Comparison of CSF biomarkers in multiple sclerosis patients treated with natalizumab and rituximab

Abstract

Background: Patients with relapsing remitting multiple sclerosis (RRMS) treated with the high-efficacy drugs natalizumab (NTZ) or rituximab (RTX) generally show no evidence of disease activity. Currently, there is no head-to-head comparison between NTZ and RTX of neurodegenerative and neuroinflammatory biomarkers in cerebrospinal fluid (CSF). Objectives: To compare CSF biomarkers in a stable RRMS cohort treated with NTZ or RTX. A secondary objective was to explore potential associations between CSF biomarkers, fatigue, and cognition. Methods: This Swedish multicentre cross-sectional study assessed kappa-free light chain (k-FLC) index, oligoclonal bands (OCBs), glial fibrillary acidic protein (GFAP) and neurofilament light (NfL) in CSF of 30 RRMS patients on NTZ or RTX for at least 24 months. A longitudinal comparison of biomarkers was performed for IgG Indices. Fatigue and cognition outcomes were explored in relation to CSF biomarkers. Results: GFAP level was significantly higher in the NTZ group compared to RTX (mean difference (CI): 2 716 (155; 5278) ng/L, p=0.047). NfL concentration did not differ between the groups. OCBs and k-FLC index were present and elevated in 97 % and 87 % of participants, respectively. IgG-index was significantly reduced only for NTZ. No significant associations were found between fatigue, cognition and the biomarkers. Conclusion: Our results support that intrathecal inflammatory activity is still ongoing in patients with NTZ and RTX. Cross-sectional GFAP might indicate a lower risk for long-term disability in the RTX group. Our data should be interpreted with caution because of small sample size, making it difficult to control for multiple confounders.