Recent statistics indicate that the attrition rates during drug development remain high. Lack of clinical efficacy has meanwhile become the most frequent cause for discontinuation of a drug development program. Consequently, attrition rates are highest in clinical Phase II, which usually includes the first evidence for pharmacodynamic action of the compound or, proof of concept. Interestingly, attrition is approximately 60-70% across a variety of therapeutic areas, including the central nervous system (where predictivity of animal models is usually low) and cardiovascular medicine (where animal models are considered to be more predictive). Obviously, the translation of animal data into clinical benefit remains suboptimal.