Opicinumab (also known as BIIB-033 or anti-LINGO-1) is a fully human monoclonal antibody that targets leucine-rich repeat and immunoglobulin-like domain-containing protein 1 (LINGO-1), a transmembrane glycoprotein expressed primarily in the central nervous system (CNS) on neurons and oligodendrocytes. LINGO-1 is a negative regulator of oligodendrocyte differentiation, myelination, and axonal regeneration. By binding to and inhibiting LINGO-1, opicinumab aims to promote remyelination and axonal repair in demyelinating diseases. It has been clinically evaluated as a remyelination and neuroprotective therapy for multiple sclerosis (MS), including relapsing and progressive forms, but has not yet demonstrated conclusive efficacy in Phase II trials.