criteria, 224 patients were left. Of those 224 patients only 4 patients had consistently normal values of CD19, representing 1.7% of the ocrelizumab group. All patients had relapsing-remitting MS and 75% were male. None experienced clinical relapse or clinical progression, with MRI and serum neurofilament data to be presented.
Conclusions:
Even though rare, a small percentage of MS patients can fail to lower their CD19 values after starting ocrelizumab. If clinical or radiological activity of MS is seen, switching to a non-B-cell depleting therapy and requesting testing for human anti-chimeric antibodies could be a wise option.