A new series of M3 muscarinic antagonists based on the 4-amino-piperidine scaffold

New psychoactive substances on dark web markets: From deal solicitation to forensic analysis of purchased substances

The dark web scene has been drawing the attention of law enforcement agencies and researchers alike. To date, most of the published works on the dark web are based on data gained by passive observation. To gain a more contextualized perspective, a study was conducted in which three vendors were selected on the "Dream Market" dark web marketplace, from whom subsequently several new psychoactive substances (NPS) were ordered. All transactions were documented from the initial drug deal solicitation to the final qualitative analysis of all received samples. From the selected vendors, a total of nine NPS samples was obtained, all of which were analyzed by NMR, HRMS, LC-UV, and two also by x-ray diffraction. According to our analyses, four of the five substances offered under already known NPS names contained a different NPS. The selected vendors therefore either did not know about their product, or deliberately deceived the buyers. Furthermore, two of three obtained samples of purportedly novel NPS were identified as already documented substances sold under a different name. However, the third characterized substance sold as "MPF-47700" was a novel, yet uncharacterized, NPS. Finally, we received a single undeclared substance, later identified as 5F-ADB. In addition to chemical analysis of the nine obtained NPS samples, the methodology used also yielded contextual information about the accessibility of NPS on the dark web, the associated purchase process, and the modus operandi of three NPS vendors. Direct participation in dark web marketplaces seems to provide additional layers of information useful for forensic studies.

Toxicokinetics and toxicodynamics of the fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine and furanoyl-1-benzyl-4-anilinopiperidine

The two fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine (4F-Cy-BAP) and furanoyl-1-benzyl-4-anilinopiperidine (Fu-BAP) have recently been seized as new psychoactive substances (NPS) on the drugs of abuse market. As their toxicokinetic and toxicodynamic characteristics are completely unknown, this study focused on elucidating their in vitro metabolic stability in pooled human liver S9 fraction (pHLS9), their qualitative in vitro (pHLS9), and in vivo (zebrafish larvae) metabolism, and their in vitro isozyme mapping using recombinant expressed isoenzymes. Their maximum-tolerated concentration (MTC) in zebrafish larvae was studied from 0.01 to 100 µM. Their µ-opioid receptor (MOR) activity was analyzed in engineered human embryonic kidney (HEK) 293 T cells. In total, seven phase I and one phase II metabolites of 4F-Cy-BAP and 15 phase I and four phase II metabolites of Fu-BAP were tentatively identified by means of liquid chromatography high-resolution tandem mass spectrometry, with the majority detected in zebrafish larvae. N-Dealkylation, N-deacylation, hydroxylation, and N-oxidation were the most abundant metabolic reactions and the corresponding metabolites are expected to be promising analytical targets for toxicological analysis. Isozyme mapping revealed the main involvement of CYP3A4 in the phase I metabolism of 4F-Cy-BAP and in terms of Fu-BAP additionally CYP2D6. Therefore, drug-drug interactions by CYP3A4 inhibition may cause elevated drug levels and unwanted adverse effects. MTC experiments revealed malformations and changes in the behavior of larvae after exposure to 100 µM Fu-BAP. Both substances were only able to produce a weak activation of MOR and although toxic effects based on MOR activation seem unlikely, activity at other receptors cannot be excluded.

Medicinal chemistry and therapeutic potential of muscarinic M3 antagonists

Muscarinic acetylcholine receptors belong to the G-protein-coupled receptors family. Currently five different receptor subtypes have been identified and cloned. M3 receptor subtypes are coupled to G(q) family proteins and increase phosphatidyl inositol hydrolysis and calcium release from internal stores. They are widely distributed both in the central nervous system and in the periphery. At the central level, M3 receptor subtypes are involved in modulation of neurotransmitter release, temperature homeostasis, and food intake, while in the periphery they induce smooth muscle contraction, gland secretion, indirect relaxation of vascular smooth muscle, and miosis. The main therapeutic applications of M3 antagonists include overactive bladder (OAB), chronic obstructive pulmonary disease (COPD), and pain-predominant irritable bowel syndrome (IBS). The introduction of selective M3 antagonists has not improved clinical efficacy compared with the old non-selective antimuscarinics but has reduced the rate of adverse events mediated by the blockade of cardiac M2 receptors (tachycardia) and central M1 receptors (cognitive impairment). Improved tolerability has been obtained also with controlled release or with inhaled formulations. However, there is still a need for safer M3 antagonists for the treatment of COPD and better-tolerated and more effective compounds for the therapy of OAB. New selective muscarinic M3 antagonists currently in early discovery and under development have been designed to address these issues. However, as M3 receptors are widely located in various tissues including salivary glands, gut smooth muscles, iris, and ciliary muscles, further clinical improvements may derive from the discovery and the development of new compounds with tissue rather than muscarinic receptor subtype selectivity.

Discovery of diaryl imidazolidin-2-one derivatives, a novel class of muscarinic M3 selective antagonists (Part 1)

Pharmacophore-based structural identification, synthesis, and structure-activity relationships of a new class of muscarinic M3 receptor antagonists, the diaryl imidazolidin-2-one derivatives, are described. The versatility of the discovered scaffold allowed for several structural modifications that resulted in the discovery of two distinct classes of compounds, specifically a class of tertiary amine derivatives (potentially useful for the treatment of overactive bladder by oral administration) and a class of quaternary ammonium salt derivatives (potentially useful for the treatment of respiratory diseases by the inhalation route of administration). In this paper, we describe the synthesis and biological activity of tertiary amine derivatives. For these compounds, selectivity for the M3 receptor toward the M2 receptor was crucial, because the M2 receptor subtype is mainly responsible for adverse systemic side effects of currently marketed muscarinic antagonists. Compound 50 showed the highest selectivity versus M2 receptor, with binding affinity for M3 receptor Ki = 4.8 nM and for M2 receptor Ki = 1141 nM. Functional in vitro studies on selected compounds confirmed the antagonist activity toward the M3 receptor and functional selectivity toward the M2 receptor.

Potent anti-muscarinic activity in a novel series of quinuclidine derivatives

The synthesis and biological evaluation of a novel family of M(3) muscarinic antagonists are described. A systematic modification of the substituents to a novel alkyne-quinuclidine scaffold yielded original compounds displaying potent in vitro anticholinergic properties.

Molecular modulation of muscarinic antagonists. Synthesis and affinity profile of 2,2-diphenyl-2-ethylthio-acetic acid esters designed to probe the binding site cavity

The synthesis and preliminary pharmacological profile of a new series of muscarinic antagonists, derived from previously studied 2,2-diphenyl-2-ethylthio-acetic acid esters, are reported. The parent molecules were decorated with linkers of different length, carrying an amino group to catch a putative anionic function outside the recognition site of the receptor. It was hoped that the interception of this function would give molecules with higher potency and selectivity. The attempt has not been successful, but a new series of compounds with a peculiar pharmacological profile has been identified.