Bioisosteric analogs of MDMA: Improving the pharmacological profile?

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is re-emerging in clinical settings as a candidate for the treatment of specific neuropsychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubations, metabolic stability studies, isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin, dopamine, and norepinephrine transporters (hSERT, hDAT, and hNET, respectively) but decreased agonist activity at 5-HT2A/2B/2C receptors. Regarding their hepatic metabolism, they differed from MDMA, with N-demethylation being the only metabolic route shared, and without forming phase II metabolites. In addition, TDMA showed an enhanced intrinsic clearance in comparison to its congeners. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane monoamine transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA bioisosteres might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT, hDAT, and hNET, but displaying a reduced activity at 5-HT2A/2B/2C receptors and alternative hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.

Bioisosteric analogs of MDMA with improved pharmacological profile.

3,4-Methylenedioxymethamphetamine (MDMA, ' ecstasy' ) is re-emerging in clinical settings as a candidate for the treatment of specific psychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubation with isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin and dopamine transporters (hSERT and hDAT, respectively) but decreased activity at 5-HT 2A/2B/2C receptors. Regarding their hepatic metabolism, they differed from MDMA, with N -demethylation being the only metabolic route shared, and without forming phase II metabolites. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA analogs might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT and hDAT, but displaying a reduced activity at 5-HT 2A/2B/2C receptors and reduced hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.

The syntheses, characterization and in vitro metabolism of nitracaine, methoxypiperamide and mephtetramine.

Three legal highs; nitracaine (3-(diethylamino)-2,2-dimethylpropyl 4-nitrobenzoate), methoxypiperamide (MEOP, (4-methoxyphenyl)(4-methylpiperazin-1-yl)methanone) and mephtetramine (MTTA, 2-((methylamino)methyl)-3,4-dihydronaphthalen-1(2H)-one) appeared in 2013 as new psychoactive substances (NPS) on Internet websites selling 'research chemicals'. These compounds were synthesized and analyzed via our synthesize, analyze, and metabolize (SAM) protocol. Nitracaine was synthesized by the transesterification of methyl 4-nitrobenzoate with 3-(diethylamino)-2,2-dimethylpropan-1-ol. Methoxypiperamide was synthesized by the reaction of 4-methoxybenzoyl chloride with 1-methylpiperazine, and mephtetramine through the Mannich reaction of 1-tetralone with paraformaldehyde and methylamine hydrochloride. Each compound was characterized by nuclear magnetic resonance (NMR), gas chromatography with electron impact mass spectrometry (GC-EIMS), liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and high resolution electrospray ionization mass spectrometry (HR-ESI-MS). A sample of nitracaine was also test-purchased from an Internet vendor and its structure confirmed by GC-EIMS and LC-ESI-MS. Finally, the in vitro metabolism of the nitracaine, mephtetramine, and methoxypiperamide was investigated, using a human microsomal liver extract, in order to tentatively identify potential metabolites that may be encountered in the analysis of biological samples in clinical or toxicology labs. The use of our SAM protocol highlights the ability of academic research labs to quickly respond to and disseminate information about emerging NPS.

Identification of (2-aminopropyl)indole positional isomers in forensic samples.

In 2012, 5-(2-aminopropyl)indole (5-API, 5-IT) was reported by Norwegian authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) via the Early Warning System (EWS). The 3- isomer, 3-(2-aminopropyl)indole (3-API, AMT, alpha-methyltryptamine), has been available on the recreational drugs market for a somewhat longer time, having first been reported to the EMCDDA by Finnish authorities in 2001. Both isomers are available from online vendors of 'legal highs'. Recently, three forensic drug cases (two tablets and one powder) were presented for routine analysis and the active constituent was tentatively identified as an API isomer. The six positional isomers (2-, 3-, 4-, 5-, 6- and 7-(2-aminopropyl)indoles) were synthesized and analyses by a combination gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS) showed that these could be readily discriminated thus facilitating the identification of 3-API in the tablets and 5-API in the powder. With exception of 5- and 6-APIs, which co-eluted, it was found possible to separate the isomers by GC without derivatization. LC separation also proved to be a feasible method for the discrimination of the isomers. Although the 2- and 7- isomers were not fully resolved by LC, it was found possible to distinguish them using their product ion spectra as the 2- isomer produced the m/z 132 fragment ion formed by loss of vinylamine, whereas the 7- isomer formed m/z 158 through loss of methylamine. In the synthesis 2-API, a novel tricyclic by-product was formed in an annulation reaction where the reaction solvent, tetrahydrofuran, was incorporated into the molecule.

