Project Summary There is a world-wide “twin epidemic” of obesity and Type 2 Diabetes (T2D), with an urgent need to find new drug treatments that induce weight loss and correct the concurrent metabolic dysfunction, including hyperglycemia. Stable derivatives of the endogenous enteroendocrine hormone, glucagon-like peptide-1 (GLP1), are in clinical use for the treatment of T2D and have more recently also been approved for the treatment of obesity. However, efficacy of even the most advanced GLP1-based drugs remains modest compared to what can be achieved by bariatric surgery, an invasive procedure that carries considerable risks but results in rapid and sustained normalization of blood glucose and then body weight. The therapeutic effects of bariatric surgery appear to rely on the simultaneous, synergistic modulation of many different endogenous glucoregulatory hormones. Inspired by this observation, there are now ongoing efforts to combine GLP1 treatment with stimulation of other hormonal regulatory pathways of metabolism, which has been shown to further increase treatment efficacy. One promising pathway that could be co-targeted relies on the hormone peptide tyrosine tyrosine (PYY), which is physiologically co-secreted from intestinal endocrine cells together with GLP1. However, PYY is rapidly N- terminally cleaved in the blood stream by the ubiquitous enzyme dipeptidyl-peptidase-4 (DPP4). As a result of this truncation, PYY loses its ability to stimulate one of its targets, the neuropeptide Y1 receptor (NPY1R) which mediates the hormone’s beneficial effects on islet integrity, insulin production, and maintenance of glucose homeostasis. While truncated PYY maintains its ability to stimulate a complementary target, the anorexic NPY2R in the brain, its therapeutic promise is diminished given the loss of concomitant NPY1R agonism. In phase 1 studies leading to the current proposal, we have been able, for the first time, to N-terminally modify PYY in a way that eliminates susceptibility to DPP4 and fully preserves this peptide’s ability to stimulate both NPY1Rs and NPY2Rs. The main goal of the current phase 2 proposal is to take the next steps to transform this stabilized NPY1R/NPY2R dual agonist into a drug, which requires further optimization to enable once-daily dosing (Aim 1) and demonstrating efficacy in protecting islet function and in reducing obesity in mouse models (Aim 2). These studies will set the stage for us to subsequently apply for IND-enabling studies. Such studies would be to pursue further development into a dual NPY1R/NPY2R companion drug, one that can be applied together with GLP1-based as well as related treatments for enhancing the treatment of diabesity. In complementary experiments, we will also explore integrating PYY functionality into recently reported monomolecular multi-agonists that are designed to, in addition to the GLP1R, simultaneously activate distinct receptors for one or two other, synergistic hormones (Aim 3). T...