1
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Yuan Y, Xu T, Huang Y, Shi J. Strategies for developing μ opioid receptor agonists with reduced adverse effects. Bioorg Chem 2024; 149:107507. [PMID: 38850778 DOI: 10.1016/j.bioorg.2024.107507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/02/2024] [Accepted: 05/28/2024] [Indexed: 06/10/2024]
Abstract
Opioids are currently the most effective and widely used painkillers in the world. Unfortunately, the clinical use of opioid analgesics is limited by serious adverse effects. Many researchers have been working on designing and optimizing structures in search of novel μ opioid receptor(MOR) agonists with improved analgesic activity and reduced incidence of adverse effects. There are many strategies to develop MOR drugs, mainly focusing on new low efficacy agonists (potentially G protein biased agonists), MOR agonists acting on different Gα subtype, targeting opioid receptors in the periphery, acting on multiple opioid receptor, and targeting allosteric sites of opioid receptors, and others. This review summarizes the design methods, clinical applications, and structure-activity relationships of small-molecule agonists for MOR based on these different design strategies, providing ideas for the development of safer novel opioid ligands with therapeutic potential.
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Affiliation(s)
- Yan Yuan
- College of Life Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 611756, China
| | - Ting Xu
- Department of Anesthesiology, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Yu Huang
- College of Life Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 611756, China
| | - Jianyou Shi
- Department of Pharmacy, Personalized Drug Therapy Key Laboratory of Sichuan Province, Sichuan Academy of Medical Science & Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu 610072, China.
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2
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De Vrieze LM, Walton SE, Pottie E, Papsun D, Logan BK, Krotulski AJ, Stove CP, Vandeputte MM. In vitro structure-activity relationships and forensic case series of emerging 2-benzylbenzimidazole 'nitazene' opioids. Arch Toxicol 2024:10.1007/s00204-024-03774-7. [PMID: 38877156 DOI: 10.1007/s00204-024-03774-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 04/24/2024] [Indexed: 06/16/2024]
Abstract
2-Benzylbenzimidazole 'nitazene' opioids are presenting a growing threat to public health. Although various nitazenes were previously studied, systematic comparisons of the effects of different structural modifications to the 2-benzylbenzimidazole core structure on μ-opioid receptor (MOR) activity are limited. Here, we assessed in vitro structure-activity relationships of 9 previously uncharacterized nitazenes alongside known structural analogues. Specifically, we focused on MOR activation by 'ring' substituted analogues (i.e., N-pyrrolidino and N-piperidinyl modifications), 'desnitazene' analogues (lacking the 5-nitro group), and N-desethyl analogues. The results from two in vitro MOR activation assays (β-arrestin 2 recruitment and inhibition of cAMP accumulation) showed that 'ring' modifications overall yield highly active drugs. With the exception of 4'-OH analogues (which are metabolites), N-pyrrolidino substitutions were generally more favorable for MOR activation than N-piperidine substitutions. Furthermore, removal of the 5-nitro group on the benzimidazole ring consistently caused a pronounced decrease in potency. The N-desethyl modifications showed important MOR activity, and generally resulted in a slightly lowered potency than comparator nitazenes. Intriguingly, N-desethyl isotonitazene was the exception and was consistently more potent than isotonitazene. Complementing the in vitro findings and demonstrating the high harm potential associated with many of these compounds, we describe 85 forensic cases from North America and the United Kingdom involving etodesnitazene, N-desethyl etonitazene, N-desethyl isotonitazene, N-pyrrolidino metonitazene, and N-pyrrolidino protonitazene. The low-to-sub ng/mL blood concentrations observed in most cases underscore the drugs' high potencies. Taken together, by bridging pharmacology and case data, this study may aid to increase awareness and guide legislative and public health efforts.
