ABSTRACT Extensive studies indicate that drugs targeting key receptor systems in the brain that regulate dopamine may provide therapies for substance use disorders (SUDs). This underlies a treatment strategy that is encouraged by this RFA-DA-020-025. The ghrelin receptor GSHR1a is a G-protein coupled receptor that modulates dopamine signaling. It is already considered a potential therapeutic target for the treatment of eating disorders, alcohol abuse, and by extension is also an excellent candidate for treating cocaine addiction. Our hypothesis is that ghrelin receptor biased-drugs, particularly analogs of the recently discovered lead compound NCATS- 4955, can selectively modulate G proteins and βarrestin signaling at the GHSR1a in a manner that blocks the addictive effects of cocaine while eliminating many unwanted side effects of ghrelin receptor therapy. The long- term goals in validating this are twofold. Our first objective is to demonstrate that antagonism of the GHSR1a βarrestin signaling arm offers a much superior drug target for pharmacotherapy of cocaine use disorder than the blanket antagonism of GHSR1a, as minimizing the GHSR1a therapeutic target size will minimize treatment side effects. We will demonstrate that this functional antagonism can be accomplished using NCATS-4955 lead compounds. Our second objective is to establish the NCATS-4955 drug series as a valid in vivo option for cocaine abuse treatment, thus providing a new, pharmacological strategy for addressing cocaine abuse disorder. Testing of our hypothesis and pursuit of these objectives for this grant proposal will be accomplished through completion of the following specific aims. Aim (1) is to determine a comprehensive signaling profile of the novel lead series NCATS-4955 at the ghrelin receptor. The strategy is to develop and use a panel of in vitro and in cellulo biochemical assays to compare and contrast between an NCATS-4955 series lead compound, ghrelin peptide, and known unbiased GHSR1a agonists and antagonists at GHSR1a their receptor binding, signaling through G proteins, and signaling through the arrestin pathway. Aim (2) is to provide in mice an in vivo behavioral profile of an NCATS-4955 series lead compound that measures efficacy for treating cocaine use disorder, and using genetically modified mice provides a measure of ghrelin receptor target validity. The strategy is to assess the effect of an NCATS-4955 series lead compound on locomotor and condition place preference (CPP) mediated behaviors in wild type C57BL/6J mice exposed to cocaine, and correspondingly in mice in which the ghrelin receptor has been knocked out, or is defective in supporting either G protein or arrestin signaling. The druggable NCATS-4955 series will produce a GHSR1 biased signaling profile effective at ameliorating the consequences of cocaine use disorder and potentially be more broadly applicable against other SUDs. The NCATS-4955 series holds promise either as valuable tool compounds in addiction research or as a basis for new SUD pharmacotherapeutics. This grant will support their development towards an Investigational New Drug Application (IND).

PROJECT NARRATIVE Cocaine dependence or abuse is a common type of substance use disorder (SUD), and a potential means to treat it relies on blocking all signaling of the brain ghrelin receptor with an antagonist drug. Such an all-inclusive, unfocused ghrelin receptor targeting, however, could lead to serious side effects because the receptor regulates many different and important physiological processes in addition to addiction related ones. We have recently discovered a new drug class that helps focus ghrelin receptor blockade on the portion of receptor signaling enabling addictive behaviors, and this project will facilitate development of that drug class into a cocaine abuse therapy by resolving the responsible portion of the ghrelin receptor signaling target.