Abstracts from 13^th NA ISSX / 20^th JSSX meeting October 23–27, Maui, Hawaii

Abstract 403

Comparative Metabolism and Excretion of a Novel CCR5 Receptor Antagonist, SCH 417690 (VICRIVIROC), in Human, Monkey and Rat

R. Ramanathan*, R. Zhong, N. Alvarez, C. Kennedy, D. Grotz, D. Rindgen, K. Cox, S. Chowdhury, M. Wirth and K. Alton

Drug Metabolism and Pharmacokinetics, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA

SCH 417690 (VICRIVIROC®, 1-[(4,6-dimethyl-5-pyrimidinyl)carbonyl]-4-[4-[2-methoxy-1(R)-4-(trifluoromethyl)phenyl]ethyl-3(S)-methyl-1-piperazinyl]-4-methylpiperidine)¹, a novel CCR5 receptor antagonist, is currently under development for the treatment of HIV infection. Metabolism and excretion of SCH 417690 were investigated following a single oral 50 mg, 5 mg/kg and 6 mg/kg administration of ¹⁴C-SCH 417690 to healthy volunteers, monkeys and rats, respectively. In healthy volunteers, radioactivity was excreted near equally in feces and urine. By contrast in rats and monkeys, a greater percent of the radiocarbon dose was excreted in the feces. Metabolites in plasma, urine and feces were profiled and characterized using liquid chromatography mass spectrometry in-line with flow scintillation analysis (LC-MS/FSA). Across all species investigated, qualitatively similar plasma LC-MS/FSA profiles were observed with unchanged drug being the major component. Major metabolites excreted in urine or feces included a glucuronide conjugate of O-desmethyl-SCH 417690 (M35), O-desmethyl-SCH 417690 (M15) and N-dealkylated SCH 417690 (M41). Other minor to trace level metabolites detected in plasma and excreta included several oxidative metabolites of SCH 417690 and M15, as well as a metabolite formed by carboxylation of SCH 417690 (M35b/M37a). The results of these studies showed that SCH 417690 is biotransformed via O-demethylation, N-dealkylation, oxidation and glucuronidation. Additionally, data also suggest that there are no human specific metabolites following single 50 mg oral administration of SCH 417690 to healthy male volunteers.

1. Tagat et al., J. Med. Chem., 2004, 47, 2405–2408.

Abstract 505

Analysis of Immune Cell-Recruitment and Tumor Suppressive Effect in Murine B16BL6 Melanoma Injected with Chemokine-Expressing Adenoviral Vector

Masakazu Niwa¹, Naoki Okada¹, Akinori Sasaki¹, Yutaka Hatanaka², Yoichi Tani², Hiroyuki Mizuguchi³, Shinsaku Nakagawa*⁴, Takuya Fujita*¹ and Akira Yamamoto*¹

¹Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan, ²DakoCytomation Co. Ltd., Shimogyo-ku, Kyoto 600-8493, Japan, ³National Institute of Biomedical Innovation, Ibaraki, Osaka 567-0085, Japan, ⁴Osaka University, Suita, Osaka 565-0871, Japan

Our goal in the present study was to evaluate frequency of tumor-infiltrating immune cells and anti-tumor effects upon intratumoral injection of RGD fiber-mutant adenoviral vector (AdRGD) encoding the chemokines CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1. Among these chemokine-expressing AdRGDs, AdRGD-CCL19-injection most efficiently induced infiltration of CD3⁺ T cells into established B16BL6 tumor parenchyma, whereas most of these T cells were perforin-negative in immunohistochemical analysis. Additionally, the growth of AdRGD-CCL19-injected tumors decreased only slightly as well as that of other tumors treated with each chemokine-expressing AdRGD, which indicated that accumulation of naive T cells in tumor tissue would not effectively damage the tumor cells. Collectively, although AdRGD-mediated chemokine gene transduction into established tumors would be useful for augmentation of tumor-infiltrating immune cells, a combinational treatment that can systemically induce tumor-specific effector T cells is necessary for satisfactory anti-tumor efficacy.

Abstract 784

Expression of Human Drug Metabolizing Enzymes in Chimeric Mice with Humanized Liver

Miki Katoh*¹, Tomohito Matsui¹, Hirotoshi Okumura¹, Miki Nakajima*^1,2, Shinsaku Naito*³, Chise Tateno⁴, Katsutoshi Yoshizato^4,5 and Tsuyoshi Yokoi*^1,2

¹Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, ²Graduate School of Medical Science, Kanazawa University, Takara-machi, Kanazawa 920-0934, ³Drug Safety and Metabolism, Otsuka Pharmaceutical Factory Inc., Tokushima, ⁴Cluster, Hiroshima Prefectural Institute of Industrial Science and Technology, Hiroshima, and ⁵Graduate School of Science, Hiroshima University, Hiroshima, Japan

A chimeric mouse line in which the liver could be replaced by more than 80% with human hepatocytes was recently established in Japan. Because the chimeric mouse produces human albumin (hAlb), replacement by human hepatocytes could be estimated by the hAlb concentration in the blood of the chimeric mice. In this study, we investigated human major drug metabolizing enzymes such as cytochrome P450 (CYP), UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) in the liver of the chimeric mice in terms of the mRNA, protein, and enzyme activity. Human mRNA and protein of CYP, UGT and SULT were expressed in the liver of the chimeric mice and the expression of each was correlated with the hAlb concentration in the blood. The enzyme activities such as diclofenac 4¢-hydroxylase activity, dexamethasone 6-hydroxylase activity, morphine 6-glucuronosyltransferase activity and estrone 3-sulfotransferase activity, which are specific to human but not to mice, were increased in a hAlb concentration-dependent manner. The chimeric mice with nearly 90% replacement by human hepatocytes demonstrated almost the same protein contents and drug metabolizing enzyme activity as those of the donor. It was confirmed that genomic DNA from the liver of the chimeric mice and that from the liver of the donor exhibited the same genotype. In conclusion, the chimeric mice exhibited a similarly efficient capacity of drug metabolism as humans.