Lorcaserin: A review of its preclinical and clinical pharmacology and therapeutic potential

A Sensitive and Selective LC-MS/MS-ESI Method for the Quantitation of Metabolites M9, M12, and M20 of Bexicaserin in Human Plasma and Urine Matrices

Bexicaserin is a highly selective 5HT2c receptor agonist being developed for the treatment of seizures associated with developmental and epileptic encephalopathies (DEEs). We report an LC-MS/MS method for the quantitative estimation of three pharmacologically inactive metabolites (M9, M12, and M20) of bexicaserin in human plasma/urine. Sample preparation involves the extraction of M9, M12, M20, and internal standards (ISs) from 25-μL plasma and 50-μL urine following protein precipitation. The chromatographic separation of analytes was achieved on a HSS T3-C18 column. The calibration curves ranged from 0.1 to 100 ng/mL for M9, 0.5-500 ng/mL for M12, and 1.0-1000 ng/mL for M20 in plasma and 2.0-2000 ng/mL for M9 and M12 and 10-10,000 ng/mL for M20 in urine. Intraday/interday precision and accuracy, linearity, matrix effect, extraction recovery, carry-over, dilution integrity, stability studies, and incurred sample reanalysis were performed in both plasma and urine. The intraday and interday accuracy and precision for metabolites met the stipulated regulatory guidelines. Stability studies in plasma and urine showed that analytes were stable at bench-top for > 23.5 h and in autosampler for > 69 h. Analytes were stable after five freeze-thaw cycles and > 552 days of long-term storage at -20°C and -80°C.

Enantioselective Synthesis of 1-Dihydrobenzazepines through Rh2(II)-Catalyzed Cycloisomerization of 1,6-Enyne

The 1-dihydrobenzazepine skeleton has emerged as a privileged structural motif in bioactive molecules. However, due to a lack of asymmetric methodology, access to chiral 1-dihydrobenzazepines has remained limited. Herein, we report the first intermolecular asymmetric cycloisomerization of benzo-fused enynes for the synthesis of chiral 1-dihydrobenzazepines via dirhodium catalysis. This methodology features high efficiency (up to 98% yield), high enantioselectivity (up to 99% ee), and broad scope of nucleophiles, including oxygen nucleophiles (alcohols, phenols, and carboxylic acids) and carbon nucleophiles (silyl enol ethers). Theoretical and experimental mechanistic studies reveal that the reaction pathway encompasses an asymmetric cycloisomerization, which gives rise to a dirhodium carbene containing a donor-acceptor (D-A) cyclopropane moiety, followed by a ring-opening process and stereoselective nucleophilic attack by external nucleophiles on the cyclopropyl ring. Control experiments demonstrate the pivotal role of the terminal group capped on the alkynyl group of substrates in achieving good efficiency.

A Highly Sensitive Triple Quad LC-MS/MS Method Development and Validation for the Determination of Bexicaserin (LP352) in Human Plasma and Urine Matrices

Bexicaserin is a highly selective agonist at the 5-HT2c receptor in clinical development for the treatment of seizures associated with developmental and epileptic encephalopathies (DEEs). We report an LC-MS/MS method for the quantitative estimation of bexicaserin in human plasma and urine. The sample preparation involves the extraction of bexicaserin and internal standard (13CD2-bexicaserin; IS) from 150 μL plasma and 50 μL urine using a solid phase extraction method. The chromatographic separation of bexicaserin and IS was achieved on a Poroshell EC-C18 column using 5 min gradient program. The calibration curve ranged from 0.1 to 100 ng/mL in plasma and 1.0 to 1000 ng/mL in urine. Intraday and interday precision and accuracy, linearity, matrix effect, extraction recovery, carry-over, dilution integrity, a battery of stability studies, and incurred sample reanalysis were performed for bexicaserin in both plasma and urine. The intraday and interday accuracy and precision were well within the acceptable limits in both plasma and urine matrices. Stability studies in plasma and urine showed that bexicaserin was stable on bench for 24 h, in autosampler over 54 h, five freeze-thaw cycles, and long-term storage at -20°C and -80°C for > 368 days. The validated methods were successfully applied in clinical study.

Promising therapeutic strategies for Lennox-Gastaut syndrome: what's new?

INTRODUCTION

The seizures in Lennox-Gastaut syndrome are typically resistant to treatment. Seven antiseizure medications (ASMs) in the US (six in the UK/EU) are licensed for the treatment of seizures in LGS: lamotrigine, topiramate, rufinamide, clobazam, felbamate (not licensed in the UK/EU), cannabidiol and fenfluramine. Other options include neurostimulation, corpus callosotomy and dietary therapies, principally the ketogenic diet and its variants. New treatments and therapeutic strategies are needed to improve management of both seizures and cognitive/behavioral comorbidities in LGS.

AREAS COVERED

Embase and Medline were searched for articles published between 1 January 2014 and 21 August 2024 reporting efficacy data for pharmacological, neurostimulation, surgical and dietary interventions in individuals with LGS focusing on recent advances. Ongoing and prospective studies were identified from the National Library of Medicine register of clinical trials.

EXPERT OPINION

LGS remains a difficult-to-treat epilepsy. Although no major breakthroughs have been reported, several established and novel ASMs, some surgical strategies and other treatment approaches are of benefit or are showing promise. Progress remains incremental but any improvements in the management of this resistant epilepsy syndrome are worthwhile.

Targeting 5-HT Is a Potential Therapeutic Strategy for Neurodegenerative Diseases

There is increasing interest in the potential therapeutic role of 5-HT (serotonin) in the treatment of neurodegenerative diseases, which are characterized by the progressive degeneration and death of nerve cells. 5-HT is a vital neurotransmitter that plays a central role in regulating mood, cognition, and various physiological processes in the body. Disruptions in the 5-HT system have been linked to several neurological and psychiatric disorders, making it an attractive target for therapeutic intervention. Although the exact causes of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS) are not fully understood, researchers believe that regulating the 5-HT system could help alleviate symptoms and potentially slow the progression of these diseases. Here, we delve into the potential of harnessing 5-HT as a therapeutic target for the treatment of neurodegenerative diseases. It is important to note that the current clinical drugs targeting 5-HT are still limited in the treatment of these complex diseases. Therefore, further research and clinical trials are needed to evaluate the feasibility and effectiveness of its clinical application.

The 5-HT-related gut-brain axis in obesity

AIMS

The incidence of obesity increases annually. It is closely related to the occurrence of cardiovascular diseases, malignant tumors, etc., and has become a major global health problem. 5-hydroxytryptamine (5-HT), a multifunctional monoamine neurotransmitter, is dispersed throughout the central nervous system and digestive tract. It is intimately related to the mechanism of obesity.

MATERIALS AND METHODS

PubMed, Web of Science and Embase were carefully searched. We collected articles that are closely related to 5-HT, the gut-brain axis, and obesity.

KEY FINGDINGS

The gut microbiota not only influences nutrient metabolism but also centrally meditates appetite and mood regulation. The gut-brain axis, a system connecting the gut and the brain, is known to participate in two-way communication between the gut flora and the central nervous system.

SIGNIFICANCE

There have been few reports on whether peripheral and central 5-HT interact bidirectionally via the gut-brain axis and jointly play a role in the pathogenesis of obesity. In this review, we summarize the rationale for the contribution of the 5-HT-related gut-brain axis to the development of obesity and explore feasible signaling pathways, which elucidates new targets for preventing and treating obesity.

