Pharmacological treatment of schizophrenia: a critical review of the pharmacology and clinical effects of current and future therapeutic agents

A critical review of pro-cognitive drug targets in psychosis: convergence on myelination and inflammation

Antipsychotic drugs have thus far focused on dopaminergic antagonism at the D2 receptors, as counteracting the hyperdopaminergia in nigrostriatal and mesolimbic projections has been considered mandatory for the antipsychotic action of the drugs. Current drugs effectively target the positive symptoms of psychosis such as hallucinations and delusions in the majority of patients, whereas effect sizes are smaller for negative symptoms and cognitive dysfunctions. With the understanding that neurocognitive dysfunction associated with schizophrenia have a greater impact on functional outcome than the positive symptoms, the focus in pharmacotherapy for schizophrenia has shifted to the potential effect of future drugs on cognitive enhancement. A major obstacle is, however, that the biological underpinnings of cognitive dysfunction remain largely unknown. With the availability of increasingly sophisticated techniques in molecular biology and brain imaging, this situation is about to change with major advances being made in identifying the neuronal substrates underlying schizophrenia, and putative pro-cognitive drug targets may be revealed. In relation to cognitive effects, this review focuses on evidence from basic neuroscience and clinical studies, taking two separate perspectives. One perspective is the identification of previously under-recognized treatment targets for existing antipsychotic drugs, including myelination and mediators of inflammation. A second perspective is the development of new drugs or novel treatment targets for well-known drugs, which act on recently discovered treatment targets for cognitive enhancement, and which may complement the existing drugs. This might pave the way for personalized treatment regimens for patients with schizophrenia aimed at improved functional outcome. The review also aims at identifying major current constraints for pro-cognitive drug development for patients with schizophrenia.

ΔFosB induction in prefrontal cortex by antipsychotic drugs is associated with negative behavioral outcomes

ΔFosB, a FosB gene product, is induced in the prefrontal cortex (PFC) by repeated exposure to several stimuli including antipsychotic drugs such as haloperidol. However, the functional consequences of increased ΔFosB expression following antipsychotic treatment have not been explored. Here, we assessed whether ΔFosB induction by haloperidol mediates the positive or negative consequences or clinical-related actions of antipsychotic treatment. We show that individuals with schizophrenia who were medicated with antipsychotic drugs at their time of death display increased ΔFosB levels in the PFC, an effect that is replicated in rats treated chronically with haloperidol. In contrast, individuals with schizophrenia who were medication-free did not exhibit this effect. Viral-mediated overexpression of ΔFosB in the PFC of rodents induced cognitive deficits as measured by inhibitory avoidance, increased startle responses in prepulse inhibition tasks, and increased MK-801-induced anxiety-like behaviors. Together, these results suggest that ΔFosB induction in the PFC by antipsychotic treatment contributes to the deleterious effects of these drugs and not to their therapeutic actions.

Imaging glutamate in schizophrenia: review of findings and implications for drug discovery

Currently, all treatments for schizophrenia (SCZ) function primarily by blocking D(2)-type dopamine receptors. Given the limitations of these medications, substantial efforts have been made to identify alternative neurochemical targets for treatment development in SCZ. One such target is brain glutamate. The objective of this article is to review and synthesize the proton magnetic resonance spectroscopy ((1)H MRS) and positron emission tomography (PET)/single-photon emission computed tomography (SPECT) investigations that have examined glutamatergic indices in SCZ, including those of modulatory compounds such as glutathione (GSH) and glycine, as well as data from ketamine challenge studies. The reviewed (1)H MRS and PET/SPECT studies support the theory of hypofunction of the N-methyl-D-aspartate receptor (NMDAR) in SCZ, as well as the convergence between the dopamine and glutamate models of SCZ. We also review several advances in MRS and PET technologies that have opened the door for new opportunities to investigate the glutamate system in SCZ and discuss some ways in which these imaging tools can be used to facilitate a greater understanding of the glutamate system in SCZ and the successful and efficient development of new glutamate-based treatments for SCZ.

Novel siRNA delivery strategy: a new "strand" in CNS translational medicine?

RNA interference has been envisaged as a powerful tool for molecular and clinical investigation with a great potential for clinical applications. In recent years, increased understanding of cancer biology and stem cell biology has dramatically accelerated the development of technology for cell and gene therapy in these areas. This paper is a review of the most recent report of innovative use of siRNA to benefit several central nervous system diseases. Furthermore, a description is made of innovative strategies of delivery into the brain by means of viral and non-viral vectors with high potential for translation into clinical use. Problems are also highlighted that might hamper the transition from bench to bed, analyzing the lack of reliable preclinical models with predictive validity and the lack of effective delivery systems, which are able to overcome biological barriers and specifically reach the brain site of action.

