Fingolimod is a second-line oral drug, approved for patients with relapsing-remitting MS.
It works by blocking the action of lymphocytes, certain white blood cells that play a role in the immune system. It prevents these cells from reaching the brain and the spinal cord, thereby reducing nerve cell damage by inflammation.
As a side-effect, fingolimod can lead to lymphopenia, a reduction in white blood cells that protect us from bacterial or viral attacks.
Because of its effect on the immune system, people who take fingolimod may acquire infections more easily.
It is important that people on fingolimod have regular blood tests and discontinue therapy if their lymphocytes fall below a certain threshold.
In a study published in Neurology, the researchers assessed whether any factors such as pretreatment-lymphocyte counts, treatment before fingolimod, age, sex, or body mass index, affect the risk of fingolimod-induced lymphopenia in patients with relapsing-remitting multiple sclerosis.
Data were obtained from a German multicentre study of patients with relapsing-remitting MS treated with fingolimod, and their findings were further confirmed in an independent Swedish national study.
Included in the study were 418 German and 438 Swedish patients; 15 per cent of all 856 patients developed lymphopenia below the threshold.
Patients with lower starting lymphocyte counts, and female patients with a body mass index lower than 18.5, were at higher risk of developing lymphopenia.
These results suggest that underweight women and patients with low baseline lymphocyte counts are at increased risk of lymphopenia, and consequently of infections, and should be monitored more closely.