Lack of dopamine D4 receptor affinity contributes to the procognitive effect of lurasidone

Cognitive Effects of Lurasidone and Cariprazine: A Mini Systematic Review

Cognitive deficits are associated with schizophrenia and show a progressive worsening, often being unresponsive to treatment. New antipsychotic molecules acting as antagonist at the serotoninergic 5-hydroxytryptamine receptor 7 (e.g. lurasidone) or partial agonists at dopamine D3 receptor (e.g. cariprazine) could have an impact on cognition in this patient group. The aim of the systematic review is to explore the efficacy of lurasidone and cariprazine in improving cognition in both animal models and human studies. The following terms: (lurasidone AND cognit*) OR (cariprazine AND cognit*) were searched in Web of Science from inception to December 2021. We included all studies that assessed changes in cognitive function after treatment with cariprazine or lurasidone. Of 201 selected articles, 36 were included. Twenty-four articles used animal models (rats, mice and marmosets), five evaluating the effects of cariprazine and 19 the effects of lurasidone. Twelve articles were clinical studies (cariprazine n = 2; lurasidone n = 10). In both animal and human studies lurasidone showed a greater efficacy on cognitive performance compared to placebo, quetiapine, ziprasidone or treatmentas- usual. Cariprazine was superior to other antipsychotics in improving cognitive functions in both animal and human studies. The cognitive effect of lurasidone could be explained by its potent antagonism at the 5-HT7 receptors combined with partial agonism at 5-HT1A receptors. The pro-cognitive effect of cariprazine is probably explained by its very high affinity for D3 receptors. Head-to-head studies comparing lurasidone and cariprazine are needed to establish the "first-choice" treatment for cognitive dysfunction associated with schizophrenia.

Lurasidone versus Quetiapine for Cognitive Impairments in Young Patients with Bipolar Depression: A Randomized, Controlled Study

The clinical efficacy of lurasidone and quetiapine, two commonly prescribed atypical antipsychotics for bipolar depression, has been inadequately studied in young patients. In this randomized and controlled study, we aimed to compare the effects of these two drugs on cognitive function, emotional status, and metabolic profiles in children and adolescents with bipolar depression. We recruited young participants (aged 10-17 years old) with a DSM-5 diagnosis of bipolar disorder during a depressive episode, who were then randomly assigned to two groups and treated with flexible doses of lurasidone (60 to 120 mg/day) or quetiapine (300 to 600 mg/day) for consecutive 8 weeks, respectively. All the participants were clinically evaluated on cognitive function using the THINC-it instrument at baseline and week 8, and emotional status was assessed at baseline and the end of week 2, 4, and 8. Additionally, the changes in weight and serum metabolic profiles (triglyceride, cholesterol, and fasting blood glucose) during the trial were also analyzed. In results, a total of 71 patients were randomly assigned to the lurasidone group (n = 35) or the quetiapine group (n = 36), of which 31 patients completed the whole treatment course. After an 8-week follow-up, participants in the lurasidone group showed better performance in the Symbol Check Reaction and Accuracy Tests, when compared to those in the quetiapine group. No inter-group difference was observed in the depression scores, response rate, or remission rate throughout the trial. In addition, there was no significant difference in serum metabolic profiles between the lurasidone group and the quetiapine group, including triglyceride level, cholesterol level, and fasting blood glucose level. However, the quetiapine group presented a more apparent change in body weight than the lurasidone group. In conclusion, the present study provided preliminary evidence that quetiapine and lurasidone had an equivalent anti-depressive effect, and lurasidone appeared to be superior to quetiapine in improving the cognitive function of young patients with bipolar depression.

Clinical Effectiveness of Lurasidone Monotherapy in Patients with Acute Episodes of Schizophrenia and Associated Symptoms of Depression

AIM

We endeavored to evaluate the efficacy of Lurasidone at doses of 40-160 mg per day on symptoms of schizophrenia associated with symptoms of depression in real clinical practice in a Russian patient population.