Typical and atypical antipsychotics do not differ markedly in their reversibility of antagonism of the dopamine D2 receptor

It has been suggested that the favorable side-effect profiles of atypical antipsychotics (e.g. clozapine and amisulpride) are related to their ∼100-fold faster dissociation from dopamine D2 receptors (D2R) compared with typical antipsychotics (e.g. haloperidol and chlorpromazine). Fast dissociation would entail rapidly reversible antagonism; however, this has not been thoroughly studied using functional assays. We compared the reversibilities of D2R antagonism by 17 compounds using an electrophysiological method to measure dopamine-evoked potassium channel activation via D2R. Varying rates and amplitudes of D2R response recovery were observed following antagonist removal. Whereas recovery rates differed 15-fold between atypical drugs, recovery from clozapine and amisulpride antagonism was, unexpectedly, less than twofold faster than from chlorpromazine. The recovery amplitude correlated with calculated water solubility and lipid/water distribution coefficients, suggesting variable drug partitioning into cell membranes. Our data do not support the notion that the rate of reversibility of D2R antagonism is what distinguishes atypical from typical antipsychotics.

Quinoline- and isoquinoline-sulfonamide analogs of aripiprazole: novel antipsychotic agents?

The introduction of typical antipsychotics over six decades ago signaled an important milestone in psychiatry. However, second-generation antipsychotics ameliorated the positive symptoms of schizophrenia but displayed limited effectiveness for the negative and cognitive symptoms. In addition, while the newer antipsychotics produced fewer motor side effects, the atypical antipsychotics still induced weight gain and endocrinopathies. In recent years, a third generation of antipsychotics was identified. Aripiprazole was the first approved drug acting as a D2 partial agonist/functionally selective ligand. This review presents the state of the development of novel antipsychotic dopaminergic and non-dopaminergic agents, supported by an overview of the compounds evaluated under advanced preclinical and clinical development (e.g., cariprazine and brexpiprazole). In line with the recent trends in the development of modern atypical antipsychotics, we present our strategic development of long-chain arylpiperazine-derived quinoline- and isoquinoline-sulfonamide displaying a multireceptor binding profile and partial D2 receptor agonism.

Torsadogenic risk of antipsychotics: combining adverse event reports with drug utilization data across Europe

BACKGROUND

Antipsychotics (APs) have been associated with risk of torsade de Pointes (TdP). This has important public health implications. Therefore, (a) we exploited the public FDA Adverse Event Reporting System (FAERS) to characterize their torsadogenic profile; (b) we collected drug utilization data from 12 European Countries to assess the population exposure over the 2005-2010 period.

METHODS

FAERS data (2004-2010) were analyzed based on the following criteria: (1) ≥ 4 cases of TdP/QT abnormalities; (2) Significant Reporting Odds Ratio, ROR [Lower Limit of the 95% confidence interval>1], for TdP/QT abnormalities, adjusted and stratified (Arizona CERT drugs as effect modifiers); (3) ≥ 4 cases of ventricular arrhythmia/sudden cardiac death (VA/SCD); (4) Significant ROR for VA/SCD; (5) Significant ROR, combined by aggregating TdP/QT abnormalities with VA and SCD. Torsadogenic signals were characterized in terms of signal strength: from Group A (very strong torsadogenic signal: all criteria fulfilled) to group E (unclear/uncertain signal: only 2/5 criteria). Consumption data were retrieved from 12 European Countries and expressed as defined daily doses per 1,000 inhabitants per day (DID).

RESULTS

Thirty-five antipsychotics met at least one criterium: 9 agents were classified in Group A (amisulpride, chlorpromazine, clozapine, cyamemazine, haloperidol, olanzapine, quetiapine, risperidone, ziprasidone). In 2010, the overall exposure to antipsychotics varied from 5.94 DID (Estonia) to 13.99 (France, 2009). Considerable increment of Group A agents was found in several Countries (+3.47 in France): the exposure to olanzapine increased across all Countries (+1.84 in France) and peaked 2.96 in Norway; cyamemazine was typically used only in France (2.81 in 2009). Among Group B drugs, levomepromazine peaked 3.78 (Serbia); fluphenazine 1.61 (Slovenia).

CONCLUSIONS

This parallel approach through spontaneous reporting and drug utilization analyses highlighted drug- and Country-specific scenarios requiring potential regulatory consideration: levomepromazine (Serbia), fluphenazine (Slovenia), olanzapine (across Europe), cyamemazine (France). This synergy should be encouraged to support future pharmacovigilance activities.

Efficacy and safety of noradrenalin reuptake inhibitor augmentation therapy for schizophrenia: a meta-analysis of double-blind randomized placebo-controlled trials

BACKGROUND

We performed an updated meta-analysis of noradrenalin reuptake inhibitor (NRI) augmentation therapy in patients with schizophrenia treated with antipsychotics based on a previous meta-analysis (Singh et al.).

METHODS

PubMed, Cochrane Library databases, and PsycINFO citations were searched from their inception to June 10, 2013 without language restrictions. We conducted a systematic review and meta-analysis of individual patient data from randomized controlled trials comparing NRI augmentation therapy with placebo. The outcome measure for efficacy was the psychopathology of schizophrenia and the measures for safety were discontinuation rate and several side effects. We used standardized mean differences (SMD) to estimate treatment effects for continuous variables, and risk ratios (RR) for dichotomous variables, with their 95% confidence intervals (CIs). A random-effects model was used.

