Abstract
In vitro techniques represent tools that the toxicologist can utilize at various stages of drug development to design and select compounds to perform specialized evaluations and to address preclinical or clinical issues that may arise. The use of in vitro technologies contributes to the scientific quality and economy of the safety assessment process as well as to the toxicologists' commitment to the four Rs of reduction, refinement, replacement, and responsibility. In vitro testing programs are facilitated by applying techniques established in other disciplines via trained personnel organized in specific experimental or investigative units. Fulfillment of scientific criteria of predictability, identity, compensatory factors, and mechanisms of injury will determine to what extent in vitro methods are incorporated into the safety assessment process. Key to the contribution of in vitro techniques to toxicology, now and in the future, is a vision and commitment to scientific excellence in the safety assessment process. This commitment requires the continual influx of state-of-the-art technology (both in vitro and in vivo), and active communication among the industrial, regulatory, and academic communities. The commitment to scientific excellence in toxicology will ensure the evolution of more relevant and efficient models of safety assessment. In vitro technologies have the potential to play an increasingly important role in this evolutionary process.