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Affiliation(s)
- Liam M De Vrieze
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
| | - Sara E Walton
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, Willow Grove, PA, 19090, USA
| | - Eline Pottie
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
| | | | - Barry K Logan
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, Willow Grove, PA, 19090, USA
- NMS Labs, Horsham, PA, 19044, USA
| | - Alex J Krotulski
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, Willow Grove, PA, 19090, USA
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
| | - Marthe M Vandeputte
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
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3
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Kozell LB, Eshleman AJ, Wolfrum KM, Swanson TL, Bloom SH, Benware S, Schmachtenberg JL, Schutzer KA, Schutzer WE, Janowsky A, Abbas AI. Pharmacologic Characterization of Substituted Nitazenes at μ, κ, and Δ Opioid Receptors Suggests High Potential for Toxicity. J Pharmacol Exp Ther 2024; 389:219-228. [PMID: 38453524 PMCID: PMC11026150 DOI: 10.1124/jpet.123.002052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 02/22/2024] [Accepted: 02/27/2024] [Indexed: 03/09/2024] Open
Abstract
The benzimidazole opioids (substituted nitazenes) are highly potent μ opiod receptor (MOR) agonists with heroin- or fentanyl-like effects. These compounds have caused hospitalizations and fatal overdoses. We characterized the in vitro pharmacology and structure-activity relationships of 19 nitazenes with substitutions at three positions of the benzimidazole core. Affinities were assessed using agonist radioligand binding assays at human μ, κ, and Δ opioid receptors (MOR, KOR, and DOR, respectively) heterologously expressed in CHO cells. Notably, for MOR binding, nine substituted nitazenes had significantly higher affinities than fentanyl including N-pyrrolidino etonitazene, N-pyrrilidino isonitazene, and N-desethyl isotonitazene; 13 had subnanomolar affinities. Only metodesnitazene and flunitazene had significantly lower affinities than fentanyl. Affinities for the substituted nitazenes at KOR and DOR relative to MOR were 46- to 2580-fold and 180- to 1280-fold lower, respectively. Functional activities were assessed using [35S]GTPγS binding assays. Four nitazenes had subnanomolar potencies at MOR: N-pyrrolidino etonitazene, N-pyrrilidino isonitazene, N-pyrrilidino protonitazene and N-desethyl isotonitazene. Ten substituted nitazenes had significantly higher potencies than fentanyl. All tested nitazenes were full MOR agonists. Potencies at KOR and DOR relative to MOR were 7.3- to 7920-fold and 24- to 9400-fold lower, respectively. Thus, many of these compounds are high affinity/high potency MOR agonists with elevated potential to elicit toxicity and overdose at low doses. SIGNIFICANCE STATEMENT: Substituted nitazenes are a growing public health threat. Although the 19 nitazenes tested vary in their opioid receptor pharmacology, a number are very high affinity, high potency, and high efficacy compounds- higher than fentanyl. Their pharmacology suggests high potential for harm.
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Affiliation(s)
- Laura B Kozell
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Amy J Eshleman
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Katherine M Wolfrum
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Tracy L Swanson
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Shelley H Bloom
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Sheila Benware
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Jennifer L Schmachtenberg
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Kamryn A Schutzer
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - William E Schutzer
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Aaron Janowsky
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
| | - Atheir I Abbas
- VA Portland Health Care System (L.B.K., A.J.E., K.M.W., T.L.S., S.H.B., S.B., J.L.S., K.A.S., W.E.S., A.J., A.I.A.), Departments of Psychiatry (L.B.K., A.J.E., T.L.S., W.E.S., A.J., A.I.A.), and Behavioral Neuroscience (L.B.K., A.J., A.I.A.), Oregon Health and Science University, Portland, Oregon
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4
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Ververi C, Galletto M, Massano M, Alladio E, Vincenti M, Salomone A. Method development for the quantification of nine nitazene analogs and brorphine in Dried Blood Spots utilizing liquid chromatography - tandem mass spectrometry. J Pharm Biomed Anal 2024; 241:115975. [PMID: 38280237 DOI: 10.1016/j.jpba.2024.115975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 12/31/2023] [Accepted: 01/08/2024] [Indexed: 01/29/2024]
Abstract
The detection of nitazenes in biological fluids is increasingly needed as they are repeatedly reported in intoxication and overdose cases. A simple method for the quantification of low levels of nine nitazene analogs and brorphine in Dried Blood Spots (DBS) was developed and validated. 10 μL of spiked whole blood is deposited on a Capitainer®B card and allowed to dry. The spot is punched out, and extracted with 500 μL methanol:acetonitrile (3:1 v/v) added with 1.5 μL of fentanyl-D5 as the internal standard. After stirring, sonication, and centrifugation of the vial, the solvent is dried under nitrogen, the extract is reconstituted in 30 μL methanol, and 1 μL is injected into a UHPLC-MS/MS instrument. The method validation showed linear calibration in the 1-50 ng/mL range, LOD values ranging between 0.3 ng/mL (isotonitazene) and 0.5 ng/mL (brorphine), average CV% and bias% within 15 % and 10 % for all compounds, respectively. The matrix effect due to blood and filter paper components was within 85-115 % while recovery was between 15-20 %. Stability tests against time and temperature showed no significant variations for storage periods up to 28 days. Room temperature proved to represent the best samples storage conditions. UHPLC-MS/MS proved capable to reliably identify all target analytes at low concentration even in small specimen volumes, as those obtained from DBS cards, which in turn confirmed to be effective and sustainable micro-sampling devices. This procedure improves the efficiency of toxicological testing and provides an innovative approach for the identification of the nitazene class of illicit compounds.
