Biomedical imaging in the safety evaluation of new drugs.

Toxicology accounts for approximately one-third of attrition in new drug development and is a major concern in the pharmaceutical industry. This paper reviews the role of biomedical imaging in the safety evaluation of new candidate drugs. Ex vivo high-resolution three-dimensional imaging of specimens can provide a quick overview of the specimens. Volumetric measurements of tissue structures and lesions can be made with higher precision and reproducibility than histology approaches. As opposed to histology, in vivo animal imaging permits longitudinal studies of the same animals over an extended period of time, with individual animals serving as their own control. Therefore, the number of animals required for a study can be significantly reduced and the intra-subject variability is minimized. Repeated in vivo imaging allows monitoring of the occurrence and progression, or regression, of various structural and functional abnormalities. Compared with other biological assays, imaging can provide anatomically specific information about tissue abnormality. Imaging offers the opportunity to carry forward the same methodology in animal experiments into human studies and has an important role in clinical trials when other safety biomarkers for early toxicities are not available.