A Non-D2-Receptor-Binding Drug for the Treatment of Schizophrenia

A Phase I, Open-Label, Fixed Sequence Study to Investigate the Effect of Cytochrome P450 2D6 Inhibition on the Pharmacokinetics of Ulotaront in Healthy Subjects

BACKGROUND

Ulotaront is a novel psychotropic agent with agonist activity at trace amine-associated receptor 1 (TAAR1) and 5-hydroxytryptamine type 1A (5-HT1A) receptors in phase III clinical development for the treatment of schizophrenia.

OBJECTIVE

This study aimed to investigate the effect of paroxetine, a strong cytochrome P450 (CYP) 2D6 inhibitor, on ulotaront pharmacokinetics (PK) in healthy volunteers.

METHODS

Subjects received a single oral dose of 25 mg ulotaront on Day 1 and an oral dose of 20 mg paroxetine once daily from Days 5 to 10 to achieve steady-state plasma paroxetine levels. On Day 11, subjects received another single oral dose of 25 mg ulotaront, with continued daily oral dosing of 20 mg paroxetine from Days 11 to 14. All 24 subjects were CYP2D6 normal metabolizers.

RESULTS

Coadministration of paroxetine increased ulotaront maximum observed plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to infinity (AUC∞) by 31% and 72%, respectively, and decreased ulotaront apparent clearance (CL/F) by approximately 42%. While coadministration of paroxetine increased AUC∞ of active but minor metabolite SEP-363854 by 32%, it had no effect on SEP-363854 Cmax, or on SEP-363854 to the ulotaront AUC from time zero to the last quantifiable concentration (AUClast) ratio. Based on the acceptable adverse event profile of ulotaront across previous phase II studies, the increase in ulotaront exposure is unlikely to be clinically meaningful.

CONCLUSIONS

Weak drug-drug interactions were observed between ulotaront and the strong CYP2D6 inhibitor paroxetine; however, dose adjustment as a precondition when ulotaront is coadministered with strong CYP2D6 inhibitors or administered to CYP2D6 poor metabolizers should not be necessary.

Emerging trends in antipsychotic and antidepressant drug development: Targeting nonmonoamine receptors and innovative mechanisms

The domain of psychiatric drug development is currently witnessing a notable transformation, with a paramount emphasis on targeting nonmonoamine receptors and exploring inventive mechanisms of action. This paper presents an overview of the ongoing advancements in antipsychotic and antidepressant drug development. Historically, antipsychotics predominantly targeted dopamine receptors, but there is now an escalating interest in drugs that act on alternative receptors, exemplified by the TAAR1 receptor. One noteworthy candidate is Ulotaront (SEP-363856), an agent acting as a TAAR1 agonist with 5-HT1A agonist activity, demonstrating promising outcomes in the treatment of schizophrenia, devoid of extrapyramidal symptoms or metabolic side-effects. Similarly, MIN-101 (Roluperidone) and KarXT are currently in development, with its focus on addressing the symptoms in schizophrenia. In the domain of antidepressants, novel therapeutic approaches have surfaced, such as Auvelity, a Food and Drug Administration (FDA)-approved NMDA receptor antagonist synergistically combined with Bupropion to enhance its effects. Another notable candidate is Zuranolone, operating as a GABA A receptor-positive allosteric modulator, showcasing efficacy in treating major depressive disorder (MDD) and postpartum depression. Additionally, TAK-653 (NBI-1065845) and MJI821 (Onfasprodil) have emerged as potential antidepressants targeting AMPA receptors and NMDA receptor 2B (NR2B) negative allosteric modulation, respectively. This paper underscores the transformative potential of these novel drug candidates in psychiatric treatment and their ability to address cases that were previously treatment-resistant. By focusing on nonmonoamine receptors and introducing innovative mechanisms, these drugs offer a promising prospect of improved outcomes for individuals suffering from schizophrenia and MDD. Thus, sustained attention and dedication to the development of such drugs are essential to augmenting the therapeutic options available for psychiatric patients.

Structural and signaling mechanisms of TAAR1 enabled preferential agonist design

Trace amine-associated receptor 1 (TAAR1) senses a spectrum of endogenous amine-containing metabolites (EAMs) to mediate diverse psychological functions and is useful for schizophrenia treatment without the side effects of catalepsy. Here, we systematically profiled the signaling properties of TAAR1 activation and present nine structures of TAAR1-Gs/Gq in complex with EAMs, clinical drugs, and synthetic compounds. These structures not only revealed the primary amine recognition pocket (PARP) harboring the conserved acidic D3.32 for conserved amine recognition and "twin" toggle switch for receptor activation but also elucidated that targeting specific residues in the second binding pocket (SBP) allowed modulation of signaling preference. In addition to traditional drug-induced Gs signaling, Gq activation by EAM or synthetic compounds is beneficial to schizophrenia treatment. Our results provided a structural and signaling framework for molecular recognition by TAAR1, which afforded structural templates and signal clues for TAAR1-targeted candidate compounds design.

Discovery of Guanfacine as a Novel TAAR1 Agonist: A Combination Strategy through Molecular Modeling Studies and Biological Assays

Trace amine-associated receptor 1 (TAAR1) is an attractive target for the design of innovative drugs to be applied in diverse pharmacological settings. Due to a non-negligible structural similarity with endogenous ligands, most of the agonists developed so far resulted in being affected by a low selectivity for TAAR1 with respect to other monoaminergic G protein-coupled receptors, like the adrenoreceptors. This study utilized comparative molecular docking studies and quantitative-structure activity relationship (QSAR) analyses to unveil key structural differences between TAAR1 and alpha2-adrenoreceptor (α2-ADR), with the aim to design novel TAAR1 agonists characterized by a higher selectivity profile and reduced off-target effects. While the presence of hydrophobic motives is encouraged towards both the two receptors, the introduction of polar/positively charged groups and the ligand conformation deeply affect the TAAR1 or α2-ADR putative selectivity. These computational methods allowed the identification of the α2A-ADR agonist guanfacine as an attractive TAAR1-targeting lead compound, demonstrating nanomolar activity in vitro. In vivo exploration of the efficacy of guanfacine showed that it is able to decrease the locomotor activity of dopamine transporter knockout (DAT-KO) rats. Therefore, guanfacine can be considered as an interesting template molecule worthy of structural optimization. The dual activity of guanfacine on both α2-ADR and TAAR1 signaling and the related crosstalk between the two pathways will deserve more in-depth investigation.

Data-Driven Taxonomy for Antipsychotic Medication: A New Classification System

BACKGROUND

Globally, there are more than 25 licensed antipsychotic medications. Antipsychotics are commonly described as either typical or atypical, but this dichotomous classification does not reflect the diversity of their pharmacological and clinical profiles. There is a need for a data-driven antipsychotic classification scheme suitable for clinicians and researchers that maps onto both pharmacological and clinical effects. Receptor affinity provides one starting point for such a scheme.

METHODS

We analyzed affinities of 27 antipsychotics for 42 receptors from 3325 in vitro receptor binding studies. We used a clustering algorithm to group antipsychotics based on receptor affinity. Using a machine learning model, we examined the ability of this grouping to predict antipsychotic-induced clinical effects quantified according to an umbrella review of clinical trial and treatment guideline data.

RESULTS

Clustering resulted in 4 groups of antipsychotics. The predominant receptor affinity and clinical effect "fingerprints" of these 4 groups were defined as follows: group 1, muscarinic (M2-M5) receptor antagonism (cholinergic and metabolic side effects); group 2, dopamine (D2) partial agonism and adrenergic antagonism (overall low side-effect burden); group 3, serotonergic and dopaminergic antagonism (overall moderate side-effect burden); and group 4, dopaminergic antagonism (extrapyramidal side effects and hyperprolactinemia). Groups 1 and 4 were more efficacious than groups 2 and 3. The classification was shown to predict out-of-sample clinical effects of individual drugs.