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Affiliation(s)
| | | | - Marta Massano
- Department of Chemistry, University of Turin, Turin, Italy
| | | | - Marco Vincenti
- Department of Chemistry, University of Turin, Turin, Italy; Centro Regionale Antidoping, Orbassano, Turin, Italy
| | - Alberto Salomone
- Department of Chemistry, University of Turin, Turin, Italy; Centro Regionale Antidoping, Orbassano, Turin, Italy
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5
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Tsai MHM, Chen L, Baumann MH, Canals M, Javitch JA, Lane JR, Shi L. In Vitro Functional Profiling of Fentanyl and Nitazene Analogs at the μ-Opioid Receptor Reveals High Efficacy for Gi Protein Signaling. ACS Chem Neurosci 2024; 15:854-867. [PMID: 38345920 DOI: 10.1021/acschemneuro.3c00750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024] Open
Abstract
Novel synthetic opioids (NSOs), including both fentanyl and non-fentanyl analogs that act as μ-opioid receptor (MOR) agonists, are associated with serious intoxication and fatal overdose. Previous studies proposed that G-protein-biased MOR agonists are safer pain medications, while other evidence indicates that low intrinsic efficacy at MOR better explains the reduced opioid side effects. Here, we characterized the in vitro functional profiles of various NSOs at the MOR using adenylate cyclase inhibition and β-arrestin2 recruitment assays, in conjunction with the application of the receptor depletion approach. By fitting the concentration-response data to the operational model of agonism, we deduced the intrinsic efficacy and affinity for each opioid in the Gi protein signaling and β-arrestin2 recruitment pathways. Compared to the reference agonist [d-Ala2,N-MePhe4,Gly-ol5]enkephalin, we found that several fentanyl analogs were more efficacious at inhibiting cAMP production, whereas all fentanyl analogs were less efficacious at recruiting β-arrestin2. In contrast, the non-fentanyl 2-benzylbenzimidazole (i.e., nitazene) analogs were highly efficacious and potent in both the cAMP and β-arrestin2 assays. Our findings suggest that the high intrinsic efficacy of the NSOs in Gi protein signaling is a common property that may underlie their high risk of intoxication and overdose, highlighting the limitation of using in vitro functional bias to predict the adverse effects of opioids. In addition, the extremely high potency of many NSOs now infiltrating illicit drug markets further contributes to the danger posed to public health.
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Affiliation(s)
- Meng-Hua M Tsai
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, United States
| | - Li Chen
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, United States
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, United States
| | - Meritxell Canals
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
- Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, Midlands NG7 2UH, U.K
| | - Jonathan A Javitch
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, United States
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York 10032, United States
- Department of Psychiatry, Vagelos College of Physicians and Surgeons, Columbia University, New York, New York 10032, United States
| | - J Robert Lane
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, U.K
- Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, Midlands NG7 2UH, U.K
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, United States
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6
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Glatfelter GC, Vandeputte MM, Chen L, Walther D, Tsai MHM, Shi L, Stove CP, Baumann MH. Alkoxy chain length governs the potency of 2-benzylbenzimidazole 'nitazene' opioids associated with human overdose. Psychopharmacology (Berl) 2023; 240:2573-2584. [PMID: 37658878 DOI: 10.1007/s00213-023-06451-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 08/15/2023] [Indexed: 09/05/2023]
Abstract
RATIONALE Novel synthetic opioids (NSOs) are emerging in recreational drug markets worldwide. In particular, 2-benzylbenzimidazole 'nitazene' compounds are problematic NSOs associated with serious clinical consequences, including fatal respiratory depression. Evidence from in vitro studies shows that alkoxy chain length can influence the potency of nitazenes at the mu-opioid receptor (MOR). However, structure-activity relationships (SARs) of nitazenes for inducing opioid-like effects in animal models are not well understood compared to relevant opioids contributing to the ongoing opioid crisis (e.g., fentanyl). OBJECTIVES Here, we examined the in vitro and in vivo effects of nitazene analogues with varying alkoxy chain lengths (i.e., metonitazene, etonitazene, isotonitazene, protonitazene, and butonitazene) as compared to reference opioids (i.e., morphine and fentanyl). METHODS AND RESULTS Nitazene analogues displayed nanomolar affinities for MOR in rat brain membranes and picomolar potencies to activate MOR in transfected cells. All compounds induced opioid-like effects on locomotor activity, hot plate latency, and body temperature in male mice, and alkoxy chain length markedly influenced potency. Etonitazene, with an ethoxy chain, was the most potent analogue in MOR functional assays (EC50 = 30 pM, Emax = 103%) and across all in vivo endpoints (ED50 = 3-12 μg/kg). In vivo SARs revealed that ethoxy, isopropoxy, and propoxy chains engendered higher potencies than fentanyl, whereas methoxy and butoxy analogues were less potent. MOR functional potencies, but not MOR affinities, were positively correlated with in vivo potencies to induce opioid effects. CONCLUSIONS Overall, our data show that certain nitazene NSOs are more potent than fentanyl as MOR agonists in mice, highlighting concerns regarding the high potential for overdose in humans who are exposed to these compounds.
