Synthetic cannabimimetic agents are a large group of diverse compounds which act as agonists at cannabinoid receptors. Since 2004, synthetic cannabinoids have been used recreationally, although several of the compounds have been shown to cause severe toxicity in humans. In this study, the metabolism of two indazole carboxamide derivatives, AB-PINACA and AB-FUBINACA, was investigated by using human liver microsomes (HLM). For both compounds, a major metabolic pathway was the enzymatic hydrolysis of the primary amide, resulting in the major metabolites AB-PINACA-COOH and AB-FUBINACA-COOH. Other major metabolic pathways were mono-hydroxylation of the N-pentyl chain in AB-PINACA and mono-hydroxylation of the 1-amino-3-methyl-1-oxobutane moiety in AB-FUBINACA. To identify the enzyme(s) responsible for the amide hydrolysis, incubations with recombinant carboxylesterases and human serum, as well as inhibition studies in HLM and human pulmonary microsomes (HPM) were performed. Carboxylesterase 1 (CES1) was identified as the major human hepatic and pulmonary enzyme responsible for the amide hydrolysis.We employed similar studies to identify the esterase(s) involved in the previously described hydrolytic metabolism of two quinolineindole synthetic cannabinoids, PB-22 and 5F-PB-22, as well as the closely related compound, BB-22. Our investigations again revealed CES1 to be the key enzyme catalyzing these reactions. The identified major metabolites of AB-PINACA and AB-FUBINACA are likely to be useful in documenting drug usage in forensic and clinical screening. Additionally, the identification of CES1 as the main enzyme hydrolyzing these compounds improves our knowledge in the emerging field of xenobiotic metabolism by esterases.

New types of synthetic cannabinoid designer drugs are constantly introduced to the illicit drug market to circumvent legislation. Recently, N-​(1-Adamant​yl)-​1-​(5-​fluoropentyl)-​1H-​indazole-​3-​carboxamide (5F-AKB-48), also known as 5F-APINACA, was identified as an adulterant in herbal products. This compound deviates from earlier JHW-type synthetic cannabinoids by having an indazole ring connected to an adamantyl group via a carboxamide linkage. Synthetic cannabinoids are completely metabolized, and identification of the metabolites is thus crucial when using urine as the sample matrix. Using an authentic urine sample and high-resolution accurate-mass Fourier transform Orbitrap mass spectrometry, we identified 16 phase-I metabolites of 5F-AKB-48. The modifications included mono-, di-, and trihydroxylation on the adamantyl ring alone or in combination with hydroxylation on the N-fluoropentylindazole moiety, dealkylation of the N-fluoropentyl side chain, and oxidative loss of fluorine as well as combinations thereof. The results were compared to human liver microsomal (HLM) incubations, which predominantly showed time-dependent formation of mono-, di-, and trihydroxylated metabolites having the hydroxyl groups on the adamantyl ring. The results presented here may be used to select metabolites specific of 5F-AKB-48 for use in clinical and forensic screening.

Flubromazolam is a triazole benzodiazepine with high potency and long-lasting central nervous system depressant effects; however, limited data about its pharmacokinetics are available. Here, we report in vitro studies of the human flubromazolam metabolism analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS). In vitro investigations were carried out in pooled human liver microsomes (pHLM) and recombinant cytochrome P450 (CYP)-enzymes. To confirm those metabolites detected in vitro, authentic samples obtained from two forensic cases were also analyzed by LC-HRMS. Additionally, determination of the unbound fraction of flubromazolam in pHLM and in plasma was performed by equilibrium dialysis with subsequent prediction of its hepatic clearance (CL ) using well-stirred and parallel-tube models. Additional findings obtained by routine screening methods of these forensic cases are also reported. Studies using incubations with nicotinamide adenine dinucleotide phosphate-fortified pHLM with or without uridine 5'-diphosphoglucuronic acid and incubations with CYP-enzymes identified the main metabolic pathway of flubromazolam as hydroxylation on the α- and/or 4-position mediated by CYP3A4 and CYP3A5, with subsequent glucuronidation of the hydroxylated metabolites as well as of the parent drug. Further, α-hydroxy-flubromazolam and its corresponding glucuronide were detected in vivo together with the N-glucuronide of flubromazolam. The predicted CL of flubromazolam using the well-stirred and parallel-tube models were 0.42 and 0.43 mL/min/kg, respectively. Based on the data presented here, flubromazolam is primarily metabolized by CYP3A4/5 with a high protein-binding and a predicted low clearance. Analysis of authentic samples suggested that analytical targets for flubromazolam should be the compound itself and α-hydroxy-flubromazolam. Copyright © 2016 John Wiley & Sons, Ltd.

Abstract. Synthetic cannabinoid designer drugs have emerged as drugs of abuse during the last decade, and acute intoxication cases are documented in the scientific literature. Synthetic cannabinoids are extensively metabolized, but our knowledge of the involved enzymes is limited. Here, we investigated the metabolism of N-(1-adamantyl)-1-pentyl-1H-indazole-3-carboxamide (AKB-48), a compound identified in herbal blends from 2012 and onwards. We screened for metabolite formation using a panel of nine recombinant cytochrome P450 (CYP) enzymes (CYP1A2, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, and 3A4) and compared the formed metabolites to human liver microsomal (HLM) incubations with specific inhibitors against CYP2D6, 2C19, and 3A4, respectively. The data reported here demonstrate CYP3A4 to be the major CYP enzyme responsible for the oxidative metabolism of AKB-48, preferentially performing the oxidation on the adamantyl moiety. Genetic polymorphisms are likely not important with regard to toxicity given the major involvement of CYP3A4. Adverse drug-drug interactions (DDIs) could potentially occur in cases with co-intake of strong CYP3A4 inhibitors, e.g., HIV antivirals and azole antifungal agents.

The review describes molecular and functional properties of the volume regulated anion channel and Ca 21-dependent Cl 2 channels belonging to the anoctamin family with emphasis on physiological importance of these channels in regulation of cell volume, cell migration, cell proliferation, and programmed cell death. Finally, we discuss the role of Cl 2 channels in various diseases.