Introduction: Fingolimod is the first approved drug with oral availability for the treatment of relapsing multiple sclerosis.
Aims: To review the mechanism of action of fingolimod and its relationship with the development of infections. To propose preventive measures for those patients who are receiving the drug or will initiate a new treatment. In addition, the role of fingolimod in the development of progressive multifocal leukoencephalopathy on the basis of recent knowledge of its pathophysiology will be discussed.
Development: The mechanism of action of fingolimod is based on an antagonic effect on the sphingosine 1-phospate receptors that will generate an inhibition of the egress of naive and central memory lymphocytes into the bloodstream, allowing the free recirculation of memory effectors T lymphocytes. This effect will produce lymphopenia. Fingolimod-associated lymphopenia is a consequence of lymphocyte redistribution, and it is selective and reversible. There is no evidence of higher number of opportunistic and non-opportunistic infections in comparison to placebo or interferon beta-1a in patients receiving fingolimod. However, two patients developed severe herpetic infections under fingolimod.
Conclusions: Fingolimod induce a selective and reversible lymphopenia that, taking into account the most recent available data, does not seem to be associated with higher risk of opportunistic infections due to a preservation of immuno-surveillance. The risk of herpesvirus infection should be taken into consideration and more studies are warranted to confirm if an association of these infections with the use of fingolimod exists.