RESULTS

Nine studies (4 atomoxetine studies, 3 reboxetine studies, 1 reboxetine-betahistine combination study and 1 mazindol study, total n=298) were identified. No statistically significant effects of NRI augmentation therapy on overall (p=0.90), positive (p=0.81), and negative (p=0.89) symptoms were found. NRI augmentation therapy was marginally superior to placebo for efficacy of depressive symptoms (SMD=-1.08, p=0.05). Dropout due to all-cause (p=0.70), inefficacy (p=0.64), or adverse events (p=0.18) was similar in both groups. NRI augmentation therapy showed a significantly lower increase or larger reduction in body weight than placebo (SMD=-0.47, p=0.03). Reboxetine augmentation was associated with less weight gain that placebo in antipsychotic treated schizophrenia patients (SMD=-0.78, p=0.0001).

CONCLUSION

NRIs may exert an effect on depressive symptoms, and seem to be well-tolerated treatments.

Secondary nonmotor negative symptoms in healthy volunteers after single doses of haloperidol and risperidone: a double-blind, crossover, placebo-controlled trial

OBJECTIVE

The effect of antipsychotics (APs) on negative symptoms is controversial. The present study assessed negative symptoms in healthy volunteers without any source of primary negative symptoms after single doses of haloperidol and risperidone.

METHODS

Twenty-five healthy subjects were included in this randomized, placebo-controlled, single-dose (haloperidol 5 mg and risperidone 2.5 mg) crossover and double-blind clinical trial. Negative symptoms were assessed by observer-rated scales and with a self-report scale. Possible confounding effects considered were extrapyramidal symptoms (EPS) and sedative effects. The occupation of striatal dopamine D2 receptors was also determined.

RESULTS

Risperidone induced a wide range of negative symptoms such as alogia, blunted affect, avolition/apathy, and attention impairment, whereas haloperidol only induced the avolition/apathy subdomain. Most of the effects of risperidone in healthy volunteers, with the exception of its effects on avolition/apathy, were attributable to AP-induced EPS. Haloperidol did not cause significant EPS after administration. No effect of sedation or psychomotor performance was observed on negative symptoms.

CONCLUSIONS

Single doses of both haloperidol and risperidone induced nonmotor secondary negative symptoms in healthy volunteers. The clinical findings are especially relevant in view of the impact of negative symptoms on poor functioning. They may help to guide clinicians in their choice of APs (http://clinicaltrials.gov/ct2/show/NCT01259973).

Administration of the Y2 receptor agonist PYY3-36 in mice induces multiple behavioral changes relevant to schizophrenia

Functional changes in neuropeptide Y (NPY) signaling at the Y2 receptor subtype have been widely implicated in stress-related neuropsychiatric illnesses such as depression and anxiety disorders. Altered Y2 receptor signaling may also play a role in the precipitation of behavioral and cognitive symptoms associated with schizophrenia. To seek preclinical evidence for this possibility, we explored the functional consequences of treatment with the selective Y2 receptor agonist PYY(3-36) using translational tests for the assessment of schizophrenia-relevant behavioral and cognitive deficits in mice. We found that acute systemic administration of PYY(3-36) at a low dose (1 μg/100 g body weight) or high dose (20 μg/100 g body weight) profoundly impaired social interaction without affecting innate anxiety. PYY(3-36) treatment at the high dose further led to a disruption of sensorimotor gating in the form of prepulse inhibition deficiency. This effect was fully antagonized by acute treatment with the preferential dopamine D2 receptor antagonist haloperidol, but not with clozapine. In addition, both doses of PYY(3-36) impaired selective associative learning in the latent inhibition paradigm and spatial working memory in a matching-to-position water maze test. The wide range of abnormalities induced by PYY(3-36) suggests that signaling at the Y2 subtype of NPY receptors is critical for a number of behavioral and cognitive functions, some of which are highly relevant to schizophrenia and related psychotic disorders. At least some of the behavioral deficits induced by augmentation of Y2 receptor signaling may involve increased dopaminergic activity.

Hallucinations in acutely admitted patients with psychosis, and effectiveness of risperidone, olanzapine, quetiapine, and ziprasidone: a pragmatic, randomized study

BACKGROUND

Hallucinations are prevalent in schizophrenia and related psychotic disorders and may have severe consequences for the affected patients. Antipsychotic drug trials that specifically address the anti-hallucinatory effectiveness of the respective drugs in representative samples are rare. The aims of the present study were to investigate the rate and severity of hallucinations in acutely admitted psychotic patients at hospital admission and discharge or after 6 weeks at the latest, if not discharged earlier (discharge/6 weeks); and to compare the anti-hallucinatory effectiveness of risperidone, olanzapine, quetiapine, and ziprasidone with up to 2 years' follow-up.

METHODS

Adult patients acutely admitted to an emergency ward for psychosis were consecutively randomized to risperidone, olanzapine, quetiapine, or ziprasidone and followed for up to 2 years in a pragmatic design. Participants were assessed repeatedly using the hallucinatory behavior item of the Positive and Negative Syndrome Scale (PANSS).

