Combining Clemastine and Aerobic Exercise to Treat Cognitive Dysfunction in Schizophrenia by Targeting Myelin Plasticity

Schizophrenia (SZ) is a broad clinical entity characterized by different subjective symptoms,behavioural signs, and disease course. Research has pointed to numerous biological indicators tentatively associated with neurocognitive dysfunction, brain structural and neurochemical alterations. Cognitive deficits occur as early as the prodromal phase of the illness and significantly determine its outcome. Pathophysiologically, SZ is regarded as a disconnectome disorder in which frontal and temporal brain regions are functionally disconnected, which contributes substantially to the development of cognitive dysfunction.

Impaired connectivity is related to synaptic (microconnectivity) and myelin (macroconnectivity) plasticity. With design-based stereology, a decreased number of oligodendrocytes (OLs) in the CA4 hippocampal subregion as the basis for disturbed myelination and impaired cognition, but also a decrease in the prefrontal cortex were observed. Animal studies demonstrated that clemastine enhances remyelination by increasing the differentiation of oligodendrocyte precursor cells (OPCs) and showed that aerobic exercise increases the rate of remyelination and proliferation of OPCs; this clinically meaningful effect of aerobic exercise is stronger in combination with clemastine. Furthermore, aerobic exercise improves everyday functioning, measured by the Global Assessment of Functioning (GAF) scale, and cognitive dysfunction in SZ and increases hippocampal volume, especially the volume in the hippocampal CA4 subregion. This regional volume change correlates negatively with global and cell-specific polygenic risk scores (PRSs), indicating that OPCs are involved in the genetic risk mechanisms and disturbed plasticity underlying SZ. In patients with multiple sclerosis, 90 days' administration of clemastine fumarate 10.72 mg/day, corresponding to clemastine 8 mg/day, significantly decreased the P100 latency delay of visual evoked potentials (VEPs) as a sign of myelin repair. In a bicentric, randomized, double-blind, controlled phase IIb clinical trial with a 2-arm parallel group design in patients with SZ, the study will compare the effects of aerobic exercise training plus clemastine vs. aerobic exercise training plus placebo over a period of 3 months on 1) everyday functioning and 2) working memory as primary outcomes.