Clinical, radiological and B cell count follow up of Egyptian patients with neuromyelitis optica spectrum disorder on rituximab therapy

Abstract Background Rituximab is a chimeric monoclonal antibody that binds to CD20 antigen on the surface of B cells and induces cytolysis of B cells. B cells are thought to contribute to myelin damage in neuromyelitis optica spectrum disorder (NMOSD). This study aimed to assess the extent of B cell depletion along the course of treatment with rituximab in Egyptian patients with NMOSD in relation to clinical and radiological outcome over 12 months. Subjects and methods This study was a prospective study included 17 Egyptian adult patients diagnosed with NMOSD according to the 2015 international consensus diagnostic criteria. Patients received rituximab for 12 months, with a fixed dose regimen of 1000 mg every 6 months. Patients were subjected to full clinical assessment, using EDSS to assess disability. We assessed cerebral and spinal MRI imaging before and after RTX treatment. Patients underwent CD19 B cell counts by flow cytometry at 4 time points (just before first, second and third rituximab doses as well as one month after the first dose). Results Females were 11 patients (64.7%), serum aquaporin 4 antibodies were positive in 11 patients (64.7%), mean age was 36.47 years, and mean duration of illness was 3.71 years. Most of the patients (88.24%) were treatment-naïve, while 11.76% had been previously treated with Azathioprine. Mean CD19 B cell count depleted significantly from 188.47 to 50.82 and 14.18 after 6 and 12 months respectively. This was associated with a significant decline in median annualized relapse rate (ARR) from 2 to 0 after 12 months of rituximab treatment. Median extended disability status scale (EDSS) declined from 5.5 to 4.5 and 4 after 6 and 12 months respectively. Fifteen patients (88.2%) showed either stationary (76.4%) or regressive (11.8%) cord lesions (as regards number and size of the lesions) and only 2 patients (11.8%) showed progression. Conclusion Repeated treatment with rituximab in NMOSD patients over 12 months using a fixed dose schedule was highly efficacious in sustained depletion of CD19 B cell count. It has acceptable tolerance, reduces relapse frequency, and improves disability in most patients.