B-cell proliferation characteristics and monitoring significance under the modified reduced-dose rituximab regimen for NMOSD: A real-world case series study

To explore the B-cell proliferation characteristics and monitoring significance under the modified reduced-dose rituximab (mRTX) regimen for neuromyelitis optica spectrum disorder (NMOSD).NMOSD patients treated with mRTX were recruited, and the percentages of total CD19+ B cells and CD27+ memory B cells were dynamically detected by flow cytometry. The annualized relapse rate (ARR) and expanded disability status scale (EDSS) scores were compared before and after mRTX treatment, and the differences in B-cell values were compared between groups.A total of 34 patients with NMOSD were ultimately enrolled. The EDSS score decreased from 2.5 (1.5, 3.0) to 1.3 (1.0, 2.0), and the ARR decreased from 1.0 (0, 2.0) to 0 (0, 0) (p < 0.001). Relapses occurred in 6 patients, with total CD19+ B-cell percentages of 3.25% (2.7%, 3.7%) and CD27+ memory B-cell percentages of 0.3% (0.2%, 0.3%) at initial relapse. Twenty-eight patients (82.4%) remained relapse-free with 84 doses of mRTX. Before 56 repeated doses, the total CD19+ B cells and CD27+ memory B cells were 4.00% (3.14%, 5.32%) and 0.26% (0.17%, 0.40%), respectively. The mean dosing interval was 9.2 months. Both total CD19+ B cells and CD27+ memory B cells proliferated over time after mRTX use, with significantly faster proliferation rates in the later stages. In 28 relapse-free patients, the mean time to reach 1% for total CD19+ B cells was 210 days, and the mean time to reach 3% was 240 days, with the mean interval from 1% to 3% of 65 days. Twenty-five relapse-free patients had no significant differences in maximum, minimum, and mean B-cell values compared to those of 6 patients with relapse.The high rate of B-cell proliferation under the mRTX regimen indicates that closer dynamic B-cell monitoring is required to guide repeated mRTX dosing. Sustained depletion of total CD19+ B cells targeting < 3% of lymphocytes may be feasible, enabling extended dosing intervals.