Clinical cancer investigation is performed throughclinical trials. Development and measurement ofclinical efficacy of new target-based agents differsfrom classic cytotoxic drugs. Whereas the aim ofchemotherapy drugs is to destroy tumoral cells,new agents try to inhibit cell profileration without aclear tumor shrinkage. The main endpoint forphase I trials is to determine the optimal biologicalresponse with the least toxicity; oncopharmacogenomicstudies must be performed in tumoral biopsiesto assess the target inhibition. Time to progressionand biological activity are the endpoints forphase II studies. Finally, phase III trials will determineoverall survival