Novel metabolic pathway for halogenated drugs of abuse - PROJECT SUMMARY New psychoactive substances (NPS) are a structurally and functionally diverse group of psychotropic molecules being sold worldwide as legal substitutes for controlled drugs. Over the past decade, NPS production and use has reached worldwide epidemic levels due to high potency, low manufacturing costs, and ambiguous legal status. By the end of 2023, synthetic cannabinoid receptor agonists (SCRA) comprised the majority of first reported NPSs and were the second most detected NPS. Use of NPSs causes hepatotoxicity, respiratory depression, cardiotoxicity, fertility issues, and psychiatric effects posing significant health and economic burdens on society. Effective responses are hampered by the rapid evolution of NPSs that introduce unknown toxic risks and avoid the identification and assessment of the scope of the problem. A common drug development strategy involves halogenation to improve pharmacodynamic and pharmacokinetic properties and is widespread among all NPS classes, i.e. sedatives, dissociatives, hallucinogens, stimulants, cannabinoids, and synthetic opioids. Favorable drug properties due to halogens are undone by metabolism. Cytochromes P450 (CYPs) account for ~75% of drug reactions including dehalogenations. For alkyl halides, CYP oxidations generate an alcohol that is oxidized into a carboxylic acid. These collective metabolic transformations decrease NPS binding to targeted biological receptors and greatly facilitate elimination. Thus, the initial dehalogenation step initiates a major detoxification pathway for NPSs. CYPs are not alone in this role. Based on research by us and others, SCRAs AM2201 and 5F-APINACA undergo novel hydrolytic dehalogenations that are mechanistically distinct from CYP- mediated metabolism. SCRAs are an ideal NPSs to study this pathway given precedence for hydrolysis, accessibility to structurally diverse SCRAs, and dominance as an NPS of concern. Our central hypothesis is that alkyl halide hydrolysis is a significant unstudied SCRA metabolic pathway for detoxification. This hypothesis will be tested by two Aims. Aim 1 will investigate how SCRA head and tail groups impact alkyl halide hydrolyses and how those properties vary across humans and animal models for drugs of abuse. Aim 2 will determine the relative significance of CYPs and the hydrolase in SCRA dehalogenations. Completion of the studies will generate critical new knowledge to advance the field. NPS development outpaces the ability to use traditional approaches accessible to marketed drug workflows, and clinical studies are not ethical for drugs of abuse. Consequently, NPS surveillance and risk assessments rely heavily on indirect methodologies. Results from this study will validate and characterize novel dehalogenation pathways to improve the accuracy and quality of information gained from microsomal studies for inferring and extrapolating human health risks from SCRAs. Further, the hydrolase specificities likely include other NSPs, natural products, and pollutants so that these findings could induce a paradigm shift in our understanding of the metabolism of biologically active molecules.
