Safety and regulatory requirements and challenge for CNS drug development

Regulations, costs, and acceptance of risks (Enna and Williams, 2009) along with adherence to the phased process of clinical drug development have caused the task or flow of performances of regulatory nonclinical safety assessment studies to be considered as occurring in three sequential parts (once the initial candidate screening and lead selection phase are complete). These are the studies (1) done to allow initiation of clinical trials, (2) done to allow initiation of clinical trials sufficient to support a marketing application, and (3) required to allow a marketing application. Employment of new technologies, such as in vivo imaging has aided, to both help understand specificity of delivery to target tissue sites and mechanisms of both action and undesirable actions.