Profiling individual clinical responses by high-frequency serum neurofilament assessment in MS.

To evaluate individual neurofilament light chain (NfL) variation over the time of disease course and the potential of NfL measurement to predict treatment response in patients with MS. We investigated 15 patients with MS after immune reconstitution treatment with alemtuzumab (ATZ). Monthly serum NfL (sNFL) measurements were correlated with Expanded Disability Status Scale (EDSS), MRI, and relapse activity over an observational period of up to 102 months. Before ATZ, sNfL was significantly increased in correlation with previous relapse/MRI activity. After ATZ, sNfL decreased quickly within the first 6 months. In patients classified as NEDA-3, sNfL declined and persisted at an individual low steady-state level of <8 pg/mL. During follow-up, 34 sNfL peaks with a >20 fold increase could be detected, which were associated with clinical or MRI disease activity. Even patient-reported relapse-suspicious symptoms, which have not been confirmed because relapses were accompanied by sNfL, increase, proposing sNfL assessment as a marker for relapse activity. sNfL started to increase earliest 5 months before, peaked at clinical onset, and recovered within 4-5 months. sNfL presented at higher levels in active patients requiring ATZ retreatment compared with responder patients. During 2 documented pregnancies, sNfL was at a low level, whereas a postpartum transient sNfL increase was seen without any signs of activity. This study applied a long-term high-frequency sNfL assessment in an ATZ-treated cohort, allowing a holistic profiling on the individual level and highlighted that sNfL can eminently complement the individual clinical and MRI monitoring in clinical practice.