Repeated neurofilament light chain measurements did not capture Riluzole therapeutic effect in amyotrophic lateral sclerosis patients

Abstract Background Little is known about the influence of Riluzole on serum neurofilament light chain (sNfL) levels, a biomarker of prognosis in amyotrophic lateral sclerosis (ALS), and variations with time of sNfL concentrations are controversial. Methods Sera from ALS patients ( n  = 141) and controls ( n  = 33) were collected at inclusion (sNfL1) and second visit (sNfL2, mean delay 10.4 ± 8.7 months). sNfL levels, determined by single‐molecule array, were compared between ALS and controls at both time points. sNfL concentration changes were compared between patients with Riluzole (w/Ril) at inclusion in the study and those who were treated by Riluzole following inclusion (w/o Ril). The factors influencing sNfL concentrations and changes were studied using linear regression and multivariate analysis. Results sNfL levels were higher in ALS patients than in controls at the two time points ( p  < 0.00001). In ALS patients, sNfL concentrations were higher in females for both sNfL1 ( p  = 0.014) and sNfL2 ( p  < 0.001). In the whole ALS group, sNfL levels were higher at sNfL2 than at sNfL1 ( p  < 0.001). sNfL1 and sNfL2 concentrations were similar between the two ALS subgroups (w/ and w/o Ril). ALS functional rating scale‐revised rate of decline and gender were the two main factors significantly influencing both sNfL1 and sNfL2 levels ( p  < 0.01). However, only gender was shown to significantly influence sNfL changes with time ( p  = 0.003). Conclusions In this study, sNfL levels increased with time in ALS patients and there was no difference between subjects already treated by Riluzole and those treated after sNfL1. Further studies with larger population samples and different sampling intervals are warranted to better determine the real potential of sNfL measurement as a tool to monitor treatment response in ALS.