Barriers and facilitators to medication-assisted treatment for cocaine use disorder among men who have sex with men: a qualitative study

BACKGROUND

Rates of cocaine use disorder (CUD) among men who have sex with men (MSM) are high and rising. Among MSM, cocaine use is associated with negative socioeconomic, medical, and psychological outcomes. There are no FDA-approved pharmacotherapy options to treat CUD, and psychosocial interventions demonstrate limited efficacy. While there have been numerous trials evaluating possible medications for CUD, there is a scarcity of qualitative data on the barriers and facilitators of medication-assisted treatment.

METHODS

Semi-structured interviews were conducted with 16 participants enrolled in a phase II randomized control trial evaluating extended-release lorcaserin among MSM with CUD. Participants were asked about their motivations for enrolling in the study, attitudes towards taking a medication for CUD, barriers and facilitators of study pill adherence, and their general study experience. Interviews were analyzed using an inductive and exploratory approach to thematic analysis.

RESULTS

Participants were highly motivated to reduce cocaine use and viewed pharmacotherapy as a viable and desirable treatment option. Pharmacotherapy was seen as having fewer access and adherence structural barriers compared to existing psychosocial therapies. Medication reminders facilitated pill taking, while side effects, travel, and active substance use presented barriers to study pill adherence. Disclosure of study participation within social networks was variable pointing to anticipated substance use and treatment stigma.

CONCLUSIONS

Our study highlights important factors affecting the acceptability and uptake of medication-assisted treatment for CUD among a diverse sample of MSM. These findings can help guide the development and implementation of future pharmacotherapy options for CUD and other substance use disorders in this key population.

Evaluating bexicaserin for the treatment of developmental epileptic encephalopathies

INTRODUCTION

Developmental epileptic encephalopathies (DEEs) pose significant challenges due to their refractory nature and limited treatment options. Despite advancements in genetic understanding, effective therapies targeting underlying pathophysiology are lacking. Serotoninergic dysfunction has been implicated in epilepsy, sparking interest in serotonin as a therapeutic target.

AREA COVERED

This article explores the potential of bexicaserin, a selective 5-HT2C receptor agonist, as an adjunctive antiseizure medication in DEEs. Bexicaserin is thought to modulate GABAergic neurotransmission, suppressing central hyperexcitability. Preclinical studies demonstrate its efficacy across various seizure models. Clinical trials, including the Pacific Study, reveal promising results in reducing motor seizures. However, challenges such as adverse effects and treatment discontinuation underscore the need for further investigation.

EXPERT OPINION

The efficacy of 5-HT2C serotoninergic agonists, validated in preclinical and clinical studies, highlights serotonin's role in DEEs. Bexicaserin offers new therapeutic possibilities, potentially synergizing with existing antiseizure medications. Polypharmacotherapy, targeting distinct pathways, may enhance therapeutic outcomes. Monitoring pharmacological interactions and addressing central nervous system comorbidities are crucial for optimizing treatment strategies. Further research is needed to elucidate bexicaserin's mechanisms and potential antiepileptogenic effects.

Advancements in the management of obesity: a review of current evidence and emerging therapies

INTRODUCTION

Obesity is the modern world's current epidemic, with substantial health and economic impact. This study aimed to provide a narrative overview of the past, currently available, and future treatment options that offer therapeutic and preventive advantages for obesity management.

AREAS COVERED

Historically, rimonabant, and lorcaserin, were approved and used for managing non-syndromic obesity. Currently, orlistat, naltrexone/bupropion, glucagon-like peptide-1 receptor agonist (GLP-1 RA), and a few promising therapeutic agents are under investigation, including retatrutide, cagrilintide and orforglipron, which show promising weight reduction effects. We have developed a search string of the Medical Subject Headings (MeSH), including the terms GLP-1 RAs, obesity, and weight loss. This string was then used to perform a systematic literature search in the database including PubMed, EMBASE, MEDLINE, and Scopus up to January 31st, 2024.

EXPERT OPINION

Managing obesity often requires medical interventions, particularly in cases of severe obesity or obesity-related comorbidities. Thus, it is important to approach obesity management holistically, considering individual needs and circumstances. In our opinion, consulting with healthcare professionals is crucial to developing a personalized plan that addresses both weight loss and overall health improvement.

Therapeutic advances in obesity management: an overview of the therapeutic interventions

Obesity has become a global epidemic in the modern world, significantly impacting the global healthcare economy. Lifestyle interventions remain the primary approach to managing obesity, with medical therapy considered a secondary option, often used in conjunction with lifestyle modifications. In recent years, there has been a proliferation of newer therapeutic agents, revolutionizing the treatment landscape for obesity. Notably, glucagon-like peptide-1 receptor agonists (GLP-1 RAs), such as semaglutide, liraglutide, and the recently approved dual GLP-1/GIP RAs agonist tirzepatide, have emerged as effective medications for managing obesity, resulting in significant weight loss. These agents not only promote weight reduction but also improve metabolic parameters, including lipid profiles, glucose levels, and central adiposity. On the other hand, bariatric surgery has demonstrated superior efficacy in achieving weight reduction and addressing overall metabolic imbalances. However, with ongoing technological advancements, there is an ongoing debate regarding whether personalized medicine, targeting specific components, will shape the future of developing novel therapeutic agents for obesity management.

Interactions between lorcaserin and opioids: Ventilation and food-versus-drug choice

Lorcaserin, a selective serotonin 2C (5-HT2C) receptor agonist, was approved for treating obesity and has been investigated for treating substance use disorders including those involving opioids. Although lorcaserin was withdrawn from the market, interest in the therapeutic potential of drugs acting at 5-HT2C receptors continues, supporting the need to further characterize potential adverse effects especially when combined with drugs of abuse. This study examined acute effects of lorcaserin on opioid-induced ventilatory depression, which is the primary cause of overdose, and opioid self-administration, which models factors contributing to opioid abuse, in male and female rhesus monkeys. In one group (n = 4), effects of morphine (0.178 to 5.6 mg/kg, s.c.), fentanyl (0.0032 to 0.1 mg/kg, s.c.), and lorcaserin (0.1 to 1.78 mg/kg, s.c.) alone as well as effects of lorcaserin with each opioid on ventilation were determined using head plethysmography. Another group (n = 5) responded under a food versus fentanyl (0.1 to 3.2 μg/kg/infusion, i.v.) choice procedure, and lorcaserin (0.32 to 1.78 mg/kg, i.v.) was given as a pretreatment. Lorcaserin dose-dependently decreased minute volume to below 70 % of baseline when administered alone and increased the potency of morphine and fentanyl. Consistent with previous studies, lorcaserin failed to alter choice of fentanyl over food. This study demonstrates the novel finding that lorcaserin alone decreases ventilation and enhances the ventilatory-depressant effects of opioids. Taken together with previous studies, these results suggest that combining a 5-HT2C receptor agonist such as lorcaserin with an opioid could increase the risk of ventilatory depression without the benefit of decreasing abuse.

