Promises of biomarkers in drug development--a reality check.

Biomarkers have been a buzz word in drug development for the last 5 years. But where do we stand now? This perspective article will demonstrate to which extent biomarkers have impacted drug development and the use of drugs. In particular, the different types of biomarkers, their identification, validation and use in different phases of drug development from drug discovery, to approval, to clinical application will be discussed as well as the state-of-the-art biomarker technologies and promising future methods. The high interest in biomarkers has generated the need for development of new technologies and refinement of existing ones. Besides discussing their perspectives of applications, the present article also illustrates the future of biomarker development in terms of qualification for regulatory use and co-development.