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Affiliation(s)
- Grant C Glatfelter
- Designer Drug Research Unit, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA.
| | - Marthe M Vandeputte
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
| | - Li Chen
- Computational Chemistry and Molecular Biophysics Section, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Donna Walther
- Designer Drug Research Unit, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Meng-Hua M Tsai
- Computational Chemistry and Molecular Biophysics Section, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium
| | - Michael H Baumann
- Designer Drug Research Unit, National Institute On Drug Abuse, Intramural Research Program, Baltimore, MD, USA
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7
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Abstract
This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, USA.
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8
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Varma M, Ugale V, Shaukat J, Hollmann M, Shete P, Shravage B, Tayade S, Kumbhar A, Butcher R, Jani V, Sonavane U, Joshi R, Lokwani D, Kulkarni P. Novel alkyl-substituted 4-methoxy benzaldehyde thiosemicarbazones: Multi-target directed ligands for the treatment of Alzheimer's disease. Eur J Pharmacol 2023; 957:176028. [PMID: 37657740 DOI: 10.1016/j.ejphar.2023.176028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 08/14/2023] [Accepted: 08/25/2023] [Indexed: 09/03/2023]
Abstract
Alzheimer's disease (AD) is a devastating neurodegenerative disorder affecting mental ability and interrupts neurocognitive functions. Treating multifactorial conditions of AD with a single-target-directed drug is highly difficult. Thus, a multi-target-directed ligand (MTDL) development strategy has been developed as a promising approach for the treatment of AD. Herein, we have synthesized two novel thiosemicarbazones as MTDLs and reported their bioactivities against diverse neuropathological events involved in AD. In vitro studies revealed that both compounds exhibited promising anticholinesterase activity (AChE, IC50 = 15.98 μM, MZET and IC50 = 30.23 μM, MZMT), well supported by a detailed computational study. Both analogs have shown good thermodynamic behaviour and stability through interactions with characteristic amino acid residues throughout simulation of 100 ns against acetylcholinesterase enzyme. In an electrophysiology assay, these analogs have shown a characteristic inhibitory response against the GluN1-1a + GluN2B subunit of N-methyl-D-aspartate receptors. Pre-treatment of BV-2 microglial cells with MZET effectively decreased nitrite production compared to nitrite produced by lipopolysaccharide-treated cells alone. Further, the effect of MZMT and MZET on autophagy regulation was determined using stably transfected SH-SY5Y neuroblastoma cells. MZET significantly enhanced the autophagy flux in neuroblastoma cells. A significant decrease in copper-catalysed oxidation of amyloid-β in presence of synthesized thiosemicarbazones was also observed. Collectively, our findings indicated that these analogs have potential as effective anti-AD candidates and can be used as a prototype to develop more safer multi-targeted anti-AD drugs.
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Affiliation(s)
- Mokshada Varma
- Bioprospecting Group, Agharkar Research Institute, Savitribai Phule Pune University, G. G. Agharkar Road, Pune, Maharashtra, 411004, India
| | - Vinod Ugale
- Bioprospecting Group, Agharkar Research Institute, Savitribai Phule Pune University, G. G. Agharkar Road, Pune, Maharashtra, 411004, India; Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany; Department of Pharmaceutical Chemistry, R. C. Patel Institute of Pharmaceutical Education and Research, Shirpur, Maharashtra, 425405, India.
