Charlotte Teunissen, PhD, VU University Medical Center, Amsterdam, The Netherlands, shares the findings of a case-control study assessing serum contactin-1 (sCNTN1) as a novel biomarker in natalizumab-treated relapsing/remitting multiple sclerosis (RRMS). Serum contactin levels were measured in 89 patients with RRMS at baseline and throughout follow-up and compared to over 200 healthy controls. Disease progression was assessed according to EDSS-plus criteria. The study demonstrated that median sCNTN1 levels in patients with RRMS were significantly lower compared to healthy controls. Additionally, baseline and 12-month sCNTN1 levels were significantly lower in those with progressive disease. These findings indicate that sCNTN1 concentrations are linked in long-term disability progression and may represent a useful liquid biomarker for RRMS. This interview took place during the European Academy of Neurology 2021 congress.