Phase I pharmacokinetic trial and correlative in vitro phase II tumor kinetic study of Apomine (SR-45023A), a novel oral biphosphonate anticancer drug.

Abstract

To study the human pharmacokinetics and in vitro cytotoxicity of Apomine, an p.o. administered, nonmyelosuppressive agent that selectively inhibits cell proliferation and induces tumor cell apoptosis through the farnesoid X receptor. Seven solid cancer patients who participated in an ongoing Phase I study of Apomine and received the starting dose level of 125 mg/m(2)/day x 14 days every 3 weeks underwent a pharmacokinetic study on day 14 of the first course. Plasma concentrations of Apomine were assayed with a Hewlett Packard gas chromatograph using a nitrogen phosphorus detector and HP-5 15m x 0.32-mm column. Fresh human ovarian cancer tumor samples were obtained during initial exploratory laparotomy from 35 chemotherapy-naive, advanced stage epithelial ovarian cancer patients. Tumor samples were tested for sensitivity to Apomine, carboplatin, cisplatin, paclitaxel, and topotecan using an in vitro clonogenic [(3)H]thymidine end point assay. Pharmacokinetic analysis revealed a mean Apomine plasma C(max) of 16.4 +/- 9.1 microg/ml (29.1 microM), a mean plasma AUC(0--12 h) of 173.4 +/- 105 microg. h/ml (308 microM. h), and a mean t(1/2 (24--192 h)) of 156.2 +/- 42.9 h. In vitro assay results showed that 63 and 91% of the ovarian cancers were sensitive (i.e., >70% inhibition of tumor cell growth) to Apomine at concentrations of 10 and 20 microM. The sensitivity rates were 91% for carboplatin (270 microM), 88% for cisplatin (33 microM), 41% for paclitaxel (5.9 microM), and 85% for topotecan (2.2 microM). These in vitro assay results, taken together with our preliminary plasma pharmacokinetic data, suggest that Apomine should be clinically active at the 125 mg/m(2) dose level.