Pharmacokinetic and biochemical studies on acivicin in phase I clinical trials

Acivicin pharmacokinetics were studied in Phase I patients receiving i.v. treatment on single-dose or daily x5 (daily times five doses) regimens repeated every 3 weeks. In 14 patients, the time course of plasma concentrations was characterized by a biexponential equation with a terminal (elimination-phase) half-life of 9.92 +/- 3.91 h (mean +/- SD), distribution phase half-life of 0.32 +/- 0.28 h, total body clearance of 1.69 +/- 0.48 liters/h/m2, and volume of distribution of 21.79 +/- 2.94 liters/m2. Acivicin kinetics appeared to be dose-independent over the range of 8.5-150 mg/m2/day. Urinary excretion of intact acivicin in nine patients ranged from 2-42% in the first 24 h following administration; interpatient variability in urinary excretion was large, but daily urinary recovery within patients on the daily x5 schedule was quite consistent. Measurements of acivicin effects on the activity of carbamyl phosphate synthetase II (CPS II) were conducted using leukocytes and/or malignant ascites of three colon cancer patients. Acivicin given to one patient at 8.5 mg/m2/day on the daily x5 schedule caused a 70% reduction in leukocyte CPS II activity within 5 h after therapy was initiated. Leukocyte CPS II activity remained suppressed at this level over the 5-day dosing regimen. In this patient, CPS II activity in malignant ascitic cells had decreased by 75% on day 4 of the daily x5 regimen. On the single dose schedule, treatment of two patients with 100 mg/m2 caused leukocyte CPS II activity to decrease by greater than 90% within 4 h of treatment with gradual recovery over the next 2 days.