The future of alzheimer disease immunotherapies in Saudi Arabia: Consensus statement of the Saudi Chapter of Cognitive and Behavioral Neurology

Alzheimer Disease (AD) constitutes a major global healthcare problem. Standard AD pharmacotherapies offer only modest transient cognitive and behavioral benefits. Aducanumab, an amyloid monoclonal antibody, was the first disease modifying agent to be approved for AD treatment. However, concerns about its efficacy and side effects led regulatory institutions around the world to restrict its use. Lecanemab was the second amyloid antibody to receive accelerated approval for use in early AD. This review and consensus statement was prepared by the Saudi Chapter of Cognitive and Behavioral Neurology to review the current developments in AD immunotherapies from a Saudi perspective. We outline recommendations with regards to offering aducanumab and other future immunotherapies to Saudi AD patients. We describe resources, infrastructure, research, and clinical practice changes that must be attained to transform the patient journey and clinical pathways of AD in Saudi Arabia to enable offering AD immunotherapies in Saudi Arabia.

Invisible wounds: Suturing the gap between the neurobiology, conventional and emerging therapies for posttraumatic stress disorder

A sharp increase in the prevalence of neuropsychiatric disorders, including major depression, anxiety, substance use disorders and posttraumatic stress disorder (PTSD) has occurred due to the traumatic nature of the persisting COVID-19 global pandemic. PTSD is estimated to occur in up to 25% of individuals following exposure to acute or chronic trauma, and the pandemic has inflicted both forms of trauma on much of the population through both direct physiological attack as well as an inherent upheaval to our sense of safety. However, despite significant advances in our ability to define and apprehend the effects of traumatic events, the neurobiology and neuroanatomical circuitry of PTSD, one of the most severe consequences of traumatic exposure, remains poorly understood. Furthermore, the current psychotherapies or pharmacological options for treatment have limited efficacy, durability, and low adherence rates. Consequently, there is a great need to better understand the neurobiology and neuroanatomy of PTSD and develop novel therapies that extend beyond the current limited treatments. This review summarizes the neurobiological and neuroanatomical underpinnings of PTSD and discusses the conventional and emerging psychotherapies, pharmacological and combined psychopharmacological therapies, including the use of psychedelic-assisted psychotherapies and neuromodulatory interventions, for the improved treatment of PTSD and the potential for their wider applications in other neuropsychiatric disorders resulting from traumatic exposure.

Zinc deficiency and supplementation in autism spectrum disorder and Phelan-McDermid syndrome

Approximately 1 in 36 children are diagnosed with autism spectrum disorder (ASD). The disorder is four times more common in males than in females. Zinc deficiency and mutations in SHANK2 and SHANK3 (members of a family of excitatory postsynaptic scaffolding proteins) are all risk factors that may contribute to the pathophysiology of the disease. The presence of shankopathies (loss of one copy of the SHANK3 gene) can lead to the development of Phelan-McDermid syndrome (PMDS)-a rare genetic disorder characterized by developmental delay, intellectual disability, poor motor tone, and ASD-like symptoms. We reviewed the relationship between zinc, ASD, and PMDS as well as the effect of zinc supplementation in improving symptoms of ASD and PMDS based on 22 studies published within 6 years (2015-2020). Zinc deficiency (assessed by either dietary intake, blood, hair, or tooth matrix) was shown to be highly prevalent in ASD and PMDS patients as well as in preclinical models of ASD and PMDS. Zinc supplements improved the behavioral deficits in animal models of ASD and PMDS. Clinical trials are still needed to validate the beneficial therapeutic effects of zinc supplements in ASD and PMDS patients.

Dopamine D3 Receptors: From Bench to Bedside

Dopamine D3 receptors belong to the dopamine D2-like receptor family, which also includes D2 and D4 receptors. These receptors have limited anatomical distribution and are mainly expressed in brain regions and pathways that typically mediate the actions of antipsychotic drugs and medication used against Parkinson's disease (PD). The development of cariprazine, the fi rst D2/D3 partial agonist with prominent affi nity and preferential activity at D3 receptors over other dopamine receptor subtypes was a landmark that provided new insights into the neurochemical and physiological functions of D3 receptors. Preclinical studies and clinical trials provided evidence for the clinical advantages of cariprazine in the treatment of schizophrenia and bipolar disorder. Cariprazine became the fi rst antipsychotic drug approved for the treatment of manic, mixed and depressive episodes in bipolar I disorder. Antagonism of D3 receptors may play a role in ameliorating symptoms of levodopa-induced dyskinesia and psychosis in PD patients treated with levodopa/carbidopa. Accordingly, D3 receptors constitute attractive targets for developing novel drugs for the improved treatment of different psychiatric and neurological disorders. (Neuropsychopharmacol Hung 2021; 23(2): 272-280).

Empagliflozin Effectively Attenuates Olanzapine-Induced Body Weight Gain in Female Wistar Rats

Atypical antipsychotic drugs are commonly associated with undesirable side effects including body weight gain (BWG) and metabolic deficits. Many pharmacological interventions have been tested in an attempt to minimize or prevent these side effects. Preliminary evidence suggests that antidiabetic drugs may be effective in attenuating antipsychotic-induced BWG. In the current study, we examined the effect of an antidiabetic drug empagliflozin (EMPA) on BWG induced by anatypical antipsychotic drug olanzapine (Ola) in female and male Wistar rats. Rats were divided into six groups based on the dose they received: group 1 (female control), group 2 (female EMPA, 20 mg/kg; IG), group 3 (female Ola, 4 mg/kg; IP), group 4 (female Ola, 4 mg/kg; IP + EMPA, 20 mg/kg; IG), group 5 (male control), and group 6 (male Ola, 4 mg/kg; IP). Ola induced sustained increase in BWG. The subsequent treatment of Group 3 and 4 with EMPA attenuated the Ola-induced BWG in female Wistar rats. In terms of the gender difference between female and male Wistar rats, the male control group 5 gained more weight throughout the study as compared to the female control group 1. Similarly, the male Ola group 6 gained more weight throughout the study as compared to the female Ola group 3. However, Ola did not cause any weight difference between male rats treated with Ola in comparison with male control group, thus showing a significant gender difference regarding body weight between male and female Wistar rats regardless of Ola administration. In addition, the present findings showed that EMPA effectively attenuates the Ola induced BWG in female Wistar rats. These novel findings should help to better understand the underlying molecular and behavioral mechanisms contributing to the observed increase in body weight after treatment with Ola and other atypical antipsychotic drugs across male and female rats.