| | - Javeria Shaukat
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Michael Hollmann
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Padmaja Shete
- Bioprospecting Group, Agharkar Research Institute, Savitribai Phule Pune University, G. G. Agharkar Road, Pune, Maharashtra, 411004, India
| | - Bhupendra Shravage
- Developmental Biology Group, Agharkar Research Institute, Savitribai Phule Pune University, Pune, Maharashtra, 411004, India
| | - Sakharam Tayade
- Department of Chemistry, Savitribai Phule Pune University, Pune, Maharashtra, 411007, India
| | - Avinash Kumbhar
- Department of Chemistry, Savitribai Phule Pune University, Pune, Maharashtra, 411007, India
| | - Ray Butcher
- Department of Chemistry, Howard University, Washington, DC, 20059, USA
| | - Vinod Jani
- HPC Medical & Bioinformatics Applications Group, Centre for Development of Advanced Computing (C-DAC), Savitribai Phule Pune University, Pune, Maharashtra, 411007, India
| | - Uddhavesh Sonavane
- HPC Medical & Bioinformatics Applications Group, Centre for Development of Advanced Computing (C-DAC), Savitribai Phule Pune University, Pune, Maharashtra, 411007, India
| | - Rajendra Joshi
- HPC Medical & Bioinformatics Applications Group, Centre for Development of Advanced Computing (C-DAC), Savitribai Phule Pune University, Pune, Maharashtra, 411007, India
| | - Deepak Lokwani
- Rajashri Shahu College of Pharmacy, Buldana, Maharashtra, India
| | - Prasad Kulkarni
- Bioprospecting Group, Agharkar Research Institute, Savitribai Phule Pune University, G. G. Agharkar Road, Pune, Maharashtra, 411004, India.
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9
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Laus A, Kumar A, Caboni P, De Luca MA, Baumann MH, Pieroni E, Tocco G. In silico characterization of ligand-receptor interactions for U-47700, N,N-didesmethyl-U-47700, U-50488 at mu- and kappa-opioid receptors. Arch Pharm (Weinheim) 2023; 356:e2300256. [PMID: 37452407 DOI: 10.1002/ardp.202300256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 07/18/2023]
Abstract
The increasing misuse of novel synthetic opioids (NSOs) represents a serious public health concern. In this regard, U-47700 (trans-3,4-dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide) and related "U-compounds" emerged on recreational drug markets as synthetic substitutes for illicit heroin and constituents of counterfeit pain medications. While the pharmacology of U-compounds has been investigated using in vitro and in vivo methods, there is still a lack of understanding about the details of ligand-receptor interactions at the molecular level. To this end, we have developed a molecular modeling protocol based on docking and molecular dynamics simulations to assess the nature of ligand-receptor interactions for U-47700, N,N-didesmethyl U-47700, and U-50488 at the mu-opioid receptor (MOR) and kappa-opioid receptor (KOR). The evaluation of ligand-receptor and ligand-receptor-membrane interaction energies enabled the identification of subtle conformational shifts in the receptors induced by ligand binding. Interestingly, the removal of two key methyl groups from U-47700, to form N,N-didesmethyl U-47700, caused a loss of hydrogen bond contact with tryptophan (Trp)229, which may underlie the lower interaction energy and reduced MOR affinity for the compound. Taken together, our results are consistent with the reported biological findings for U-compounds and provide a molecular basis for the MOR selectivity of U-47700 and KOR selectivity of U-50488.
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MESH Headings
- Receptors, Opioid, kappa/chemistry
- Receptors, Opioid, kappa/metabolism
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/pharmacology
- Ligands
- Structure-Activity Relationship
- Receptors, Opioid, mu/metabolism
- Analgesics, Opioid/pharmacology
- Analgesics, Opioid/chemistry
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Affiliation(s)
- Antonio Laus
- Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, Cagliari, Italy
| | - Amit Kumar
- Department of Electrical and Electronic Engineering, University of Cagliari, Cagliari, Italy
| | - Pierluigi Caboni
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, Cagliari, Italy
| | - Maria A De Luca
- Department of Biomedical Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, Cagliari, Italy
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, USA
| | - Enrico Pieroni
- CRS4, Modelling, Simulation and Data Analysis Program, Pula, Italy
| | - Graziella Tocco
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, Cagliari, Italy
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10
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Vandeputte MM, Tsai MHM, Chen L, Glatfelter GC, Walther D, Stove CP, Shi L, Baumann MH. Comparative neuropharmacology of structurally distinct non-fentanyl opioids that are appearing on recreational drug markets worldwide. Drug Alcohol Depend 2023; 249:109939. [PMID: 37276825 PMCID: PMC10330921 DOI: 10.1016/j.drugalcdep.2023.109939] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/28/2023] [Accepted: 05/18/2023] [Indexed: 06/07/2023]
Abstract
BACKGROUND The emergence of novel synthetic opioids (NSOs) is contributing to the opioid overdose crisis. While fentanyl analogs have historically dominated the NSO market, a shift towards non-fentanyl compounds is now occurring. METHODS Here, we examined the neuropharmacology of structurally distinct non-fentanyl NSOs, including U-47700, isotonitazene, brorphine, and N-desethyl isotonitazene, as compared to morphine and fentanyl. Compounds were tested in vitro using opioid receptor binding assays in rat brain tissue and by monitoring forskolin-stimulated cAMP accumulation in cells expressing the human mu-opioid receptor (MOR). Compounds were administered subcutaneously to male Sprague-Dawley rats, and hot plate antinociception, catalepsy score, and body temperature changes were measured. RESULTS Receptor binding results revealed high MOR selectivity for all compounds, with MOR affinities comparable to those of morphine and fentanyl (i.e., nM). All drugs acted as full-efficacy MOR agonists in the cyclic AMP assay, but nitazene analogs had greater functional potencies (i.e., pM) compared to the other drugs (i.e., nM). When administered to rats, all compounds induced opioid-like antinociception, catalepsy, and body temperature changes, but nitazenes were the most potent. Similar to fentanyl, the nitazenes had faster onset and decline of in vivo effects when compared to morphine. In vivo potencies to induce antinociception and catalepsy (i.e., ED50s) correlated with in vitro functional potencies (i.e., EC50s) but not binding affinities (i.e., Kis) at MOR. CONCLUSIONS Collectively, our findings indicate that non-fentanyl NSOs pose grave danger to those individuals who use opioids. Continued vigilance is needed to identify and characterize synthetic opioids as they emerge in clandestine drug markets.