RESULTS

A total of 226 patients, 30.5% of those assessed for eligibility, were randomized and 68% were hallucinating at baseline. This proportion was reduced to 33% at discharge/6 weeks. In the primary analyses based on intention to treat groups of patients experiencing frequent hallucinations, the quetiapine and ziprasidone groups both had faster decreases of the mean hallucination scores than the risperidone group.

CONCLUSIONS

Hallucinations are fairly responsive to antipsychotic drug treatment and differential anti-hallucinatory effectiveness may be found among existing antipsychotic drugs. If replicated, this could pave the way for a more targeted pharmacotherapy based on individual symptom profiles, rather than on the diagnostic category.

TRIAL REGISTRATION

ClinicalTrials.gov ID; NCT00932529.

Glutamatergic postsynaptic density protein dysfunctions in synaptic plasticity and dendritic spines morphology: relevance to schizophrenia and other behavioral disorders pathophysiology, and implications for novel therapeutic approaches

Emerging researches point to a relevant role of postsynaptic density (PSD) proteins, such as PSD-95, Homer, Shank, and DISC-1, in the pathophysiology of schizophrenia and autism spectrum disorders. The PSD is a thickness, detectable at electronic microscopy, localized at the postsynaptic membrane of glutamatergic synapses, and made by scaffolding proteins, receptors, and effector proteins; it is considered a structural and functional crossroad where multiple neurotransmitter systems converge, including the dopaminergic, serotonergic, and glutamatergic ones, which are all implicated in the pathophysiology of psychosis. Decreased PSD-95 protein levels have been reported in postmortem brains of schizophrenia patients. Variants of Homer1, a key PSD protein for glutamate signaling, have been associated with schizophrenia symptoms severity and therapeutic response. Mutations in Shank gene have been recognized in autism spectrum disorder patients, as well as reported to be associated to behaviors reminiscent of schizophrenia symptoms when expressed in genetically engineered mice. Here, we provide a critical appraisal of PSD proteins role in the pathophysiology of schizophrenia and autism spectrum disorders. Then, we discuss how antipsychotics may affect PSD proteins in brain regions relevant to psychosis pathophysiology, possibly by controlling synaptic plasticity and dendritic spine rearrangements through the modulation of glutamate-related targets. We finally provide a framework that may explain how PSD proteins might be useful candidates to develop new therapeutic approaches for schizophrenia and related disorders in which there is a need for new biological treatments, especially against some symptom domains, such as negative symptoms, that are poorly affected by current antipsychotics.

Peptide POP inhibitors for the treatment of the cognitive symptoms of schizophrenia

Schizophrenia is a serious life-long disease that affects a significant part of the adult population. Although there is considerably effective medication for the positive symptoms of the disease, none are available for the associated cognitive deficits. These deficits are a core feature of schizophrenia, and they severely impair the functionality and social integration of patients. POP is a promising target for the treatment of the cognitive deficits of schizophrenia. Inhibitors of this peptidase show cognition-enhancing properties, act through a complex mechanism and have suitable pharmacological properties. Nevertheless, several studies must be carried out in order to improve the design and clinical evaluation of these substances. Permeability to the brain, appropriate animal models and suitable indications are the main issues that must be addressed. However, current information supports the potential of POP as an interesting drug target for the treatment of the cognitive deficits related to schizophrenia.

Randomized trial of clozapine vs. risperidone in treatment-naïve first-episode schizophrenia: results after one year

In first-episode patients with psychosis, clozapine may be potentially valuable as an initial treatment seeking to limit early on clinical and cognitive deterioration. Nevertheless, until recently its restricted use has limited the study of this possibility. Our research group is developing a non-commercial, multicentric and open label study on the differential efficacy between clozapine and risperidone in first-episode schizophrenia. In this paper, we present the results related to clinical variables after a one-year follow-up. So far, we have recruited 30 patients diagnosed with schizophrenia or schizophreniform disorder with illness duration of less than two years. The patients had not received any previous treatment and they were randomized to treatment with clozapine or risperidone. Our results indicate that on average, patients on clozapine adhered to their original treatment for a longer time period than patients on risperidone. By last observation carried forward (LOCF) analysis, patients on clozapine and risperidone displayed similar clinical improvements, although marginally greater improvements in positive and total symptoms scores were found in the clozapine group. At the 12-month point we observed a marginal improvement in negative symptom scores in patients on clozapine. Subjective secondary effects, as measured with the Udvalg for KliniskeUndersøgelser (UKU) scale, correlated negatively with negative symptoms at follow-up. Our data, although preliminary, suggest that clozapine may have a slightly superior efficacy in the initial year of treatment of first-episode treatment-naïve patients with schizophrenia, and this can be explained for the most part by greater adherence to this treatment.

