Potent Antitumor Activity of a Novel Nucleoside Analogue, BCH-4556 (β-l-Dioxolane-cytidine), in Human Renal Cell Carcinoma Xenograft Tumor Models

Abstract

β-l-Dioxolane-cytidine (BCH-4556) is a novel anticancer nucleoside analogue with a stereochemically unnatural β-l configuration. This compound was previously shown to have a potent antitumor activity in human prostate and hepatocellular xenograft tumor models (K. L. Grove et al., Cancer Res., 55: 3008–3011, 1995). Herein, we extended the efficacy validation of BCH-4556 to renal cell carcinoma (RCC) cell lines both in vitro and in vivo. In vitro cytotoxicity and proliferation inhibition deter-minations in human RCC cell lines CAKI-1, CAKI-2, 786-0, and A498 produced IC₅₀ concentrations ranging from 15–35 ηm. In vivo antitumor activity was consistent with the in vitro sensitivity. BCH-4556 was very effective in human RCC tumor xenograft models, including CAKI-1, A498, RXF-393, and SN12C carcinomas. Very good responses were observed in animals bearing CAKI-1, A498, and RXF-393 RCC tumors given i.p. doses of 10, 25, and 50 mg/kg twice a day for 5 days, with complete regression recorded in most of the animals tested. Curative activity was also observed, with 40–60% of animals remaining tumor free in all three RCC models at the day of study termination. Significant tumor shrinkage was also evident in the SN12C model. BCH-4556 efficacy evaluation in the orthotopic subrenal capsule tumor models demonstrated a potent tumor growth inhibition against human CAKI-1 xenografts and tumor stasis against mouse Renca tumors. BCH-4556 was also effective in inhibiting the growth of rebound CAKI-1 tumors after the administration of a second treatment cycle. The observed antitumor activity of BCH-4556 in several RCC human solid tumor xenografts, including the lethal RXF-393 model, warrants further investigation of this novel nucleoside analogue in clinical trials of RCC.