Prospective analysis of a completed or on-going phase 3 oncology drug study to assess device effectiveness in the context of drug-diagnostic co-development. The Vectibix-KRAS experience in colorectal cancer will be used as an example. Also considered will be examples of prospective drug-diagnostic designs either with a clear biomarker hypothesis or when a place-holder is desired for one due to a lag in diagnostic development. A flexible regulatory pathway in these areas will impact the ability to fulfill the promise of personalized medicine.