Selective serotonin 3 receptor antagonist treatment for schizophrenia: meta-analysis and systematic review

Double-blinded, randomized, placebo-control trials of selective serotonin 3 receptor antagonists (5-HT3R-ANTs) for schizophrenia have differed in outcome. This meta-analysis tests the hypothesis that 5-HT3R-ANTs are effective for the treatment for schizophrenia. We searched PubMed, the Cochrane Library database, and PsycINFO up to June 15, 2013. We conducted a systematic review and meta-analysis of individual patient data from randomized controlled trials comparing 5-HT3R-ANTs add-on therapy with placebo. The risk ratio (RR), 95 % confidence intervals (CI), and standardized mean difference (SMD) were calculated. A random-effects model was used. Six studies (total n = 311) were identified. These included one granisetron plus risperidone study, one ondansetron plus risperidone study, one ondansetron plus haloperidol, and three tropisetron plus risperidone studies. The statistically significant effects of 5-HT3R-ANTs add-on therapy on Positive and Negative Syndrome Scale (PANSS) total scores were SMD = -1.03, CI = -1.70 to -0.36, p = 0.003 (I (2) = 82 %, 5 studies, n = 261); on negative scores were SMD = -1.10, CI = -1.82 to -0.39, p = 0.002 (I (2) = 84 %, 5 studies, n = 261); and on PANSS general scores were SMD = -0.70, CI = -1.23 to -0.17, p = 0.01 (I (2) = 73 %, 5 studies, n = 261). However, 5-HT3R-ANTs add-on therapy was not superior to placebo in PANSS positive scores (SMD = -0.12, p = 0.33). Dropout due to all cause (RR = 0.80, p = 0.50), inefficacy (RR = 0.76, p = 0.65), or adverse events (RR = 0.84, p = 0.75) was similar in both groups. Constipation occurred significantly more often with 5-HT3R-ANTs than placebo (RR = 2.05, CI = 1.07-3.91, p = 0.03, NNH = 11, p = 0.02). 5-HT3R-ANTs add-on therapy is more beneficial on the psychopathology (especially negative symptoms) than controls in patients with schizophrenia, and 5-HT3R-ANTs seem to be well-tolerated treatments.

Noninvasive remote activation of the ventral midbrain by transcranial direct current stimulation of prefrontal cortex

The midbrain lies deep within the brain and has an important role in reward, motivation, movement and the pathophysiology of various neuropsychiatric disorders such as Parkinson's disease, schizophrenia, depression and addiction. To date, the primary means of acting on this region has been with pharmacological interventions or implanted electrodes. Here we introduce a new noninvasive brain stimulation technique that exploits the highly interconnected nature of the midbrain and prefrontal cortex to stimulate deep brain regions. Using transcranial direct current stimulation (tDCS) of the prefrontal cortex, we were able to remotely activate the interconnected midbrain and cause increases in participants' appraisals of facial attractiveness. Participants with more enhanced prefrontal/midbrain connectivity following stimulation exhibited greater increases in attractiveness ratings. These results illustrate that noninvasive direct stimulation of prefrontal cortex can induce neural activity in the distally connected midbrain, which directly effects behavior. Furthermore, these results suggest that this tDCS protocol could provide a promising approach to modulate midbrain functions that are disrupted in neuropsychiatric disorders.

Epigenetic dysregulation in schizophrenia: molecular and clinical aspects of histone deacetylase inhibitors

Notwithstanding the considerable advances in the treatment options for schizophrenia, the cognitive symptoms in particular are not receptive to antipsychotic treatment and considered one of the main predictors for poor social and functional outcome of the disease. Recent findings in preclinical model systems indicate that epigenetic modulation might emerge as a promising target for the treatment of cognitive disorders. The aim of this review is to introduce some of the principles of chromatin biology to the reader and to discuss a possible role in the neurobiology and pathophysiology of schizophrenia. We will discuss potential epigenetic targets for drug therapy, including histone deacetylase inhibitors (HDACi). In a second part, conceptual and practical challenges associated with clinical trials of chromatin-modifying drugs in psychiatric patient populations are discussed, including safety profiles, the potential for adverse effects and general issues revolving around pharmacokinetics and pharmacodynamics. Additional investigations are required in order to fully evaluate the potential of HDACi and similar "epigenetic therapies" as novel treatment options for schizophrenia and other psychotic disease.

Neuropsychopharmacology of auditory hallucinations: insights from pharmacological functional MRI and perspectives for future research

Experiencing auditory verbal hallucinations is a prominent symptom in schizophrenia that also occurs in subjects at enhanced risk for psychosis and in the general population. Drug treatment of auditory hallucinations is challenging, because the current understanding is limited with respect to the neural mechanisms involved, as well as how CNS drugs, such as antipsychotics, influence the subjective experience and neurophysiology of hallucinations. In this article, the authors review studies of the effect of antipsychotic medication on brain activation as measured with functional MRI in patients with auditory verbal hallucinations. First, the authors examine the neural correlates of ongoing auditory hallucinations. Then, the authors critically discuss studies addressing the antipsychotic effect on the neural correlates of complex cognitive tasks. Current evidence suggests that blood oxygen level-dependant effects of antipsychotic drugs reflect specific, regional effects but studies on the neuropharmacology of auditory hallucinations are scarce. Future directions for pharmacological neuroimaging of auditory hallucinations are discussed.