An unusual presentation of a customs importation seizure containing amphetamine, possibly synthesized by the APAAN-P2P-Leuckart route.

During the analysis of an Irish customs seizure (14 packages each containing approximately one kilogram of a white wet paste) were analysed for the suspected presence of controlled drugs. The samples were found to contain amphetamine and also characteristic by-products including benzyl cyanide, phenylacetone (P2P), methyl-phenyl-pyrimidines, N-formylamphetamine, naphthalene derivatives and amphetamine dimers. The analytical results corresponded with the impurity profile observed and recently reported for the synthesis of 4-methylamphetamine from 4-methylphenylacetoacetonitrile [1]. The synthesis of amphetamine from alpha-phenylacetoacetonitrile (APAAN) was performed (via an acid hydrolysis and subsequent Leuckart reaction) and the impurity profile of the product obtained was compared to those observed in the customs seizure. Observations are made regarding the route specificity of these by-products.

Crystal structures of 2-meth-oxy-isoindoline-1,3-dione, 1,3-dioxoisoindolin-2-yl methyl carbonate and 1,3-dioxo-2,3-di-hydro-1H-benzo[de]isoquinolin-2-yl methyl carbonate: three anti-convulsant compounds.

The title compounds, C9H7NO3, (1), C10H7NO5, (2), and C14H9NO5, (3), are three potentially anti-convulsant compounds. Compounds (1) and (2) are isoindoline derivatives and (3) is an iso-quinoline derivative. Compounds (2) and (3) crystallize with two independent mol-ecules (A and B) in their asymmetric units. In all three cases, the isoindoline and benzoiso-quinoline moieties are planar [r.m.s. deviations are 0.021 Šfor (1), 0.04 and 0.018 Šfor (2), and 0.033 and 0.041 Šfor (3)]. The substituents attached to the N atom are almost perpendicular to the mean planes of the heterocycles, with dihedral angles of 89.7 (3)° for the N-O-Cmeth-yl group in (1), 71.01 (4) and 80.00 (4)° for the N-O-C(=O)O-Cmeth-yl groups in (2), and 75.62 (14) and 74.13 (4)° for the same groups in (3). In the crystal of (1), there are unusual inter-molecular C=O⋯C contacts of 2.794 (1) and 2.873 (1) Špresent in mol-ecules A and B, respectively. There are also C-H⋯O hydrogen bonds and π-π inter-actions [inter-centroid distance = 3.407 (3) Å] present, forming slabs lying parallel to (001). In the crystal of (2), the A and B mol-ecules are linked by C-H⋯O hydrogen bonds, forming slabs parallel to (10-1), which are in turn linked via a number of π-π inter-actions [the most significant centroid-centroid distances are 3.4202 (7) and 3.5445 (7) Å], forming a three-dimensional structure. In the crystal of (3), the A and B mol-ecules are linked via C-H⋯O hydrogen bonds, forming a three-dimensional structure, which is consolidated by π-π inter-actions [the most significant inter-centroid distances are 3.575 (3) and 3.578 (3) Å].

3-(4-Chloro-benzene-sulfonamido)-5-methyl-cyclo-hex-2-en-1-one.

For the title compound, C(13)H(14)ClNO(3)S, geometrical parameters, determined using X-ray diffraction techniques, are compared with those calculated by density functional theory (DFT), using hybrid exchange-correlation functional, B3LYP methods. The dihedral angle between the benzene ring and the conjugated part of the cyclo-hexene ring is 87.47 (5)°. The cyclo-hexene ring and its substituents are disordered over two conformations, with occupancies of 0.786 (3) and 0.214 (3). In the crystal, mol-ecules are linked into chains in the c-axis direction by inter-molecular N-H⋯O(C=O) hydrogen bonds. C-H⋯O inter-actions are also observed.

3-(4-Chloro-anilino)-2,5-dimethyl-cyclo-hex-2-en-1-one.