CONCLUSIONS

A receptor affinity-based grouping not only reflects compound pharmacology but also detects meaningful clinical differences. This approach has the potential to benefit both patients and researchers by guiding treatment and informing drug development.

Adjunctive agents to antipsychotics in schizophrenia: a systematic umbrella review and recommendations for amino acids, hormonal therapies and anti-inflammatory drugs

QUESTION

This umbrella review and guidelines aimed to provide evidence to support the rational choice of selected adjunctive therapies for schizophrenia.

STUDY SELECTION AND ANALYSIS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and World Federation of Societies of Biological Psychiatry (WFSBP)-grading recommendations, 63 randomised control trials (RCTs) (of which 4219 unique participants have completed the RCTs) and 29 meta-analyses were analysed.

FINDINGS

Provisional recommendations (WFSBP-grade 1) could be made for two molecules in augmentation to antipsychotics: (1) N-acetyl-cysteine (NAC, 1200-3600 mg/day, for >12 consecutive weeks) in improving negative symptoms, general psychopathology (positive and negative syndrome scale for schizophrenia (PANSS) general psychopathology factor (G)-G subscale), with the RCTs with the longer duration showing the most robust findings; (2) polyunsaturated fatty acids (3000 mg/day of eicosapentaenoic acid, for >12 weeks) in improving general psychopathology. Weaker recommendations (ie, WFSBP-grade 2) could be drawn for sarcosine (2 g/day) and minocycline (200-300 mg/day) for improving negative symptoms in chronic schizophrenia (not early schizophrenia), and NAC for improving positive symptoms and cognition. Weak recommendations are not ready for clinical practice. There is provisional evidence that oestrogens and raloxifene are effective in some patients, but further research is needed to determine their benefit/risk ratio.

CONCLUSIONS

The results of this umbrella review should be interpreted with caution as the number of RCTs included in the meta-analyses was generally small and the effect sizes were weak or medium. For NAC, two RCTs with low risk of bias have provided conflicting results and the WFSBP-grade recommendation included also the results of meta-analyses. These drugs could be provisionally prescribed for patients for whom no other treatments have been effective, but they should be discontinued if they prove ineffective.

Ulotaront: review of preliminary evidence for the efficacy and safety of a TAAR1 agonist in schizophrenia

Ulotaront is a trace amine-associated receptor 1 (TAAR1) agonist in Phase 3 clinical development for the treatment of schizophrenia. Ulotaront was discovered through a unique, target-agnostic approach optimized to identify drug candidates lacking D2 and 5-HT2A receptor antagonism, while demonstrating an antipsychotic-like phenotypic profile in vivo. The mechanism of action (MOA) of ulotaront is thought to be mediated by agonism at TAAR1 and serotonin 5-HT1A receptors. Ulotaront has completed two Phase 2 trials (4-week acute study and 26-week open-label extension) which led to Breakthrough Therapy Designation from the US Food and Drug Administration for the treatment of schizophrenia. In the double-blind, placebo-controlled, acute study, ulotaront was associated with significant (p < 0.001) improvement in Positive and Negative Syndrome Scale (PANSS) total score (effect size [ES]: 0.45), with improvements vs. placebo also observed across secondary endpoints. Post-hoc analyses of the acute trial revealed additional evidence to support the effect of ulotaront on negative symptoms. In the 4-week study, ulotaront was well-tolerated, with an incidence of adverse events (AEs) numerically lower compared to placebo (45.8% vs. 50.4%; with a number needed to harm [NNH] for individual ulotaront AEs all > 40). The open-label extension demonstrated further improvement across schizophrenia symptoms and confirmed the tolerability of ulotaront, with a 6-month completion rate of 67%. Based on current data, ulotaront shows potential to be a first-in-class TAAR1 agonist for the treatment of schizophrenia with a safety and efficacy profile distinct from current antipsychotics.

In Vitro Comparison of Ulotaront (SEP-363856) and Ralmitaront (RO6889450): Two TAAR1 Agonist Candidate Antipsychotics

BACKGROUND

Trace amine-associated receptor-1 (TAAR1) agonists have been proposed as potential antipsychotics, with ulotaront and ralmitaront having reached clinical trials. While ulotaront demonstrated efficacy in a recent Phase II trial, a corresponding study studies of ralmitaront failed to show efficacy as a monotherapy or as an adjunct to atypical antipsychotics. In addition to TAAR1 agonism, ulotaront is a partial agonist at the serotonin 1A receptor (5-HT1AR). However, little is known about ralmitaront.

METHODS

We compared ulotaront and ralmitaront at TAAR1, 5-HT1AR, and dopamine D2 using luciferase complementation-based G protein recruitment, cAMP accumulation, and G protein-coupled inward rectifier potassium channel activation assays.

RESULTS

Ralmitaront showed lower efficacy at TAAR1 in G protein recruitment, cAMP accumulation, and GIRK activation assays. Moreover, ralmitaront lacked detectable activity at 5-HT1AR and dopamine D2.

CONCLUSIONS

Compared with ulotaront, ralmitaront shows lower efficacy and slower kinetics at TAAR1 and lacks efficacy at 5-HT1AR. These data may be relevant to understanding differences in clinical profiles of these 2 compounds.

Trace amine-associated receptor 1 (TAAR1) agonists for psychosis: protocol for a living systematic review and meta-analysis of human and non-human studies

BACKGROUND

There is an urgent need to develop more effective and safer antipsychotics beyond dopamine 2 receptor antagonists. An emerging and promising approach is TAAR1 agonism. Therefore, we will conduct a living systematic review and meta-analysis to synthesize and triangulate the evidence from preclinical animal experiments and clinical studies on the efficacy, safety, and underlying mechanism of action of TAAR1 agonism for psychosis.

METHODS

Independent searches will be conducted in multiple electronic databases to identify clinical and animal experimental studies comparing TAAR1 agonists with licensed antipsychotics or other control conditions in individuals with psychosis or animal models for psychosis, respectively. The primary outcomes will be overall psychotic symptoms and their behavioural proxies in animals. Secondary outcomes will include side effects and neurobiological measures. Two independent reviewers will conduct study selection, data extraction using predefined forms, and risk of bias assessment using suitable tools based on the study design. Ontologies will be developed to facilitate study identification and data extraction. Data from clinical and animal studies will be synthesized separately using random-effects meta-analysis if appropriate, or synthesis without meta-analysis. Study characteristics will be investigated as potential sources of heterogeneity. Confidence in the evidence for each outcome and source of evidence will be evaluated, considering the summary of the association, potential concerns regarding internal and external validity, and reporting biases. When multiple sources of evidence are available for an outcome, an overall conclusion will be drawn in a triangulation meeting involving a multidisciplinary team of experts. We plan trimonthly updates of the review, and any modifications in the protocol will be documented. The review will be co-produced by multiple stakeholders aiming to produce impactful and relevant results and bridge the gap between preclinical and clinical research on psychosis.

PROTOCOL REGISTRATION

PROSPERO-ID: CRD42023451628.

Novel Compounds in the Treatment of Schizophrenia-A Selective Review

Schizophrenia is a chronic neuropsychiatric syndrome that significantly impacts daily function and quality of life. All of the available guidelines suggest a combined treatment approach with pharmacologic agents and psychological interventions. However, one in three patients is a non-responder, the effect on negative and cognitive symptoms is limited, and many drug-related adverse effects complicate clinical management. As a result, discovering novel drugs for schizophrenia presents a significant challenge for psychopharmacology. This selective review of the literature aims to outline the current knowledge on the aetiopathogenesis of schizophrenia and to present the recently approved and newly discovered pharmacological substances in treating schizophrenia. We discuss ten novel drugs, three of which have been approved by the FDA (Olanzapine/Samidorphan, Lumateperone, and Pimavanserin). The rest are under clinical trial investigation (Brilaroxazine, Xanomeline/Trospium, Emraclidine, Ulotaront, Sodium Benzoate, Luvadaxistat, and Iclepertin). However, additional basic and clinical research is required not only to improve our understanding of the neurobiology and the potential novel targets in the treatment of schizophrenia, but also to establish more effective therapeutical interventions for the syndrome, including the attenuation of negative and cognitive symptoms and avoiding dopamine blockade-related adverse effects.