Lorcaserin: Worthy of Further Insights? Results from Recent Research

Lorcaserin is a 3-benzazepine that binds 5-HT2C serotonin receptors in the hypothalamus, where it mediates lack of hunger and/or satiety, and in the ventral tegmental area, the site of origin of the mesolimbic and mesocortical dopaminergic projections, which mediate pleasure and reward. The drug has been first developed for the treatment of obesity, where it has shown efficacy, and subsequently trialed to counter substance use (mostly cocaine, cannabis, opioids, and nicotine) and craving, but showed inconsistent effects. Since 2020, the US Food and Drug Administration obtained that the drug was voluntarily withdrawn from the US market on the grounds that its long-term use was found to be associated with a greater incidence of some types of cancer. Provided it can show to be free from cancerogenic effects, ongoing research suggests that lorcaserin may have therapeutic potential for a variety of disorders and conditions beyond obesity. Since 5-HT2C receptors are involved in many diversified physiological functions (mood, feeding, reproductive behavior, neuronal processes related to impulsiveness, and modulating reward-related mechanisms) this drug has the potential to treat different central nervous system conditions, such as depression and schizophrenia.

Clinical and Genetic Features of Dravet Syndrome: A Prime Example of the Role of Precision Medicine in Genetic Epilepsy

Dravet syndrome (DS), also known as severe myoclonic epilepsy of infancy, is a rare and drug-resistant form of developmental and epileptic encephalopathies, which is both debilitating and challenging to manage, typically arising during the first year of life, with seizures often triggered by fever, infections, or vaccinations. It is characterized by frequent and prolonged seizures, developmental delays, and various other neurological and behavioral impairments. Most cases result from pathogenic mutations in the sodium voltage-gated channel alpha subunit 1 (SCN1A) gene, which encodes a critical voltage-gated sodium channel subunit involved in neuronal excitability. Precision medicine offers significant potential for improving DS diagnosis and treatment. Early genetic testing enables timely and accurate diagnosis. Advances in our understanding of DS's underlying genetic mechanisms and neurobiology have enabled the development of targeted therapies, such as gene therapy, offering more effective and less invasive treatment options for patients with DS. Targeted and gene therapies provide hope for more effective and personalized treatments. However, research into novel approaches remains in its early stages, and their clinical application remains to be seen. This review addresses the current understanding of clinical DS features, genetic involvement in DS development, and outcomes of novel DS therapies.

μ-opioid receptor agonists and psychedelics: pharmacological opportunities and challenges

Opioid misuse and opioid-involved overdose deaths are a massive public health problem involving the intertwined misuse of prescription opioids for pain management with the emergence of extremely potent fentanyl derivatives, sold as standalone products or adulterants in counterfeit prescription opioids or heroin. The incidence of repeated opioid overdose events indicates a problematic use pattern consistent with the development of the medical condition of opioid use disorder (OUD). Prescription and illicit opioids reduce pain perception by activating µ-opioid receptors (MOR) localized to the central nervous system (CNS). Dysregulation of meso-corticolimbic circuitry that subserves reward and adaptive behaviors is fundamentally involved in the progressive behavioral changes that promote and are consequent to OUD. Although opioid-induced analgesia and the rewarding effects of abused opioids are primarily mediated through MOR activation, serotonin (5-HT) is an important contributor to the pharmacology of opioid abused drugs (including heroin and prescription opioids) and OUD. There is a recent resurgence of interest into psychedelic compounds that act primarily through the 5-HT2A receptor (5-HT 2A R) as a new frontier in combatting such diseases (e.g., depression, anxiety, and substance use disorders). Emerging data suggest that the MOR and 5-HT2AR crosstalk at the cellular level and within key nodes of OUD circuitry, highlighting a major opportunity for novel pharmacological intervention for OUD. There is an important gap in the preclinical profiling of psychedelic 5-HT2AR agonists in OUD models. Further, as these molecules carry risks, additional analyses of the profiles of non-hallucinogenic 5-HT2AR agonists and/or 5-HT2AR positive allosteric modulators may provide a new pathway for 5-HT2AR therapeutics. In this review, we discuss the opportunities and challenges associated with utilizing 5-HT2AR agonists as therapeutics for OUD.

The Relationship Between Oxytocin and Alcohol Dependence

The hypothalamic neuropeptide oxytocin (OT) is well known for its prosocial, anxiolytic, and ameliorating effects on various psychiatric conditions, including alcohol use disorder (AUD). In this chapter, we will first introduce the basic neurophysiology of the OT system and its interaction with other neuromodulatory and neurotransmitter systems in the brain. Next, we provide an overview over the current state of research examining the effects of acute and chronic alcohol exposure on the OT system as well as the effects of OT system manipulation on alcohol-related behaviors in rodents and humans. In rodent models of AUD, OT has been repeatedly shown to reduce ethanol consumption, particularly in models of acute alcohol exposure. In humans however, the results of OT administration on alcohol-related behaviors are promising but not yet conclusive. Therefore, we further discuss several physiological and methodological limitations to the effective application of OT in the clinic and how they may be mitigated by the application of synthetic OT receptor (OTR) agonists. Finally, we discuss the potential efficacy of cutting-edge pharmacology and gene therapies designed to specifically enhance endogenous OT release and thereby rescue deficient expression of OT in the brains of patients with severe forms of AUD and other incurable mental disorders.

Visceral adipose tissue and residual cardiovascular risk: a pathological link and new therapeutic options

Obesity is a heterogeneous disease that affects almost one-third of the global population. A clear association has been established between obesity and cardiovascular disease (CVD). However, CVD risk is known to be related more to the local distribution of fat than to total body fat. Visceral adipose tissue (VAT) in particular has a high impact on CVD risk. This manuscript reviews the role of VAT in residual CV risk and the available therapeutic strategies for decreasing residual CV risk related to VAT accumulation. Among the many pathways involved in residual CV risk, obesity and particularly VAT accumulation play a major role by generating low-grade systemic inflammation, which in turn has a high prognostic impact on all-cause mortality and myocardial infarction. In recent years, many therapeutic approaches have been developed to reduce body weight. Orlistat was shown to reduce both weight and VAT but has low tolerability and many drug-drug interactions. Naltrexone-bupropion combination lowers body weight but has frequent side effects and is contraindicated in patients with uncontrolled hypertension. Liraglutide and semaglutide, glucagon-like peptide 1 (GLP-1) agonists, are the latest drugs approved for the treatment of obesity, and both have been shown to induce significant body weight loss. Liraglutide, semaglutide and other GLP-1 agonists also showed a positive effect on CV outcomes in diabetic patients. In addition, liraglutide showed to specifically reduce VAT and inflammatory biomarkers in obese patients without diabetes. GLP-1 agonists are promising compounds to limit inflammation in human visceral adipocytes.

Pharmacological strategies for appetite modulation in eating disorders: a narrative review

BACKGROUND

A substantial increase in the prevalence of eating disorders has been noticed over the past decades. Priority in the treatment of eating disorders is justifiably given to psychosocial interventions. However, it is also well known that centrally acting drugs can significantly affect appetite and food consumption.

AIM

To narratively review the available neurobiological data on the mechanisms of central regulation of eating behavior as a rationale to summarize pharmacological strategies for appetite modulation in eating disorders.

METHODS

The authors have carried out a narrative review of scientific papers published from January 2013 to March 2023 in the PubMed and Web of Science electronic databases. Studies were considered eligible if they included data on the neurobiological mechanisms of appetite regulation or the results of clinical trials of centrally acting drugs in eating disorders. Relevant studies were included regardless of their design. Descriptive analysis was used to summarize the obtained data.

