The contemporary drug development process: advances and challenges in preclinical and clinical development.

We are in a new era of drug discovery, in which it is feasible to develop therapeutic agents targeted at a particular protein or biological activity in a living cell. This has been made possible by major advances in our understanding of cell and molecular biology, epitomized by the 2001 Nobel prize award for Physiology or Medicine to Lee Hartwell, Tim Hunt and Paul Nurse, who were recognised for their work on key regulators of the cell cycle. Technological advances have also played a decisive role, leading to the sequencing of the human genome and increased throughput at many stages of the drug discovery and development process. For example, developments in high throughput screening, structural biology and microarray technology are increasing the speed of drug discovery. In this chapter we focus on the long, and often difficult, pathway which leads from identification of a hit in a screen to regulatory approval of a drug for disease treatment. The emphasis in this chapter is on the development of anticancer drugs, as this is our own area of expertise and also because cancer is a disease in which the cell cycle is already a major target for therapeutic intervention. However, many of the concepts, approaches and issues are generally common to other therapeutic areas.