METHODS

One hundred sixty eight patients aged 18-65 years old, who at the time of the start of the observation were being treated in a hospital or day hospital due to an exacerbation of paranoid schizophrenia accompanied by symptoms of depression, were prescribed lurasidone. Treatment with lurasidone and other concomitant drugs, their prescription, withdrawal, selection, and dose modifications were determined based on the indications for the use of those drugs and the recommended doses in the instructions, clinical need, and patient interests, rather than by the goals of the study. During the observation period, the severity of depressive symptoms according to the Calgary Depression Scale (CDSS) and that of psychotic symptoms according to the Positive and Negative Syndrome Scale (PANSS) were assessed six times (before the start of treatment and then on the 4th, 7th, 14th, 28th, and 42nd days).

RESULTS

A statistically significant reduction in the severity of the symptoms was observed with the use of lurasidone in doses ranging from 40 mg to 160 mg per day. The fastest and most significant (p <0.001) reductions in the total PANSS and CDSS scores were observed with lurasidone 120 mg. A somewhat lower efficacy of lurasidone was observed at a dose of 160 mg. The largest reductions in the total PANSS and CDSS scores with lurasidone 120 mg were associated with the highest survival rate and the longest median time from treatment initiation to discontinuation or follow-up. The most commonly reported side effects with lurasidone in this study (nausea, akathisia, tremor and drowsiness) were consistent with the known safety profile of the drug. Adverse events in most cases were assessed as mild, or occasionally moderate.

CONCLUSION

A six-week prospective observational study of the real-world clinical effectiveness of lurasidone in doses ranging from 40 mg to 160 mg per day established statistically and clinically significant improvements in both psychotic and depressive symptoms in patients with acute exacerbation of schizophrenia and associated symptoms of depression.

Pharmacological Treatment of Early-Onset Schizophrenia: A Critical Review, Evidence-Based Clinical Guidance and Unmet Needs

Early-onset schizophrenia (EOS) – onset before age 18 – is linked with great disease burden and disability. Decision-making for EOS pharmacological treatment may be challenging due to conflicting information from evidence and guidelines and unidentified care needs may remain unmet.

We searched for systematic reviews, meta-analyses and umbrella reviews of EOS pharmacological treatment published in PubMed over the past 10 years and selected five clinical guidelines from Europe, North-America and Australia. Based on predefined outcomes, we critically compared the evidence supporting EOS-approved drugs in Europe and/or North-America with guidelines recommendations. We also evaluated the coverage of these outcomes to identify unmet needs.

One systematic review, nine meta-analyses and two umbrella reviews (k=203 trials, N=81,289 participants, including duplicated samples across selected articles) were retrieved. Evidence supported the efficacy of aripiprazole, clozapine, haloperidol, lurasidone, molindone, olanzapine, quetiapine, risperidone and paliperidone in EOS, all of which obtained approval for EOS either in Europe and/or in North-America. Cognition, functioning and quality of life, suicidal behaviour and mortality and services utilisation and cost-effectiveness were poorly covered/uncovered.

Among the antipsychotics approved for EOS, aripiprazole, lurasidone, molindone, risperidone, paliperidone and quetiapine emerged as efficacious and comparably safe options. Olanzapine is known for a high risk of weight gain and haloperidol for extrapyramidal side-effects. Treatment-resistant patients should be offered clozapine. Future long-term trials looking at cognition, functioning, quality of life, suicidal behaviour, mortality, services utilisation and cost-effectiveness are warranted. Closer multi-agency collaboration may bridge the gap between evidence, guidelines and approved drugs.

Effect of dopamine receptor-related compounds on naive common marmosets for auditory steady state response

Abnormalities of auditory steady state responses (ASSR) and the effects of antipsychotic drugs on ASSR have been investigated in patients with schizophrenia. It is presumed that effects of drugs do not directly reflect on ASSR, because of ASSR abnormalities associated with schizophrenia. Therefore, to investigate the direct effect of drugs on ASSR, we established an ASSR evaluation system for common marmosets in a naïve state. Dopamine D1 receptor stimulation (SKF-81297, 2 mg/kg, intraperitoneal) significantly increased evoked power (EP) at 40 Hz. The phase locking factor (PLF) was increased significantly at 20, 30, 40, and 80 Hz. However, the administration of a dopamine D1 receptor antagonist (SCH-39166, 0.3 mg/kg intraperitoneal) resulted in a significant decrease in EP and PLF at 30 Hz. Dopamine D2 receptor stimulation (quinpirole, 1 mg/kg, intramuscular) tended to increase EP and induced power (IP) at all frequencies, and a significant difference was observed at 30 Hz IP. There was no change in PLF at all frequencies. In addition, dopamine D2 receptor blockade (raclopride, 3 mg/kg, intraperitoneal) reduced EP and PLF at 30 Hz. Subcutaneous administration of the serotonin dopamine antagonist, risperidone (0.3 mg/kg), tended to increase IP and decrease PLF, but not significantly. Taken together, it is possible to compare the differences in the mode of action of drugs on ASSR using naïve non-human primates.