RESULTS

The review included 51 studies. The available neurobiological and clinical data allowed us to identify the following pharmacological strategies for appetite modulation in eating disorders: serotonergic, catecholaminergic, amino acidergic and peptidergic. However, implementation of these data into clinical practice difficult due to an insufficient number of good-quality studies, which is particularly relevant for adolescents as there is a research gap in this population.

CONCLUSION

The progress in neurobiological understanding of the mechanisms of central regulation of appetite opens opportunities for new pharmacotherapeutic approaches aimed at changing the patterns of eating behavior. Obviously, treatment of eating disorders is a much broader problem and cannot be reduced to the correction of eating patterns. Nevertheless, at certain stages of treatment, drug-induced modulation of appetite can play an important role among multi-targeted biological and psychosocial interventions. Translation of neurobiological data into clinical practice requires a large number of clinical studies to confirm the long-term efficacy and safety of pharmacotherapeutic approaches and to develop personalized algorithms for the treatment of various forms of eating disorders in different age groups.

Open Label Pilot of Lorcaserin (a serotonin 2C-receptor agonist) for Cannabis Use Disorder

Background And Objective

Cannabis Use Disorder (CUD) has no FDA approved treatment. Serotonin-2c (5HT2c) agonists have preclinical and human laboratory evidence for potential efficacy for CUD. We assessed the tolerability and effects of lorcaserin (5HT2c agonist) on CUD.

Methods

In a 10-week, open label, uncontrolled trial, the tolerability of lorcaserin was tested in outpatients with CUD. Adverse events (AE) were assessed weekly. Cannabis use was assessed twice weekly by the Timeline follow-back and quantitative urine metabolites.

Results

17 participants enrolled, and 14 received medication. Participants' average age was 35 years; majority were male (N=12). The medication was well tolerated in males. There were no serious adverse events (SAE). The most common AE's were headache/migraine (N=4, all females), anorexia (N=3), and irritability (N=2). Participants decreased their frequency of cannabis use significantly (p < 0.001), adjusted for baseline use. By the end of the trial, participants decreased by 1.76 (SE=0.47) cannabis using days/week. Average daily amount of cannabis and urine THC metabolite levels did not change significantly.

Conclusions

Lorcaserin was well tolerated in males but not females suggesting possible sex differences. Future trials of other 5HT2c agonists (lorcaserin was withdrawn at the request of the FDA) should consider longer dose titration phases.

Trial Registration

NCT02932215.

Epilepsy in Dravet Syndrome—Current and Future Therapeutic Opportunities

Dravet Syndrome (DS) is a developmental epileptic encephalopathy characterized by drug-resistant seizures and other clinical features, including intellectual disability and behavioral, sleep, and gait problems. The pathogenesis is strongly connected to voltage-gated sodium channel dysfunction. The current consensus of seizure management in DS consists of a combination of conventional and recently approved drugs such as stiripentol, cannabidiol, and fenfluramine. Despite promising results in randomized clinical trials and extension studies, the prognosis of the developmental outcomes of patients with DS remains unfavorable. The article summarizes recent changes in the therapeutic approach to DS and discusses ongoing clinical research directions. Serotonergic agents under investigation show promising results and may replace less DS-specific medicines. The use of antisense nucleotides and gene therapy is focused not only on symptom relief but primarily addresses the underlying cause of the syndrome. Novel compounds, after expected safe and successful implementation in clinical practice, will open a new era for patients with DS. The main goal of causative treatment is to modify the natural course of the disease and provide the best neurodevelopmental outcome with minimum neurological deficit.

New Insight into Selective Serotonin Receptor Agonists in the Central Nervous System, Studied with WAY163909 in Obese and Diabetic Wistar Rats

Background and aims: We investigated the effect of WAY-163909, a novel 5-hydroxytryptamine selective 2C receptor agonist on body weight, blood glucose levels, and insulin resistance in obese and diabetic Wistar rats. Materials and methods: We used twenty male Wistar rats with obesity and obesity-induced diabetes and twenty healthy Wistar rats as a control group. Each of these groups was separated into two subgroups: one with a daily intraperitoneal application of WAY-163909 (1 mg/kg) and one without. During the study, body weight, blood glucose levels, and immunoreactive insulin were tracked. Results: A reduction of 5.5% (p < 0.05) in body weight was registered in the rat group with diabetes and obesity and 2.56% in the control group with a daily application of WAY-163909 (1 mg/kg) at the end of the study. Decreases of 35.4% in blood glucose levels at week four in the diabetic and obese rat group with a daily application of WAY-163909 (1 mg/kg) were registered. A reduction of insulin levels of 4.1% (p < 0.05) in the diabetic and obese rats group using WAY-163909 was also observed. Conclusion: In our study, using WAY-163909 (1 mg/kg) led to a reduction of blood glucose levels, immunoreactive insulin, and body weight.

Advancing targeted protein degradation for metabolic diseases therapy

The development and application of traditional drugs represented by small molecule chemical drugs and biological agents, especially inhibitors, have become the mainstream drug development. In recent years, targeted protein degradation (TPD) technology has become one of the most promising methods to remove specific disease-related proteins using cell self-destruction mechanisms. Many different TPD strategies are emerging based on the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP), including but not limited to proteolysis-targeting chimeras (PROTAC), molecular glues (MG), lysosome targeting chimeras (LYTAC), chaperone-mediated autophagy (CMA)-targeting chimeras, autophagy-targeting chimera (AUTAC), autophagosome-tethering compound (ATTEC), and autophagy-targeting chimera (AUTOTAC). The advent of targeted degradation technology can change most protein targets in human cells from undruggable to druggable, greatly expanding the therapeutic prospect of refractory diseases such as metabolic syndrome. Here, we summarize the latest progress of major TPD technologies, especially in metabolic syndrome and look forward to providing new insights for drug discovery.

Reverse Engineering Drugs: Lorcaserin as an Example

Novel central nervous system (CNS)-based therapies have been difficult to produce due to the complexity of the brain, limited knowledge of CNS-based disease development and associated pathways, difficulty in penetrating the blood brain barrier, and a lack of reliable biomarkers of disease. Reverse engineering in drug development allows the utilization of new knowledge of disease pathways and the use of innovative technology to develop medications with enhanced efficacy and reduced toxicities. Lorcaserin was developed as a specific 5HT_2C serotonin receptor agonist for the treatment of obesity with limited off-target effects at the 5HT_2A and 5HT_2B receptors. This receptor specificity limited the hallucinogenic and cardiovascular side effects noted with other serotonin receptor agonists. Reverse engineering approaches to drug development reduce the cost of producing new medications, identify specific populations of patients that will derive the most benefit from therapy, and produce novel therapies with greater efficacy and limited toxicity.