Effects of ulotaront on brain circuits of reward, working memory, and emotion processing in healthy volunteers with high or low schizotypy

Ulotaront, a trace amine-associated receptor 1 (TAAR1) and serotonin 5-HT1A receptor agonist without antagonist activity at dopamine D2 or the serotonin 5-HT2A receptors, has demonstrated efficacy in the treatment of schizophrenia. Here we report the phase 1 translational studies that profiled the effect of ulotaront on brain responses to reward, working memory, and resting state connectivity (RSC) in individuals with low or high schizotypy (LS or HS). Participants were randomized to placebo (n = 32), ulotaront (50 mg; n = 30), or the D2 receptor antagonist amisulpride (400 mg; n = 34) 2 h prior to functional magnetic resonance imaging (fMRI) of blood oxygen level-dependent (BOLD) responses to task performance. Ulotaront increased subjective drowsiness, but reaction times were impaired by less than 10% and did not correlate with BOLD responses. In the Monetary Incentive Delay task (reward processing), ulotaront significantly modulated striatal responses to incentive cues, induced medial orbitofrontal responses, and prevented insula activation seen in HS subjects. In the N-Back working memory task, ulotaront modulated BOLD signals in brain regions associated with cognitive impairment in schizophrenia. Ulotaront did not show antidepressant-like biases in an emotion processing task. HS had significantly reduced connectivity in default, salience, and executive networks compared to LS participants and both drugs reduced this difference. Although performance impairment may have weakened or contributed to the fMRI findings, the profile of ulotaront on BOLD activations elicited by reward, memory, and resting state is compatible with an indirect modulation of dopaminergic function as indicated by preclinical studies. This phase 1 study supported the subsequent clinical proof of concept trial in people with schizophrenia.Clinical trial registration: Registry# and URL: ClinicalTrials.gov NCT01972711, https://clinicaltrials.gov/ct2/show/NCT01972711.

Negative symptoms in schizophrenia: Newly emerging measurements, pathways, and treatments

The negative symptoms of schizophrenia, which often appear earlier than any other symptom, are prominent and clinically relevant in the majority of patients. As a result, interest in their treatment has increased. Patients who exhibit significant negative symptoms have worse functional outcomes than those without, resulting in impairments in occupational, household, and recreational functioning, as well as difficulties in relationships. Yet treatment with currently available medications does not lead to any significant improvements in this core component of schizophrenia. An increased understanding of the pathophysiology underlying negative symptoms and the discovery of novel treatments that do not directly target dopamine offer the potential to develop therapies that may reduce negative symptoms and increase quality of life for patients. The current article will discuss the impact of negative symptoms, outline current measurement tools for the assessment of negative symptoms, and examine how these measures may be improved. Insights into the neural circuitry underlying negative symptoms will be discussed, and promising targets for the development of effective treatments for these symptoms will be identified. As more prospective, large-scale, randomized studies focus on the effects of treatments on negative symptoms, progress in this area is foreseeable. However, improvements in clinical assessment instruments, a better understanding of the underlying neural mechanisms, development of novel treatments with varied targets, and a greater focus on personalized treatment are all important to produce significant benefits for patients with negative symptoms of schizophrenia.

Ulotaront, a Trace Amine-Associated Receptor 1/Serotonin 5-HT1A Agonist, in Patients With Parkinson Disease Psychosis: A Pilot Study

Background and Objectives

Ulotaront (SEP-363856) is a trace amine-associated receptor 1 agonist with 5-HT_1A receptor agonist activity currently in phase 3 clinical development for the treatment of schizophrenia. In this exploratory, flexibly dosed study, ulotaront was evaluated for the treatment of Parkinson disease psychosis (PDP).

Methods

Patients with PDP requiring antipsychotic therapy were randomized, double-blind to ulotaront (25, 50, or 75 mg/d) or placebo. Mixed Model for Repeated Measures was used to assess change from baseline in the Scale for the Assessment of Positive Symptoms for Parkinson Disease (SAPS-PD) at 6 weeks (primary end point).

Results

The efficacy analysis sample comprised 38 patients (ulotaront, n = 24; placebo, n = 14). SAPS-PD total scores were numerically reduced in ulotaront-treated vs placebo-treated patients from week 1 to week 6: Least squares mean (95% confidence interval) difference in change from baseline at week 6 was -1.1 (-6.5, 4.3, p = 0.681). PDP symptom complete remission (≥100% improvement [reduction] from baseline in SAPS-PD total score) was observed in 25% of ulotaront-treated vs 0% of placebo-treated patients. SAPS-PD and Neuropsychiatric Inventory hallucinations subscales were numerically reduced vs placebo, and SAPS-PD total scores were reduced in patients with greater cognitive impairment (baseline Mini-Mental State Examination [MMSE] scores ≤24). Ulotaront improved Scales for Outcomes in Parkinson Disease Sleep Scale - Daytime Sleepiness scores (p = 0.022). There was no worsening of Unified Parkinson Disease Rating Scale Part III motor score, MMSE, or vital signs. Adverse events (≥10%) with ulotaront vs placebo included hallucinations (24% vs 14%), confusional state (20% vs 14%), dizziness (16% vs 7%), nausea (12% vs 7%), and falls (12% vs 21%).

Discussion

In this exploratory pilot study, ulotaront may decrease PDP symptoms without worsening motor function, particularly in patients with cognitive impairment.

Trial Registration Information

ClinicalTrials.gov identifier: NCT02969369; submitted: November 17, 2016; study start date: December 31, 2016.

Classification of Evidence

This Class II study was an exploratory pilot study that was underpowered to detect a statistically significant difference between ulotaront and placebo in the treatment of patients with Parkinson disease psychosis without worsening motor function.

T1AM/TAAR1 System Reduces Inflammatory Response and β-Amyloid Toxicity in Human Microglial HMC3 Cell Line

Microglial dysfunction is one of the hallmarks and leading causes of common neurodegenerative diseases (NDDs), including Alzheimer's disease (AD) and Parkinson's disease (PD). All these pathologies are characterized by aberrant aggregation of disease-causing proteins in the brain, which can directly activate microglia, trigger microglia-mediated neuroinflammation, and increase oxidative stress. Inhibition of glial activation may represent a therapeutic target to alleviate neurodegeneration. Recently, 3-iodothyronamine (T1AM), an endogenous derivative of thyroid hormone (TH) able to interact directly with a specific GPCR known as trace amine-associated receptor 1 (TAAR1), gained interest for its ability to promote neuroprotection in several models. Nevertheless, T1AM's effects on microglial disfunction remain still elusive. In the present work we investigated whether T1AM could inhibit the inflammatory response of human HMC3 microglial cells to LPS/TNFα or β-amyloid peptide 25-35 (Aβ25-35) stimuli. The results of ELISA and qPCR assays revealed that T1AM was able to reduce microglia-mediated inflammatory response by inhibiting the release of proinflammatory factors, including IL-6, TNFα, NF-kB, MCP1, and MIP1, while promoting the release of anti-inflammatory mediators, such as IL-10. Notably, T1AM anti-inflammatory action in HMC3 cells turned out to be a TAAR1-mediated response, further increasing the relevance of the T1AM/TAAR1 system in the management of NDDs.

