Pharmacological fMRI to Identify New Anxiolytics: A Human Bioassay

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DESCRIPTION (provided by applicant): The long-term objective of this application is to validate and optimize a human, in vivo bioassay for dentifying pharmaceutical compounds that are highly likely to have anti-anxiety properties. No new classes of anxiolytic medications have entered the marketplace in the past two decades, and the current drug development pathway suffers from many costly, time-consuming failures of compounds that enter Phase studies. The FDA has pointed to this "pipeline problem" as a significant challenge to drug development in the 21st century. Among their recommendations is the need to invent new drug development tools to enhance the movement along the "critical path" from Phase I to Phase III. This proposal outlines a series of studies aimed at determining whether functional magnetic resonance imaging (fMRI) in conjunction with the administration of pharmacological agents can be used as a human, in vivo bioassay at the juncture between Phase I and Phase II drug development for anxiety disorders. This predictive tool would be used to guide selection of lead compound(s) and optimal dosing, and would increase the prior probability of success in Phase II. In this application, we propose to examine the sensitivity, specificity, and reliability of a two emotion-processing tasks during blood oxygen dependent (BOLD) and arterial spin labeling (ASL) fMRI to probe the activation in amygdala, insula, and medial prefrontal cortex with standard anxiolytic and other psychopharmacological agents. A goal of this line of research is to be able to relate the degree of attenuation of the BOLD-fMRI signal in the target areas to the anxiolytic potential of a novel drug. The studies proposed here over 3 years are intended to establish the utility of these techniques for this purpose. Studies in healthy volunteers will optimize the procedures and paradigms and document their sensitivity and reliability (Aim #1). Dose-response studies in anxious subjects will examine sensitivity and specificity of the procedures to known anxiolytic agents in the contexts of acute dose-response (alprazolam and pregabalin) and subchronic (4 weeks of escitalopram) administration (Aim #2). Anxiety disorders are the most prevalent form of mental disorder in the United States, and are disabling to individuals and costly to society. Current pharmacotherapies fail to provide complete relief to 50% of patients. Enhancing the development of new treatments for anxiety is a public health priority. The projects proposed in this application have the potential to achieve this important aim.