Sensitivity of a fentanyl-vs.-social interaction choice procedure to environmental and pharmacological manipulations

Recent studies have shown that social interaction can serve as an alternative reinforcer to opioid self-administration under a choice context in rats. However, additional parametric studies are needed to evaluate the sensitivity of opioid-vs.-social interaction procedures relative to more established opioid-vs.-food procedures. The current study evaluated the sensitivity of a novel fentanyl-vs.-social interaction choice procedure to environmental and pharmacological manipulations previously shown to affect fentanyl-vs.-food choice. Male and female rats (responder rats; n = 6/sex) were trained to respond in a discrete-trial choice procedure for either 30-s access to a same-sex "partner" rat or an intravenous fentanyl infusion. Once trained, the effects of fentanyl unit dose (0, 0.32-10 μg/kg/inf), partner rat presence, opioid-dependence status, chronic naltrexone administration (0.032, 0.1 mg/kg/h), and response requirement for fentanyl self-administration (fixed ratio 1-320) were determined across weeks. The fentanyl-vs.-social interaction choice procedure was sensitive to the unit dose of fentanyl, chronic naltrexone treatment, and fentanyl response requirement. However, the magnitude of these effects on fentanyl choice was smaller than those reported in published fentanyl-vs.-food choice studies. Furthermore, fentanyl-vs.-social interaction choice was not sensitive to removal of the partner rat or opioid-dependence status. Minimal sex differences were detected. These results suggest that this fentanyl-vs.-social interaction choice procedure is less sensitive to environmental and pharmacological interventions than previously established opioid-vs.-food choice procedures. The observed discrepancy in sensitivity between the procedures suggests that social interaction may have qualitatively different reinforcing properties compared to more commonly assessed alternative reinforcers such as food (preclinical) or money (human laboratory).

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): II. Drugs in more advanced clinical development

The Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI) was held in Madrid, Spain on May 22-25, 2022 and was attended by 157 delegates from 26 countries representing basic and clinical science, regulatory agencies, and pharmaceutical industries. One day of the conference was dedicated to sessions presenting and discussing investigational compounds under development for the treatment of seizures and epilepsy. The current progress report summarizes recent findings and current knowledge for seven of these compounds in more advanced clinical development for which either novel preclinical or patient data are available. These compounds include bumetanide and its derivatives, darigabat, ganaxolone, lorcaserin, soticlestat, STK-001, and XEN1101. Of these, ganaxolone was approved by the US Food and Drug Administration in March 2022 for the treatment of seizures associated with cyclin-dependent kinase-like 5 deficiency disorder in patients 2 years of age and older.

The serotonergic system dysfunction in diabetes mellitus

Most peripheral serotonin (5-HT) is synthesized in enterochromaffin cells, and most circulating 5-HT is stored in platelets. As a monoamine, 5-HT has several functions in various non-neuronal and neuronal systems. In the central nervous system, it functions as a neurotransmitter to modulate feeding behavior and mood. Numerous clinical trials have focused on increasing 5-HT activation in the central nervous system, including those involving anti-obesity drugs currently in the market, although severe side effects on peripheral system can lead to the withdrawal of certain drugs. Recent studies have revealed that both the peripheral and central serotonergic systems play a vital role in diabetes and its complications. This review summarizes the roles of the serotonergic system in blood glucose regulation, diabetic macroangiopathy, diabetic peripheral neuropathy, and diabetic encephalopathy, indicating its potential clinical significance as a therapeutic target for the treatment of diabetes and its complications.

Biphasic reward effects are characteristic of both lorcaserin and drugs of abuse: implications for treatment of substance use disorders

Lorcaserin is a modestly selective agonist for 2C serotonin receptors (5-HT2CR). Despite early promising data, it recently failed to facilitate cocaine abstinence in patients and has been compared with dopamine antagonist medications (antipsychotics). Here, we review the effects of both classes on drug reinforcement. In addition to not being effective treatments for cocaine use disorder, both dopamine antagonists and lorcaserin can have biphasic effects on dopamine and reward behavior. Lower doses can cause enhanced drug taking with higher doses causing reductions. This biphasic pattern is shared with certain stimulants, opioids, and sedative-hypnotics, as well as compounds without abuse potential that include agonists for muscarinic and melatonin receptors. Additional factors associated with decreased drug taking include intermittent dosing for dopamine antagonists and use of progressive-ratio schedules for lorcaserin. Clinically relevant doses of lorcaserin were much lower than those that inhibited cocaine-reinforced behavior and can also augment this same behavior in different species. Diminished drug-reinforced behavior only occurred in animals after higher doses that are not suitable for use in patients. In conclusion, drugs of abuse and related compounds often act as biphasic modifiers of reward behavior, especially when evaluated over a broad range of doses. This property may reflect the underlying physiology of the reward system, allowing homeostatic influences on behavior.

Tobacco and nicotine use

Tobacco smoking is a major determinant of preventable morbidity and mortality worldwide. More than a billion people smoke, and without major increases in cessation, at least half will die prematurely from tobacco-related complications. In addition, people who smoke have a significant reduction in their quality of life. Neurobiological findings have identified the mechanisms by which nicotine in tobacco affects the brain reward system and causes addiction. These brain changes contribute to the maintenance of nicotine or tobacco use despite knowledge of its negative consequences, a hallmark of addiction. Effective approaches to screen, prevent and treat tobacco use can be widely implemented to limit tobacco's effect on individuals and society. The effectiveness of psychosocial and pharmacological interventions in helping people quit smoking has been demonstrated. As the majority of people who smoke ultimately relapse, it is important to enhance the reach of available interventions and to continue to develop novel interventions. These efforts associated with innovative policy regulations (aimed at reducing nicotine content or eliminating tobacco products) have the potential to reduce the prevalence of tobacco and nicotine use and their enormous adverse impact on population health.

Lorcaserin for Dravet Syndrome: A Potential Advance Over Fenfluramine?

Lorcaserin, a selective serotonin 5-HT_2C receptor agonist, was developed as an appetite suppressant with the rationale of minimizing the risk of cardiovascular toxicity associated with non-selective serotoninergic agents such as fenfluramine. Eight years after FDA approval, however, it was withdrawn from the market, when a large safety study suggested a potential cancer risk. Following in the fenfluramine footsteps and utilizing the repurposing approach coupled with the regulatory orphan drug designation, lorcaserin is currently in clinical development for the treatment of epilepsy. This potential novel indication builds on the evidence that 5-HT_2C receptor stimulation can protect against seizures, and accounts at least in part for fenfluramine's antiseizure effects in Dravet syndrome models. In animal models, lorcaserin shows a narrower range of antiseizure activity than fenfluramine. In particular, lorcaserin is inactive in classical acute seizure tests such as maximal electroshock and subcutaneous pentylenetetrazole in mice and rats, and the 6-Hz stimulation model in mice. However, it is active in the GAERS absence seizure model, and in mutant zebrafish models of Dravet syndrome. Preliminary uncontrolled studies in patients with Dravet syndrome have yielded promising results, and a phase III, double-blind, placebo-controlled, parallel group trial is currently ongoing to assess its efficacy and safety in children and adults with Dravet syndrome.

Chronic Treatment With Psilocybin Decreases Changes in Body Weight in a Rodent Model of Obesity

BACKGROUND

There are currently relatively few effective pharmacological treatments for obesity, and existing ones may be associated with limiting side-effects. In the search for novel anti-obesity agents, drugs that modify central serotonergic systems have historically proven to be effective in promoting weight loss. Psilocin, which is rapidly metabolized from psilocybin, is an agonist at multiple serotonin receptors. In the present study we assessed the effects of psilocybin and a positive control (metformin) on changes in body weight in a rat model of obesity.

METHODS

Five groups of adult male rats were pre-conditioned with a cafeteria diet until obese (>600 g) and then treated with either psilocybin (0.1, 1, or 5 mg/kg, i.p.), metformin (300 mg/kg, p.o.) or vehicle control. Treatments were for 27 consecutive weekdays, and body weights and high calorie food intake were recorded daily. Fasting glucose levels were recorded after 11 days of treatment. At the end of treatment rats completed a glucose tolerance test, and multiple fat pads were dissected out to assess adiposity.