In the title compound, C(14)H(16)ClNO, the dihedral angle between the benzene ring and the conjugated part of the cyclo-hexene ring is 61.7 (2)°. Part of the cyclo-hexene ring and one of the attached methyl groups are disordered over two orientations with occupancies of 0.602 (7) and 0.398 (7). In addition, the crystal studied was a racemic twin [Flack parameter = 0.58 (4)]. In the crystal, the mol-ecules are linked into chains in the b-axis direction by inter-molecular N-H⋯O hydrogen bonds. C-H⋯O and C-H⋯Cl inter-actions are also observed.

2,5-Dimethyl-3-[4-(trifluoro-meth-oxy)anilino]-cyclo-hex-2-enone.

In the title compound, C(15)H(16)F(3)NO(2), the dihedral angle between the benzene ring and the conjugated part of the cyclo-hexene ring is 60.00 (8)°. The non-conjugated part of the cyclohexene ring and the trifluoro-methyl group are both disordered over two sets of sites with occupancies of 0.835 (2) and 0.165 (2). In the crystal, mol-ecules are linked into chains along [010] by inter-molecular N-H⋯O hydrogen bonds. Weak inter-molecular C-H⋯O inter-actions also occur.

A substituted anilino enaminone acts as a novel positive allosteric modulator of GABA(A) receptors in the mouse brain.

A small library of anilino enaminones was analyzed for potential anticonvulsant agents. We examined the effects of three anilino enaminones on neuronal activity of output neurons, mitral cells (MC), in an olfactory bulb brain slice preparation using whole-cell patch-clamp recording. These compounds are known to be effective in attenuating pentylenetetrazol-induced convulsions. Among the three compounds tested, 5-methyl-3-(4-trifluoromethoxy-phenylamino)-cyclohex-2-enone (KRS-5Me-4-OCF3) showed potent inhibition of MC activity with an EC50 of 24.5 µM. It hyperpolarized the membrane potential of MCs accompanied by suppression of spontaneous firing. Neither ionotropic glutamate receptor blockers nor a GABA(B) receptor blocker prevented the KRS-5Me-4-OCF(3)-evoked inhibitory effects. In the presence of GABA(A) receptor antagonists, KRS-5Me-4-OCF(3) completely failed to evoke inhibition of MC spiking activity, suggesting that KRS-5Me-4-OCF3-induced inhibition may be mediated by direct action on GABA(A) receptors or indirect action through the elevation of tissue GABA levels. Neither vigabatrin (a selective GABA-T inhibitor) nor 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid hydrochloride (NNC-711) (a selective inhibitor of GABA uptake by GABA transporter 1) eliminated the effect of KRS-5ME-4-OCF3 on neuronal excitability, indicating that the inhibitory effect of the enaminone resulted from direct activation of GABA(A) receptors. The concentration-response curves for GABA are left-shifted by KRS-5Me-4-OCF3, demonstrating that KRS-5Me-4-OCF3 enhanced GABA affinity and acted as a positive allosteric modulator of GABA(A) receptors. The effect of KRS-5Me-4-OCF3 was blocked by applying a benzodiazepine site antagonist, suggesting that KRS-5Me-4-OCF3 binds at the classic benzodiazepine site to exert its pharmacological action. The results suggest clinical use of enaminones as anticonvulsants in seizures and as a potential anxiolytic in mental disorders.

tert-Butyl 6-methyl-2-oxo-4-[4-(trifluoro-meth-oxy)anilino]cyclo-hex-3-ene-1-carboxyl-ate.

In the title compound, C(19)H(22)F(3)NO(4), the dihedral angle between the benzene ring and the conjugated part of the enaminone ring is 42.5 (1)°. The ester substituent makes a dihedral angle of 81.3 (2)° with this latter moiety. The crystal structure is held together by strong N-H⋯O and weak C-H⋯O inter-molecular inter-actions. The enaminone ring is disordered over two orientations with relative occupancies of 0.794 (4) and 0.206 (4).

tert-Butyl 4-(4-chloro-anilino)-6-methyl-2-oxocyclo-hex-3-ene-carboxyl-ate.

In the title compound, C(18)H(22)ClNO(3), the dihedral angle between the benzene ring and the conjugated part of the enaminone ring is 55.19 (9)°. The ester substituent makes a dihedral angle of 81.0 (2)° with this latter moiety. The crystal structure features N-H⋯O and weak C-H⋯O inter-molecular inter-actions.