Relationship Between Public Mental Health and Immune Status During the COVID-19 Pandemic: Cross-Sectional Data from Saudi Arabia

PURPOSE

Coronavirus disease 2019 (COVID-19) has evolved into a worldwide pandemic and continues to escalate exponentially in many countries across the globe. Recently, higher rates of psychological distress have been reported in several countries during the pandemic. Accordingly, the study aim was to investigate the relationship between public mental health and immune status during the COVID-19 pandemic.

METHODS

Participants of this cross-sectional study were 2252 national and foreign residents of Saudi Arabia. We used a web-based self-rated questionnaire to measure the association between psychological distress (Depression, Anxiety and Stress Scales [DASS-21]) and immune status (Immune Status Questionnaire [ISQ]) during the COVID-19 pandemic. We also investigated predictors of reduced immune status using binary logistic regression analyses.

RESULTS

Data from 1721 respondents showed that 17.5% of participants scored below the immune status cutoff (ISQ ˂ 6). Mean (± standard deviation) depression, anxiety, and stress scores in the reduced immune status group (ISQ ˂ 6) indicated moderate depression, anxiety, and stress (19.1 ± 11.4; 15.0 ± 9.6; 21.8 ± 11.2, respectively) and were significantly higher than scores in the normal immune status group (ISQ ≥ 6) (8.6 ± 9.1, P ˂ 0.0001; 5.0 ± 6.7, P ˂ 0.0001; 9.3 ± 9.3, P ˂ 0.0001, respectively). The regression analysis showed that age, anxiety, and stress were the only factors that significantly predicted the presence of reduced immune status.

CONCLUSION

There is an association between mental health problems during the COVID-19 pandemic and immune response in the public, especially in elderly people.

Standardizing the Effective Correlated Dosage of Olanzapine and Empagliflozin in Female Wistar Rats

AIM

The primary aim of this study was to standardize the correlated effective dosage of the antidiabetic drug empagliflozin (EMPA) and the antipsychotic drug olanzapine (Ola).

BACKGROUND

Atypical antipsychotics are associated with BWG and metabolic disturbances for which many approaches have been used to minimize these issues, including antidiabetic drugs. The antidiabetic drugs have been quite effective in reversing BWG induced by the administration of antipsychotic drugs in patients who have psychosis, schizophrenia and bipolar disorder.

OBJECTIVE

The objective of this study was to standardize the correlated effective dosage of EMPA and Ola.

METHODS

The study was carried out for 28 days to represent the chronic effect of Ola on female Wistar rats. Rats were divided into three groups based on the dose they received: control (vehicle), Ola-4 and Ola-8 (4 and 8 mg/kg/OD, respectively), and EMPA-10 and EMPA-20 (10 and 20 mg/kg/OD, respectively).

RESULTS

Both doses of Ola produced a significant increase in the percentage of BWG, however, Ola-4 produced a higher BWG. Also, both the doses of EMPA were able to reverse the effect of Ola-induced BWG; however, EMPA-20 produced a higher reversal in BWG and normalized the rat's body weight.

CONCLUSION

We conclude that Ola-4 and EMPA-20 were the most effective dosage for experimental purposes in female Wistar rats. The findings of this study standardized the effective correlated dosage of olanzapine and empagliflozin in female Wistar rats that will help understand the underlying molecular and behavioral mechanisms.

What's Love Got to do with it: Role of oxytocin in trauma, attachment and resilience

Oxytocin (OT) is a neurohypophysial hormone and neuropeptide produced by the hypothalamus and released by the pituitary gland. It has multiple physiological roles including stimulation of parturition and lactation, and promotion of pro-adaptive social behaviors necessary for mammalian survival. OT interacts with one receptor subtype: the OT receptor (OTR) which, upon stimulation, triggers different intracellular signal transduction cascades to mediate its physiological actions. Preclinical studies show that OT regulates social behaviors such as pair bonding, recognition and social interaction. It also coordinates the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the release of corticotrophin-releasing hormone. Further evidence suggests that OT plays an important role in regulating caloric intake and metabolism, and in maintaining electrolyte and cardiovascular homeostasis. OT is also involved in attenuating the neurophysiological and neurochemical effects of trauma on the brain and body by facilitating both physical attachment such as wound healing, and psychological/social attachment, thereby increasing resilience to subsequent traumatic events. Clinical trials have reported that intranasal administration of OT provides therapeutic benefits for patients diagnosed with traumatic stress-related diseases such as major depressive disorders and post-traumatic stress disorder. OT's therapeutic benefits may result from context-dependent interactions with key neural pathways (social, cognitive, and reward), neurotransmitters (dopamine, norepinephrine, serotonin, and endogenous opioids), and biomarkers (adrenocorticotropic hormone, cortisol, and dehydroepiandrosterone sulfate), that lead to a decrease in stress -associated behaviors, and facilitate post-traumatic growth, ultimately leading to increased resilience, through improved social cohesion and attachment. OT induced-augmentation of physical and cognitive resilience may play a significant role in both the prevention of, and improved clinical outcomes for, traumatic stress-related disorders following either acute or enduring traumatic experiences.

