Anti-Rituximab antibody in patients with NMOSDs treated with low dose Rituximab

Background Rituximab is a mouse-human chimeric anti-CD20 monoclonal antibody and has been increasingly used for preventing relapses in NMOSDs. The clinical relevance of Anti-Rituximab antibodies (ARA) against Rituximab in NMOSDs is unknown. Methods Nineteen NMOSDs patients receiving repeated 100 mg Rituximab treatment were recruited. The ARA was quantitatively analyzed by enzyme linked immunoassay. Annualized relapse rate (ARR) and Expanded Disability Status Scale (EDSS) were analyzed concurrently. Results ARR was reduced markedly since starting Rituximab therapy in the majority (78.9%) of NMOSDs patients. 36.9% (7/19) patients were ARA positive. There was no significant difference in the improvement of ARR and EDSS after treatment with Rituximab in either ARA positive or negative groups. The frequency of Rituximab reinfusion was higher in patients with ARA, suggesting that the presence of ARA led to an increased frequency of Rituximab reinfusion to maintain B cell depletion. Conclusion The majority of (78.9%) patients with NMOSDs were responsive to low dose Rituximab. The presence of ARA is associated with the requirement for increased frequency of Rituximab reinfusion to maintain treatment response in NMOSDs. In patients with ARA it might be necessary to detect ARA levels and monitor B cell depletion closely, or even attempt other treatments.