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Affiliation(s)
- Marthe M Vandeputte
- Laboratory of Toxicology, Department of Bioanalysis, Ghent University, Ghent, Belgium
| | - Meng-Hua M Tsai
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Li Chen
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Grant C Glatfelter
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Donna Walther
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Ghent University, Ghent, Belgium
| | - Lei Shi
- Computational Chemistry and Molecular Biophysics Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA.
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11
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Zawilska JB, Adamowicz P, Kurpeta M, Wojcieszak J. Non-fentanyl new synthetic opioids - An update. Forensic Sci Int 2023; 349:111775. [PMID: 37423031 DOI: 10.1016/j.forsciint.2023.111775] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 07/11/2023]
Abstract
BACKGROUND New synthetic opioids (NSO) constitute one of the fastest-growing group of New Psychoactive Substances, which emerged on the illicit drug marker in the second half of 2000's. The most popular and the largest NSO subgroup are high potency fentanyl and its analogs. Subsequent to core-structure scheduling of fentanyl-related substances many opioids with different chemical structures are now emerging on the illicit drug market, rendering the landscape highly complex and dynamic. METHODS PubMed, Scopus and Google Scholar were searched for appropriate articles up to December 2022. Moreover, a search for reports was conducted on Institutional websites to identify documentation published by World Health Organization, United Nations Office on Drugs and Crime, United States Drug Enforcement Administration, and European Monitoring Centre for Drugs and Drug Addiction. Only articles or reports written in English were selected. RESULTS Non-fentanyl derived synthetic opioids, i.e., 2-benzylbenzimidazoles (nitazenes), brorphine, U-compounds, AH-7921, MT-45 and related compounds are characterized, describing them in terms of available forms, pharmacology, metabolism as well as their toxic effects. Sample procedures and analytical techniques available for detection and quantification of these compounds in biological matrices are also presented. Finally, as overdoses involving highly potent NSO may be difficult to reverse, the effectiveness of naloxone as a rescue agent in NSO overdose is discussed. CONCLUSIONS Current review presents key information on non-fentanyl derived NSO. Access to upto-date data on substances of abuse is of great importance for clinicians, public health authorities and professionals performing analyses of biological samples.
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Affiliation(s)
- Jolanta B Zawilska
- Department of Pharmacodynamics, Medical University of Lodz, Muszynskiego 1, 90-151 Lodz, Poland.
