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The objective of this study was to investigate the efficacy and safety of adjunctive lanicemine (NMDA channel blocker) in the treatment of major depressive disorder (MDD) over 12 weeks. This phase IIb, randomized, parallel-arm, double-blind, placebo-controlled study was conducted at 49 centers in four countries between December 2011 and August 2013 in 302 patients aged 18-70 years, meeting criteria for single episode or recurrent MDD and with a history of inadequate treatment response. Patients were required to be taking an allowed antidepressant for at least four weeks prior to screening. Patients were randomized equally to receive 15 double-blind intravenous infusions of adjunctive lanicemine 50 mg, lanicemine 100 mg, or saline over a 12-week course, in addition to ongoing antidepressant. The primary efficacy end point was change in Montgomery-Åsberg Depression Rating Scale (MADRS) total score from baseline to week 6. Secondary efficacy outcome variables included change in MADRS score from baseline to week 12, response and remission rates, and changes in Clinical Global Impression scale, Quick Inventory of Depressive Symptomology Self-Report score, and Sheehan Disability Scale score. Of 302 randomized patients, 240 (79.5%) completed treatment. Although lanicemine was generally well tolerated, neither dose was superior to placebo in reducing depressive symptoms on the primary end point or any secondary measures. There was no significant difference between lanicemine and placebo treatment on any outcome measures related to MDD. Post hoc analyses were performed to explore the possible effects of trial design and patient characteristics in accounting for the contrasting results with a previously reported trial.

Ketamine, an N -methyl- D -aspartate receptor (NMDAR) channel blocker, has been found to induce rapid and robust antidepressant-like effects in rodent models and in treatment-refractory depressed patients. However, the marked acute psychological side effects of ketamine complicate the interpretation of both preclinical and clinical data. Moreover, the lack of controlled data demonstrating the ability of ketamine to sustain the antidepressant response with repeated administration leaves the potential clinical utility of this class of drugs in question. Using quantitative electroencephalography (qEEG) to objectively align doses of a low-trapping NMDA channel blocker, AZD6765 (lanicemine), to that of ketamine, we demonstrate the potential for NMDA channel blockers to produce antidepressant efficacy without psychotomimetic and dissociative side effects. Furthermore, using placebo-controlled data, we show that the antidepressant response to NMDA channel blockers can be maintained with repeated and intermittent drug administration. Together, these data provide a path for the development of novel glutamatergic-based therapeutics for treatment-refractory mood disorders.

The present study predicts effective doses of a set of phenethylamine (PEA) analogues that are frequently present in pre-workout and weight-loss food supplements, to prioritize these compounds for further risk assessment. In vitro determined EC 50 values of PEA analogues for multiple human adrenergic receptor (ADR) subtypes (ADRα 1A , α 1B , α 1D , α 2A , β 1 , β 2 ) and trace-amine associated receptor 1 (TAAR1) were extrapolated to human ED 50 values by using physiologically based kinetic (PBK) modelling-based reverse dosimetry combined with in silico and in vitro determined PBK model input parameters. The predicted ED 50 values of the studied PEAs for activation of ADRα 1A/B/D , ADRα 2A , ADRβ 1 and TAAR1 were within a range of 0.914–29.7 mg/kg body weight (bw), 139–234 mg/kg bw, 0.0839–38.8 mg/kg bw and 0.995–264 mg/kg bw, respectively. Comparison of the predicted ED 50 values with reported intake values revealed that particularly the exposure of the PEA analogues higenamine, isopropyloctopamine, β-methylphenethylamine and p-synephrine is in the same range or exceeds the predicted ED 50 values. This suggests that these PEAs can (in)directly affect the cardiovascular system after the intake of food supplements. These PEA analogues should therefore be considered as high priority compounds for further risk assessment. In conclusion, our study shows that the use of quantitative in vitro-to-in vivo extrapolation (QIVIVE) of adrenergic and TAAR1 potencies using a generic PBK model can serve as an efficient prioritization method for a whole set of chemical analogues.

RationaleSynthetic phenethylamine (PEA) analogs, such as β-methylphenethylamine (BMPEA) and N,α-diethylphenethylamine (DEPEA), are often found in dietary supplements, despite regulations prohibiting their sale. PEA analogs are structurally related to amphetamine, and we have shown that BMPEA and DEPEA produce cardiovascular stimulation mimicking the effects of amphetamine. However, few studies have examined behavioral effects of BMPEA, DEPEA, and other PEA analogs.ObjectivesHere, we examined the reinforcing effects of α-ethylphenethylamine (AEPEA, 1 mg/kg/injection), DEPEA (1 mg/kg/injection), and BMPEA (3 mg/kg/injection) as compared to amphetamine (0.1 mg/kg/injection) using a fixed-ratio 1 self-administration paradigm in male rats.MethodsMale rats were trained in self-administration chambers containing 2 nose-poke holes. A nose-poke response in the active hole delivered drug or saline, whereas a nose-poke response in the inactive hole had no programmed consequence. Four groups of rats were initially trained for 10 days with the doses noted above. Upon acquisition of drug self-administration, a dose–effect function was determined by training rats on 3 additional doses for 3 days each. A separate group of rats was trained with saline.ResultsMale rats self-administered each PEA analog and amphetamine, as shown by significant increases in active responses versus inactive responses. Subsequent dose–response testing showed clear differences in potency of the compounds. Amphetamine showed a typical inverted U-shaped dose–effect function, peaking at 0.1 mg/kg/injection. AEPEA and DEPEA also showed inverted dose–effect functions, with each peaking at 0.3 mg/kg/injection. BMPEA did not show an inverted U-shaped dose–effect function, but active responding slowly increased up to a dose of 6 mg/kg/injection.ConclusionsTaken together, our findings indicate that dietary supplements containing PEA analogs may have significant abuse liability when used recreationally.

