Summary
This study investigated the safety, pharmacokinetics and pharmacodynamics of multiple
oral doses of R1663, a factor Xa inhibitor, and explored the influence of age and
gender on pharmacokinetics and pharmacodynamics of R1663. This was a single-blind,
randomised, placebo-controlled, dose escalation study in 48 healthy male volunteers
aged 18 to 44 years. R1663 doses up to 300 mg twice daily or 400 mg once daily were
administered for seven days. The exploration of gender and age effect was carried
out in separate cohorts of eight male and eight female volunteers aged 45 to 65 years.
Multiple oral doses of R1663 were safe and well tolerated. Pharmacokinetics was linear
and showed moderate variability. Plasma concentrations peaked at 3 hour. Terminal
half-life at steady state was 3–5 hours. Accumulation of R1663 was minimal. R1663
prolonged clotting times, inhibited thrombin generation (peak height and endogenous
thrombin potential [ETP]) and anti-factor Xa activity in a concentration-dependent
manner without increasing bleeding time. Pharmacodynamic parameters were strongly
correlated to R1663 plasma concentrations. The inhibition was more pronounced on peak
height (IC50 = 194 ng/ml) than on ETP (2790 ng/ml). Pharmacokinetics and pharmacodynamics of R1663
appeared not to be substantially affected by age or gender but remained to be confirmed
in larger clinical trials including older patients. Meanwhile, dose adjustments based
on age and gender are not anticipated.
Keywords Factor Xa inhibitor - multiple ascending dose study - healthy volunteers - gender
and age effect