Discovery of alpha4beta2 Nicotinic Receptor Antagonists as Alcohol Abuse Medications

项目总结

PROJECT SUMMARY Alcohol addiction and disorders associated to excessive alcohol use are a serious public health problem in the United States and in other parts of the world. Current pharmacotherapies for the treatment of these disorders show limited efficacy. Preclinical and clinical findings point to nicotinic acetylcholine receptors (nAChRs) as an alternative, promising target for the development of novel and effective medications. However, it is unclear which specific nAChR subtypes serve as mediators of the rewarding effects of alcohol due, in part, to the complexity of the different possible combinations of the subunits that compose nAChRs and the lack of potent and selective ligands. Using combinatorial libraries, scaffold ranking and position scanning strategies, Assuage Pharmaceuticals, in collaboration with Torrey Pines Institute for Molecular Studies has discovered new scaffolds that have produced high affinity nAChR antagonists with exquisite selectivity for 42 nAChRs over 34 nAChRs, with respect to both binding affinity and in vitro functional activity. When tested in rats, one lead compound, TPI-202 as well as varenicline (a partial agonist of 42 nAChRs), but not 34 nAChR directed ligands, attenuated both alcohol- and nicotine-taking behaviors in a paradigm in which the two reinforcers were concurrently available. The 34 nAChR directed ligands were only effective in reducing nicotine self- administration. These initial findings led us to hypothesize that 42 nAChRs may serve as a viable target for developing pharmacotherapies to treat alcohol dependence. To verify this hypothesis, here we propose to use the Assuage compounds to examine whether novel, high affinity and selective 42 nAChR antagonists are effective in reducing important aspects of alcohol addiction including excessive alcohol intake and vulnerability to relapse. To accomplish this objective two specific aims have been proposed. The purpose of Specific Aim 1 is to (A) re-synthesize selective 42 nAChR compounds (TPI-202, -211, -412, and -421) and (B) determine in vitro functional activities prior to in vivo testing. Specific Aim 2 is aimed at testing the in vivo efficacy of these compounds. It will determine whether the selective 42 antagonists block (A) both operant and excessive home cage alcohol drinking and (B) relapse into alcohol seeking as assessed by both cue-induced and stress- induced reinstatement paradigms. We expect this multidisciplinary proposal to identify novel pharmacological tools that can be optimized in a future Phase II application, and ultimately to be used as medications for excessive alcohol use and dependence.