Background: The aim of this study was to evaluate the significance of serum concentrations of the inflammatory marker osteopontin, the blood–brain barrier damage marker occludin, and the neurodegeneration marker neurofilament light chain (NFL) in patients with relapsing-remitting multiple sclerosis (RRMS) for predicting disease activity and progression. This evidence concerns the gene SPP1 and relapsing-remitting multiple sclerosis.