Beyond Histamine Blockade: Clemastine Fumarate as a Promoter of Myelin Regeneration, Inflammatory Regulation, and Neuroimmune Modulation in CNS Disorders.

Clemastine fumarate, a first-generation H1 antihistamine, has emerged as a promising candidate for drug repurposing in neurodegenerative and neuropsychiatric disorders owing to its ability to cross the blood-brain barrier and interact with multiple central nervous system targets. Experimental studies indicate that clemastine promotes remyelination by stimulating the differentiation of oligodendrocyte precursor cells into mature, myelin-producing oligodendrocytes, thereby restoring myelin integrity and improving axonal function in experimental models. In addition to its remyelinating properties, preclinical evidence suggests that clemastine may attenuate neuroinflammation by modulating microglial activation and suppressing pro-inflammatory signalling pathways. These effects have been associated with improved structural and functional outcomes in experimental models of multiple sclerosis, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, spinal cord injury, stroke, and several neuropsychiatric disorders. Mechanistically, clemastine primarily acts through muscarinic M1 receptor antagonism to promotes remyelination, while additional pathways including PI3K/Akt, ERK1/2, autophagy-related signalling, inflammasome modulation, and sigma-1 receptor signalling have been proposed based on experimental evidence but remain incompletely understood and require further mechanistic validation. Among the neurological disorders investigated multiple sclerosis currently has the strongest clinical evidence with early clinical trials demonstrating modest remyelinating activity. In contrast, evidence supporting the use of clemastine in other neurological disorders remains largely confined to preclinical studies. Several translational challenges also remain unresolved including dose optimisation, treatment timing, long-term safety, sedative and anticholinergic adverse effects, and patient selection. Future research should focus on refining pharmacokinetic properties, optimising dosing strategies, evaluating rational combination therapies, and identifying predictive biomarkers to facilitate clinical translation. Although current evidence highlights the therapeutic potential of clemastine fumarate, its application beyond multiple sclerosis remains investigational and will require rigorous mechanistic studies together with well-designed clinical trials before broader clinical use can be established.