Investigation of bioavailability and pharmacokinetics of treosulfan capsules in patients with relapsed ovarian cancer.

PURPOSE

Treosulfan (L-threitol-1,4-bis-methanesulfonate, Ovastat) is a prodrug of a bifunctional alkylating agent with activity in ovarian carcinoma and other solid tumors. In a pharmacologic study of the bioavailability of treosulfan in a capsule formulation, patients with relapsed ovarian carcinoma were treated with alternating doses of oral and intravenous (i.v.) treosulfan of 1.5 or 2.0 g daily for 5 to 8 days.

METHODS

A sensitive method for the determination of treosulfan in plasma and urine by reversed-phase high-performance liquid chromatography had previously been developed. Pharmacokinetic analyses of treosulfan were carried on plasma and urine samples from 20 i.v. courses and 20 courses of oral administration.

RESULTS

The bioavailability ratio (f) of oral to i.v. administration was calculated as 0.97 +/- 0.18 (mean +/- SD) using the values AUC oral = 82.1 +/- 39.4 microg/ml h and AUC i.v. = 85.4 +/- 30.3 microg/ml h. The peak plasma concentration cmax (29 +/- 14 microg/ml vs 65 +/- 23 microg/ml) was significantly (P < 0.01) higher after i.v. administration and the tmax after oral administration was 1.5 +/- 0.34 h. The terminal half-life of treosulfan was about 1.8 h. The mean urinary excretion of the parent compound was about 15% of the administered total dose over 24 h (range 6-26%).

CONCLUSIONS

The high and relatively constant bioavailability of treosulfan indicates that capsules provide a satisfactory noninvasive treatment alternative. A feasible and reliable oral treosulfan formulation could provide the basis for the development of long-term low-dose outpatient treatment of patients with malignant diseases.