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

Purpose: 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.

Experimental Design: 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.

Results: 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).

Conclusions: 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.