Some imminent but overlooked preanalytical and analytical challenges currently facing biomarkers and companion diagnostics.

An incredibly high failure rate in the pharmaceutical industry has positioned personalized medicine with its prerequisite drug-diagnostic codevelopment, commonly known as companion diagnostics (CDx), in the frontline as an potential rescuer. This hopefulness is potentiated by the recent major advances and competitiveness in molecular diagnostics, making laboratory tests widely accessible at affordable prices. If executed correctly, biomarkers and CDx can potentially help the drug industry by enhancing the probability of success and possibly accelerating time to market; help the diagnostics industry develop tests utilizing precious, clinically annotated human samples; and, more importantly, benefit patients by supporting accurate diagnosis and selection of the most efficacious and least toxic therapies. However, this spectacular road is not yet paved, and it faces an enormous number of challenges. This paper will list these challenges and highlight some critical problems with representative examples of imminent but still overlooked preanalytical and analytical variables that can defeat the whole purpose of biomarkers and CDx and mislead drug developers and clinicians. The paper will provide some suggestions for mitigation.