Vitamin D supplementation ameliorates severity of generalized anxiety disorder (GAD)

This study investigated the effects of vitamin D supplementation on Generalized Anxiety Disorder (GAD) clinical symptoms and neurochemical biomarkers including serotonin, neopterin and kynurenine. Thirty male and female patients diagnosed with GAD and had vitamin D deficiency were recruited from the psychiatric clinic at King Abdulaziz University Hospital and divided into two groups; one group of patients (n = 15) received standard of care (SOC) plus 50,000 IU vitamin D (once/week) for 3 months, while the other group (n = 15) received SOC alone. Biochemical parameters including serum vitamin D, serotonin, neopterin and kynurenine were measured for all patients enrolled in the trial. In addition, the Generalized Anxiety Disorder 7-item (GAD-7) scale was used to measure the severity of GAD symptoms in both vitamin D treated- and untreated-patients. Significant improvements in GAD scores were observed in the vitamin D-treated group compared to the group that did not receive vitamin D. In addition, serum serotonin concentrations were significantly increased while serum neopterin were significantly decreased in vitamin D-treated vs. untreated patients. In contrast, no significant differences were found in serum kynurenine concentrations at the end of the study period between the two groups. No changes either in GAD-7 scores or in any of the biochemical measurements were observed in the group that received only SOC after 3 months. Vitamin D supplementation was effective in ameliorating the severity of GAD symptoms by increasing serotonin concentrations and decreasing the levels of the inflammatory biomarker neopterin in GAD patients.

Long-term effects of iloperidone on cerebral dopamine receptor subtypes

The atypical antipsychotic drug iloperidone has high affinity for a wide range of neurotransmitter receptors, including dopaminergic (DA), serotonergic, and adrenergic receptors. We examined the long-term effects of multiple doses of iloperidone on DA D1 , D2 , D3 , and D4 receptor subtypes. Sprague-Dawley adult rats (n = 8/group) received daily intraperitoneal injections of iloperiodone (0.5, 1, or 5 mg/kg) or vehicle for 4 weeks. Receptor autoradiography quantified the levels of DA receptors in medial prefrontal cortex (MPC), dorsolateral frontal cortex (DFC), caudate putamen (CPu), nucleus accumbens (NAc), and hippocampus (HIP). Four weeks of iloperidone treatment at 5 mg/kg significantly increased D1 receptors in NAc (36%) and CPu (38%). Iloperidone (1.5 and 5 mg/kg) dose-dependently increased D2 receptors in MPC (37 and 47%) and HIP (32 and 40%). Only the high dose of iloperidone (5 mg/kg) increased D2 receptors in NAc (39%) and CPu (38%). Repeated treatment with iloperidone (1.5 and 5 mg/kg) increased D4 receptors in the NAc (39 and 78%), CPu (42 and 83%) and HIP (54 and 72%). The three doses of iloperidone failed to alter D3 receptors in the brain regions examined in this study. These results suggest that iloperidone exerts region- and dose-specific effects on forebrain DA receptor subtypes, which may contribute to its therapeutic benefits in improving the positive and negative symptoms of schizophrenia with minimal extrapyramidal side effects.

Autism Spectrum Disorder: Classification, diagnosis and therapy

Autism Spectrum Disorder (ASD) refers to a group of neurodevelopmental disorders including autism, Asperger's syndrome (AS) and pervasive developmental disorder-not otherwise specified (PDD-NOS). The new diagnostic criteria of ASD focuses on two core domains: social communication impairment and restricted interests/repetitive behaviors. The prevalence of ASD has been steadily increasing over the past two decades, with current estimates reaching up to 1 in 36 children. Hereditary factors, parental history of psychiatric disorders, pre-term births, and fetal exposure to psychotropic drugs or insecticides have all been linked to higher risk of ASD. Several scales such as the Childhood Autism Rating Scale (CARS), The Autism Spectrum Disorder-Observation for Children (ASD-OC), The Developmental, Dimensional, and Diagnostic Interview (3di), are available to aid in better assessing the behaviors and symptoms associated with ASD. Nearly 75% of ASD patients suffer from comorbid psychiatric illnesses or conditions, which may include attention-deficit hyperactivity disorder (ADHD), anxiety, bipolar disorder, depression, Tourette syndrome, and others. Both pharmacological and non-pharmacological interventions are available for ASD. Pharmacological treatments include psychostimulants, atypical antipsychotics, antidepressants, and alpha-2 adrenergic receptor agonists. These medications provide partial symptomatic relief of core symptoms of ASD or manage the symptoms of comorbid conditions. Non-pharmacological interventions, which show promising evidence in improving social interaction and verbal communication of ASD patients, include music therapy, cognitive behavioral therapy and social behavioral therapy. Hormonal therapies with oxytocyin or vasopressin receptor antagonists have also shown some promise in improving core ASD symptoms. The use of vitamins, herbal remedies and nutritional supplements in conjunction with pharmacological and behavioral treatment appear to have some effect in symptomatic improvement in ASD, though additional studies are needed to confirm these benefits. Developing novel disease-modifying therapies may prove to be the ultimate intervention for sustained improvement of symptoms in ASD.

Pimavanserin: novel pharmacotherapy for Parkinson's disease psychosis

INTRODUCTION

Pimavanserin is the first FDA-approved atypical antipsychotic drug indicated for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis (PDP). Areas covered: This review focuses on the preclinical discovery of pimavanserin. It analyzes the pharmacological, behavioral and molecular mechanisms of pimavanserin and their contribution to the therapeutic advantages of the drug as reported in published preclinical and clinical studies, press releases and product labels. Expert opinion: Pimavanserin exhibits a unique pharmacological profile with nanomolar affinity at serotonin 5-HT_2A and 5-HT_2C receptors. Functionally, it acts as a potent inverse agonist at 5-HT_2A receptors, with selectivity over 5-HT_2C receptors and no appreciable activity at other neurotransmitter receptors. Behavioral studies found that pimavanserin reversed impaired behaviors in animal models predictive of antipsychotic activity, and with no impairment of motor functions. The drug exhibits long plasma half-life (57 hours), which support its once/day administration. A pivotal phase III clinical trial demonstrated significant improvement in PDP symptoms in patients receiving pimavanserin compared to placebo-treated patients. The drug also displayed relatively benign safety and tolerability profiles. Pimavanserin's mechanism of action might contribute to its unique psychopharmacological properties in the improved treatment of PDP, and perhaps psychosis in other diseases including schizophrenia and dementia-related psychosis.

