oa Editorial [Hot Topic:The Role of Radiopharmaceuticals in Drug Discovery (Guest Editors: Dr. Kalevi Kairemo and Dr. Kim Bergstrom)]

In this first thematic issue of Current Radiopharmaceuticals, the contributors have covered in great detail articles relating to the drug development process within the emphasis of the journal scope. Radionuclide imaging together with other non-invasive imaging techniques have found a prominent place in the whole drug discovery and development process. The application of imaging has the potential to alter the direction of the development process. The fundamental questions to address are when in the development timeline do you use these imaging techniques and what is the current utilization of these imaging technologies? Novel ‘imaging’ targets may have uncertain relationship to specific disease states. Acceptable target is of little value if its action cannot be modulated by therapeutics. Imaging is a perfect method to assess these target biology questions. Functional imaging endpoints can be used to evaluate target effects in normal and diseased models, in different species, and in the initial clinical studies. The longitudinal results from functional imaging can be extremely valuable in the evaluation of data from early clinical trials. The translational potential of functional imaging techniques is most evident. The uncertainty in potential drug candidates for example the efficacy and toxicity can be quickly addressed to determine the course of action. A preclinical imaging study may produce quantitative results which can answer these types of translational questions. Interest in functional imaging techniques has been motivated especially by Food and Drug Administration (FDA) exploratory Investigational New Drug (xIND) guidelines. Big Pharma has made substantial investments in imaging centers throughout the world to assist in the drug development process. Especially in the area of oncology research by applying radionuclide imaging techniques to determine the optimal protocol in early clinical trials. It seems evident that non-invasive imaging and especially radionuclide techniques will see increasing use in the drug discovery and development process. In-house imaging resources are increasing together with Contract Research Organisation (CRO) services. The ideas for these articles in this issue originated from two symposia held in December 2006: one in Geneva organized by GE Healthcare and another in Copenhagen, organized by Encorium and Imanext. These Symposia were dedicated to Imaging in the Drug Development Process. Similarly, The World Pharmaceutical Congress held in June 2007 in Philadelphia had a dedicated two-day symposium for ‘first-in-human’ phase 0 trial and microdosing studies. All these activities demonstrate that imaging will be a keynote figure in constructing new pharmaceuticals, already recognized by authorities. In this issue regulatory aspects have been reviewed both from the EU (Salvadori) and US perspectives (VanBroncklin). It is hard to imagine future neuropsychiatric pharmaceuticals without any imaging data and is reviewed explicitly by (Parsey et al.). The receptor occupancy studies and brain receptor quantification are an essential part in lead candidate selection (Seo et al.). Cancer drugs are often chosen for further development according to their tumor targeting abilities. Imaging techniques usually characterize tumor tissue in a different manner; however, radionuclide methods are most effective in the studies of pharmacodynamics and pharmacokinetic models. In this issue the role of systems biology has been reviewed in the development of cancer drugs (Mitrasinovic and Mihajlovic). Drug delivery systems couple the other imaging modalities (e.g. magnetic resonance imaging (MRI), ultrasound (US) and optical) to functional imaging modalities may find application in tumor targeting compounds (Kairemo et al.). Bioengineered chamelid antibodies (nanobodies) are a good example of using radionuclide methods in targeted nanoparticle systems, and possibly in cancer drug applications (Cortez-Retamozo et al.). Anti-inflammatory and antibiotic drugs are a major group of pharmaceuticals, where tissue targeting maybe of importance. These compounds have been reviewed by (Laverman et al.) in this issue. New possibilities have been developed to facilitate the drug development process, such as exploratory IND and microdosing. The concept of microdosing was originally linked to accelerator mass spectrometry (AMS), but criteria can be fulfilled with positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging studies. Hopefully, this first issue of Current Radiopharmaceuticals will help the pharmaceutical industry to interact with the functional imaging community. Today, radiopharmaceuticals are a prerequisite for this communication; we hope that Current Radiopharmaceuticals serves as a good forum.