The 2010 US FDA-Drug Industry Association (DIA) Pharmacogenomics Workshop, the 
fifth in a series of meetings that begun in 2002, brought together 
multidisciplinary experts from regulatory authorities, medical research, 
healthcare and drug development. This article summarizes the 'Designing 
Pharmacogenomic Studies to be Fit for Purpose' track in which considerations 
regarding the use of retrospective and prospective studies were examined in 
relation to their ability to influence treatment decisions and labeling for 
drugs. The aim of the session, using real-world examples (KRAS/panitumumab and 
HLA-B*5701/abacavir), was to identify good scientific principles that would 
guide the design of studies to identify subgroups of responders during 
development programs (including marketed drugs), which could subsequently be 
used to guide treatment decisions.