RESULTS

The medium dose psilocybin group had to be terminated from the study prematurely. Both the low and high dose psilocybin groups caused a significant decrease in changes in body weight compared to controls. The metformin group produced a greater decrease in change in body weight than either psilocybin groups or controls. Both high dose psilocybin and metformin decreased consumption of the high calorie diet, and exhibited decreased central adiposity.

CONCLUSION

Psilocybin demonstrated modest but significant effects on weight gain. Further study is recommended.

Environmental influence on the preclinical evaluation of substance use disorder therapeutics

Substance use disorders (SUD) develop as a result of complex interactions between the environment, the subject, and the drug of abuse. Preclinical basic research investigating each of these tripartite components of SUD individually has resulted in advancements in our fundamental knowledge regarding the progression from drug abuse to SUD and severe drug addiction and the underlying behavioral and neurobiological mechanisms. How these complex interactions between the environment, the subject, and the drug of abuse impact the effectiveness of candidate or clinically used medications for SUD has not been as extensively investigated. The focus of this chapter will address the current state of our knowledge how these environmental, subject, and pharmacological variables have been shown to impact candidate or clinical SUD medication evaluation in preclinical research using drug self-administration procedures as the primary dependent measure. The results discussed in this chapter highlight the importance of considering environmental variables such as the schedule of reinforcement, concurrent availability of alternative nondrug reinforcers, and experimental housing conditions in the context of SUD therapeutic evaluation. The thesis of this chapter is that improved understanding of environmental variables in the context of SUD research will facilitate the utility of preclinical drug self-administration studies in the evaluation and development of candidate SUD therapeutics.

Targeting strategies for oxaliplatin-induced peripheral neuropathy: clinical syndrome, molecular basis, and drug development

Oxaliplatin (OHP)-induced peripheral neurotoxicity (OIPN) is a severe clinical problem and potentially permanent side effect of cancer treatment. For the management of OIPN, accurate diagnosis and understanding of significant risk factors including genetic vulnerability are essential to improve knowledge regarding the prevalence and incidence of OIPN as well as enhance strategies for the prevention and treatment of OIPN. The molecular mechanisms underlying OIPN are complex, with multi-targets and various cells causing neuropathy. Furthermore, mechanisms of OIPN can reinforce each other, and combination therapies may be required for effective management. However, despite intense investigation in preclinical and clinical studies, no preventive therapies have shown significant clinical efficacy, and the established treatment for painful OIPN is limited. Duloxetine is the only agent currently recommended by the American Society of Clinical Oncology. The present article summarizes the most recent advances in the field of studies on OIPN, the overview of the clinical syndrome, molecular basis, therapy development, and outlook of future drug candidates. Importantly, closer links between clinical pain management teams and oncology will advance the effectiveness of OIPN treatment, and the continued close collaboration between preclinical and clinical research will facilitate the development of novel prevention and treatments for OIPN.

Novel and emerging therapeutics for genetic epilepsies

INTRODUCTION

Disease-specific treatments are available only for a minority of patients with genetic epilepsies, while the rest are treated with anticonvulsants, which are ineffective in almost one-third of patients.

AREAS COVERED

Recently approved and the most effective emerging therapeutics under development for the treatment of genetic epilepsies are overviewed after systematic search and analysis of relevant literature.

EXPERT OPINION

New and emerging drugs for genetic epilepsies exploit one of the two approaches: inhibiting hyperactive brain foci through blocking excitatory or augmenting inhibitory neurotransmission, or correcting the underlying genetic defect. The first is limited by insufficient selectivity of available compounds, and the second by imperfection of currently used vectors of genetic material, unselective and transient transgene expression. Besides, the treatment may come too late, after structural abnormalities and epilepsy deterioration takes place. However, with recent improvements, we can expect to see soon gradual decline in the number of patients with therapy-resistant genetic epilepsies.

The serotonin 2C receptor agonist lorcaserin, alone and in combination with the opioid receptor antagonist naltrexone, attenuates binge-like ethanol drinking

The serotonin (5-HT) system has been implicated in the pathophysiology of alcohol (ethanol; EtOH) use disorders. Lorcaserin, a 5-HT_2C receptor agonist, attenuates drug self-administration in animal models. We investigated the effects of lorcaserin on EtOH intake using the drinking-in-the-dark (DID) procedure, an animal model of binge-like drinking. We compared the effects of lorcaserin to those of the Food and Drug Administration (FDA)-approved drug naltrexone and examined the effects of combining lorcaserin and naltrexone. To examine whether effects were specific for EtOH, we examined the effects of lorcaserin and naltrexone, administered alone and in combination, on saccharin intake. Adult male C57BL/6J mice received EtOH access (20% v/v) for 2 h in the home-cage during the first 3 days of the DID procedure, beginning 3 h into the dark cycle. On day 4, mice were injected with lorcaserin, naltrexone, or a combination of lorcaserin and naltrexone prior to a 4-h EtOH access. Intake was measured at 2 and 4 h. Lorcaserin reduced EtOH intake in a dose-dependent fashion over the 2- and 4-h measurement periods. Naltrexone also reduced EtOH intake when administered alone, with dose-dependent effects being more pronounced over 2 h rather than the full 4-h session. Combining lorcaserin and naltrexone reduced binge-like EtOH drinking to a greater extent than either drug alone. A similar pattern of results was obtained for saccharin intake. These results suggest that lorcaserin and naltrexone can have additive effects on binge-like EtOH drinking. They also support continued research into the therapeutic potential of lorcaserin for alcohol use disorders.

Case Report: Bilateral Ciliary Body Detachment in a Patient Taking Oral Diet Pills

SIGNIFICANCE

The use of antiobesity drugs is becoming more widespread, and the resulting adverse effects are also increasing. Visual impairments caused by weight-loss pills need a timely and accurate diagnosis and treatment. Prompt diagnosis and treatment can achieve a satisfactory prognosis.

PURPOSE

This report describes a case of a significant decline in bilateral visual acuity caused by taking diet pills and explores the possible pathogenesis.

CASE REPORT

A 32-year-old Chinese woman showed shallow anterior chambers, and intraocular pressure (IOP) was 38 mmHg bilaterally after taking Korean prescription diet pills for 6 days. The best-corrected visual acuity of both eyes was 0.03. The ultrasound biomicroscopy showed complete ciliary body detachment accompanied with angle closure. The central anterior chamber depths were 1.70 mm in the right eye and 1.61 mm in the left eye. The patient was diagnosed with ciliary body detachment with secondary elevated IOP. The patient was treated with pilocarpine, carteolol hydrochloride, brinzolamide, mannitol, and dexamethasone sodium phosphate. The patient had rewarding prognosis after treatment with discontinuation of diet pills, control of IOP, and glucocorticoids.

CONCLUSIONS

Extensive publicity and education are needed to ensure that consumers do not abuse diet pills; meanwhile, a timely diagnosis and withdrawal are crucial for a desirable prognosis. Clinicians need to consider the possibility of drug-secondary ocular diseases.

Pilot study of extended-release lorcaserin for cocaine use disorder among men who have sex with men: A double-blind, placebo-controlled randomized trial

OBJECTIVE

To determine if men who have sex with men (MSM) with cocaine use disorder (CUD) and actively-using cocaine could be enrolled and retained in a pharmacologic intervention trial of lorcaserin-a novel 5-HT2cR agonist-and determine the degree to which participants would adhere to study procedures.

