Microglial suppression by myeloperoxidase inhibitor does not delay neurodegeneration in a mouse model of progressive multiple sclerosis.

Drugs able to efficiently counteract the progression of multiple sclerosis (MS) are still an unmet need. Numerous preclinical evidence indicates that reactive oxygen-generating enzyme myeloperoxidase (MPO), expressed by neutrophils and microglia, might play a key role in neurodegenerative disorders. Then, the MPO inhibition has been evaluated in clinical trials in Parkinson's and multiple system atrophy patients, and a clinical trial for the treatment of amyotrophic lateral sclerosis is underway. The effects of MPO inhibition on MS patients have not yet been explored. In the present study, by adopting the NOD mouse model of progressive MS (PMS), we evaluated the pharmacological effects of the MPO inhibitor verdiperstat (also known as AZD3241) on functional, immune, and mitochondrial parameters during disease evolution. We found that daily treatment with verdiperstat did not affect the pattern of progression as well as survival, despite its ability to reduce mitochondrial reactive oxygen species and microglia activation in the spinal cord of immunized mice. Remarkably, verdiperstat did not affect adaptive immunity, neutrophils invasion as well as mitochondrial derangement in the spinal cords of immunized mice. Data suggest that microglia suppression is not sufficient to prevent disease evolution, corroborating the hypothesis that immune-independent components drive neurodegeneration in progressive MS.