Unlocking the Therapeutic Potential of Ulotaront as a Trace Amine-Associated Receptor 1 Agonist for Neuropsychiatric Disorders

All antipsychotics currently used in clinic block D2 dopamine receptors. Trace amine-associated receptor 1 is emerging as a new therapeutic target for schizophrenia and several other neuropsychiatric disorders. SEP-363856 (International Nonproprietary Name: Ulotaront) is an investigational antipsychotic drug with a novel mechanism of action that does not involve antagonism of dopamine D2 receptors. Ulotaront is an agonist of trace amine-associated receptor 1 and serotonin 5-HT1A receptors, but can modulate dopamine neurotransmission indirectly. In 2019, the United States Food and Drug Administration granted Breakthrough Therapy Designation for ulotaront for the treatment of schizophrenia. Phase 2 clinical studies indicated that ulotaront can reduce both positive and negative symptoms of schizophrenia without causing the extrapyramidal or metabolic side effects that are inherent to most currently used antipsychotics. At present, it is in phase 3 clinical development for the treatment of schizophrenia and is expected to be introduced into clinical practice in 2023-2024. Clinical studies evaluating the potential efficacy of ulotaront in Parkinson's disease psychosis, generalized anxiety disorder, and major depressive disorder have also been started. The aim of this scoping review is to summarize all currently available preclinical and clinical evidence on the utility of ulotaront in the treatment of schizophrenia. Here, we show the main characteristics and distinctive features of this drug. Perspectives and limitations on the potential use of ulotaront in the pharmacotherapy of several other neuropsychiatric disorders are also discussed.

Increased Metabolic Potential, Efficacy, and Safety of Emerging Treatments in Schizophrenia

Patients with schizophrenia experience a broad range of detrimental health outcomes resulting from illness severity, heterogeneity of disease, lifestyle behaviors, and adverse effects of antipsychotics. Because of these various factors, patients with schizophrenia have a much higher risk of cardiometabolic abnormalities than people without psychiatric illness. Although exposure to many antipsychotics increases cardiometabolic risk factors, mortality is higher in patients who are not treated versus those who are treated with antipsychotics. This indicates both direct and indirect benefits of adequately treated illness, as well as the need for beneficial medications that result in fewer cardiometabolic risk factors and comorbidities. The aim of the current narrative review was to outline the association between cardiometabolic dysfunction and schizophrenia, as well as discuss the confluence of factors that increase cardiometabolic risk in this patient population. An increased understanding of the pathophysiology of schizophrenia has guided discovery of novel treatments that do not directly target dopamine and that not only do not add, but may potentially minimize relevant cardiometabolic burden for these patients. Key discoveries that have advanced the understanding of the neural circuitry and pathophysiology of schizophrenia now provide possible pathways toward the development of new and effective treatments that may mitigate the risk of metabolic dysfunction in these patients. Novel targets and preclinical and clinical data on emerging treatments, such as glycine transport inhibitors, nicotinic and muscarinic receptor agonists, and trace amine-associated receptor-1 agonists, offer promise toward relevant therapeutic advancements. Numerous areas of investigation currently exist with the potential to considerably progress our knowledge and treatment of schizophrenia.

An international research agenda for clozapine-resistant schizophrenia

Treatment-resistant symptoms occur in about a third of patients with schizophrenia and are associated with a substantial reduction in their quality of life. The development of new treatment options for clozapine-resistant schizophrenia constitutes a crucial, unmet need in psychiatry. Additionally, an overview of past and possible future research avenues to optimise the early detection, diagnosis, and management of clozapine-resistant schizophrenia is unavailable. In this Health Policy, we discuss the ongoing challenges associated with clozapine-resistant schizophrenia faced by patients and health-care providers worldwide to improve the understanding of this condition. We then revisit several clozapine guidelines, the diagnostic tests and treatment options for clozapine-resistant schizophrenia, and currently applied research approaches in clozapine-resistant schizophrenia. We also suggest methodologies and targets for future research, divided into innovative nosology-oriented field trials (eg, examining dimensional symptom staging), translational approaches (eg, genetics), epidemiological research (eg, real-world studies), and interventional studies (eg, non-traditional trial designs incorporating lived experiences and caregivers' perspectives). Finally, we note that low-income and middle-income countries are under-represented in studies on clozapine-resistant schizophrenia and propose an agenda to guide multinational research on the cause and treatment of clozapine-resistant schizophrenia. We hope that this research agenda will empower better global representation of patients living with clozapine-resistant schizophrenia and ultimately improve their functional outcomes and quality of life.

TAAR1 Regulates Purinergic-induced TNF Secretion from Peripheral, But Not CNS-resident, Macrophages

Trace amine-associated receptor 1 (TAAR1) is an established neuroregulatory G protein-coupled receptor with recent studies suggesting additional functions related to immunomodulation. Our lab has previously investigated TAAR1 expression within cells of the innate immune system and herein we aim to further elucidate TAAR1 function in both peripherally-derived and CNS-resident macrophages. The selective TAAR1 agonist RO5256390 was used in combination with common damage associated molecular patterns (ATP and ADP) to observe the effect of TAAR1 agonism on modulating cytokine secretion and metabolic profiles. In mouse bone-marrow derived macrophages, TAAR1 agonism inhibited TNF secretion following ATP stimulation, which appeared to be downstream of an associated pro-inflammatory shift in metabolic profile and transcriptional regulation of TNF synthesis. In contrast, TAAR1 agonism had no effect on ADP-induced TNF and IL-6 secretion in mouse microglia in either the presence or absence of astrocytes. In summary, we report a novel interaction between TAAR1 and purinergic signaling in peripherally-derived, but not CNS-resident, macrophages. These findings provide the first evidence of trace aminergic and purinergic crosstalk, and support the potential for TAAR1 as a novel therapeutic target in inflammatory disorders.

Towards Novel Potential Molecular Targets for Antidepressant and Antipsychotic Pharmacotherapies

Depression and schizophrenia are two highly prevalent and severely debilitating neuropsychiatric disorders. Both conventional antidepressant and antipsychotic pharmacotherapies are often inefficient clinically, causing multiple side effects and serious patient compliance problems. Collectively, this calls for the development of novel drug targets for treating depressed and schizophrenic patients. Here, we discuss recent translational advances, research tools and approaches, aiming to facilitate innovative drug discovery in this field. Providing a comprehensive overview of current antidepressants and antipsychotic drugs, we also outline potential novel molecular targets for treating depression and schizophrenia. We also critically evaluate multiple translational challenges and summarize various open questions, in order to foster further integrative cross-discipline research into antidepressant and antipsychotic drug development.

Dynamic Stability of Volatile Organic Compounds in Respiratory Air in Schizophrenic Patients and Its Potential Predicting Efficacy of TAAR Agonists

OBJECTIVES

Volatile organic compounds (VOCs) in the breathing air were found to be altered in schizophrenia patients compared to healthy participants. The aim of this study was to confirm these findings and to examine for the first time whether these VOCs are stable or change in concentration during the early treatment course. Moreover, it was investigated whether there is a correlation of the VOCs with the existing psychopathology of schizophrenia patients, i.e., whether the concentration of masses detected in the breath gas changes when the psychopathology of the participants changes.

METHODS

The breath of a total of 22 patients with schizophrenia disorder was examined regarding the concentration of VOCs using proton transfer reaction mass spectrometry. The measurements were carried out at baseline and after two weeks at three different time points, the first time immediately after waking up in the morning, after 30 min, and then after 60 min. Furthermore, 22 healthy participants were investigated once as a control group.

RESULTS

Using bootstrap mixed model analyses, significant concentration differences were found between schizophrenia patients and healthy control participants (m/z 19, 33, 42, 59, 60, 69, 74, 89, and 93). Moreover, concentration differences were detected between the sexes for masses m/z 42, 45, 57, 69, and 91. Mass m/z 67 and 95 showed significant temporal changes with decreasing concentration during awakening. Significant temporal change over two weeks of treatment could not be detected for any mass. Masses m/z 61, 71, 73, and 79 showed a significant relationship to the respective olanzapine equivalents. The length of hospital stay showed no significant relationship to the masses studied.