The Preclinical and Clinical Effects of Vilazodone for the Treatment of Major Depressive Disorder

INTRODUCTION

Major depressive disorder (MDD) is the leading cause of disability worldwide, and according to the STAR*D trial, only 33% of patients with MDD responded to initial drug therapy. Augmentation of the leading class of antidepressant treatment, selective serotonin reuptake inhibitors (SSRIs), with the 5-HT1A receptor agonist buspirone has been shown to be effective in treating patients that do not respond to initial SSRI therapy. This suggests that newer treatments may improve the clinical picture of MDD. The US Food and Drug Administration (FDA) approved the antidepressant drug vilazodone (EMD 68843), a novel SSRI and 5-HT1A receptor partial agonist. Vilazodone has a half-life between 20-24 hours, reaches peak plasma concentrations at 3.7-5.3 hours, and is primarily metabolized by the hepatic CYP450 3A4 enzyme system.

AREAS COVERED

The authors review the preclinical and clinical profile of vilazodone. The roles of serotonin, the 5-HT1A receptor, and current pharmacotherapy approaches for MDD are briefly reviewed. Next, the preclinical pharmacological, behavioral, and physiological effects of vilazodone are presented, followed by the pharmacokinetic properties and metabolism of vilazodone in humans. Last, a brief summary of the main efficacy, safety, and tolerability outcomes of clinical trials of vilazodone is provided.

EXPERT OPINION

Vilazodone has shown efficacy versus placebo in improving depression symptoms in several double-blind, placebo-controlled trials. The long-term safety and tolerability of vilazodone treatment has also been established. Further studies are needed that directly compare patients treated with an SSRI (both with and without an adjunctive 5-HT1A partial agonist) versus patients treated with vilaozodone.

Gene-environment interaction in major depression: focus on experience-dependent biological systems

Major depressive disorder (MDD) is a multifactorial and polygenic disorder, where multiple and partially overlapping sets of susceptibility genes interact each other and with the environment, predisposing individuals to the development of the illness. Thus, MDD results from a complex interplay of vulnerability genes and environmental factors that act cumulatively throughout individual's lifetime. Among these environmental factors, stressful life experiences, especially those occurring early in life, have been suggested to exert a crucial impact on brain development, leading to permanent functional changes that may contribute to lifelong risk for mental health outcomes. In this review, we will discuss how genetic variants (polymorphisms, SNPs) within genes operating in neurobiological systems that mediate stress response and synaptic plasticity, can impact, by themselves, the vulnerability risk for MDD; we will also consider how this MDD risk can be further modulated when gene × environment interaction is taken into account. Finally, we will discuss the role of epigenetic mechanisms, and in particular of DNA methylation and miRNAs expression changes, in mediating the effect of the stress on the vulnerability risk to develop MDD. Taken together, we aim to underlie the role of genetic and epigenetic processes involved in stress- and neuroplasticity-related biological systems on the development of MDD after exposure to early life stress, thereby building the basis for future research and clinical interventions.

Emerging therapies for Parkinson's disease: from bench to bedside

The prevalence of Parkinson's disease (PD) increases with age and is projected to increase in parallel to the rising average age of the population. The disease can have significant health-related, social, and financial implications not only for the patient and the caregiver, but for the health care system as well. While the neuropathology of this neurodegenerative disorder is fairly well understood, its etiology remains a mystery, making it difficult to target therapy. The currently available drugs for treatment provide only symptomatic relief and do not control or prevent disease progression, and as a result patient compliance and satisfaction are low. Several emerging pharmacotherapies for PD are in different stages of clinical development. These therapies include adenosine A2A receptor antagonists, glutamate receptor antagonists, monoamine oxidase inhibitors, anti-apoptotic agents, and antioxidants such as coenzyme Q10, N-acetyl cysteine, and edaravone. Other emerging non-pharmacotherapies include viral vector gene therapy, microRNAs, transglutaminases, RTP801, stem cells and glial derived neurotrophic factor (GDNF). In addition, surgical procedures including deep brain stimulation, pallidotomy, thalamotomy and gamma knife surgery have emerged as alternative interventions for advanced PD patients who have completely utilized standard treatments and still suffer from persistent motor fluctuations. While several of these therapies hold much promise in delaying the onset of the disease and slowing its progression, more pharmacotherapies and surgical interventions need to be investigated in different stages of PD. It is hoped that these emerging therapies and surgical procedures will strengthen our clinical armamentarium for improved treatment of PD.

Effects of antidepressant drug exposure on gene expression in the developing cerebral cortex

To clarify the basis of limited responses in children and adolescents to antidepressant treatments considered standard in the treatment of adult major depressive disorder, juvenile Sprague-Dawley rats were subjected to 21-day treatment with dissimilar antidepressant drugs fluoxetine, imipramine, or vehicle control. Total RNA was extracted from brain frontal cortices and hybridized to the Affymetrix 230.2 chip. A total of 18 microarrays were analyzed (i.e., six biological replicates in three treatment groups). Transcripts identified were validated using Taqman real-time quantitative PCR methodology, and the relative expression of each gene was also determined. In both the imipramine- and fluoxetine-treated animals, expression of six genes was down-regulated (ANOVA-filtered gene expression data using dChip [version 2005]): Gpd1; Lrrn3; Sult1A1; Angptl4; Mt1a; Unknown. Furthermore, four genes were over-expressed: P4Ha1; RDG1311476; Rgc32; and SLC25A18-like by both imipramine and fluoxetine. These data demonstrate that antidepressant drugs interfere with the expression of genes involved in cell signaling, survival, and protein metabolism. Our results show that antidepressants regulate the induction of highly specific transcriptional programs in the developing frontal cortex. These findings provide novel insights into the long-term molecular actions of antidepressant drugs in the developing brain.

