Development of Novel Therapies for Methamphetamine Abuse

Methamphetamine (METH) abuse continues to escalate and effective treatments are not currently available. METH interacts with the vesicular monoamine transporter-2 (VMAT2), promoting both dopamine (DA) release into the cytosol and reversal of the DA transporter to increase extracellular DA concentrations, which is thought to be associated with its abuse liability. The overall objective of this project is to provide a clinical candidate for the treatment of METH abuse. Recently, we identified a novel small molecule (GZ-793A), which potently and selectively inhibits DA uptake by VMAT2, inhibits METH-evoked DA release from synaptic striatal vesicles and slices, and exhibits selectivity does not interact with nicotinic receptors or DA transporters. Off-target evaluation at a cadre of neurotransmitter-related, steroid and ion channel sites, second messenger, prostaglandin, growth factor and hormones, brain/gut peptides and enzymes revealed outstanding selectivity. Translation to whole animals models revealed that GZ-793A specifically decreases METH self-administration without altering responding for sucrose, does not produce tolerance to the decrease in METH selfadministration upon repeated administration, and decreases METH seeking in the cue-induced reinstatement. Acute GZ793A pretreatment also protects against the neurotoxic effects of METH as measured by striatal DA depletion. Although the physicochemical properties of GZ-793A are favorable in terms of druggability, GZ-793A has only 2-3% oral bioavailability, likely due to the presence of the hydroxyl functionalities in the molecule which are likely sites for high first-pass metabolism. Thus, new optimized analogs of GZ-793A are the focus of the current application with the goal of identifying analogs with the required pharmacological properties, druggability, increased oral bioavailability, and acceptable pharmacokinetic profile. Compounds with these characteristics would be high value preclinical candidates for advancement toward clinical trials as treatments for METH abuse. Thus, we propose to expand our existing molecular library of analogs by performing the final steps of optimization of GZ-793A to identify a high value preclinical candidate as a potential therapeutics for METH abuse. In future work, the best candidate will undergo comprehensive toxicological evaluation for subsequent preparation of an Investigational New Drug application to the FDA as a proposed treatment for methamphetamine abuse.