CONCLUSION

Breath gas analysis is an easy-to-use method to detect differences in VOCs in the breath of schizophrenia patients with high temporal stability. m/z 60 corresponding to trimethylamine might be of potential interest because of its natural affinity to TAAR receptors, currently a novel therapeutic target under investigation. Overall, breath signatures seemed to stable over time in patients with schizophrenia. In the future, the development of a biomarker could potentially have an impact on the early detection of the disease, treatment, and, thus, patient outcome.

A new era for schizophrenia drug development - Lessons for the future

For many patients and their treating clinicians, the pharmacological management of psychotic symptoms centres on trying to find a regime that balances efficacy and quality of life, impairing side effects associated with dopamine antagonism. Recent reports of a positive Phase III study from Karuna Therapeutics indicate that the first primarily non-dopamine-based treatment for schizophrenia may come to market soon with the potential for substantially reduced or differentiated side effects. Against a background of repeated failures, Karuna's success promises a desperately needed new treatment option for patients. It also reflects some hard-won lessons about the methodology for schizophrenia drug development. Teaser A positive Phase II study and positive media report from a Phase III study with xanomeline/trospium may herald the first truly new treatment option for schizophrenia patients in decades. This drug's journey to this point reflects some hard-won lessons about the methodology for schizophrenia drug development.

Cognitive impairment in schizophrenia: aetiology, pathophysiology, and treatment

Cognitive deficits are a core feature of schizophrenia, account for much of the impaired functioning associated with the disorder and are not responsive to existing treatments. In this review, we first describe the clinical presentation and natural history of these deficits. We then consider aetiological factors, highlighting how a range of similar genetic and environmental factors are associated with both cognitive function and schizophrenia. We then review the pathophysiological mechanisms thought to underlie cognitive symptoms, including the role of dopamine, cholinergic signalling and the balance between GABAergic interneurons and glutamatergic pyramidal cells. Finally, we review the clinical management of cognitive impairments and candidate novel treatments.

Efficacy, safety, and tolerability of ulotaront (SEP-363856, a trace amine-associated receptor 1 agonist) for the treatment of schizophrenia and other mental disorders with similar pathophysiology: a systematic review of preclinical and clinical trials

INTRODUCTION

Schizophrenia is a mental illness that can disrupt emotions, perceptions, cognition, and reduce quality of life. The classical approach to treat schizophrenia uses typical and atypical antipsychotics; however, limitations include low efficacy in mitigating negative symptoms and cognitive dysfunctions, and a range of adverse effects. Evidence has accumulated on trace amine-associated receptor 1 (TAAR1) as a novel therapeutic target for treating schizophrenia. This systematic review investigates the available evidence on a TAAR1 agonist, ulotaront, as a treatment for schizophrenia.

METHODS

A systematic search was conducted on PubMed/MEDLINE, and Ovid databases for English-published articles from inception to December 18, 2022. Literature focusing on the association between ulotaront and schizophrenia were evaluated based on an inclusion/exclusion criterion. Selected studies were assessed for risk of bias, using Cochrane Collaboration tool, and summarized in a table to generate discussion topics.

RESULTS

Three clinical, two comparative, and five preclinical studies examining ulotaront's pharmacology, tolerability and safety, and/or efficacy were identified. Results indicate that ulotaront has a differing adverse effects profile from other antipsychotics, may mitigate metabolic-related adverse effects commonly associated with antipsychotics, and may be effective for treating positive and negative symptoms.

CONCLUSIONS

Findings from available literature present ulotaront as a potential and promising alternative treatment method for schizophrenia. Despite this, our results were limited due to lack of clinical trials on ulotaront's long-term efficacy and mechanisms of action. Future research should focus on these limitations to elucidate ulotaront's efficacy and safety for the treatment of schizophrenia and other mental disorders with similar pathophysiology.

Electroacupuncture alleviated depression‐like behaviors in ventromedial prefrontal cortex of chronic unpredictable mild stress‐induced rats: Increasing synaptic transmission and phosphorylating dopamine transporter

AIMS

Electroacupuncture (EA) shows advantages in both clinical practice and depression animal models. Dopaminergic-related dysfunction in the prefrontal cortex (PFC) may be a hidden antidepressant mechanism of EA, where dopamine transporter (DAT) plays an essential role. This study aimed to investigate the synaptic transmission and DAT-related changes of EA in depression.

METHODS

Male Sprague-Dawley rats were subjected to 3-week chronic unpredictable mild stress (CUMS). The successfully modeled rats were then randomly and equally assigned to CUMS, selective serotonin reuptake inhibitor (SSRI), and EA or SSRI + EA groups, followed by a 2-week treatment respectively. After monitoring body weight and behavioral tests of all rats, the ventromedial PFC (vmPFC) tissue was collected for electrophysiology and the expression detection of DAT, phosphorylated DAT (p-DAT), cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), and trace amine-associated receptor 1 (TAAR1).

RESULTS

Depressive-like behaviors induced by CUMS were alleviated by EA, SSRI, and SSRI + EA treatments through behavioral tests. Compared with CUMS group, EA improved synaptic transmission in vmPFC by upregulating spontaneous excitatory postsynaptic currents amplitude. Molecularly, EA reversed the increased total DAT and p-DAT expression as well as the decreased ratio of p-DAT/total DAT along with the activation of TAAR1, cAMP, and PKA in vmPFC.

CONCLUSION

We speculated that the antidepressant effect of EA was associated with enhanced synaptic transmission in vmPFC, and the upregulated phosphorylation of DAT relevant to TAAR1, cAMP, and PKA may be the potential mechanism.

Approach to schizophrenia

Schizophrenia is the most common of a group of psychotic disorders that occur in approximately 3% of the population over the lifespan. It has clear genetic antecedents, which are shared across the spectrum of psychotic disorders; however, a range of other biological and social factors influence the onset and treatment of the disorder. Schizophrenia is diagnosed by a characteristic set of symptoms (positive, negative, disorganisation, cognitive and affective) accompanied by a functional decline. Investigations are used to exclude other organic causes of psychosis and to provide a baseline for the negative effects of pharmacological treatments. Treatment requires a combination of pharmacological and psychosocial interventions. Physical health is poor in this group of people and this is not helped by inconsistent care from health services. Although earlier intervention has improved the immediate outcomes, the longer-term outcome has not significantly shifted.

Cross-diagnostic determinants of cognitive functioning: the muscarinic cholinergic receptor as a model system

Cognitive impairment is a predictor of disability across different neuropsychiatric conditions, and cognitive abilities are also strongly related to educational attainment and indices of life success in the general population. Previous attempts at drug development for cognitive enhancement have commonly attempted to remedy defects in transmitters systems putatively associated with the conditions of interest such as the glutamate system in schizophrenia. Recent studies of the genomics of cognitive performance have suggested influences that are common in the general population and in different neuropsychiatric conditions. Thus, it seems possible that transmitter systems that are implicated for cognition across neuropsychiatric conditions and the general population would be a viable treatment target. We review the scientific data on cognition and the muscarinic cholinergic receptor system (M1 and M4) across different diagnoses, in aging, and in the general population. We suggest that there is evidence suggesting potential beneficial impacts of stimulation of critical muscarinic receptors for the enhancement of cognition in a broad manner, as well as the treatment of psychotic symptoms. Recent developments make stimulation of the M1 receptor more tolerable, and we identify the potential benefits of M1 and M4 receptor stimulation as a trans-diagnostic treatment model.