Bapineuzumab and solanezumab for Alzheimer's disease: is the 'amyloid cascade hypothesis' still alive?

INTRODUCTION

The 'amyloid cascade hypothesis' remains the leading hypothesis to explain the pathophysiology of Alzheimer's disease (AD). Immunotherapeutic agents have been developed to remove the neurotoxic amyloid β42 protein and prevent the hypothesized amyloid β42-induced neurotoxicity and neurodegeneration. The most notable of these immunotherapies are bapineuzumab and solanezumab.

AREAS COVERED

This article briefly reviews the experimental agents in development for treatment of AD and then discusses the results of bapineuzumab and solanezumab in AD patients, as reported in preclinical studies, clinical trials and press releases.

EXPERT OPINION

Phase III trials showed that bapineuzumab failed to improve cognitive and functional performances in AD patients, and was associated with a high incidence of amyloid-related imaging abnormalities (ARIA). Solanezumab's two Phase III trials in AD patients failed to meet endpoints when analyzed independently. However, analysis of pooled data from both trials showed a significant reduction in cognitive decline in mild AD patients. The improvement was associated with an increase in plasma amyloid-β (Aβ) levels and a low incidence of ARIA in solanezumab-treated patients. The marginal benefits of solanezumab are encouraging to support continued evaluation in future studies, and offer small support in favor of the ongoing viability of the 'amyloid cascade hypothesis' of AD.

A translational approach to evaluate the efficacy and safety of the novel AMPA receptor positive allosteric modulator org 26576 in adult attention-deficit/hyperactivity disorder

BACKGROUND

It has been posited that glutamate dysregulation contributes to the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). Modulation of glutamate neurotransmission may provide alternative therapeutic options. The novel 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid receptor positive allosteric modulator Org 26576 was investigated with a translational approach including preclinical and clinical testing.

METHODS

Neonatal rat 6-hydroxydopamine lesion-induced hyperactivity was used as preclinical model. Seventy-eight ADHD adults entered a multicenter, double-blind, placebo-controlled, two-period crossover trial. After 1 week placebo lead-in, 67 subjects were randomized into one of four treatment sequences: sequence A (n = 15) Org 26576 (100 mg b.i.d.) for 3 weeks, followed by a 2-week placebo crossover and 3 weeks placebo; sequence B (n = 16) 5 weeks placebo followed by 3 weeks Org 26576 (100 mg b.i.d.); sequence C (n = 18) Org 26576 flexible dose (100-300 mg b.i.d.) for 3 weeks, then 5 weeks placebo; sequence D (n = 18) 5 weeks placebo followed by 3 weeks Org 26576 (100-300 mg b.i.d.). The Adult ADHD Investigator Symptom Rating Scale was used to assess changes in ADHD symptomatology.

RESULTS

Org 26576 (1, 3, 10 mg/kg intraperitoneal) produced dose-dependent inhibition of locomotor hyperactivity in 6-hydroxydopamine-lesioned rats. Org 26576 (100 mg b.i.d.) was superior to placebo in treating symptoms of adult ADHD subjects. The primary Adult ADHD Investigator Symptom Rating Scale results were supported by some secondary analyses. However, Org 26576 (100-300 mg b.i.d.) did not confirm these results. Most frequently reported adverse events were nausea, dizziness, and headache.

CONCLUSIONS

These preclinical and clinical findings suggest that Org 25676 may have utility in the treatment of ADHD.

Iloperidone, asenapine and lurasidone: a primer on their current status

INTRODUCTION

Three newer atypical antipsychotic drugs were FDA-approved in 2009 and 2010 in the following order: iloperidone, asenapine and lurasidone. The three drugs are indicated for the treatment of acute schizophrenia. Asenapine is also approved for treatment of manic or mixed episodes associated with bipolar I disorder, for the maintenance treatment of schizophrenia and as an adjunctive therapy with lithium or valproate for the acute treatment of manic or mixed episodes associated with bipolar I disorder in adults.

AREAS COVERED

This review compares and contrasts the current preclinical, clinical, safety and tolerability profiles of the three newer drugs, as reported in published preclinical and clinical studies, product labels, poster presentations and press releases.

EXPERT OPINION

Preclinical studies have reported that the three drugs have variable affinities for a wide range of neurotransmitter receptors, and are active in animal models predictive of antipsychotic activity. Asenapine is the first antipsychotic to be administered sublingually, whereas iloperidone requires titration to minimize orthostatic hypotension. Asenapine and lurasidone are associated with dose-related akathisia, whereas iloperidone is not. The three drugs appear to have relatively benign metabolic profiles. The availability of the three novel antipsychotics should provide additional options for improved treatment of schizophrenia and other psychotic disorders.

Alterations in dopamine and glutamate neurotransmission in tetrahydrobiopterin deficient spr-/- mice: relevance to schizophrenia

Tetrahydrobiopterin (BH4) is a pivotal cofactor for enzymes responsible for the synthesis and release of monoamine neurotransmitters including dopamine (DA) and serotonin (5-HT) as well as the release of glutamate (Glu). Deficiencies in BH4 levels and reduced activities of BH(4)-associated enzymes have been recently reported in patients with schizophrenia. Accordingly, it is possible that abnormalities in the biochemical cascades regulated by BH(4) may alter DA, 5-HT and Glu neurotransmission, and consequently contribute to the pathophysiology of different neuropsychiatric diseases including schizophrenia. The development of a novel strain of mutant mice that is deficient in BH(4) by knocking out the expression of a functional sepiapterin reductase gene (spr -/-) has added new insights into the potential role of BH(4) in the pathophysiology and improved treatment of schizophrenia.

