Aims: To investigate the tolerability, safety and pharmacokinetics of S-3304 in healthy volunteers treated with high doses of S-3304 for 28 days.
Methods: Thirty-two healthy volunteers were recruited. Four male and four female subjects were allocated to one of four doses (800 mg, 1600 mg, 2400 mg and 3200 mg). At each dose six volunteers took active medication and two volunteers took placebo in a double-blind fashion. Volunteers took a single dose on days 1 and 28 for pharmacokinetic purposes, and took twice daily doses from day 3-27. The pharmacokinetics of S-3304 and its hydroxy metabolites were evaluated. Tolerance was based on subjective adverse events, clinical examination, vital signs, ECG and laboratory tests including haematology and biochemistry profiles using CTC grading.
Results: Doses up to 2400 mg twice daily were generally well tolerated. At 3200 mg twice daily, five volunteers including one randomized to placebo were withdrawn from treatment mainly due to alanine aminotransferase (ALT) elevation. C(max) of S-3304 on day 1, whose geometric mean and 95% confidence interval were 66.3 microg ml(-1) (48.8, 90.0) for 800 mg, 82.6 microg ml(-1) (69.3, 98.6) for 1600 mg, 89.5 microg ml(-1) (79.5, 100.7) for 2400 mg, and 110.5 microg ml(-1) (88.9, 137.7) for 3200 mg, respectively, was correlated with the log-transformed peak ALT (P < 0.0001 for male and P = 0.048 for female volunteers).
Conclusions: In healthy volunteers the maximum tolerated dose of S-3304 was 2400 mg twice daily. ALT elevation was the most frequent dose-limiting factor and was correlated with C(max) on day 1.