The International Life Sciences Institute's Role in the Evaluation of Alternative Methodologies for the Assessment of Carcinogenic Risk

The current approach for carcinogenicity testing usually incorporates a genetic toxicity screen, 14and 90day subchronic toxicity studies in rats and mice, toxicokinetic and disposition studies, and 2-yr chronic bioassays in rats and mice. The 2-yr bioassays are both time and resource intensive, and questions have been raised regarding the relevance of some of the carcinogenic responses in rodents for human risk assessment. At the 1996 meeting of the International Conference on Harmonization (ICH) Expert Working Group on Safety, the international pharmaceutical and regulatory communities acknowledged the limited utility of certain aspects of conventional rodent studies and proposed a new scheme for carcinogenicity testing for pharmaceuticals (Fed. Reg. 61: 43298-43300). The proposed strategy incorporates a conventional bioassay in a single rodent species and the option to conduct a shortor medium-term in vivo assay with a tumor end point in place of the second species bioassay. The available alternative models include initiation-promotion assays, newborn rodent assays, and several transgenic mouse assays that have recently been developed. The willingness of the regulatory authorities to accept data from these new experimental approaches as part of the safety assessment process for pharmaceuticals has stimulated international interest in gaining experience and a greater understanding of the strengths and limitations of the specific models. These new methods have not been fully characterized, and the scientific community is considering their most appropriate application(s). The Alternatives to Carcinogenicity Testing Technical Committee was formed under the auspices of the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute to assist in the further evaluation of these new experimental approaches for carcinogenicity testing. Through the efforts of this committee, which is composed of interested scientists from industry, government, and academia, an international collaborative research program was established. The goals of this research program, currently being conducted in more than 45 laboratories in the United States, Europe, and Japan, are: to expand the data base on several of these new test methods; to enhance the understanding of the specific responses of each model to compounds representing a range of chemical and pharmaceuticalltherapeutic classes, including various modes of toxic and carcinogenic action; to evaluate potential criteria that should be considered in the selection of one model over another for a particular