[11C]Cimbi-36 is a recently developed serotonin 2A (5-HT2A) receptor agonist positron emission tomography (PET) radioligand that has been successfully applied for human neuroimaging. Here, we investigate the test–retest variability of cerebral [11C]Cimbi-36 PET and compare [11C]Cimbi-36 and the 5-HT2A receptor antagonist [18F]altanserin. Sixteen healthy volunteers (mean age 23.9±6.4years, 6 males) were scanned twice with a high resolution research tomography PET scanner. All subjects were scanned after a bolus of [11C]Cimbi-36; eight were scanned twice to determine test–retest variability in [11C]Cimbi-36 binding measures, and another eight were scanned after a bolus plus constant infusion with [18F]altanserin. Regional differences in the brain distribution of [11C]Cimbi-36 and [18F]altanserin were assessed with a correlation of regional binding measures and with voxel-based analysis. Test–retest variability of [11C]Cimbi-36 non-displaceable binding potential (BPND) was consistently <5% in high-binding regions and lower for reference tissue models as compared to a 2-tissue compartment model. We found a highly significant correlation between regional BPNDs measured with [11C]Cimbi-36 and [18F]altanserin (mean Pearson's r: 0.95±0.04) suggesting similar cortical binding of the radioligands. Relatively higher binding with [11C]Cimbi-36 as compared to [18F]altanserin was found in the choroid plexus and hippocampus in the human brain. Excellent test–retest reproducibility highlights the potential of [11C]Cimbi-36 for PET imaging of 5-HT2A receptor agonist binding in vivo. Our data suggest that Cimbi-36 and altanserin both bind to 5-HT2A receptors, but in regions with high 5-HT2C receptor density, choroid plexus and hippocampus, the [11C]Cimbi-36 binding likely represents binding to both 5-HT2A and 5-HT2C receptors. •[11C]Cimbi-36 demonstrated excellent reproducibility as a 5-HT2A receptor agonist PET radioligand in healthy volunteers.•In vivo binding of [11C]Cimbi-36 and [18F]altanserin was highly correlated demonstrating that they both image 5-HT2A receptors in the human brain•In choroid plexus and hippocampus, [11C]Cimbi-36 binding exceeded [18F]altanserin binding suggesting high density of 5-HT2C receptors here.•[11C]Cimbi-36 may be used to detect both 5-HT2A and 5-HT2C receptor binding in the human brain

New groups of synthetic “designer drugs” have increased in popularity over the past several years. These products mimic the euphoric effects of other well-known illicit drugs but are advertised as “legal” highs and are sold over the internet, at raves and night clubs, and in head shops. The 2C series drugs are ring-substituted phenethylamines that belong to a group of designer agents similar in structure to 3,4-methylenedioxy- N -methylamphetamine (MDMA, Ecstasy). Understanding the pharmacology and toxicology of these agents is essential in order to provide the best medical care for these patients. This review focuses on the pharmacology, pharmacokinetics, clinical effects, and treatment of 2C drug intoxication based on available published literature. Multiple names under which 2C drugs are sold were identified and tabulated. Common features identified in patients intoxicated with 2Cs included hallucinations, agitation, aggression, violence, dysphoria, hypertension, tachycardia, seizures, and hyperthermia. Patients may exhibit sympathomimetic symptoms or symptoms consistent with serotonin toxicity, but an excited delirium presentation seems to be consistent amongst deaths attributed to 2C drugs; at least five deaths have been reported in the literature in patients intoxicated with 2C drugs. 2C drugs are a group of designer intoxicants, many of which are marketed as legal, but may carry risks that consumers are unaware of. These drugs may be characterized by either serotonergic toxicity or a sympathomimetic toxidrome, but a presentation consistent with excited delirium is consistent amongst the reported 2C-related deaths. Treatment of 2C intoxication is primarily supportive, but immediate action is required in the context of excited delirium, hyperthermia, and seizure activity.