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Comparative Bioequivalence of Tablet and Capsule Formulations of Ulotaront and the Effect of Food on the Pharmacokinetics of the Tablet Form in Humans

INTRODUCTION

Ulotaront (SEP-363856), a dual trace animeassociated receptor 1 (TAAR1) and 5-HT_1A receptor agonist, is in phase 3 clinical development for the treatment of schizophrenia. This study evaluated the comparative bioequivalence (BE) between tablet and capsule formulations of ulotaront and the food effect (FE) on pharmacokinetics (PK) of tablet form in healthy adult human subjects.

METHODS

The BE study applied an open-label two-period crossover design in 24 healthy volunteers. Subjects were randomly assigned (1:1) to dosing sequence AB or BA (A, 25 mg ulotaront tablet; B, 25 mg ulotaront capsule). The FE study also used an open-label randomized two-period crossover design in 20 healthy volunteers. Subjects were fasted overnight then randomly assigned (1:1) to dosing sequence AB or BA (A, fasted condition; B, fed condition). Dosing periods were separated by 1 week for both studies. Serial plasma samples from each period were collected and analyzed by LC-MS/MS. PK parameters were calculated using Phoenix WinNonlin_® software.

RESULTS

For the BE study, geometric mean ulotaront C_max values were 93.28 and 86.98 ng/mL for tablet and capsule, respectively. C_max ratio was 107.25% (90% CI 101.84-112.94%). Geometric mean ulotaront area under the plasma concentration-time curve from time 0 to infinity (AUC_0-∞) values were 868.8 and 829.3 ng·h/mL for tablet and capsule, respectively. AUC_0-∞ ratio was 104.76% (90% CI 100.68109.01%). For the FE study, geometric mean ulotaront C_max was 157.89 and 157.95 ng/mL under fed and fasted conditions, respectively. Geometric mean ratio of C_max was 99.96% (90% CI 94.48-105.77%). Geometric mean ulotaront AUC_0-∞ was 1584.2 ng·h/mL fed and 1589.2 ng·h/mL fasted. Geometric mean ratio for AUC_0-∞ was 99.69% (90% CI 95.02-104.58%). There was a delay in t_max (median difference 1.47 h) in the fed condition.

CONCLUSIONS

The results showed geometric mean ratios and 90% CIs for both C_max and AUC_0-∞ for ulotaront were well within typical bioequivalence criteria of 80-125% for both the BE and FE studies, thereby confirming the bioequivalence of the two dosage forms and no significant food effect.

Pharmacotherapies for Treatment-Resistant Depression: How Antipsychotics Fit in the Rapidly Evolving Therapeutic Landscape

One in three adults with major depressive disorder (MDD) do not experience clinically significant improvement after multiple sequential courses of antidepressants and have treatment-resistant depression (TRD). The presence of TRD contributes to the morbidity and excess mortality associated with MDD and has been linked to significantly increased health care expenses. In the absence of a consensus definition of TRD, this report takes a broad approach by considering inadequate response to one or more courses of antidepressants and focuses on atypical antipsychotics that are approved by the U.S. Food and Drug Administration for treatment of depression (aripiprazole, brexpiprazole, cariprazine, extended-release quetiapine, and olanzapine-fluoxetine combination). While multiple acute-phase studies have demonstrated the efficacy of these medications in improving depressive symptoms, clinically meaningful improvement (i.e., remission) remains limited, with significant concerns about side effects (including weight gain, metabolic dysfunction, extrapyramidal symptoms, and tardive dyskinesia), especially with long-term use. With the rapidly evolving landscape of antidepressant treatments over the past few years, which has witnessed approval of rapid-acting antidepressants (e.g., esketamine nasal spray and dextromethorphan-bupropion combination) and several more in the late-stage pipeline (e.g., zuranolone and psilocybin), it remains to be seen whether the use of atypical antipsychotics will go the way of the older and rarely prescribed antidepressants (such as tricyclics and monoamine oxidase inhibitors). Pragmatic clinical trials are needed to compare the effectiveness of atypical antipsychotics with TRD-specific pharmacotherapies and neuromodulation treatments and to identify the optimal sequencing of these varied approaches for patients with MDD. When using atypical antipsychotics, clinicians and patients are encouraged to use a shared decision-making approach by personalizing treatment selection based on anticipated side effects, tolerability, cost, and feasibility.

Recent Advances in Psychopharmacology: From Bench to Bedside Novel Trends in Schizophrenia

Research in the field of psychopharmacology is ongoing to develop novel compounds which can revolutionize the treatment of psychiatric disorders. The concept of bench-to-bedside is a tedious process, transforming the initial research performed in the laboratories into novel treatment options. Schizophrenia (SCZ) is a chronic psychiatric illness with significant morbidity and mortality. SCZ not only presents with psychotic symptoms including hallucinations and delusions but also with negative and cognitive symptoms. The negative symptoms include the diminished ability to express emotions, loss of pleasure, and motivation with minimal social interactions. Conventional antipsychotics primarily target positive symptoms with minimal therapeutic benefits for negative and cognitive symptoms along with metabolic side effects. Researchers have explored novel targets to develop new compounds to overcome the above limitations. The glutamatergic system has provided new hope in treating schizophrenia by targeting negative and cognitive symptoms. Other receptor modulators, including serotonergic, phosphodiesterase, trans-amine-associated receptors, etc., are novel targets for developing new compounds. Future research is required in this field to explore novel compounds and establish their efficacy and safety for the treatment of schizophrenia. Last but not least, pharmacogenomics has effectively utilized genetic information to develop novel compounds by minimizing the risk of failure of the clinical trials and enhancing efficacy and safety.

Domesticated HERV-W env contributes to the activation of the small conductance Ca2+-activated K+ type 2 channels via decreased 5-HT4 receptor in recent-onset schizophrenia

The human endogenous retroviruses type W family envelope (HERV-W env) gene is located on chromosome 7q21-22. Our previous studies show that HERV-W env is elevated in schizophrenia and HERV-W env can increase calcium influx. Additionally, the 5-HTergic system and particularly 5-hydroxytryptamine (5-HT) receptors play a prominent role in the pathogenesis and treatment of schizophrenia. 5-hydroxytryptamine receptor 4 (5-HT4R) agonist can block calcium channels. However, the underlying relationship between HERV-W env and 5-HT4R in the etiology of schizophrenia has not been revealed. Here, we used enzyme-linked immunosorbent assay to detect the concentration of HERV-W env and 5-HT4R in the plasma of patients with schizophrenia and we found that there were decreased levels of 5-HT4R and a negative correlation between 5-HT4R and HERV-W env in schizophrenia. Overexpression of HERV-W env decreased the transcription and protein levels of 5-HT4R but increased small conductance Ca2+-activated K+ type 2 channels (SK2) expression levels. Further studies revealed that HERV-W env could interact with 5-HT4R. Additionally, luciferase assay showed that an essential region (-364 to -176 from the transcription start site) in the SK2 promoter was required for HERV-W env-induced SK2 expression. Importantly, 5-HT4R participated in the regulation of SK2 expression and promoter activity. Electrophysiological recordings suggested that HERV-W env could increase SK2 channel currents and the increase of SK2 currents was inhibited by 5-HT4R. In conclusion, HERV-W env could activate SK2 channels via decreased 5-HT4R, which might exhibit a novel mechanism for HERV-W env to influence neuronal activity in schizophrenia.

