An Observation Monocentric Study to Analyse the Possible Neuroprotective Effect of Ocrelizumab Via VEGF Protein Expression in Relapsing Multiple Sclerosis Patients

Ocrelizumab (OCR) is a humanized monoclonal anti-CD20 antibody approved by the FDA in 2017 and by the European Medicines Agency in 2018 for treatment of adult patients with Relapsing Multiple Sclerosis (RMS). In addition, having shown neuroprotective effects, OCR is the first drug ever approved for early treatment of Primary Progressive MS (PPMS). Currently, OCR is thought to mostly act via the rapid depletion of the B cells expressing CD20. Additionally, this depletion most likely causes long-lasting changes in the profile of B cells, characterized by a reduction of their pro-inflammatory phenotype, as demonstrated with other anti-CD20 antibodies.

Of interest, previous studies on other anti-CD20 drugs, mainly rituximab, have shown that anti-CD20 agents also exert interesting effects on additional intracellular signaling pathways, such as those involving serine/threonine and tyrosine kinases, as well as c-myc. Considering the structural, pharmacokinetic and pharmacodynamic similarities between OCR and rituximab, it can be hypothesized that the efficacy of OCR in delaying disease progression and neuroprotection might also stem from such intracellular effects.

Among the various intracellular effects elicited by rituximab through the binding with CD20, stimulation of the Protein Kinase C (PKC) pathway is of potential significance. The term PKC encompasses a family of several serine/threonine protein kinases of which the isoform β has been implicated in pathological processes, such as diabetic retinopathy, via a specific PKCβ/HuR/Vascular Endothelial Growth Factor (VEGF) pathway (Amadio et al. 2010). Notably, HuR belongs to a family of RNA-binding proteins, named ELAV, which are able to influence virtually any aspect of the post-synthesis fate of the targeted transcripts, including VEGF.

VEGF is a signaling molecule involved in vital processes such as angiogenesis, endothelial proliferation and cellular response to hypoxia. The possible role of VEGF in MS pathogenesis and evolution has not been explored until recently, but mounting evidence points to the conclusion that VEGF might play a significant noxious role in the relapsing stage of MS, for instance by mediating an increase in blood-brain barrier (BBB) permeability, while playing a beneficial, neuroprotective role in the late, progressive stage of the disease. Of note, VEGF has a primary role in promoting vascular hyperpermeability, indeed via phosphorylation of endothelial tight junction proteins modulates their degradation, finally leading to BBB disruption. Further, it also regulates vessel growth and is chemotactic for monocytes and lymphocytes, promoting neuroinflammation.

Of interest, a significant increase in VEGF was observed in mice in the acute phase of murine MOG-induced MS, which correlates to the clinical score, and in sera of MS patients during clinical disease relapses.