Novel Functionally-Selective Serotonin 5HT2 Drugs for Amphetamines Abuse/Disorder

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ABSTRACT: This research is to advance novel internationally-patented phenylaminotetralin (PAT) analogs as functionally-selective serotonin 5HT2 receptor-based drug development candidates to treat amphetamine and methamphetamine addiction and drug-induced psychotic disorders. Activation of brain 5HT2C receptors or antagonism/inverse agonism of 5HT2A receptors attenuates psychostimulant effects in rodents. With the exception of PATs, all compounds reported in the literature that activate 5HT2C receptors also activate 5HT2A and/or 5HT2B receptors-unfortunately, activation of brain 5HT2A receptors produces psychotomimetic effects and activation of peripheral 5HT2B receptors produces cardiac valvulopathy and pulmonary hypertension. Conversely, co-antagonism of 5HTC and 5HT2A receptors contributes to weight-gain associated with antipsychotic drugs. PATs uniquely demonstrate 5HT2C receptor agonism simultaneously with 5HT2A and 5HT2B inverse agonism-this 5HT2 functional selectivity translates in vivo to therapeutic activity in behavioral models of amphetamine/methamphetamine addiction and induced psychoses, with no overt adverse effects (including, weight-gain) after peripheral administration in rodents. This novel 5HT2 functionally-selective single molecule approach is an advance over approaches targeting dopamine neuronal proteins that have proven to be sub-optimal for drug addiction pharmacotherapy, while multiple or bi-valent serotonin 5HT2 compounds pose numerous ADMET limitations. Based on a preliminary in vivo structure-activity relationship, we will optimize the PAT molecular scaffold for activity to attenuate amphetamine/methamphetamine addiction by synthesis of at least 50 novel single-enantiomer PATs with modifications to the (C2) amine, (C4) pendant phenyl, and tetrahydronaphthyl moieties. In vitro pharmacology studies include determination of PAT 5HT2A, 2B, and 2C affinity (Ki) and function (EC50/IC50). PAT docking studies using 5HT2 receptor molecular models will characterize PAT-5HT2 molecular interactions for design of additional target molecules. Modeling of 5HT2 GPCRs is based on homology to the structure of the human adrenergic ¿2 GPCR, an innovative advance over previous models that used homology to the bovine rhodopsin GPCR. Potent and efficacious PAT 5HT2C agonists with 5HT2A/2B inverse agonism are promoted to preclinical studies to evaluate pharmacotherapeutic efficacy in vivo to attenuate amphetamine and methamphetamine addiction and drug-induced psychotic disorders. A systematic behavioral analysis of PATs is undertaken to provide information on pharmacokinetic variables, functional activity in the 5HT2 system regarding 5HT2A inverse agonism vs. 5HT2C agonism, and attenuation of drug-induced psychotic disorders. Studies include using amphetamine and methamphetamine drug discrimination and self-administration procedures to validate 5HT2 receptor systems as targets for stimulant pharmacotherapies and assess attenuation of the reinforcing effects of these stimulants in a variety of behavioral procedures designed to mimic critical aspects of an addiction-like behavioral phenotype.