Although biomarkers have been the essence of laboratory medicine since its inception, they are relatively new tools in the development of pharmaceutical compounds. The main utility of biomarkers for pharmaceutical companies has been in making drug development a more efficient and a cost-effective process. This is primarily the case because of the drastic and perhaps alarming increase seen in the development cost of new drugs in the last few decades, which has been accompanied by a decrease in the number of drugs obtaining regulatory approval. Furthermore, the Critical Path Initiative of the US Food and Drug Administration has identified biomarkers as important tools that may help to correct this imbalance. As will become apparent in the discussion below from 4 biomarker groups in leading companies, a large number of these biomarkers have been successfully used for internal decision-making, yet they may have never left the pharmaceutical space. At present, biomarkers, at a growing number, are being codeveloped along with the therapeutic compound as companion diagnostics; this is part of the Precision Medicine paradigm of delivering the right medicine to the right patient. This development will undoubtedly move biomarkers beyond the pharmaceutical space and into the clinical laboratory, thus influencing the practice of laboratory medicine. It will also become apparent that biomarkers developed by the pharmaceutical industry must be evaluated and validated using rigorous procedures. Clinical chemists can certainly assist in this endeavor. This may, in turn, lead to a larger number of useful biomarkers, not only in drug development but also in the clinical laboratory, as companion diagnostics. Biomarkers are extensively used throughout the process of drug development. In your experience, what are the most prominent or illuminating examples of how biomarkers directly impacted the development of a drug? Sanofi team: Biomarkers have played critical roles in the development and …