METHODS

This was a phase II randomized, double-blind, placebo-controlled pilot study with 2:1 random parallel group assignment to daily extended-release oral lorcaserin 20 mg versus placebo (clinicaltrials.gov identifier-NCT03192995). Twenty-two of a planned 45 cisgender MSM with CUD were enrolled and had weekly follow-up visits during a 12-week treatment period, with substance use counseling, urine specimen collection, and completion of audio-computer assisted self-interview (ACASI) behavioral risk assessments. Adherence was measured by medication event monitoring systems (MEMS) caps and self-report. This study was terminated early because of an FDA safety alert for lorcaserin's long-term use.

RESULTS

Eighty-six percent completed the trial, with 82% of weekly study follow-up visits completed. Adherence was 55.3% (lorcaserin 51.6% vs. placebo 66.2%) by MEMS cap and 56.9% (56.5% vs. placebo 57.9%) by self-report and did not differ significantly by treatment assignment. Intention-to-treat analyses (ITT) did not show differences in cocaine positivity by urine screen between the lorcaserin and placebo groups by 12 week follow-up (incidence risk ratio [IRR]: 0.96; 95%CI = 0.24-3.82, P = 0.95). However, self-reported cocaine use in timeline follow-back declined more significantly in the lorcaserin group compared to placebo (IRR: 0.66; 95%CI = 0.49-0.88; P = 0.004).

CONCLUSION

We found that it is feasible, acceptable, and tolerable to conduct a placebo-controlled pharmacologic trial for MSM with CUD who are actively using cocaine. Lorcaserin was not associated with significant reductions in cocaine use by urine testing, but was associated with significant reductions in self-reported cocaine use. Future research may be needed to continue to explore the potential utility of 5-HT2cR agonists.

Evaluation of lorcaserin as an anticonvulsant in juvenile Fmr1 knockout mice

Recent preclinical and clinical studies suggest that lorcaserin, a preferential serotonin 2C receptor (5-HT_2CR) agonist that was approved for the treatment of obesity, possesses antiepileptic properties. Here, we tested whether lorcaserin (1, 3, 5.6, 10 mg/kg) is prophylactic against audiogenic seizures (AGSs) in juvenile Fmr1 knockout mice, a mouse model of fragile X syndrome (FXS). MPEP (30 mg/kg), a non-competitive mGluR5 receptor antagonist, was used as a positive control. As lorcaserin likely engages 5-HT_2ARs at therapeutic doses, we pretreated one group of mice with the selective 5-HT_2AR antagonist/inverse agonist, M100907 (0.03 mg/kg), alone or before administering lorcaserin (5.6 mg/kg), to discern putative contributions of 5-HT_2ARs to AGSs. We also assessed lorcaserin's in vitro pharmacology at human (h) and mouse (m) 5-HT_2CRs and 5-HT_2ARs and its in vivo interactions at m5-HT_2CRs and m5-HT_2ARs. MPEP significantly decreased AGS prevalence (P = 0.011) and lethality (P = 0.038). Lorcaserin, 3 mg/kg, attenuated AGS prevalence and lethality by 14 % and 32 %, respectively, however, results were not statistically significant (P = 0.5 and P = 0.06); other doses and M100907 alone or with lorcaserin also did not significantly affect AGSs. Lorcaserin exhibited full efficacy agonist activity at h5-HT_2CRs and m5-HT_2CRs, and near full efficacy agonist activity at h5-HT_2ARs and m5-HT_2ARs; selectivity for activation of 5-HT_2CRs over 5-HT_2ARs was greater for human (38-fold) compared to mouse (13-fold) receptors. Lorcaserin displayed relatively low affinities at antagonist-labeled 5-HT_2CRs and 5-HT_2ARs, regardless of species. Lorcaserin (3 and 5.6 mg/kg) increased the 5-HT_2AR-dependent head-twitch response (HTR) elicited by (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) in mice (P = 0.03 and P = 0.02). At 3 mg/kg, lorcaserin alone did not elicit an HTR. If mice were treated with the selective 5-HT_2CR antagonist SB 242084 (0.5 or 1 mg/kg) plus lorcaserin (3 mg/kg), a significantly increased HTR was observed, relative to vehicle (P = 0.01 and P = 0.03), however, the HTR was much lower than what was elicited by DOI or DOI plus lorcaserin. Lorcaserin, 3 mg/kg, significantly reduced locomotor activity on its own, an effect reversed by SB 242084, and lorcaserin also dose-dependently reduced locomotor activity when administered prior to DOI (Ps<0.002). These data suggest that lorcaserin may engage 5-HT_2CRs as well as 5-HT_2ARs in mice at doses as low as 3 mg/kg. The similar activity at m5-HT_2CRs and m5-HT_2ARs suggests careful dosing of lorcaserin is necessary to selectively engage 5-HT_2CRs in vivo. In conclusion, lorcaserin was ineffective at preventing AGSs in Fmr1 knockout mice. Lorcaserin may not be a suitable pharmacotherapy for seizures in FXS.

Converging vulnerability factors for compulsive food and drug use

Highly palatable foods and substance of abuse have intersecting neurobiological, metabolic and behavioral effects relevant for understanding vulnerability to conditions related to food (e.g., obesity, binge eating disorder) and drug (e.g., substance use disorder) misuse. Here, we review data from animal models, clinical populations and epidemiological evidence in behavioral, genetic, pathophysiologic and therapeutic domains. Results suggest that consumption of highly palatable food and drugs of abuse both impact and conversely are regulated by metabolic hormones and metabolic status. Palatable foods high in fat and/or sugar can elicit adaptation in brain reward and withdrawal circuitry akin to substances of abuse. Intake of or withdrawal from palatable food can impact behavioral sensitivity to drugs of abuse and vice versa. A robust literature suggests common substrates and roles for negative reinforcement, negative affect, negative urgency, and impulse control deficits, with both highly palatable foods and substances of abuse. Candidate genetic risk loci shared by obesity and alcohol use disorders have been identified in molecules classically associated with both metabolic and motivational functions. Finally, certain drugs may have overlapping therapeutic potential to treat obesity, diabetes, binge-related eating disorders and substance use disorders. Taken together, data are consistent with the hypotheses that compulsive food and substance use share overlapping, interacting substrates at neurobiological and metabolic levels and that motivated behavior associated with feeding or substance use might constitute vulnerability factors for one another. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

Serotonin/dopamine interaction: Electrophysiological and neurochemical evidence

The interaction between serotonin (5-HT) and dopamine (DA) in the central nervous system (CNS) plays an important role in the adaptive properties of living animals to their environment. These are two modulatory, divergent systems shaping and regulating in a widespread manner the activity of neurobiological networks and their interaction. The concept of one interaction linking these two systems is rather elusive when looking at the mechanisms triggered by these two systems across the CNS. The great variety of their interacting mechanisms is in part due to the diversity of their neuronal origin, the density of their fibers in a given CNS region, the distinct expression of their numerous receptors in the CNS, the heterogeneity of their intracellular signaling pathway that depend on the cellular type expressing their receptors, and the state of activity of neurobiological networks, conditioning the outcome of their mutual influences. Thus, originally conceptualized as inhibition of 5-HT on DA neuron activity and DA neurotransmission, this interaction is nowadays considered as a multifaceted, mutual influence of these two systems in the regulation of CNS functions. These new ways of understanding this interaction are of utmost importance to envision the consequences of their dysfunctions underlined in several CNS diseases. It is also essential to conceive the mechanism of action of psychotropic drugs directly acting on their function including antipsychotic, antidepressant, antiparkinsonian, and drug of abuse together with the development of therapeutic strategies of Alzheimer's diseases, epilepsy, obsessional compulsive disorders. The 5-HT/DA interaction has a long history from the serendipitous discovery of antidepressants and antipsychotics to the future, rationalized treatments of CNS disorders.