Asenapine maleate: a new drug for the treatment of schizophrenia and bipolar mania

Schizophrenia and bipolar disorder are serious neuropsychiatric disorders with substantial health risks for patients that result in major socioeconomic burdens on society. Current therapeutic agents fail to adequately address patient needs in terms of efficacy, tolerability and treatment-related adverse events. Consequently there is an urgent need to develop more effective and better tolerated pharmacotherapies for improved treatment of these illnesses. Asenapine maleate is a novel drug recently approved by the Food and Drug Administration for treatment of acute schizophrenia and for manic or mixed episodes of bipolar I disorder with or without psychotic features in adults. It has a unique pharmacologic profile as it targets multiple dopamine, serotonin and adrenergic receptor subtypes with variable affinities. Such drug/receptor interactions contribute to the antipsychotic and antimanic efficacy of asenapine. Asenapine was effective in animal models predictive of antipsychotic activity and clinical trials indicate that it improves the symptoms of acute schizophrenia and bipolar mania, is well tolerated and has a favorable safety profile. This monograph provides an up to date review of the preclinical and clinical profiles of asenapine, including new clinical data in patients with schizophrenia and bipolar mania.

Asenapine induces differential regional effects on serotonin receptor subtypes

Asenapine, a novel psychopharmacologic agent being developed for the treatment of schizophrenia and bipolar disorder, has high affinity for a wide range of receptors, including the serotonergic receptors 5-HT(1A), 5-HT(1B), 5-HT(2A), 5-HT( 2B), 5-HT(2C), 5-HT(5A), 5-HT(6) and 5-HT( 7). We examined the long-term effects in rat brain of multiple doses of asenapine on representative serotonin receptor subtypes: 5-HT(1A), 5-HT(2A) and 5-HT(2C). Rats were given asenapine (0.03, 0.1 or 0.3 mg/kg) subcutaneously twice daily or vehicle for 4 weeks. Brain sections were collected from the medial prefrontal cortex (mPFC), dorsolateral frontal cortex (DFC), caudate putamen, nucleus accumbens, hippocampal CA( 1) and CA(3) regions, and entorhinal cortex and processed for in-vitro receptor autoradiography. Asenapine 0.1 and 0.3 mg/kg significantly increased 5-HT(1A) binding in mPFC (by 24% and 33%, respectively), DFC (27%, 31%) and hippocampal CA(1) region (23%, 25%) (all P < 0.05). All three asenapine doses (0.03, 0.1 and 0.3 mg/kg) significantly decreased 5-HT(2A) binding by a similar degree in mPFC (40%, 44%, 47%, respectively) and DFC (45%, 51%, 52%) (all P < 0.05), but did not alter 5-HT(2A) binding in the other brain regions studied. In contrast to the effects on 5-HT(1A) and 5-HT(2A) receptors, asenapine did not alter 5-HT(2C) binding in any brain region examined at the doses tested. Our results indicate that repeated administration of asenapine produces regional-specific effects on 5-HT(1A) and 5-HT(2A) receptors in rat forebrain regions, which may contribute to the distinctive psychopharmacologic profile of asenapine.

Effects of repeated risperidone exposure on serotonin receptor subtypes in developing rats

Risperidone is an atypical antipsychotic drug that is widely prescribed to young patients with different psychotic disorders. The long-term effects of this antipsychotic agent on neuronal receptors in developing brain remain unclear and require further investigation. In this study, we examined the effects of long-term treatment of risperidone on two serotonin receptor subtypes in brain regions of juvenile rat. Levels of 5-HT(1A) and 5-HT(2A) receptors in forebrain regions of juvenile rats were quantified after 3 weeks of treatment with three different doses of risperidone (0.3, 1.0 and 3.0mg/kg). Findings were compared to previously reported changes in 5-HT receptors after risperidone treatment (3.0mg/kg) in adult rat brain. The three doses of risperidone selectively and dose-dependently increased levels of 5-HT(1A) receptors in medial-prefrontal and dorsolateral-frontal cortices of juvenile animals. The higher doses (1.0 and 3.0mg/kg) of risperidone also increased 5-HT(1A) receptor binding in hippocampal CA(1) region of juvenile but not adult rats. In contrast, the three doses of risperidone significantly reduced 5-HT(2A) labeling in medial-prefrontal and dorsolateral-frontal cortices in juvenile as well as in adult animals in an equipotent fashion. 5-HT(1A) and 5-HT(2A) receptors in other forebrain regions were not altered by repeated risperidone treatment. These findings indicate that there are differential effects of risperidone on 5-HT(1A) and 5-HT(2A) receptors in juvenile animals, and that the 5-HT system in developing animals is more sensitive than adults to the long-term effects of risperidone.