Lurasidone for Adolescents With Complex Mental Disorders: A Case Series

OBJECTIVES

Lurasidone is a new second generation (atypical) antipsychotic agent with unique receptor affinity and side-effect profiles, but limited literature is available on its use in adolescent populations. Contrasting with research treatment trials which typically recruit patients by stringent selection criteria, this case series examined the effects and tolerability of using lurasidone in adolescents within real-life clinical settings in treating complex cases who had not responded to other therapy options.

METHODS

We conducted a retrospective case-note audit of 6 adolescents aged 14 to 17 years old attending community child and adolescent mental health services (CAMHS) who were prescribed lurasidone.

RESULTS

Lurasidone had been prescribed for a range of "hard-to-manage" conditions with complex comorbidities, in adolescents in relation to specific use of lurasidone on the basis of clinical and pharmacological indications after exhausting more conventional treatment options. Case-note review suggested response to lurasidone was clinically positive in 3 cases, equivocal/marginal in 2 cases, and ineffective in 1 case. There were no cases of poor tolerance or adverse effects. Notably, positive responses for depressive and irritable mood symptoms were specifically recorded by prescribing clinicians, indicative of benefits on symptom improvement. No lurasidone attributed weight gain, galactorrhoea, metabolic abnormalities, sexual dysfunction or intolerance were reported. Pro-cognitive effects were not detected; but our findings were constrained by the non-systematic and incomplete information ascertainment, typical in retrospective case-note review.

CONCLUSION

This case series provides preliminary data supporting lurasidone's potential use in adolescents of complex clinical needs (but without a clinical diagnosis of bipolar disorder) within real-life clinical settings. Lurasidone appears to show a weight-sparing effect, in addition to improving mood symptoms in some cases. Lurasidone deserves further study for its use in the adolescent population (outside the remit of FDA) given its potential more favorable risk-benefit profile in young people. The favorable tolerability appear to be borne out by the pharmacodynamic predictions in our complex patients who would be excluded in formal clinical trial studies.

Recent findings leading to the discovery of selective dopamine D4 receptor ligands for the treatment of widespread diseases

Since its discovery, the dopamine D₄ receptor (D₄R) has been suggested to be an attractive target for the treatment of neuropsychiatric diseases. Novel findings have renewed the interest in such a receptor as an emerging target for the management of different diseases, including cancer, Parkinson's disease, alcohol or substance use disorders, eating disorders, erectile dysfunction and cognitive deficits. The recently resolved crystal structures of D₄R in complexes with the potent ligands nemonapride and L-745870 strongly improved the knowledge on the molecular mechanisms involving the D₄R functions and may help medicinal chemists in drug design. This review is focused on the recent development of the subtype selective D₄R ligands belonging to classical or new chemotypes. Moreover, ligands showing functional selectivity toward G protein activation or β-arrestin recruitment and the effects of selective D₄R ligands on the above-mentioned diseases are discussed.