The future of psychopharmacology: a critical appraisal of ongoing phase 2/3 trials, and of some current trends aiming to de-risk trial programmes of novel agents

Despite considerable progress in pharmacotherapy over the past seven decades, many mental disorders remain insufficiently treated. This situation is in part due to the limited knowledge of the pathophysiology of these disorders and the lack of biological markers to stratify and individualize patient selection, but also to a still restricted number of mechanisms of action being targeted in monotherapy or combination/augmentation treatment, as well as to a variety of challenges threatening the successful development and testing of new drugs. In this paper, we first provide an overview of the most promising drugs with innovative mechanisms of action that are undergoing phase 2 or 3 testing for schizophrenia, bipolar disorder, major depressive disorder, anxiety and trauma-related disorders, substance use disorders, and dementia. Promising repurposing of established medications for new psychiatric indications, as well as variations in the modulation of dopamine, noradrenaline and serotonin receptor functioning, are also considered. We then critically discuss the clinical trial parameters that need to be considered in depth when developing and testing new pharmacological agents for the treatment of mental disorders. Hurdles and perils threatening success of new drug development and testing include inadequacy and imprecision of inclusion/exclusion criteria and ratings, sub-optimally suited clinical trial participants, multiple factors contributing to a large/increasing placebo effect, and problems with statistical analyses. This information should be considered in order to de-risk trial programmes of novel agents or known agents for novel psychiatric indications, increasing their chances of success.

Treatment with the novel TAAR1 agonist ulotaront is associated with reductions in quantitative polysomnographic REM sleep without atonia in healthy human subjects: Results of a post-hoc analysis

BACKGROUND

Isolated REM sleep behavior disorder (RBD) is a potentially injurious parasomnia lacking an established treatment. Ulotaront is a trace amine-associated receptor 1 (TAAR1) agonist with 5-HT_1A receptor agonist activity that has demonstrated efficacy in patients with schizophrenia. In a single dose challenge study in humans, ulotaront 50 mg demonstrated significant REM suppressant effects. We now report post-hoc exploratory analyses designed to evaluate the effect of ulotaront on quantitative REM sleep without atonia (RSWA).

METHODS

Young healthy adult men (ages 19-35) were randomized to double-blind, cross-over treatment (after 7-day wash-out) with single doses of ulotaront (50 mg or 10 mg) versus placebo followed by polysomnography (PSG) on each of the nights following treatment. Quantitative RSWA was analyzed in a blinded fashion using established visual and automated methods.

RESULTS

Subjects received 50 mg (n = 11) or 10 mg (n = 9) of ulotaront. Treatment with ulotaront 50 mg was associated with lower RSWA (p < 0.05), with greatest RSWA reduction (vs. placebo) observed in subjects with RSWA levels above the mean on the baseline night. RSWA levels were similar between treatment with ulotaront 10 mg and placebo.

CONCLUSION

Treatment with ulotaront 50 mg (but not 10 mg) was associated with reductions in RSWA levels in healthy subjects, especially in subjects with higher baseline RSWA levels, providing proof-of-concept for ulotaront efficacy in reducing RSWA levels. However, whether ulotaront might have efficacy as a treatment for human RBD awaits double-blind trials with ulotaront in clinical RBD populations.

The Evolving Role of Animal Models in the Discovery and Development of Novel Treatments for Psychiatric Disorders

Historically, animal models have been routinely used in the characterization of novel chemical entities (NCEs) for various psychiatric disorders. Animal models have been essential in the in vivo validation of novel drug targets, establishment of lead compound pharmacokinetic to pharmacodynamic relationships, optimization of lead compounds through preclinical candidate selection, and development of translational measures of target occupancy and functional target engagement. Yet, with decades of multiple NCE failures in Phase II and III efficacy trials for different psychiatric disorders, the utility and value of animal models in the drug discovery process have come under intense scrutiny along with the widespread withdrawal of the pharmaceutical industry from psychiatric drug discovery. More recently, the development and utilization of animal models for the discovery of psychiatric NCEs has undergone a dynamic evolution with the application of the Research Domain Criteria (RDoC) framework for better design of preclinical to clinical translational studies combined with innovative genetic, neural circuitry-based, and automated testing technologies. In this chapter, the authors will discuss this evolving role of animal models for improving the different stages of the discovery and development in the identification of next generation treatments for psychiatric disorders.

The Difficult Path to the Discovery of Novel Treatments in Psychiatric Disorders

CNS diseases, including psychiatric disorders, represent a significant opportunity for the discovery and development of new drugs and therapeutic treatments with the potential to have a significant impact on human health. CNS diseases, however, present particular challenges to therapeutic discovery efforts, and psychiatric diseases/disorders may be among the most difficult. With specific exceptions such as psychostimulants for ADHD, a large number of psychiatric patients are resistant to existing treatments. In addition, clinicians have no way of knowing which psychiatric patients will respond to which drugs. By definition, psychiatric diagnoses are syndromal in nature; determinations of efficacy are often self-reported, and drug discovery is largely model-based. While such models of psychiatric disease are amenable to screening for new drugs, whether cellular or whole-animal based, they have only modest face validity and, more importantly, predictive validity. Multiple academic, pharmaceutical industry, and government agencies are dedicated to the translation of new findings about the neurobiology of major psychiatric disorders into the discovery and advancement of novel therapies. The collaboration of these agencies provide a pathway for developing new therapeutics. These efforts will be greatly helped by recent advances in understanding the genetic bases of psychiatric disorders, the ongoing search for diagnostic and therapy-responsive biomarkers, and the validation of new animal models.

Biological evaluation and in silico studies of novel compounds as potent TAAR1 agonists that could be used in schizophrenia treatment

Introduction: Schizophrenia is a serious mental illness that requires effective treatment with minimal adverse effects. As preclinical and clinical research progresses, trace amine-associated receptor 1 (TAAR1) is becoming a potential new target for the treatment of schizophrenia. Methods: We used molecular docking and molecular dynamics (MD) simulations to discover TAAR1 agonists. The agonistic or inhibitory effects of compounds on TAAR1, 5-HT1A, 5-HT2A, and dopamine D₂-like receptors were determined. We used an MK801-induced schizophrenia-like behavior model to assess the potential antipsychotic effects of compounds. We also performed a catalepsy assay to detect the adverse effects. To evaluate the druggability of the compounds, we conducted evaluations of permeability and transporter substrates, liver microsomal stability in vitro, human ether-à-go-go-related gene (hERG), pharmacokinetics, and tissue distribution. Results: We discovered two TAAR1 agonists: compounds 50A and 50B. The latter had high TAAR1 agonistic activity but no agonistic effect on dopamine D₂-like receptors and demonstrated superior inhibition of MK801-induced schizophrenia-like behavior in mice. Interestingly, 50B had favorable druggability and the ability to penetrate the blood-brain barrier (BBB) without causing extrapyramidal symptoms (EPS), such as catalepsy in mice. Conclusion: These results demonstrate the potential beneficial role of TAAR1 agonists in the treatment of schizophrenia. The discovery of a structurally novel TAAR1 agonist (50B) may provide valuable assistance in the development of new treatments for schizophrenia.

Schizophrenia: One Name, Many Different Manifestations

Schizophrenia is a disabling condition impacting approximately 1% of the worldwide population. Symptoms include positive symptoms (eg, hallucinations, delusions), negative symptoms (eg, avolition, anhedonia), and cognitive impairment. There are likely many different environmental and pathophysiologic etiologies involving distinct neurotransmitters and neurocircuits. Pharmacologic treatment at present consists of dopamine receptor antagonists, which are reasonably effective at treating positive symptoms, but less effective at treating cognitive and negative symptoms. Nondopaminergic medications targeting alternative receptors are under investigation. Supportive psychosocial treatments can work in tandem with antipsychotic medications and optimize patient care.

