Biomarkers in oncology drug development: rescuers or troublemakers?

Oncology is considered as the pioneer indication for the clinical application of molecular biomarkers. Newly developed targeted anticancer therapies call for the implementation of molecular biomarker strategies but even novel cytotoxic treatments use biomarkers for the assessment of efficacy and toxicity. Biomarkers may play several roles in the progression of a drug from research to personalised medicine. In particular biomarkers are used to understand the mechanism of action of a drug, monitor the modulation of the intended target, assess efficacy and safety, adapt dosing and schedule, select patients and prognosticate the clinical outcome. Nowadays, the use of biomarkers in oncology is still challenged as only a limited number of oncology drugs on the market have a companion biomarker test to be mandatorily performed before treatment. This is in contradiction with the current major investment the pharmaceutical sector is devoting to biomarker identification and development. What are the measurable milestones and outcomes of these investments? How does biomarker development contribute to reaching the ultimate goal of finding the right molecules for the right targets at the right doses and schedules for the right patients? This review provides a critical overview of recent salient achievements in the identification and development of biomarkers.