More on PML in Patients Treated with Dimethyl Fumarate. Author reply

A case series of persistent lymphopaenia following treatment with fumaric acid esters for psoriasis

WHAT IS KNOWN AND OBJECTIVE

Fumaric acid esters (FAEs) have been used for fifty years to treat moderate-to-severe psoriasis. However, recent case reports of progressive multifocal leukoencephalopathy, associated with FAE-induced lymphopaenia, have been a cause for concern (J Dtsch Dermatol Ges. 2009;7:603).

CASE SERIES

We report six cases of persistent lymphopaenia following cessation of treatment with FAEs, with a mean duration of lymphopaenia of 33 months.

WHAT IS NEW AND CONCLUSION

Given the lack of evidence regarding expected recovery of lymphocyte counts, further research is required to guide physicians in the risk stratification of patients prior to considering treatment with FAEs.

Dual action by fumaric acid esters synergistically reduces adhesion to human endothelium

OBJECTIVE

Dimethyl fumarate (DMF) is prescribed against relapsing-remitting multiple sclerosis (MS). Here, we investigated the effects of DMF and monomethyl fumarate (MMF), its metabolite in vivo, at the (inflamed) blood-brain barrier (BBB).

METHODS

Effects of fumaric acid esters were analyzed using primary human brain-derived microvascular endothelial cells (HBMECs) in combination with peripheral blood mononuclear cells (PBMCs) derived from DMF-treated MS patients.

RESULTS

MMF-binding to brain endothelium cells leads to activation of nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2)-induced downregulation of vascular cell adhesion molecule 1 (VCAM-1). This might be mediated via the G-protein-coupled receptor (GPCR) hydroxycarboxylic acid receptor 2 (HCA₂), a known molecular target of MMF, as we could demonstrate its expression and regulation on HBMECs. DMF treatment in vivo led to a strongly reduced expression of VCAM-1's ligand very late antigen 4 (VLA-4) by selectively reducing integrin high-expressing memory T cells of MS patients, potentially due to inhibition of their maturation by reduced trans-localization of NFκB.

CONCLUSION

DMF-mediated VCAM-1 downregulation on the endothelial side and reduction in T cells with a migratory phenotype on the lymphocyte side result in a synergistic reduction in T-cell adhesion to activated endothelium and, therefore, to reduced BBB transmigration in the setting of MS.

Disease-modifying therapies and infectious risks in multiple sclerosis

Immunomodulatory and immunosuppressive treatments for multiple sclerosis (MS) are associated with an increased risk of infection, which makes treatment of this condition challenging in daily clinical practice. Use of the expanding range of available drugs to treat MS requires extensive knowledge of treatment-associated infections, risk-minimizing strategies and approaches to monitoring and treatment of such adverse events. An interdisciplinary approach to evaluate the infectious events associated with available MS treatments has become increasingly relevant. In addition, individual stratification of treatment-related infectious risks is necessary when choosing therapies for patients with MS, as well as during and after therapy. Determination of the individual risk of infection following serial administration of different immunotherapies is also crucial. Here, we review the modes of action of the available MS drugs, and relate this information to the current knowledge of drug-specific infectious risks and risk-minimizing strategies.