Pitx3-deficient aphakia mice display unique behavioral responses to psychostimulant and antipsychotic drugs

The dorsal (A9) and ventral striatum (A10) of the midbrain mediate many of the effects of psychoactive drugs that alter emotion, cognition, and motor activity within the contexts of therapy or abuse. Although transgenic and knockout technologies have enabled development of genetic models to dissect contributions of specific dopamine (DA) receptor subtypes to psychoactive drug effects, few models exist that can distinguish contributions of A9 versus A10 circuits. Pitx3 is a transcription factor enriched in DA neurons. Aphakia (ak) mice deficient in Pitx3 show selective loss of nigrostriatal DA, while other DA pathways are relatively spared, and therefore could be a useful tool for investigating the role of this subclass of DA projections. We investigated the effects of stimulants amphetamine, apomorphine, and MK-801 and the antipsychotic drug haloperidol on behavior in ak mice. Whereas wild-type mice showed the characteristic locomotor hyperactivity in response to amphetamine (5 mg/kg) and apomorphine (4 mg/kg), these drugs caused a paradoxical suppression of locomotor hyperactivity in ak mice. MK-801 (0.2 mg/kg) induced hyperactivity was maintained in both wt and ak mice. Additionally, mutant but not wild-type mice were insensitive to the cataleptic effects of haloperidol (1 mg/kg). These studies indicate that the nigrostriatal DA circuit plays a critical role in maintaining normal responsiveness to psychotropic drugs that either stimulate or block DA neurotransmission. We propose that ak mice may represent a valuable genetic model not only to study Parkinson's disease, but also to dissect the pathophysiologic and pharmacotherapuetic mechanisms of other DA-mediated disorders such as attention-deficit hyperactivity disorder, drug abuse and schizophrenia.

Effects of risperidone on glutamate receptor subtypes in developing rat brain

Levels of ionotropic glutamate (Glu) N-methyl-d-aspartic acid (NMDA), 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA), and kainic acid (KA) receptors in forebrain regions of juvenile rats (age 42 days) were quantified after 3 weeks of treatment with three different doses of risperidone (0.3, 1.0 and 3.0 mg/kg) and compared findings to those in adult rats treated with risperidone (3.0 mg/kg/day) previously. Risperidone (at 0.3 mg/kg/day) did not alter levels of three ionotropic Glu receptors in all brain regions examined. Risperidone (at 1.0 and 3.0 mg/kg/day) significantly decreased NMDA binding in caudate-putamen of juvenile and adult animals. In contrast, the same two doses of risperidone decreased NMDA receptors in nucleus accumbens of juveniles and not adults. Risperidone (at 1.0 and 3.0 mg/kg/day) increased AMPA receptors in medial prefrontal cortex and caudate-putamen of juvenile animals, whereas risperidone (at 3.0 mg/kg) increased AMPA receptors in caudate-putamen and hippocampus of adults. Kainate receptors were not altered by any dose of risperidone in any brain region examined in developing and mature animals. The findings indicate that risperidone exerts dose-dependent effects on Glu receptor subtypes in developing animals, and that Glu receptor responses to repeated administration of risperidone are different in juvenile animals than adults.

Differential regional and dose-related effects of asenapine on dopamine receptor subtypes

RATIONALE

The novel psychopharmacologic agent, asenapine, has high affinity for a range of receptors including the dopaminergic receptors.

OBJECTIVE

We examined the long-term effects of multiple doses of asenapine on dopamine receptor subtypes: D(1)-like (D(1) and D(5)), D(2), D(3), and D(4).

METHODS

Rats were given asenapine 0.03, 0.1, or 0.3 mg/kg (subcutaneously, twice daily) or vehicle for 4 weeks. Receptor binding was determined by autoradiography from brain sections collected from the medial prefrontal cortex (mPFC), dorsolateral frontal cortex, caudate putamen (CPu), nucleus accumbens (NAc), and hippocampus (HIP).

RESULTS

Four weeks of asenapine at 0.3 mg/kg significantly (P < 0.05) increased D(1)-like binding in the mPFC (by 26%), NAc (59%), and CPu (55%). Asenapine (0.1 and 0.3 mg/kg) also increased D(2) binding in mPFC (43% and 55%, respectively). All doses of asenapine dose-dependently increased D(2) binding in HIP (by 32%, 45%, and 63%, respectively). In contrast, only 0.3 mg/kg of asenapine significantly (P < 0.05) increased D(2) binding in the NAc (32%) and CPu (41%). Repeated treatment with 0.1 and 0.3 mg/kg of asenapine increased D(4) binding in the NAc (36% and 71%), CPu (27% and 70%), and HIP (48% and 77%). However, asenapine, at the doses tested, did not significantly alter D(3) binding in the brain regions examined in this study.

CONCLUSIONS

These results indicate that asenapine has region-specific and dose-dependent effects on dopamine receptor subtypes in rat forebrain, which may contribute to asenapine's unique psychopharmacological properties.

R-(−)-N-alkyl-11-hydroxy-10-hydroxymethyl- and 10-methyl-aporphines as 5-HT1A receptor ligands

Several N-substituted-11-hydroxy-10-hydroxymethyl- and 11-hydroxy-10-methylaporphines were synthesized and their binding affinities at dopamine D(1) and D(2) receptors and serotonin 5-HT(1A) and 5-HT(2A) receptors in rat forebrain tissue were evaluated. Tested compounds displayed moderate to high affinity to 5-HT(1A) receptors but low affinity to D(1) and D(2) receptors. The most potent novel 5-HT(1A) agent was R-(-)-N-methyl-10-hydroxymethyl-11-hydroxyaporphine.

Long-term Effects of JL 13, a Potential Atypical Antipsychotic, on Ionotropic Glutamate Receptors

Changes in ionotropic glutamate (Glu) N-methyl-d-aspartic acid (NMDA), and 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptors in rat forebrain regions were autoradiographically quantified after continuous infusion of JL 13 [(5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5]benzoxazepine fumarate] for 28 days using osmotic minipumps, and compared to the effects of representative typical (haloperidol) and atypical (clozapine, olanzapine, and risperidone) antipsychotic drugs from previous studies. Similar to other atypical and not typical antipsychotics, JL 13 decreased labeling of NMDA receptors in medial and lateral caudate-putamen (CPu; by 40%). These findings indicate that down-regulation of NMDA receptors by JL 13 and other atypical antipsychotic agents in CPu may contribute to their low risk of extrapyramidal side effects. In addition, and similar to olanzapine and risperidone, JL 13 increased AMPA receptor binding in CPu (by 42%). Changes in AMPA receptors may contribute to psychopharmacological properties of JL 13 and other atypical agents. Similar to clozapine, JL 13 did not alter levels of NMDA and AMPA receptors in hippocampus and entorhinal cortex. Long-term effects of JL 13 on ionotropic Glu receptors, as well as on other dopamine and serotonin receptors, support the atypical antipsychotic profile of this novel agent.

