Change in serum neurofilament light chain and glial fibrillary acidic protein levels with high-efficacy and low-efficacy early therapy in multiple sclerosis.

Introduction: Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) are associated with multiple sclerosis (MS) outcomes. We compare how high-efficacy early therapy (HEET) and lower-efficacy early therapy (LEET) affect serum NfL and GFAP at the initiation of disease-modifying therapy (DMT) and in the years afterwards.

Methods: Adults diagnosed with MS within 5 years of symptom onset at our centre were eligible. Records from DMT-naïve patients with serum NfL and GFAP drawn in the year before treatment start and follow-up samples 6-36 months after treatment initiation were included in the 'pre-initiation' cohort. Those with baselines after DMT initiation and follow-up samples within 5 years were included in the 'post-initiation' cohort.

Results: There were 155 pre-initiation patients (HEET: 85, LEET: 70) and 213 post-initiation (HEET: 55, LEET: 158). NfL levels were reduced following DMT initiation but did not differ significantly between HEET and LEET in either cohort. GFAP was not substantially impacted by either HEET or LEET.

Conclusion: The difference in NfL reduction with HEET and LEET may be smaller than anticipated, perhaps reflecting that disease activity risk is considered in real-world DMT selection. There is minimal impact of HEET or LEET on GFAP, at least over several years.