| | - Piotr Adamowicz
- Department of Forensic Toxicology, Institute of Forensic Research, Westerplatte 9, 31-033 Krakow, Poland
| | - Marta Kurpeta
- Department of Pharmacodynamics, Medical University of Lodz, Muszynskiego 1, 90-151 Lodz, Poland
| | - Jakub Wojcieszak
- Department of Pharmacodynamics, Medical University of Lodz, Muszynskiego 1, 90-151 Lodz, Poland
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12
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Edinoff AN, Martinez Garza D, Vining SP, Vasterling ME, Jackson ED, Murnane KS, Kaye AM, Fair RN, Torres YJL, Badr AE, Cornett EM, Kaye AD. New Synthetic Opioids: Clinical Considerations and Dangers. Pain Ther 2023; 12:399-421. [PMID: 36826742 PMCID: PMC9950705 DOI: 10.1007/s40122-023-00481-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 01/30/2023] [Indexed: 02/25/2023] Open
Abstract
Since the early 2010s, synthetic opioids have significantly contributed to overall opioid-related overdose mortalities. For point of reference, of the 68,630 opioid-related deaths recorded in 2020, 56,516 involved synthetic opioids. During much of this period, fentanyl has been the most commonly used synthetic opioid. This time when fentanyl was the most popular opioid has been called the "third wave" of the opioid crisis, partly because it led to a sharp rise in deaths from overdoses. Other synthetic opioids, such as carfentanil, protonitazene, and isotonitazene, have also become more widely diverted for nonmedical used. Carfentanil is an even more potent fentanyl derivative that was initially used in the mid-1980s as a general anesthetic for large animals such as elephants. Related to its strong affinity for mu opioid receptors, carfentanil is still utilized in medicine and science today as a radiotracer for positron emission tomography imaging. Protonitazene and isotonitazene belong to a novel class of synthetic opioids called benzimidazoles that were manufactured in the 1950s as novel analgesics. These agents have come under recent scrutiny as designer synthetic opioids becoming more prevalent. However, to date, there is incomplete data regarding the prevalence of synthetic opioids, as traditional toxicology screenings may not be sensitive to detect these compounds at such low doses post-mortem, particularly when blood is drawn from the periphery instead of central tissues such as the brain, lung, or heart. This narrative review aims to highlight the clinical challenges presented by these new synthetic opioids.
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Affiliation(s)
- Amber N Edinoff
- Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital, 55 Fruit St, Boston, MA, 02114, USA.
- Louisiana Addiction Research Center, Shreveport, LA, 71103, USA.
| | - David Martinez Garza
- Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital, 55 Fruit St, Boston, MA, 02114, USA
| | - Stephen P Vining
- Louisiana State University Health Science Center at Shreveport, School of Medicine, Shreveport, LA, 71103, USA
| | - Megan E Vasterling
- Louisiana State University Health at New Orleans, School of Medicine, New Orleans, LA, 70112, USA
| | - Eric D Jackson
- University of Arizona College of Medicine - Phoenix, Phoenix, AZ, 85004, USA
| | - Kevin S Murnane
- Louisiana Addiction Research Center, Shreveport, LA, 71103, USA
- Department of Psychiatry and Behavioral Medicine, Louisiana State University Health Science Center at Shreveport, Shreveport, LA, 71130, USA
- Department of Pharmacology, Toxicology & Neuroscience, Louisiana State University Health Science Center at Shreveport, Shreveport, LA, 71103, USA
| | - Adam M Kaye
- Department of Pharmacy Practice, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA, 95211, USA
| | - Richard N Fair
- Department of Anesthesiology, Louisiana State University Health Science Center at Shreveport, 1501 Kings Highway, Shreveport, LA, 71130-3932, USA
| | - Yair Jose Lopez Torres
- Department of Anesthesiology, Louisiana State University Health Science Center at Shreveport, 1501 Kings Highway, Shreveport, LA, 71130-3932, USA
| | - Ahmed E Badr
- Department of Anesthesiology, Louisiana State University Health Science Center at Shreveport, 1501 Kings Highway, Shreveport, LA, 71130-3932, USA
| | - Elyse M Cornett
- Louisiana Addiction Research Center, Shreveport, LA, 71103, USA.
- Department of Anesthesiology, Louisiana State University Health Science Center at Shreveport, 1501 Kings Highway, Shreveport, LA, 71130-3932, USA.
- Department of Pharmacology, Toxicology & Neuroscience, Louisiana State University Health Science Center at Shreveport, Shreveport, LA, 71103, USA.
