The pharmacokinetics and lymphocyte responses to the immunomodulator fingolimod (FTY720) were characterized after oral and intravenous administration.Methods.
In this randomized, two-period crossover study 11 evaluable healthy subjects received single doses of fingolimod 1.25mg orally and 1mg intravenously infused over 2h. The pharmacokinetics of fingolimod, blood lymphocyte counts and heart rate were characterized for 28 days after each dose.Results.
After oral administration, Cmax was 1.1 ± 0.2ng/ml occurring at 12 h postdose and the AUC was 201 ±31ng.h/ml. After intravenous infusion, Cmax was 4.9 ± 0.8ng/ml, AUC was 175 ± 50 ng. h/ml, clearance was 6.3 ± 2.3l/h and distribution volume was 1199 ± 260l. The oral/intravenous ratio of dose-normalized AUCs was 0.94 (95%CI: 0.78-1.12). The pharmacologically active metabolite fingolimod-phosphate was quantifiable near its peak after oral administration but not after intravenous administration. The mean lymphocyte nadir occurred on day 1 and was 35% lower after oral (0.74 × 109/l) than after intravenous (1.15 × 109/l) administration. Lymphocytes recovered to the normal range by day 15 for both treatments. The mean heart rate nadir occurred 3-4 h postdose and was 11% lower after oral administration (47bpm) versus intravenous administration (53bpm).Conclusions.
Average systemic exposure to fingolimod was similar after oral and intravenous administration. However, the acute decrease in lymphocyte counts was weaker after intravenous administration, likely because of lower blood levels of the active metabolite fingolimod-phosphate compared with oral administration.