Xanomeline-Trospium and Muscarinic Involvement in Schizophrenia

Schizophrenia is a severe mental illness that has its onset in late adolescence or early adulthood and is associated with significant dysfunction across multiple domains. The pathogenesis of schizophrenia remains unknown, but physiologic understanding of the illness has been driven by the dopamine hypothesis. However, acetylcholine (ACh) clearly plays a role with mixed results regarding effect on psychosis. Selective muscarinic M₁ and M₄ agonists, such as xanomeline, originally developed to aid in cognitive loss with Alzheimer's, showed promise in proof-of-concept study in 20 patients with schizophrenia. Unfortunately, tolerability problems made muscarinic agonists impractical in either condition. However, coadministration of trospium, a lipophobic, non-selective muscarinic antagonist previously used for the treatment of overactive bladder, with xanomeline resulted in a significant reduction of cholinergic adverse effects. A recent randomized, placebo-controlled study of the antipsychotic effects of this combination in 182 patients with acute psychosis revealed improved tolerability with 80% of subjects staying to the end of the 5 weeks study. At the end of the trial, the treatment group saw a -17.4 change in the positive and negative symptom scale (PANSS) score from baseline compared to a -5.9 change in the placebo arm (P < 0.001). Furthermore, the negative symptom subscore, was also superior in the active arm (P < 0.001). These early studies are exciting because they suggest that the cholinergic system may be recruited to treat a severe and disabling disorder with suboptimal treatment options. Xanomeline-trospium combination is currently in phase III studies.

Trace amine-associated receptor 1 (TAAR1) agonism as a new treatment strategy for schizophrenia and related disorders

Schizophrenia remains a major health burden, highlighting the need for new treatment approaches. We consider the potential for targeting the trace amine (TA) system. We first review genetic, preclinical, and clinical evidence for the role of TAs in the aetiopathology of schizophrenia. We then consider how the localisation and function of the trace amine-associated receptor 1 (TAAR1) position it to modulate key brain circuits for the disorder. Studies in rodents using Taar1 knockout (TAAR1-KO) and overexpression models show that TAAR1 agonism inhibits midbrain dopaminergic and serotonergic activity, and enhances prefrontal glutamatergic function. TAAR1 agonists also reduce hyperactivity, attenuate prepulse inhibition (PPI) deficits and social withdrawal, and improve cognitive measures in animal models. Finally, we consider findings from clinical trials of TAAR1 agonists and how this approach may address psychotic and negative symptoms, tolerability issues, and other unmet needs in the treatment of schizophrenia.

Pushing the boundaries of behavioral analysis could aid psychiatric drug discovery

Drug discovery for psychiatric conditions is stagnating. Behavioral changes could be used as a primary phenotypic screen for new drug candidates, if enough useful data can be generated from behavioral models. Could machine learning be the answer to extracting the data we need?

Ulotaront: a TAAR1/5-HT1A agonist in clinical development for the treatment of schizophrenia

INTRODUCTION

Current antipsychotics are postsynaptic dopamine-2(D₂) receptor blockers, which often, but not always, effectively improve acute psychotic symptoms and prevent relapse in schizophrenia and other severe mental disorders, but are associated with various side effects, including parkinsonism, akathisia, sedation/somnolence, and cardiometabolic alterations. Furthermore, the efficacy of current antipsychotics for negative and cognitive symptoms in schizophrenia is limited. Ulotaront is a novel trace-amine-associated receptor-1(TAAR1) agonist with serotonin-1A receptor agonist activity, and without postsynaptic D2-receptor antagonism. Phase 2 clinical data for ulotaront in patients with acutely exacerbated schizophrenia are promising regarding the potential improvement in positive, negative, and depressive symptoms.

AREAS COVERED

An overview of the pharmacokinetic and pharmacodynamic properties of ulotaront is given. Summary of clinical efficacy and safety/tolerability from Phase 1/2-trials, and of ongoing Phase 3-trials, is also given.

EXPERT OPINION

Ulotaront is a promising agent for the treatment of schizophrenia with an apparent benign safety profile, which might provide a much-needed new and different treatment option for various domains of schizophrenia. Data from larger Phase 3-trials, including for relapse prevention, schizophrenia subdomains, and in adolescents, are awaited. If ongoing Phase 3-trials in adults are successful, further research on combination regimens with existing antipsychotics, and in treatment-resistant schizophrenia as well as in mood disorders would be desirable.

TAAR1 dependent and independent actions of the potential antipsychotic and dual TAAR1/5-HT1A receptor agonist SEP-383856

SEP-383856 (SEP-856) is a novel antipsychotic under clinical development. It displays a unique pattern of receptor interaction, with only weak (partial agonist) activity at dopamine D₂ receptors, yet more potent agonist activity at the trace amine associated receptor (TAAR1) and 5-hydroxytryptamine 1 A receptor (5-HT_1A). Nonetheless, these observations await independent confirmation and more detailed characterization of the in vitro and in vivo actions of SEP-856 at TAAR1 and 5-HT_1A receptors would be instructive. Herein, we employed luminescence complementation technology in heterologous live cell systems, confocal microscopy, voltage clamp electrophysiology, behavioral readouts and TAAR1 knockout (KO) mice to study SEP-856 in further detail. We provide evidence for the ability of SEP-856 to activate TAAR1 at the surface plasma membrane, and show that this interaction results in Gα_s recruitment (pEC₅₀: 6.08 ± 0.22 E_MAX: 96.41% ± 15.26) and by extension, to G-protein inwardly rectifying potassium (GIRK) channel activation. Using TAAR1-KO mice, we find TAAR1 to be indispensable for SEP-856 control of body temperature, baseline locomotion reduction and for "antipsychotic-like" efficacy as characterized by a reversal of dizocilipine (MK-801) mediated disruption of pre-pulse inhibition. Conversely, the inhibition by SEP-856 of MK-801 induced locomotion was unaffected in TAAR1 KO mice. SEP-856 behaved as a low-potency, partial agonist at the 5-HT_1A receptor, while it partially inhibited recruitment of D₂ receptor-coupled Gα and GIRK by DA and acted as a weak partial agonist with low potency at the same receptor when applied alone. Our findings corroborate and extend previous observations on the molecular substrates engaged by this unique, dual TAAR1/5-HT_1A receptor agonist and potential antipsychotic that could prove to have major advantages in the treatment of schizophrenia and other psychotic disorders.

Effects of add-on Celecoxib treatment on patients with schizophrenia spectrum disorders and inflammatory cytokine profile trial (TargetFlame): study design and methodology of a multicentre randomized, placebo-controlled trial

Neuroinflammation has been proposed to impact symptomatology in patients with schizophrenia spectrum disorders. While previous studies have shown equivocal effects of treatments with add-on anti-inflammatory drugs such as Aspirin, N-acetylcysteine and Celecoxib, none have used a subset of prospectively recruited patients exhibiting an inflammatory profile. The aim of the study is to evaluate the efficacy and safety as well as the cost-effectiveness of a treatment with 400 mg Celecoxib added to an ongoing antipsychotic treatment in patients with schizophrenia spectrum disorders exhibiting an inflammatory profile. The “Add-on Celecoxib treatment in patients with schizophrenia spectrum disorders and inflammatory cytokine profile trial (TargetFlame)” is a multicentre randomized, placebo-controlled phase III investigator-initiated clinical trial with the following two arms: patients exhibiting an inflammatory profile receiving either add-on Celecoxib 400 mg/day or add-on placebo. A total of 199 patients will be assessed for eligibility by measuring blood levels of three pro-inflammatory cytokines, and 109 patients with an inflammatory profile, i.e. inflamed, will be randomized, treated for 8 weeks and followed-up for additional four months. The primary endpoint will be changes in symptom severity as assessed by total Positive and Negative Syndrome Scale (PANSS) score changes from baseline to week 8. Secondary endpoints include various other measures of psychopathology and safety. Additional health economic analyses will be performed. TargetFlame is the first study aimed at evaluating the efficacy, safety and cost-effectiveness of the antiphlogistic agent Celecoxib in a subset of patients with schizophrenia spectrum disorders exhibiting an inflammatory profile. With TargetFlame, we intended to investigate a novel precision medicine approach towards anti-inflammatory antipsychotic treatment augmentation using drug repurposing.

Clinical trial registration:http://www.drks.de/DRKS00029044 and https://trialsearch.who.int/Trial2.aspx?TrialID=DRKS00029044