A real-world study of interleukin-6 receptor blockade in patients with neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing autoimmune disease that can cause permanent neurological disabilities. However, the interleukin-6 (IL-6) signaling pathway is a promising therapeutic target for relapse prevention. Therefore, this study evaluated the long-term effectiveness of tocilizumab, a humanized anti-IL-6 receptor antibody, for NMOSD. We enrolled 65 patients with NMOSD who received regular intravenous administration of tocilizumab (8 mg/kg) between October 2017 and January 2022. Then, we retrospectively collected data on the clinical characteristics and baseline glial fibrillary acidic protein (GFAP) and neurofilament light chain levels. The primary outcome was the annualized relapse rate (ARR). Risk factors were assessed using a multivariable logistic regression model. During the median follow-up of 34.1 (interquartile range: 25.5–39.3) months, 23% (15/65) of patients relapsed during tocilizumab treatment, but the median ARR decreased from 1.9 (range 0.12–6.29) to 0.1 (range 0–1.43, p < 0.0001). A prolonged infusion interval (> 4 weeks, odds ratio [OR]: 10.7, 95% confidence interval [CI]: 1.6–71.4, p = 0.014) and a baseline plasma GFAP level of > 220 pg/mL (OR: 20.6, 95% CI 3.3–129.4, p = 0.001) were risk factors for future relapses. During treatment, the median Expanded Disability Status Scale score significantly decreased in aquaporin-4 antibody-positive and -negative patients, but the pain did not considerably improve. There were no severe safety concerns. Tocilizumab treatment significantly reduced the relapse rate in patients with NMOSD. However, prolonged infusion intervals and high baseline plasma GFAP levels may increase the relapse risk during tocilizumab therapy.