Optogenetics in psychiatric animal models

Optogenetics is the optical control of neuronal excitability by genetically delivered light-activated channels and pumps and represents a promising tool to fuel the study of circuit function in psychiatric animal models. This review highlights three developments. First, we examine the application of optogenetics in one of the neuromodulators central to the pathophysiology of many psychiatric disorders, the dopaminergic system. We then discuss recent work in translating functional magnetic resonance imaging in small animals (in which optogenetics can be employed to reveal physiological mechanisms underlying disease-related alterations in brain circuits) to patients. Finally, we describe emerging technological developments for circuit manipulation in freely behaving animals.

Use of allosteric targets in the discovery of safer drugs

The need for drugs with fewer side effects cannot be overemphasized. Today, most drugs modify the actions of enzymes, receptors, transporters and other molecules by directly binding to their active (orthosteric) sites. However, orthosteric site configuration is similar in several proteins performing related functions and this leads to a lower specificity of a drug for the desired protein. Consequently, such drugs may have adverse side effects. A new basis of drug discovery is emerging based on the binding of the drug molecules to sites away (allosteric) from the orthosteric sites. It is possible to find allosteric sites which are unique and hence more specific as targets for drug discovery. Of many available examples, two are highlighted here. The first is caloxins - a new class of highly specific inhibitors of plasma membrane Ca²⁺ pumps. The second concerns the modulation of receptors for the neurotransmitter acetylcholine, which binds to 12 types of receptors. Exploitation of allosteric sites has led to the discovery of drugs which can selectively modulate the activation of only 1 (M1 muscarinic) out of the 12 different types of acetylcholine receptors. These drugs are being tested for schizophrenia treatment. It is anticipated that the drug discovery exploiting allosteric sites will lead to more effective therapeutic agents with fewer side effects.

Asenapine, iloperidone and lurasidone: critical appraisal of the most recently approved pharmacotherapies for schizophrenia in adults

This article reviews the pharmacological profile and published efficacy and tolerability/safety data of iloperidone, asenapine and lurasidone, the most recent atypical antipsychotics to be approved in the USA for the treatment of schizophrenia. All three agents are similar in terms of overall efficacy and low propensity for clinically significant weight gain or adverse changes in glycemic or lipid profile. However, these agents differ from one another in terms of formulations, pharmacokinetics, and dosing and nonmetabolic adverse effect profile. For each drug, comparative and real-world effectiveness studies are lacking, as are effectiveness and safety data in elderly, young and pregnant/nursing patients. As such, the exact place of iloperidone, asenapine and lurasidone within the broader antipsychotic armamentarium is currently difficult to establish.

Drug-induced hypo- and hyperprolactinemia: mechanisms, clinical and therapeutic consequences

INTRODUCTION

The altered profiles of prolactin secretion in the anterior hypophysis, generated by pathological, pharmacological or toxicological causes, have special consequences on multiple functions in both genders.

AREAS COVERED

This selective review presents the main mechanisms controlling prolactin secretion, focusing on the interplay of various neurotransmitters or xenobiotics, but also on the role of psychic or posttraumatic stress. A detailed analysis of several pharmacotherapeutic groups with hyperprolactinemic effects emphasize on the relevance of the pharmacokinetic/pharmacodynamic mechanisms and the clinical significance of the long term administration.

EXPERT OPINION

Accurate monitoring and evaluation of the hyperprolactinemia induced by xenobiotics is strongly recommended. The typical antipsychotics and some of the atypical agents (amisulpride, risperidone, paliperidone), as well as some antidepressants, antihypertensives and prokinetics, are the most important groups inducing hyperprolactinemia. The hyperprolactinemic effects are correlated with their affinity for dopamine D2 receptors, their blood-brain barrier penetration and, implicitly, the requested dose for adequate occupancy of cerebral D2 receptors. Consequently, integration of available pharmacokinetic and pharmacodynamic data supports the idea of therapeutic switch to non-hyperprolactinemic agents (especially aripiprazole) or their association, for an optimal management of antipsychotic-induced hyperprolactinemia. Possible alternative strategies for counteracting the xenobiotics-induced hyperprolactinemia are also mentioned.

Kami-ondam-tang, a traditional herbal prescription, attenuates the prepulse inhibition deficits and cognitive impairments induced by MK-801 in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Kami-ondam-tang (KODT) has been used to treat neuropsychiatric disorders, including neurosis and insomnia, in traditional herbal medicine. However, the mechanisms of this drug have not been well characterized in the treatment of schizophrenia-like behaviors.

AIM OF THE STUDY

We investigated whether schizophrenia-like behaviors induced by MK-801, a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, could be attenuated by KODT.

MATERIALS AND METHODS

Acute systemic administration of MK-801 was used to establish an animal model of schizophrenia. The effects of KODT on the MK-801-induced prepulse inhibition (PPI) deficits, hyperlocomotion, social withdrawal, and cognitive impairment were assessed. We also examined the changes in the expression levels of Akt and extracellular signal-regulated kinase (ERK) after the administration of KODT with MK-801 in the cortical and hippocampal tissues.

