The complexity of drug discovery faces many challenges; principally, the failure of drug candidates during the development process as a result of adverse effects or lack of efficacy.  A key reason for this high attrition rate is that we are only just beginning to understand the complexity of the response(s) from a biological system to perturbations, such as a disease state or drug treatment. Subsequently, a deeper insight into the molecular mechanisms underlying both disease processes and drug action will ultimately contribute to increased productivity through the drug discovery process.