Lurasidone Sub-Chronically Activates Serotonergic Transmission via Desensitization of 5-HT1A and 5-HT7 Receptors in Dorsal Raphe Nucleus

Lurasidone is an atypical mood-stabilizing antipsychotic agent with unique receptor-binding profile, including 5-HT7 receptor (5-HT7R) antagonism. Effects of 5-HT7R antagonism on transmitter systems of schizophrenia and mood disorders, however, have not been well clarified. Thus, this study examined the mechanisms underlying the clinical effects of lurasidone by measuring mesocortical serotonergic transmission. Following systemic and local administrations of lurasidone, MK801 and 5-HT receptor modulators, we determined releases of 5-HT in dorsal raphe nucleus (DRN), mediodorsal thalamic nucleus (MDTN) and medial prefrontal cortex (mPFC) and γ-aminobutyric acid (GABA) in DRN using multiprobe microdialysis with ultra-high-performance liquid chromatography (UHPLC). Serotonergic and GABAergic neurons in the DRN are predominantly regulated by inhibitory 5-HT1A receptor (5-HT1AR) and excitatory 5-HT7R, respectively. Lurasidone acutely generates GABAergic disinhibition by 5-HT7R antagonism, but concomitant its 5-HT1AR agonism prevents serotonergic hyperactivation induced by 5-HT7R inhibition. During treatments with 5-HT1AR antagonist in DRN, lurasidone dose-dependently increased 5-HT release in the DRN, MDTN and mPFC. Contrary, lurasidone chronically enhanced serotonergic transmission and GABAergic disinhibition in the DRN by desensitizing both 5-HT1AR and 5-HT7R. These effects of lurasidone acutely prevented MK801-evoked 5-HT release by GABAergic disinhibition via N-methyl-D-aspartate (NMDA)/glutamate receptor (NMDA-R)-mediated inhibition of 5-HT1AR function, but enhanced MK801-induced 5-HT release by desensitizing 5-HT1AR and 5-HT7R. These results indicate that acutely lurasidone fails to affect 5-HT release, but chronically enhances serotonergic transmission by desensitizing both 5-HT1AR and 5-HT7R. These unique properties of lurasidone ameliorate the dysfunctions of NMDA-R and augment antidepressive effects.

Lurasidone in Children and Adolescents: Systematic Review and Case Report

OBJECTIVE

To perform a systematic review of studies of lurasidone in children and/or adolescents and to present a case report aimed to add further insights into its use in clinical practice with youth.

METHODS

We searched the following databases for empirical studies, of any design, focusing on the pharmacokinetics, efficacy, or safety of lurasidone in children and/or adolescents: Pubmed (Medline), OVID (PsycInfo, EMBASE+EMBASE classic, OVID Medline), Web of Knowledge, and ClinicalTrials.gov (last search January 23, 2018).

RESULTS

From a pool of 301 potentially relevant references, we retained 12 pertinent studies (reported in 28 references), including 1 pharmacokinetics study, 1 double blind randomized controlled trial (RCT) for bipolar depression (BD) with 1 related interim analysis study of its extension phase and 1 related external posterior predictive check study, 1 double blind RCT for schizophrenia with 3 related interim analyses of its extension phase, 1 RCT and 1 case report for autism spectrum disorder, and 2 open-label studies focusing on a variety of disorders. Overall, these studies show that lurasidone is significantly more efficacious than placebo, with moderate effect sizes, and is well tolerated for BD and schizophrenia in youth. Published studies in youth have in general used doses up to 80 mg/day. Our case report suggests that high doses of lurasidone (148 mg/day) were well tolerated and might have contributed to substantial functional improvement in a 14-year old girl with psychosis and a previous history of anorexia nervosa, who had not responded to previous antipsychotics (olanzapine, risperidone, aripiprazole).

CONCLUSIONS

There is increasing evidence that lurasidone may be moderately effective and well tolerated for the treatment of BD and psychosis in youth and may have procognitive effects. Our case report suggests that future RCTs should assess the efficacy and tolerability of high doses (>80 mg/day) of lurasidone in youth.

Neuronal correlates of ketamine and walking induced gamma oscillations in the medial prefrontal cortex and mediodorsal thalamus