RESULTS

The acoustic startle response test showed that the acoustic startle enhancement and PPI deficits induced by MK-801 were attenuated by KODT. Moreover, KODT ameliorated social and objective recognition impairments that were induced by MK-801 in the social novelty preference test and the novel object recognition test. In addition, the upregulation of phosphorylated Akt or phosphorylated ERK expression induced by MK-801 was blocked by KODT in the cortex. However, MK-801-induced hyperlocomotion was not affected by KODT in the open field test.

CONCLUSION

These findings suggest that KODT attenuates MK-801-induced PPI disruption, social interaction deficits, and cognitive impairments, possibly, by regulating of cortical Akt and ERK signaling.

NMDA hypofunction as a convergence point for progression and symptoms of schizophrenia

Schizophrenia is a disabling mental illness that is now recognized as a neurodevelopmental disorder. It is likely that genetic risk factors interact with environmental perturbations to affect normal brain development and that this altered trajectory results in a combination of positive, negative, and cognitive symptoms. Although the exact pathophysiology of schizophrenia is unknown, the N-methyl-D-aspartate receptor (NMDAR), a major glutamate receptor subtype, has received great attention. Proper expression and regulation of NMDARs in the brain is critical for learning and memory processes as well as cortical plasticity and maturation. Evidence from both animal models and human studies implicates a dysfunction of NMDARs both in disease progression and symptoms of schizophrenia. Furthermore, mutations in many of the known genetic risk factors for schizophrenia suggest that NMDAR hypofunction is a convergence point for schizophrenia. In this review, we discuss how disrupted NMDAR function leads to altered neurodevelopment that may contribute to the progression and development of symptoms for schizophrenia, particularly cognitive deficits. We review the shared signaling pathways among the schizophrenia susceptibility genes DISC1, neuregulin1, and dysbindin, focusing on the AKT/GSK3β pathway, and how their mutations and interactions can lead to NMDAR dysfunction during development. Additionally, we explore what open questions remain and suggest where schizophrenia research needs to move in order to provide mechanistic insight into the cause of NMDAR dysfunction, as well as generate possible new avenues for therapeutic intervention.

Alternative pharmacologic targets for the treatment of schizophrenia: results from phase I and II trials

PURPOSE OF REVIEW

The current article provides a brief review of the clinical efficacy and safety outcomes from selected phase I and II clinical trials of compounds in development acting on targets beyond the dopamine D2 receptor in patients with schizophrenia.

RECENT FINDINGS

A number of experimental pharmacological targets have been studied in clinical trials. Among those, glutamatergic and nicotinergic pathways have received most attention. Glycine transporter 1 inhibitors used adjunctively with antipsychotics suggest efficacy for negative symptoms of schizophrenia. Adjunctive alpha7 nicotinic acetylcholine receptor agonists and minocycline may improve negative symptoms and cognitive deficits. Adjunctive oxytocin may benefit psychotic symptoms and social cognitive deficits. Adjunctive erythropoietin may improve cognitive function.

SUMMARY

Experimental therapeutic research for schizophrenia is rapidly expanding and a number of compounds with novel mechanisms of action are demonstrating encouraging evidence for efficacy across a range of symptoms. However, much work still needs to be conducted before these new agents can be considered for routine clinical treatment. In particular, further assessment of efficacy and longer term safety and tolerability monitoring are required.

Drug treatment developments in schizophrenia and bipolar mania: latest evidence and clinical usefulness

Schizophrenia and bipolar disorder are often highly debilitating with chronic courses, and psychotropic drugs represent cornerstones in the treatment. The primary aim of the review was to summarize the latest evidence with regards to the efficacy and effectiveness of drug treatment of schizophrenia and the manic phases of bipolar disorder. Schizophrenia systematic reviews conclude that antipsychotic drugs are effective in treating overall symptoms of psychosis and in preventing relapse. Some of the newer agents, the second-generation antipsychotics (SGAs), have demonstrated superiority compared with the older first-generation drugs and other SGAs but side-effect differences among the drugs are of a greater magnitude than effect differences. The pragmatic randomized trials of effectiveness have shown a longer time until treatment discontinuation for olanzapine compared with other antipsychotics. Cohort studies have found superiority for the long-acting injection formulations compared with the oral formulations of the drugs, and lower total mortality risk in users of antipsychotics compared with non-users. In bipolar mania SGAs have shown superior antimanic efficacy compared with other mood-stabilizing drugs. In conclusion antipsychotics, in particular some of the SGAs, seem to be drugs of first choice for both schizophrenia and bipolar mania. This perspective review focused on mean effects but the group means may not always be particularly useful as schizophrenia and bipolar mania are biologically heterogeneous disorders with large inter-individual variations in drug response and tolerance. In patients with a prior drug history the different pharmacological and clinical profiles may be exploited in subsequent choices of drugs.

Attaining and sustaining remission of predominant negative symptoms

BACKGROUND

Evidence is lacking on remission in the presence of predominant negative symptoms.

AIMS

To examine remission rates and their variation by antipsychotic medication in predominant negative symptoms.