National patterns of dementia treatment among elderly ambulatory patients.

PURPOSES: To assess patterns of dementia/Alzheimer's disease (AD) management and to investigate predictive factors of cholinesterase inhibitor prescriptions. METHODOLOGY: A cross-sectional study was conducted using a national survey among the elderly aged >60 from 2000 to 2002. Visit characteristics and cholinesterase inhibitor prescriptions associated with dementia/AD status were evaluated. MAIN FINDINGS: A total of 25,561 visit records were identified. Of the total visits, only 0.6% had dementia/AD records. Most of the dementia/AD visits were made by women (60.6%) and white patients (93.5%). Of the dementia/AD visits, about half (46.5%) were prescribed with one or more cholinesterase inhibitors. Donepezil was the most prevalent agent (68.0%) followed by rivastigmine (26.0%). Logistic regression analyses indicated that the physician's specialty was a strong predictor for cholinesterase inhibitor prescription; psychiatrists [odds ratio (OR)=5.5; p<0.01] and neurologists (OR=2.6; p<0.03) were more likely to prescribe cholinesterase inhibitor than other physicians. Other characteristics including race did not show significant association. CONCLUSIONS: The study findings suggest that physicians who specialized in psychiatry and neurology predominantly provided ambulatory care services for dementia patients. More efforts should be given to detect and to treat dementia patients with cognitive-enhancing agents after the formal diagnosis in the ambulatory care setting.

DM27, an enaminone, modifies the in vitro transport of antiviral therapeutic agents.

OBJECTIVE: For most antiviral drugs, low or variable bioavailability is attributed to poor absorption, susceptibility to efflux, or first pass metabolism. Enaminones are beta dicarbonyl compounds, which display P-glycoprotein (P-gp) substrate properties with high efflux ratios. This study investigates the influence of DM27, an enaminone, on the in vitro transport of antiviral agents and the possibility of using DM27 as a P-gp inhibitor to prevent the efflux of certain antiretroviral agents. METHODS: The transport of [3H]amprenavir, [3H]saquinavir, [3H]ritonavir, [14C]zidovudine (AZT) and [3H]acyclovir was evaluated across Caco-2 cells with DM27 (10(-10)-10(-4) M). In addition, the effect of DM27 (10(-6) M) on the transport of transcellular and paracellular markers was tested to evaluate its influence on these transport pathways. The apparent permeability coefficient (Papp) for each drug or marker was calculated with/without DM27 and toxicity evaluation for DM27 was performed using the MTS assay. RESULTS: The mean Papp for the investigated antiviral agents significantly increased by 22%-51% after DM27 incubation without any toxicity to the Caco-2 cells. In addition, DM27 did not influence the transcellular or paracellular transport of propranolol and mannitol, respectively. CONCLUSIONS: DM27, an enaminone, increased the transport of antiretroviral drugs and acyclovir in a nontoxic manner without affecting the paracellular or transcellular transport of these drugs. This study suggests that DM27 may be used as a P-gp efflux inhibitor to enhance the oral bioavailability of antiviral drugs and that drug-drug interactions will most probably be encountered upon co-administration of P-gp substrate drugs with enaminones.

The influence of enaminones on the transport and oral bioavailability of P-glycoprotein substrate therapeutic agents.

OBJECTIVE: The enaminones have shown high P-gp affinity and may act as P-gp modulators. This study investigated the potential inhibition of the enaminones on paclitaxel efflux in vitro compared to cyclosporin A, a known P-gp inhibitor, and the effectiveness of select enaminones on paclitaxel oral absorption in rats. METHODS: Caco-2 transport of [14C]paclitaxel was evaluated in presence of various enaminones at 10(-5)M. Concentration-effect (10(-10)M to 10(-4)M) profiles for the enaminones, DM27 and/or DM40, with paclitaxel and cyclosporin A were determined. Male Sprague-Dawley (250-275 g) rats were orally administered either [14C]paclitaxel (30 microCi/kg) or [14C]paclitaxel/DM27 (7 mg/kg) and blood samples were collected. Paclitaxel brain concentrations were measured. RESULTS: Papp(A-B) of [14C]paclitaxel, with DM27 and DM40 at 10(-5)M, was significantly (P < 0.05) higher versus control. DM27 produced a 360% and a 139% increase in Papp(A-B)Paclitaxel and Papp(A-B)Cyclosporin, respectively. DM40 displayed a 131% increase in Papp(A-B)Paclitaxel whereas cyclosporin A produced a 213% increase in Papp(A-B)Paclitaxel. Rats in the DM27 group displayed large Vdss/F values (23.35 liters/kg versus 14.62 liters/kg) and lower AUC (5.47 microg/ml min versus 8.74 microg/ml min) versus control. However, significantly higher levels (2.25-fold) of paclitaxel were observed in the brains of the DM27 group. CONCLUSION: This study presents the enaminones as promising P-gp inhibitors with comparable potency to other P-gp inhibitors. Furthermore, the enaminones may improve conventional therapy when used in combination with P-gp substrate drugs.