Effects of risperidone on dopamine receptor subtypes in developing rat brain

The atypical antipsychotic risperidone is often prescribed to pediatric patients with neuropsychiatric disorders, though its effects on the developing brain remain unclear. Accordingly, we studied the effects of repeated treatment of risperidone on dopamine receptors in brain regions of juvenile rat. Levels of dopamine receptors (D(1), D(2), D(3), D(4)) in forebrain regions of juvenile rats were quantified after 3 weeks of treatment with three different doses of risperidone (0.3, 1.0 and 3.0 mg/kg) and compared findings to those in adult rats treated with risperidone (3.0 mg/kg/day) previously. Risperidone (at 1.0 and 3.0 mg/kg/day) increased levels of D(1) receptors in nucleus accumbens and caudate-putamen of juvenile, but not adult rats. Conversely, all three doses of risperidone dose-dependently increased D(2) labeling in medial prefrontal cortex and hippocampus, and D(4) receptor in nucleus accumbens, caudate-putamen and hippocampus of juvenile animals as well as in adults. Only the high dose of risperidone (3.0 mg/kg) increased D(2) receptors in caudate-putamen in both juvenile and adult brain. D(3) receptors were not altered by risperidone in any brain region at any dose or age. The findings indicate dose-dependent effects of risperidone on dopamine receptors in developing animals, and that juvenile animals are more sensitive than adults to the cerebral effects of risperidone.

Development of SPECT imaging agents for the norepinephrine transporters: [123I]INER

A series of reboxetine analogs was synthesized and evaluated for in vitro binding as racemic mixtures. The best candidate (INER) was synthesized as the optically pure (S,S) enantiomer, labeled with iodine-123 and its in vivo binding determined by SPECT imaging in baboons. The in vivo specificity, selectivity, and kinetics of [123I]INER make it a promising agent for imaging NET in vivo by noninvasive SPECT imaging.

Long-term effects of JL 13, a potential atypical antipsychotic, on rat dopamine and serotonin receptor subtypes

Changes in dopamine (DA) D(1), D(2), D(3), and D(4) receptors and serotonin 5-HT(1A) and 5-HT(2A) receptors in rat forebrain regions were autoradiographically quantified after continuous infusion of JL 13 [(5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5]benzoxazepine fumarate] for 28 days with osmotic minipumps and compared with the effects of other typical (fluphenazine) and atypical (clozapine, olanzapine, and risperidone) antipsychotic drugs from previous studies. Similar to other typical and atypical antipsychotics, JL 13 increased labeling of D(2) receptors in medial prefrontal cortex (MPC) and hippocampus (HIP) and D(4) receptors in nucleus accumbens (NAc), caudate-putamen (CPu), and HIP. In addition, JL 13 increased 5-HT(1A) and decreased 5-HT(2A) receptors in MPC and dorsolateral frontal cortex (DFC), an effect shared by atypical antipsychotics, and may contribute to their psychopharmacological properties. Clozapine and JL 13, but not other antipsychotics, spared D(2) receptors in CPu, which may reflect their ability to induce minimal extrapyramidal side effects. In addition, JL 13 but not other typical and atypical antipsychotic drugs increased abundance of D(1) receptors in CPu and NAc. JL 13 as well as other antipsychotic agents did not alter levels of forebrain D(3) receptors. An atypical-like profile of JL 13 on DA and 5-HT receptor subtypes should encourage further development of this compound as a novel atypical antipsychotic drug.

3,4-dihydroxyphenylalanine reverses the motor deficits in Pitx3-deficient aphakia mice: behavioral characterization of a novel genetic model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by a loss of dopaminergic neurons in the substantia nigra. There is a need for genetic animal models of PD for screening and in vivo testing of novel restorative therapeutic agents. Although current genetic models of PD produce behavioral impairment and nigrostriatal dysfunction, they do not reproduce the loss of midbrain dopaminergic neurons and 3,4-dihydroxyphenylalanine (L-DOPA) reversible behavioral deficits. Here, we demonstrate that Pitx3-deficient aphakia (ak) mice, which have been shown previously to exhibit a major loss of substantia nigra dopaminergic neurons, display motor deficits that are reversed by L-DOPA and evidence of "dopaminergic supersensitivity" in the striatum. Thus, ak mice represent a novel genetic model exhibiting useful characteristics to test the efficacy of symptomatic therapies for PD and to study the functional changes in the striatum after dopamine depletion and L-DOPA treatment.

Atomoxetine blocks motor hyperactivity in neonatal 6-hydroxydopamine-lesioned rats: implications for treatment of attention-deficit hyperactivity disorder

We recently reported that selective inhibitors of neuronal transport of norepinephrine (NE), desipramine and nisoxetine, reversed motor hyperactivity in an animal model of attention-deficit hyperactivity disorder (ADHD). In this study, we examined behavioural effects of atomoxetine, a potent new NE reuptake blocker, in juvenile male rats with neonatal 6-hydroxydopamine (6-OHDA) lesions of dopamine projections to the forebrain. 6-OHDA (100 microg) was administered intracisternally on postnatal day (PD) 5 following desipramine (25 mg/kg s.c.) pretreatment to protect noradrenergic neurons. Atomoxetine (1 mg/kg) was given intraperitoneally before recording motor activity for 90 min at PD 23-26 in a novel environment. Atomoxetine greatly reduced motor hyperactivity in 6-OHDA-lesioned rats while exhibiting transient sedative effects in sham controls. The observed effects in this animal model for ADHD are consistent with the emerging clinical use of atomoxetine as a novel, non-stimulant treatment for ADHD.