| | - Alan D Kaye
- Louisiana Addiction Research Center, Shreveport, LA, 71103, USA
- Department of Anesthesiology, Louisiana State University Health Science Center at Shreveport, 1501 Kings Highway, Shreveport, LA, 71130-3932, USA
- Department of Pharmacology, Toxicology & Neuroscience, Louisiana State University Health Science Center at Shreveport, Shreveport, LA, 71103, USA
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13
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Deventer MH, Persson M, Laus A, Pottie E, Cannaert A, Tocco G, Gréen H, Stove CP. Off-target activity of NBOMes and NBOMe analogs at the µ opioid receptor. Arch Toxicol 2023; 97:1367-1384. [PMID: 36853332 DOI: 10.1007/s00204-023-03465-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 02/16/2023] [Indexed: 03/01/2023]
Abstract
New psychoactive substances (NPS) are introduced on the illicit drug market at a rapid pace. Their molecular targets are often inadequately elucidated, which contributes to the delayed characterization of their pharmacological effects. Inspired by earlier findings, this study set out to investigate the µ opioid receptor (MOR) activation potential of a large set of psychedelics, substances which typically activate the serotonin (5-HT2A) receptor as their target receptor. We observed that some substances carrying the N-benzyl phenethylamine (NBOMe) structure activated MOR, as confirmed by both the NanoBiT® βarr2 recruitment assay and the G protein-based AequoScreen® Ca2+ release assay. The use of two orthogonal systems proved beneficial as some aspecific, receptor independent effects were found for various analogs when using the Ca2+ release assay. The specific 'off-target' effects at MOR could be blocked by the opioid antagonist naloxone, suggesting that these NBOMes occupy the same common opioid binding pocket as conventional opioids. This was corroborated by molecular docking, which revealed the plausibility of multiple interactions of 25I-NBOMe with MOR, similar to those observed for opioids. Additionally, structure-activity relationship findings seen in vitro were rationalized in silico for two 25I-NBOMe isomers. Overall, as MOR activity of these psychedelics was only noticed at high concentrations, we consider it unlikely that for the tested compounds there will be a relevant opioid toxicity in vivo at physiologically relevant concentrations. However, small modifications to the original NBOMe structure may result in a panel of more efficacious and potent MOR agonists, potentially exhibiting a dual MOR/5-HT2A activation potential.
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Affiliation(s)
- Marie H Deventer
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000, Ghent, Belgium
| | - Mattias Persson
- Department of Forensic Genetic and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden
| | - Antonio Laus
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Eline Pottie
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000, Ghent, Belgium
| | - Annelies Cannaert
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000, Ghent, Belgium
| | - Graziella Tocco
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Henrik Gréen
- Department of Forensic Genetic and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.,Division of Clinical Chemistry and Pharmacology, Department of Biomedical and Clinical Sciences, Faculty of Medicine and Health Sciences, Linköping University, Linköping, Sweden
| | - Christophe P Stove
- Laboratory of Toxicology, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000, Ghent, Belgium.
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14
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Walton SE, Krotulski AJ, Glatfelter GC, Walther D, Logan BK, Baumann MH. Plasma pharmacokinetics and pharmacodynamic effects of the 2-benzylbenzimidazole synthetic opioid, isotonitazene, in male rats. Psychopharmacology (Berl) 2023; 240:185-198. [PMID: 36526866 DOI: 10.1007/s00213-022-06292-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022]
Abstract
RATIONALE Isotonitazene is an illicit synthetic opioid associated with many intoxications and fatalities. Recent studies show that isotonitazene is a potent µ-opioid receptor (MOR) agonist in vitro, but little information is available about its in vivo effects. OBJECTIVES The aims of the present study were to investigate the pharmacokinetics of isotonitazene in rats, and relate pharmacokinetic parameters to pharmacodynamic effects. METHODS Isotonitazene and its metabolites were identified and quantified by liquid chromatography tandem quadrupole mass spectrometry (LC-QQQ-MS). Male Sprague-Dawley rats with jugular catheters and subcutaneous (s.c.) temperature transponders received isotonitazene (3, 10, 30 µg/kg, s.c.) or its vehicle. Blood samples were drawn at 15, 30, 60, 120, and 240 min post-injection, and plasma was assayed using LC-QQQ-MS. At each blood draw, body temperature, catalepsy scores, and hot plate latencies were recorded. RESULTS Maximum plasma concentrations of isotonitazene rose in parallel with increasing dose (range 0.2-9.8 ng/mL) and half-life ranged from 23.4 to 63.3 min. The metabolites 4'-hydroxy nitazene and N-desethyl isotonitazene were detected, and plasma concentrations were below the limit of quantitation (0.5 ng/mL) but above the limit of detection (0.1 ng/mL). Isotonitazene produced antinociception (ED50 = 4.22 µg/kg), catalepsy-like symptoms (ED50 = 8.68 µg/kg), and hypothermia (only at 30 µg/kg) that were significantly correlated with concentrations of isotonitazene. Radioligand binding in rat brain tissue revealed that isotonitazene displays nM affinity for MOR (Ki = 15.8 nM), while the N-desethyl metabolite shows even greater affinity (Ki = 2.2 nM). CONCLUSIONS In summary, isotonitazene is a potent MOR agonist whose pharmacodynamic effects are related to circulating concentrations of the parent drug. The high potency of isotonitazene portends substantial risk to users who are exposed to the drug.
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Affiliation(s)
- Sara E Walton
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA
| | - Alex J Krotulski
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA.
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA.
| | - Grant C Glatfelter
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
| | - Donna Walther
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
| | - Barry K Logan
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA
- NMS Labs, 200 Welsh Road, Horsham, PA, 19044, USA
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
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