In Vivo Proof of Concept and Target Identification Using Small Molecule Stimulators of Brown Adipogenesis

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PROJECT SUMMARY/ABSTRACT Obesity has reached epidemic proportions in the U.S. and plays a major role in the development of type 2 diabetes, dyslipidemia, and cardiovascular disease. There remains a very significant need for better non- surgical treatments. While most current weight loss agents act by suppressing appetite, strategies that can safely enhance energy expenditure have the potential to effectively treat obesity. Brown adipose tissue (BAT) is a thermogenic tissue that uniquely expresses mitochondrial UnCoupling Protein-1 (UCP1). This protein dissipates, in a regulated fashion, the electrochemical gradient in the mitochondria of brown adipocytes as heat, and thus plays an important role in the maintenance of body temperature and energy balance in rodents and humans. BAT is a flexible tissue that normally enlarges or atrophies over time depending on environmental temperature. In many different rodent models, enhancement of BAT mass has convincingly been shown to lead to weight loss and diabetes resistance. While BAT was until recently thought to be effectively nonexistent in adult humans, data obtained in the past several years show that adults in fact have significant BAT and that this tissue is functional. It has been well established that a higher amount of active BAT in individuals is strongly correlated with leanness. Cold exposure in humans leads to increased BAT formation, thermogenesis, insulin sensitivity, and lipolysis, demonstrating that BAT can be recruited and lead to metabolic benefits. Moreover, the genetic locus most tightly linked with general obesity causes defective recruitment of new brown adipocytes. Until recently no brown adipocyte stem cell had been identified. We discovered human brown adipocyte progenitor cells that under appropriate conditions become fully functional brown adipocytes, with high levels of UCP1 and a very high metabolic rate. These cells are a unique tool that we used to develop an assay for identifying compounds with the capacity to recruit new BAT. We recently used this assay for high throughput screening and obtained several high quality hits with good activity, potency, and analogability. We have now created a series of novel analogs of the best hits with excellent activity and desirable physicochemical and ADME properties. In the proposed work, we aim to demonstrate in vivo proof of concept with this series of analogs by studying the compounds' pharmacokinetics and efficacy in a high quality mouse model of obesity and insulin resistance. We will also investigate the molecular mechanism of the compound series. If this work is successful we plan to advance to compound optimization, selection of a development candidate and backup, and generation of IND-enabling safety data.