Biomarkers


Figure 1


Illustration of personalised medicine reflecting deeper understanding of disease- and patient-heterogeneity. [Sources: Adapted from Erasmus, MC at University Medical Center


Rotterdam in Genomic Variation: The Search for Our Past and Our Future by Chakma Justin (Journal of Young Investigators. 2009. Volume 16)]


information providing this understanding and dif- ferentiation. The personalised medicine concept is shown in Figure 1.


Definition: A biomarker is “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a thera- peutic intervention”1. While this article focuses on protein biomarkers, many other types of biomark- ers are being used (including RNA, DNA, metabo- lites, but also modalities such as medical imaging, verbal tests, physical assessment, etc).


Biomarker versus diagnostic: The terms diagnos- tic or diagnostic testing are often used inter- changeably with biomarker and biomarker test- ing. However, while all diagnostics are biomark-


BIOMARKER Prognostic Diagnostic Predictive TEST BRCA1 and BRCA2 Serum PSA K-RAS DISEASE Breast Cancer Prostate Cancer Colorectal Cancer Table 1: Personalised medicine for disease management – current examples 20


ers, the reverse is not true: what is commonly referred to as a ‘biomarker’ most often only has the potential to become a diagnostic. In other words, most so-called biomarkers are still in an exploratory phase, and are thus assayed by research-grade tests, requiring laboratories with highly trained specialists. On the other hand, diagnostic tests are fully developed and highly validated ‘kit’ products that are more straightfor- ward to use. Diagnostic kits can therefore be used in doctor’s offices, hospitals, and even by the patient as over-the-counter products, as is the case with home pregnancy tests. This article focuses specifically on biomarkers in the develop- mental phase, and in particular on markers where the analyte is a protein.


Value of biomarkers: Biomarkers are increasingly viewed as a key adjuvant to drug discovery and de- velopment to mitigate the low success rate and high cost the pharmaceutical industry is experienc- ing. The role of biomarkers spans all aspects of drug discovery and development. Biomarkers may be used as tools for target discovery, early target assessment, for evaluation of a medicine’s mecha- nism of action, for dose determination, for predic- tion of drug effects (efficacy as well as adverse reaction), for patient selection/stratification, for


Drug Discovery World Winter 2010/11


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