Applications of emerging technologies in toxicology and safety assessment

Standardized protocols for repeat-dose toxicity studies have many advantages, including experimental redundancy (i.e., the use of more than a single experimental approach in the assessment of a given organ or tissue) and evaluation of numerous tissues to ensure detection of adverse effects, as well as the ability to develop robust historical control databases. However, traditional toxicology study designs may not adequately address questions of a mechanistic nature that might provide insights on whether particular toxicology findings in animals are relevant to humans. Such questions may be more readily answered using mechanism-based technologies such as toxicogenomics, proteomics, or metabonomics. Such newer approaches may permit, for example, the detailed assessment of the transcriptional profile differences that distinguish a normal healthy tissue from a diseased or damaged tissue. The resultant information can be used to elucidate the mechanism and accompanying biomarkers for toxicity, as well as to identify potential molecular targets for therapeutic intervention by drugs. Despite their conceptual appeal, the use of emerging technologies in toxicology is accompanied by significant challenges. For example, toxicogenomic assessments entail the generation of large amounts of bioinformatic data that must be interpretable for their full value to be realized. Also, none of these newer approaches have established uniformly acceptable quality standards (e.g., such as may be defined in interlaboratory validation studies) or a track record of achievement in guiding regulatory decisions. As a result, newer techniques, at least for the present, are more likely to be focused on mechanistic questions with compounds of known toxicity (either positive indicator compounds or "failed" pharmaceutical candidates). If the use of a nascent or emerging technology is contemplated for mechanistic studies of pharmaceutical compounds later in preregistration development, it will be crucial for toxicologists to engage their regulatory colleagues in discussions at an early stage to ensure closer alignment in thought. The successful use of emerging technologies to address toxicology issues will require a close partnership between industry and regulatory agencies.