Phase I and pharmacokinetic study of intraperitoneal thioTEPA in patients with ovarian cancer

Summary A total of 15 patients with residual ovarian cancer confined to the peritoneal cavity after first-line systemic chemotherapy were treated with triethylene-thiophosphoramide (thioTEPA) in a phase I study. A total of 50 courses of thioTEPA were given intraperitoneally in doses ranging from 30 to 80 mg/m². The dose limiting toxicity was myelosuppression, which occurred at 80 mg/m² and was frequently prolonged. Short-lived nausea and vomiting was easily controlled, and there was no local toxicity. Three patients remain free of disease progression at 6, 6 and 12 months. ThioTEPA concentrations were measured by gas chromatography. Peritoneal fluid concentrations declined rapidly in a first-order fashion, with a half-life of 0.96 ± 0.1 h. A mean of 93% of the drug was absorbed during the 4-h dwell time. Peak plasma levels were achieved 30–60 min after drug instillation and were substantially lower than corresponding peritoneal levels. A pharmacokinetic advantage for intraperitoneal delivery was detected for peak drug concentration (24.9 ± 8.5) and AUC (9.2 ± 4.8). Based on this study, the recommended dose for intraperitoneal thioTEPA is 60 mg/m² every 3–4 weeks. However, the rapid absorption of this drug from the peritoneum, secondary to thioTEPA’s small molecular weight and lipophilic nature, suggests that it has only a limited role in intraperitoneal therapy.