In vitro teratology.

The purpose of this conference was to reevaluate the need for and use of in vitro teratology assays; to examine the validation process for in vitro tests; and to discuss progress in the validation of in vitro teratology screens. Participants enthusiastically supported further development of short-term in vivo and in vitro systems both as prescreens for developmental toxicity and as experimental systems to explore mechanisms of action of toxicants. The group strongly endorsed the development of an updated reference list ("gold standard") of known developmental toxicants and nontoxicants as essential to further progress in developing and validating prescreening efforts. Independently, an expert group should further evaluate the performance characteristics for a validated prescreen. The limits of usefulness of prescreens for product development, regulatory use, and mechanistic investigations need to be clearly defined. Finally, too few in vitro teratology prescreens have been evaluated under multiple-laboratory conditions with common, agreed-upon test agents to draw firm conclusions regarding the merit and reproducibility of in vitro teratology prescreens. There was general agreement regarding the need to move several of the assays further along the validation pathway, at least using a short list of reference compounds.