Determination of Seminal Concentration of Fingolimod and Fingolimod-Phosphate in Multiple Sclerosis Patients Receiving Chronic Treatment With Fingolimod.

The safety profile of fingolimod 0.5 mg, approved therapy for relapsing multiple sclerosis, is well established in clinical and real-world studies. As fingolimod is teratogenic in rats, it was considered important to assess the concentrations of fingolimod and its active metabolite, fingolimod-phosphate, in the semen of male patients on treatment and the risk of harming a fetus in a pregnant partner. In this multicenter open-label study, 13 male patients receiving fingolimod for at least 6 months provided 1 semen and 1 blood sample for analyte concentration measurements. The steady-state seminal concentrations of fingolimod and fingolimod-phosphate were close to those simultaneously observed in blood. The amount of fingolimod-related material in 10 mL of ejaculate was estimated to be 47.5 ng. The estimated fingolimod and fingolimod-phosphate blood C values in a woman having regular sexual intercourse with a male patient treated with fingolimod 0.5 mg were approximately 400 and 2400 times smaller than the estimated values in the embryo-fetal development study in rats at the no-observed-adverse-event level. Consequently, the risk of harming a fetus in a pregnant woman is considered extremely unlikely.