The View From Here

William C Eckelman

Imaging Biomarkers

Molecular Imaging is being touted as an important biomarker in drug development.  Of the various imaging approaches that have shown promise, molecular targeting of low-density sites such as receptors, transporters, and some enzymes is of particular interest given the emphasis on targeted drug therapy by the pharmaceutical companies. The effort in pharmaceutical research to develop single target drugs is in concert with the ability of targeted imaging to monitor changes at a single site. Single gene diseases are relatively rare, but fortunately other diseases that are clearly not single gene diseases appear to be controlled by a single drug target. The current best examples for targeted drugs are tyrosine kinase inhibitors.

Of course, external imaging is important for noninvasive monitoring of anatomy, physiology, and high-density targets.  But imaging a low density site is closely related to the targeting of a drug to a single control point and has been the province of radiotracers that monitor changes in receptors, enzymes, tumor antigens, etc.  In the post genomic era of more abundant and better-annotated targets, there is a closer link between targeted imaging and drug development.

Much is to be learned in the design of targeted imaging agents, not the least of which is to develop a radiotracer that will have clinical impact.  If the imaging agent is developed in concert with the drug development there is a built in synergy that is expected to accelerate the drug development process and targeted imaging as well. In addition, many aspects of radiotracer design can be adapted from principles of drug design.

Several of the Editor’s Choices in 2006 addressed the issue of imaging in drug discovery.  This month’s review articles should further expand on those concepts toward developing biomarkers.

Enjoy!

William C Eckelman, PhD
Professor
Department of Radiology
University of California, San Diego
San Diego, CA