Preclinical evaluation of the pharmacokinetics, brain uptake and metabolism of E121, an antiepileptic enaminone ester, in rats.

The present study describes the brain uptake, pharmacokinetics and metabolism of an anticonvulsant enaminone ester E121, which belongs to a new and active series of compounds with potential in vivo anticonvulsant activity in rodent models, in rats. A single dose of E121 was administered i.p. to male Sprague Dawley rats at 10 mg E121/kg body weight. Cohorts of animals (n=3) were killed at varying times over 0-24 h to collect plasma and brain samples. Urinary excretion of E121 was studied in a separate group of five rats at the same dose. A validated HPLC method was used to quantify E121 and its metabolites in plasma, brain and urine. LC-MS/MS was used to characterize the metabolites. The plasma and brain Cmax of 11.0+/-3.0 mg/l and 10.4+/-1.4 mg/kg, respectively, were observed for E121 at 15 min post dose and they declined in a mono-exponential fashion. The plasma Cl/F and t1/2 were 0.57 l/h/kg and 0.75 h, respectively. The brain uptake ratio of E121 was 0.9. Mass spectral analysis of urine showed two major metabolites (m/z 280) and one minor metabolite (m/z 236) that were consistent with initial hydrolysis of the compound to the acid followed by further decarboxylation and appears to be the major route of elimination of E121. The rapid and moderate brain uptake of E121 correlates well with its potential anticonvulsant activity (ED50 3.0 mg/kg p.o. in rats). The brain uptake, pharmacokinetic and metabolic profile of E121 supports the need to further evaluate this compound for its potential as an antiepileptic.

Effect of P-glycoprotein on the pharmacokinetics and tissue distribution of enaminone anticonvulsants: analysis by population and physiological approaches.

Multidrug resistance (MDR), mediated by P-glycoprotein (Pgp) has been identified as altering the disposition of structurally diverse compounds. Previous in vitro studies in bovine brain microvascular endothelial cells and MCF/Adr [Adriamycin (doxorubicin)-resistant human breast cancer] cells displayed that the transport of enaminone anticonvulsants was influenced by Pgp. Therefore the objectives of this study was to further evaluate the influence of Pgp on the pharmacokinetics and tissue distribution of the enaminone analogs. mdr1ab (+/+) and mdr1ab (-/-) male mice (20 +/- 5 g) were administered DM5 (methyl 4-[(4'-chlorophenyl)amino]-6-methyl-2-oxo-3-cyclohexene-1-carboxylate) or DM44 (12.5 mg/kg, i.v.). Cohorts (n = 3) were sacrificed over a 12-h period, and samples were analyzed by a validated UV-high performance liquid chromatography assay method. Population analysis was used to estimate pharmacokinetic parameters and partition coefficients were determined for tissues. The clearance (0.51 versus 0.33 l/h/kg) and V(d) (1.25 versus 0.93 l/kg) of DM5 were found to be higher (p < 0.05), however the area under the curve (26.1 versus 38.2 microg/ml. h) was lower (p < 0.05) in mdr1a/1b (-/-) versus mdr1a/1b (+/+) mice, respectively. Similar findings were observed for DM44. Tissues known to express Pgp such as the heart, liver, lung, and brain displayed 2-fold or higher tissue levels in mdr1a/1b (-/-) versus mdr1a/1b (+/+) mice. These results strongly suggest that Pgp may influence enaminone tissue distribution and pharmacokinetics and may play a significant role in the effective treatment of epilepsy with these analogs.