The incidence of metabolic syndrome is significantly higher in patients with irritable bowel syndrome (IBS), but the mechanisms involved remain unclear. Gut microbiota is causatively linked with the development of both metabolic dysfunctions and gastrointestinal disorders, thus gut dysbiosis in IBS may contribute to the development of metabolic syndrome. Here, we show that human gut bacterium Ruminococcus gnavus -derived tryptamine and phenethylamine play a pathogenic role in gut dysbiosis-induced insulin resistance in type 2 diabetes (T2D) and IBS. We show levels of R. gnavus , tryptamine, and phenethylamine are positively associated with insulin resistance in T2D patients and IBS patients. Monoassociation of R. gnavus impairs insulin sensitivity and glucose control in germ-free mice. Mechanistically, treatment of R. gnavus -derived metabolites tryptamine and phenethylamine directly impair insulin signaling in major metabolic tissues of healthy mice and monkeys and this effect is mediated by the trace amine-associated receptor 1 (TAAR1)-extracellular signal-regulated kinase (ERK) signaling axis. Our findings suggest a causal role for tryptamine/phenethylamine-producers in the development of insulin resistance, provide molecular mechanisms for the increased prevalence of metabolic syndrome in IBS, and highlight the TAAR1 signaling axis as a potential therapeutic target for the management of metabolic syndrome induced by gut dysbiosis. Here, the authors show a causal role for gut bacteria-derived metabolites tryptamine and phenethylamine in contributing to insulin resistance and the development of metabolic syndrome in patients with irritable bowel syndrome and type 2 diabetes.

Dofetilide is an effective antiarrhythmic medication for rhythm control in atrial fibrillation, but carries a significant risk of pro-arrhythmia and requires meticulous dosing and monitoring. The cornerstone of this monitoring, measurement of the QT/QTc interval, is an imperfect surrogate for plasma concentration, efficacy, and risk of pro-arrhythmic potential. The aim of our study was to test the application of a deep learning approach (using a convolutional neural network) to assess morphological changes on the surface ECG (beyond the QT interval) in relation to dofetilide plasma concentrations. We obtained publically available serial ECGs and plasma drug concentrations from 42 healthy subjects who received dofetilide or placebo in a placebo-controlled cross-over randomized controlled clinical trial. Three replicate 10-s ECGs were extracted at predefined time-points with simultaneous measurement of dofetilide plasma concentration We developed a deep learning algorithm to predict dofetilide plasma concentration in 30 subjects and then tested the model in the remaining 12 subjects. We compared the deep leaning approach to a linear model based only on QTc. Fourty two healthy subjects (21 females, 21 males) were studied with a mean age of 26.9 ± 5.5 years. A linear model of the QTc correlated reasonably well with dofetilide drug levels (r = 0.64). The best correlation to dofetilide level was achieved with the deep learning model (r = 0.85). This proof of concept study suggests that artificial intelligence (deep learning/neural network) applied to the surface ECG is superior to analysis of the QT interval alone in predicting plasma dofetilide concentration.

Protein dynamics play a crucial role in various physiological functions, including enzyme catalysis. To explore conformational changes during enzyme catalysis, we conduct mix-and-inject serial crystallography, an advanced technique to capture time-resolved protein structures in real time, using the microcrystals of bacterial copper amine oxidase containing a protein-derived quinone cofactor. Within 50 ms of mixing the microcrystals (<4 μm) with a preferred substrate (2-phenylethylamine) under anaerobic conditions (reductive half-reaction), we observe domain movements associated with substrate binding and formation of a metastable reaction intermediate, a product Schiff-base of the quinone cofactor. At 100–1000 ms after mixing, conformational transition from aminoresorcinol to the semiquinone radical forms of the reduced cofactor progresses gradually, likely depending on the replacement of the product aldehyde by the next-cycle amine substrate that triggers the cofactor conformational change. Overall, this study provides structural insight into enzyme catalysis accompanying the active-site conformational changes that are hardly scrutinized by studies in solution. Protein motion is essential for biological processes like enzyme function. Here the authors report the time-resolved protein structures captured during catalysis of copper amine oxidase using mix-and-inject serial femtosecond X-ray crystallography.

Accumulating evidence suggests a key role of the gut–microbiota–brain axis in the antidepressant actions of certain compounds. Ketamine, an N -methyl-D-aspartate receptor (NMDAR) antagonist, showed rapid and sustained antidepressant effects in treatment-resistant depressed patients. In contrast, another NMDAR antagonist, lanicemine, did not exhibit antidepressant effects in such patients. ( R )-ketamine, the ( R )-enantiomer of ketamine, has rapid-acting and long-lasting antidepressant effects in rodent models of depression. Here we compared the effects of ( R )-ketamine and lanicemine on depression-like phenotype and the composition of the gut microbiota in susceptible mice after chronic social defeat stress (CSDS). In behavioral tests, ( R )-ketamine showed antidepressant effects in the susceptible mice, whereas lanicemine did not. The 16S ribosomal RNA gene sequencing of feces demonstrated that ( R )-ketamine, but not lanicemine, significantly attenuated the altered levels of Bacteroidales , Clostridiales and Ruminococcaceae in the susceptible mice after CSDS. At the genus level, ( R )-ketamine significantly attenuated the marked increase of Clostridium in the susceptible mice. In contrast, the effects of lanicemine were less potent than those of ( R )-ketamine. This study suggests that the antidepressant effects of ( R )-ketamine might be partly mediated by the restoration of altered compositions of the gut microbiota in a CSDS model.