Alterations in the function of the medial prefrontal cortex (mPFC) and its major thalamic source of innervation, the mediodorsal (MD) thalamus, have been hypothesized to contribute to the symptoms of schizophrenia. The NMDAR antagonist ketamine, used to model schizophrenia, elicits a brain state resembling early stage schizophrenia characterized by cognitive deficits and increases in cortical low gamma (40-70 Hz) power. Here we sought to determine how ketamine differentially affects spiking and gamma local field potential (LFP) activity in the rat mPFC and MD thalamus. Additionally, we investigated the ability of drugs targeting the dopamine D4 receptor (D4R) to modify the effects of ketamine on gamma activity as a measure of potential cognitive therapeutic efficacy. Rats were trained to walk on a treadmill to reduce confounds related to hyperactivity after ketamine administration (10 mg/kg s.c.) while recordings were obtained from electrodes chronically implanted in the mPFC and MD thalamus. Ketamine increased gamma LFP power in mPFC and MD thalamus in a similar frequency range, yet did not increase thalamocortical synchronization. Ketamine also increased firing rates and spike synchronization to gamma oscillations in the mPFC but decreased both measures in MD thalamus. Conversely, walking alone increased both firing rates and spike-gamma LFP correlations in both mPFC and MD thalamus. The D4R antagonist alone (L-745,870) had no effect on gamma LFP power during treadmill walking, although it reversed increases induced by the D4R agonist (A-412997) in both mPFC and MD thalamus. Neither drug altered ketamine-induced changes in gamma power or firing rates in the mPFC. However, in MD thalamus, the D4R agonist increased ketamine-induced gamma power and prevented ketamine's inhibitory effect on firing rates. Results provide new evidence that ketamine differentially modulates spiking and gamma power in MD thalamus and mPFC, supporting a potential role for both areas in contributing to ketamine-induced schizophrenia-like symptoms.

Dopamine D4 receptor stimulation contributes to novel object recognition: Relevance to cognitive impairment in schizophrenia

Several atypical antipsychotic drugs (APDs) have high affinity for the dopamine (DA) D₄ receptor, but the relevance to the efficacy for the treatment of cognitive impairment associated with schizophrenia (CIAS) is poorly understood. The aim of this study was to investigate the effects of D₄ receptor stimulation or blockade on novel object recognition (NOR) in normal rats and on the sub-chronic phencyclidine (PCP)-induced novel object recognition deficit. The effect of the D₄ agonist, PD168077, and the D₄ antagonist, L-745,870, were studied alone, and in combination with clozapine and lurasidone. In normal rats, L-745,870 impaired novel object recognition, whereas PD168077 had no effect. PD168077 acutely reversed the sub-chronic phencyclidine-induced novel object recognition deficit. Co-administration of a sub-effective dose (SED) of PD168077 with a sub-effective dose of lurasidone also reversed this deficit, but a sub-effective dose of PD168077 with a sub-effective dose of clozapine, a more potent D₄ antagonist than lurasidone, did not reverse the sub-chronic phencyclidine-induced novel object recognition deficit. At a dose that did not induce a novel object recognition deficit, L-745,870 blocked the ability of clozapine, but not lurasidone, to reverse the novel object recognition deficit. D₄ receptor agonism has a beneficial effect on novel object recognition in sub-chronic PCP-treated rats and augments the cognitive enhancing efficacy of an atypical antipsychotic drug that lacks affinity for the D₄ receptor, lurasidone.

Detour Behavior of Mice Trained with Transparent, Semitransparent and Opaque Barriers

Detour tasks are commonly used to study problem solving skills and inhibitory control in canids and primates. However, there is no comparable detour test designed for rodents despite its significance for studying the development of executive skills. Furthermore, mice offer research opportunities that are not currently possible to achieve when primates are used. Therefore, the aim of the study was to translate the classic detour task to mice and to compare obtained data with key findings obtained previously in other mammals. The experiment was performed with V-shaped barriers and was based on the water escape paradigm. The study showed that an apparently simple task requiring mice to move around a small barrier constituted in fact a challenge that was strongly affected by the visibility of the target. The most difficult task involved a completely transparent barrier, which forced the mice to resolve a conflict between vision and tactile perception. The performance depended both on the inhibitory skills and on previous experiences. Additionally, all mice displayed a preference for one side of the barrier and most of them relied on the egocentric strategy. Obtained results show for the first time that the behavior of mice subjected to the detour task is comparable to the behavior of other mammals tested previously with free-standing barriers. This detailed characterization of the detour behavior of mice constitutes the first step toward the substitution of rodents for primates in laboratory experiments employing the detour task.

