Lower dosages of rituximab used successfully in the treatment of anti-NMDA receptor encephalitis without tumour.

Objective: The aim of this study was to evaluate the use and efficacy of lower dosages of rituximab for treating anti N-methyl-d-aspartate receptor (NMDAR) encephalitis without tumour.

Methods: We performed a prospective study of 10 patients with anti-NMDAR encephalitis who did not respond to 10 to 14days first-line immunotherapy and received rituximab administered intravenously (IV) at a dosage of 100mg once per week for 4 consecutive weeks. Reinfusion of rituximab was given when CD19+ B-cell counts of total lymphocytes in peripheral blood >1%. The annualized relapse rate (ARR), modified Rankin scale (mRS) and CD19+ B-cell counts were measured every 4 to 10weeks after initial rituximab treatment in order to assess the clinical outcome and efficacy of rituximab.

Results: Lower dosages of rituximab led to a significant reduction of mRS and CD19+ B-cells when compared with before the rituximab infusion (P<0.05) and allowed 9 (90%) patients to maintain a stabilised neurological status. One patient experienced a relapse at 19weeks after initial rituximab infusion. Although ARR reduction of all 10 patients did not achieve statistical significance (P>0.05), in the 4 patients who had relapses before rituximab treatment there was an apparent reduction in ARR over 56weeks. At the last follow up, 9 patients (90%) had a good outcome (mRS≤2) including 3 patients (30%) who recovered completely (mRS=0). Transient infusion adverse events occurred in 2 patients. We observed no serious delayed adverse events during the 56weeks follow-up.

Conclusions: In patients with anti-NMDAR encephalitis who did not respond to first-line immunotherapy, early application of lower dosages of rituximab could efficiently reduce CD19+ B-cell counts of peripheral blood and improve the prognosis of anti-NMDAR encephalitis.