Genetic Polymorphisms of 5-HT Receptors and Antipsychotic-Induced Metabolic Dysfunction in Patients with Schizophrenia

BACKGROUND

Antipsychotic-induced metabolic syndrome (MetS) is a multifactorial disease with a genetic predisposition. Serotonin and its receptors are involved in antipsychotic-drug-induced metabolic disorders. The present study investigated the association of nine polymorphisms in the four 5-hydroxytryptamine receptor (HTR) genes HTR1A, HTR2A, HTR3A, and HTR2C and the gene encoding for the serotonin transporter SLC6A4 with MetS in patients with schizophrenia.

METHODS

A set of nine single-nucleotide polymorphisms of genes of the serotonergic system was investigated in a population of 475 patients from several Siberian regions (Russia) with a clinical diagnosis of schizophrenia. Genotyping was performed and the results were analyzed using chi-square tests.

RESULTS

Polymorphic variant rs521018 (HTR2C) was associated with higher body mass index in patients receiving long-term antipsychotic therapy, but not with drug-induced metabolic syndrome. Rs1150226 (HTR3A) was also associated but did not meet Hardy-Weinberg equilibrium.

CONCLUSIONS

Our results indicate that allelic variants of HTR2C genes may have consequences on metabolic parameters. MetS may have too complex a mechanistic background to be studied without dissecting the syndrome into its individual (causal) components.

A Systems Biology Approach to Investigating the Interaction between Serotonin Synthesis by Tryptophan Hydroxylase and the Metabolic Homeostasis

Obesity has become a global public health and economic problem. Obesity is a major risk factor for a number of complications, such as type 2 diabetes, cardiovascular disease, fatty liver disease, and cancer. Serotonin (5-hydroxytryptamine [5-HT]) is a biogenic monoamine that plays various roles in metabolic homeostasis. It is well known that central 5-HT regulates appetite and mood. Several 5-HT receptor agonists and selective serotonin receptor uptake inhibitors (SSRIs) have shown beneficial effects on appetite and mood control in clinics. Although several genetic polymorphisms related to 5-HT synthesis and its receptors are strongly associated with obesity, there is little evidence of the role of peripheral 5-HT in human metabolism. In this study, we performed a systemic analysis of transcriptome data from the Genotype-Tissue Expression (GTEX) database. We investigated the expression of 5-HT and tryptophan hydroxylase (TPH), the rate-limiting enzyme of 5-HT biosynthesis, in the human brain and peripheral tissues. We also performed differential gene expression analysis and predicted changes in metabolites by comparing gene expressions of tissues with high TPH expression to the gene expressions of tissues with low TPH expression. Our analyses provide strong evidence that serotonin plays an important role in the regulation of metabolic homeostasis in humans.

The role of new medical treatments for the management of developmental and epileptic encephalopathies: Novel concepts and results

Developmental and epileptic encephalopathies (DEEs) are among the most challenging of all epilepsies to manage, given the exceedingly frequent and often severe seizure types, pharmacoresistance to conventional antiseizure medications, and numerous comorbidities. During the past decade, efforts have focused on development of new treatment options for DEEs, with several recently approved in the United States or Europe, including cannabidiol as an orphan drug in Dravet and Lennox-Gastaut syndromes and everolimus as a possible antiepileptogenic and precision drug for tuberous sclerosis complex, with its impact on the mammalian target of rapamycin pathway. Furthermore, fenfluramine, an old drug, was repurposed as a novel therapy in the treatment of Dravet syndrome. The evolution of new insights into pathophysiological processes of various DEEs provides possibilities to investigate novel and repurposed drugs and to place them into the context of their role in future management of these patients. The purpose of this review is to provide an overview of these new medical treatment options for the DEEs and to discuss the clinical implications of these results for improved treatment.

Oxytocin signaling in the treatment of drug addiction: Therapeutic opportunities and challenges

Drug addiction is one of the leading causes of mortality worldwide. Despite great advances were achieved in understanding the neurobiology of drug addiction, the therapeutic options are severely limited, with poor effectiveness and serious side effects. The neuropeptide oxytocin (OXT) is well known for its effects on uterine contraction, sexual/maternal behaviors, social affiliation, stress and learning/memory by interacting with the OXT receptor and other neuromodulators. Emerging evidence suggests that the acute or chronic exposure to drugs can affect the OXT system. Additionally, OXT administration can ameliorate a wide range of abused drug-induced neurobehavioral changes. Overall, OXT not only suppresses drug reward in the binge stage of drug addiction, but also reduces stress responses and social impairments during the withdrawal stage and, finally, prevents drug/cue/stress-induced reinstatement. More importantly, clinical studies have also shown that OXT can exert beneficial effects on reducing substance use disorders of a series of drugs, such as heroin, cocaine, alcohol, cannabis and nicotine. Thus, the present review focuses on the role of OXT in treating drug addiction, including the preclinical and clinical therapeutic potential of OXT and its analogs on the neurobiological perspectives of drugs, to provide a better insight of the efficacy of OXT as a clinical addiction therapeutic agent.

5-HT2A and 5-HT2C receptors as potential targets for the treatment of nicotine use and dependence

Nicotine use and dependence, typically achieved through cigarette smoking, but increasingly through vape products, is the leading cause of preventable death today. Despite a recognition that many current smokers would like to quit, the success rate at doing so is low and indicative of the persistent nature of nicotine dependence and the high urge to relapse. There are currently three main forms of pharmacotherapy approved as aids to treat nicotine dependence: a variety of nicotine replacement products (NRT's), the mixed NA/DA reuptake inhibitor bupropion (Zyban®), and the preferential nicotinic α4β2 receptor agonist drug, varenicline (Chantix®); the latter being generally recognized to be the most effective. However, each of these approaches afford only limited efficacy, and various other pharmacological approaches are being explored. This chapter focusses on approaches targeted to the serotonin (5-HT) system, namely, selective serotonin reuptake inhibitors (SSRI's) which served a pioneer role in the investigation of serotoninergic modulators in human smoking cessation trials; and secondly drugs selectively interacting with the 5-HT2A and 5-HT2C receptor systems. From an efficacy perspective, measured as smoking abstinence, the 5-HT2A agonist psychedelics, namely psilocybin, seem to show the most promise; although as the article highlights, these findings are both preliminary and there are significant challenges to the route to approval, and therapeutic use of this class should they reach approval status. Additional avenues include 5-HT2C receptor agonists, which until recently was pioneered by lorcaserin, and 5-HT2A receptor antagonists represented by pimavanserin. Each of these approaches has distinct profiles across preclinical tests of nicotine dependence, and may have therapeutic potential. It is anticipated as diagnostic and predictive biomarkers emerge, they may provide opportunities for subject stratification and opportunities for personalizing smoking cessation treatment. The clinical assessment of SSRI, 5-HT2A and/or 5-HT2C receptor-based treatments may be best served by this process.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.