The atypical antipsychotic blonanserin reverses (+)-PD-128907- and ketamine-induced deficit in executive function in common marmosets

Antagonism of the dopamine D3 receptor is considered a promising strategy for the treatment of cognitive impairment associated with schizophrenia. We have previously reported that the atypical antipsychotic blonanserin, a dopamine D2/D3 and serotonin 5-HT2A receptor antagonist, highly occupies dopamine D3 receptors at its antipsychotic dose range in rats. In the present study, we evaluated the effects of blonanserin on executive function in common marmosets using the object retrieval with detour (ORD) task. The dopamine D3 receptor-preferring agonist (+)-PD-128907 at 1mg/kg decreased success rate in the difficult trial, but not in the easy trial. Since the difference between the two trials is only cognitive demand, our findings indicate that excess activation of dopamine D3 receptors impairs executive function in common marmosets. Blonanserin at 0.1mg/kg reversed the decrease in success rate induced by (+)-PD-128907 in the difficult trial. This finding indicates that blonanserin has beneficial effect on executive function deficit induced by activation of the dopamine D3 receptor in common marmosets. Next, and based on the glutamatergic hypothesis of schizophrenia, the common marmosets were treated with the N-methyl-d-aspartate (NMDA) receptor antagonist ketamine. Ketamine at sub-anesthetic doses decreased success rate in the difficult trial, but not in the easy trial. Blonanserin at 0.1mg/kg reversed the decrease in success rate induced by ketamine in the difficult trial. The findings of this study suggest that blonanserin might have beneficial effect on executive dysfunction in patients with schizophrenia.

The dopamine D1 receptor agonist SKF-82958 effectively increases eye blinking count in common marmosets

Eye blinking is a spontaneous behavior observed in all mammals, and has been used as a well-established clinical indicator for dopamine production in neuropsychiatric disorders, including Parkinson's disease and Tourette syndrome [1,2]. Pharmacological studies in humans and non-human primates have shown that dopamine agonists/antagonists increase/decrease eye blinking rate. Common marmosets (Callithrix jacchus) have recently attracted a great deal of attention as suitable experimental animals in the psychoneurological field due to their more developed prefrontal cortex than rodents, easy handling compare to other non-human primates, and requirement for small amounts of test drugs. In this study, we evaluated the effects of dopamine D1-4 receptors agonists on eye blinking in common marmosets. Our results show that the dopamine D1 receptor agonist SKF-82958 and the non-selective dopamine receptor agonist apomorphine significantly increased common marmosets eye blinking count, whereas the dopamine D2 agonist (+)-PHNO and the dopamine D3 receptor agonist (+)-PD-128907 produced somnolence in common marmosets resulting in a decrease in eye blinking count. The dopamine D4 receptor agonists PD-168077 and A-41297 had no effect on common marmosets' eye blinking count. Finally, the dopamine D1 receptor antagonist SCH 39166 completely blocked apomorphine-induced increase in eye blinking count. These results indicate that eye blinking in common marmosets may be a useful tool for in vivo screening of novel dopamine D1 receptor agonists as antipsychotics.

Effect of dopamine D4 receptor agonists on sleep architecture in rats

Dopamine plays a key role in the regulation of sleep-wake states, as revealed by the observation that dopamine-releasing agents such as methylphenidate have wake-promoting effects. However, the precise mechanisms for the wake-promoting effect produced by the enhancement of dopamine transmission are not fully understood. Although dopamine D1, D2, and D3 receptors are known to have differential effects on sleep architecture, the role of D4 receptors (D4Rs), and particularly the influence of D4R activation on the sleep-wake state, has not been studied so far. In this study, we investigated for the first time the effects of two structurally different D4R agonists, Ro 10-5824 and A-412997, on the sleep-wake states in rats. We found that both D4R agonists generally increased waking duration, and conversely, reduced non-rapid eye movement (NREM) sleep duration in rats. The onset of NREM sleep was also generally delayed. However, only the A-412997 agonist (but not the Ro 10-5824) influenced rapid eye movement sleep onset and duration. Furthermore, these effects were accompanied with an enhancement of EEG spectral power in the theta and the gamma bands. Our results suggest the involvement of dopamine D4R in the regulation of sleep-wake states. The activation of the D4R could enhance the arousal states as revealed by the behavioral and electrophysiological patterns in this study. Dopamine D4R may contribute to the arousal effects of dopamine-releasing agents such as methylphenidate.

Behavioral and neurophysiological effects of Ro 10-5824, a dopamine D4 receptor partial agonist, in common marmosets

RATIONALE

Growing evidence suggests that dopamine D4 receptors (D4Rs) are involved in controlling executive functions. We have previously demonstrated that Ro 10-5824, a D4R partial agonist, improves the performance of common marmosets in the object retrieval detour (ORD) task. However, the neural mechanisms underlying this improvement are unknown.

OBJECTIVES

We investigated the behavioral and neurophysiological effects of Ro 10-5824 in common marmosets.

METHODS

The effects of Ro 10-5824 on cognitive function were evaluated using the ORD task. The neurophysiological effects of Ro 10-5824 were investigated by quantitative electroencephalography, especially on baseline gamma band activity in the frontal cortex. The effects of Ro 10-5824 on spontaneous locomotion were also assessed.

RESULTS

Systemic administration of Ro 10-5824 at 3 mg/kg significantly increased the success rate in the ORD task. At doses of 1 and 3 mg/kg, Ro 10-5824 increased baseline gamma band activity in the frontal cortex. Ro 10-5824 had no effect on spontaneous locomotion.

CONCLUSIONS

Activation of D4R by Ro 10-5824 improves the success rate in the ORD task and increases baseline gamma band activity in the frontal cortex without affecting locomotion in common marmosets. These findings highlight the role of D4R in gamma oscillations of non-human primates. As gamma oscillations are thought to be involved in attention and behavioral inhibition, our results suggest D4R agonists may improve these cognitive functions by modulating baseline gamma band activity in the frontal cortex.

Understanding responder neurobiology in schizophrenia using a quantitative systems pharmacology model: application to iloperidone

The concept of targeted therapies remains a holy grail for the pharmaceutical drug industry for identifying responder populations or new drug targets. Here we provide quantitative systems pharmacology as an alternative to the more traditional approach of retrospective responder pharmacogenomics analysis and applied this to the case of iloperidone in schizophrenia. This approach implements the actual neurophysiological effect of genotypes in a computer-based biophysically realistic model of human neuronal circuits, is parameterized with human imaging and pathology, and is calibrated by clinical data. We keep the drug pharmacology constant, but allowed the biological model coupling values to fluctuate in a restricted range around their calibrated values, thereby simulating random genetic mutations and representing variability in patient response. Using hypothesis-free Design of Experiments methods the dopamine D4 R-AMPA (receptor-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor coupling in cortical neurons was found to drive the beneficial effect of iloperidone, likely corresponding to the rs2513265 upstream of the GRIA4 gene identified in a traditional pharmacogenomics analysis. The serotonin 5-HT3 receptor-mediated effect on interneuron gamma-aminobutyric acid conductance was identified as the process that moderately drove the differentiation of iloperidone versus ziprasidone. This paper suggests that reverse-engineered quantitative systems pharmacology is a powerful alternative tool to characterize the underlying neurobiology of a responder population and possibly identifying new targets.

The pharmacodynamic properties of lurasidone and their role in its antidepressant efficacy in bipolar disorder

The treatment of bipolar depression is one of the most challenging issues in contemporary psychiatry. Currently only quetiapine, the olanzapine-fluoxetine combination and recently lurasidone are officially FDA-approved against this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain elusive. The current study investigated whether the pharmacodynamic properties of lurasidone fit to a previously developed model which was the first to be derived on the basis of the strict combination of clinical and preclinical data with no input from theory or opinion. The authors performed a complete and systematic review of the literature to identify the pharmacodynamic properties of lurasidone. The original model suggests that a constellation of effects on different receptors are necessary but the serotonin reuptake inhibition does not seem to play a significant role for bipolar depression. On the contrary norepinephrine activity seems to be very important. Probably the early antidepressant effect can be achieved through an agonistic activity at 5HT-1A and antagonism at alpha1 noradrenergic and 5-HT2A receptors, but the presence of a norepinephrine reuptake inhibition is essential in order to sustain it. Overall the properties of lurasidone fit well the model and add to its validity. A point that needs clarification is norepinephrine reuptake inhibition which is not yet studied for lurasidone.