METHODS

Data were reanalyzed on patients (n=383) who had participated in two double blind randomized placebo-controlled clinical trials of predominant negative symptoms lasting to 84 and 360days. Symptom remission was defined with the Remission in Schizophrenia Working Group remission criteria of attaining and maintaining mild ratings on eight SANS items. Remission rates were examined to 90days, survival analysis computed to ascertain time to attain symptom remission, binary logistic models used to predict the remission rate and 2 persistent months of symptom remission, and ANCOVA used to predict percent time in remission.

RESULTS

Symptomatic remission rates were: 22.72% at any visit during 90days, and 3.66% lasting 2months. Kaplan-Meier and Cox survival models to adjust for baseline symptom severity showed that compared with the placebo group the amisulpride group attained significantly (p<.05) more remission sooner (HR=2.321, 95% CI=1.36, to 3.97, p<.05). ANCOVA showed that compared with placebo the amisulpride group spent significantly (p<.05) more percent time in remission (ES=.28). Specificity analysis showed that: across trials the negative symptom remission rate was 25.1%; and in one 360-day trial the six-month remission criteria were attained and maintained by 6.4% of participants.

CONCLUSIONS

Presented with predominant negative symptoms the Working Group Remission criteria appear not to be a pragmatic therapeutic objective. Modified remission symptom and time criteria may be an effective way to examine remission.

Gene-microRNA interactions associated with antipsychotic mechanisms and the metabolic side effects of olanzapine

RATIONALE

Changes in the cortical expression of small non-coding microRNA (miRNA) have been observed in postmortem analysis of psychotic disorders. Antipsychotic drugs (APDs) are the most effective treatment option for these disorders and have been associated with changes in gene expression. MicroRNA regulate numerous genes involved in brain development and function. It is therefore plausible to question whether miRNA expression is also altered and hence whether they take part in the neuroleptic mechanism of action.

OBJECTIVES

We sought to investigate whether treatment with APDs induces changes in miRNA expression and query the functional implications of such changes. Furthermore, we investigated the possible functional interplay of miRNA-gene regulatory interactions.

METHOD

High-throughput miRNA profiling of the whole brain of C57BL/6 mice treated with haloperidol, olanzapine or clozapine for 7 days was performed. Functional analysis was conducted on the putative targets of altered microRNA. Significant miRNA-gene regulatory interactions were evaluated by the integration of genome-wide mRNA expression analysis using the Bayesian networks with splitting-averaging strategy and functional analysis conducted.

RESULTS

Small subsets of miRNA were altered with each treatment with potential neurologically relevant influence. Metabolic pathways were enriched in olanzapine and clozapine treatments, possibly associated with their weight gain side effects. Neurologically and metabolically relevant miRNA-gene interaction networks were identified in the olanzapine treatment group.

CONCLUSION

This study is the first to suggest a role for miRNA in the mechanism of APD action and the metabolic side effects of the atypical ADPs, and adds support for their consideration in pharmacogenomics.

Profile of blonanserin for the treatment of schizophrenia

Blonanserin was developed as an antipsychotic drug in Japan and approved for the treatment of schizophrenia. It belongs to a series of 4-phenyl-2-(1-piperazinyl)pyridines and acts as an antagonist at dopamine D2, D3, and serotonin 5-HT2A receptors. Blonanserin has low affinity for 5-HT2C, adrenergic α1, histamine H1, and muscarinic M1 receptors, but displays relatively high affinity for 5-HT6 receptors. In several short-term double-blind clinical trials, blonanserin had equal efficacy as haloperidol and risperidone for positive symptoms in patients with chronic schizophrenia and was also superior to haloperidol for improving negative symptoms. Blonanserin is generally well tolerated and has a low propensity to cause metabolic side effects and prolactin elevation. We recently reported that blonanserin can improve some types of cognitive function associated with prefrontal cortical function in patients with first-episode and chronic schizophrenia. Taken together, these results suggest that blonanserin may be a promising candidate for a first-line antipsychotic for acute and maintenance therapy for schizophrenia. Further comparative studies are warranted to clarify the benefit/risk profile of blonanserin and its role in the treatment of schizophrenia.

Implications of aneuploidy for stem cell biology and brain therapeutics

Understanding the cellular basis of neurological disorders have advanced at a slow pace, especially due to the extreme invasiveness of brain biopsying and limitations of cell lines and animal models that have been used. Since the derivation of pluripotent stem cells (PSCs), a novel source of cells for regenerative medicine and disease modeling has become available, holding great potential for the neurology field. However, safety for therapy and accurateness for modeling have been a matter of intense debate, considering that genomic instability, including the gain and loss of chromosomes (aneuploidy), has been repeatedly observed in those cells. Despite the fact that recent reports have described some degree of aneuploidy as being normal during neuronal differentiation and present in healthy human brains, this phenomenon is particularly controversial since it has traditionally been associated with cancer and disabling syndromes. It is therefore necessary to appreciate, to which extent, aneuploid pluripotent stem cells are suitable for regenerative medicine and neurological modeling and also the limits that separate constitutive from disease-related aneuploidy. In this review, recent findings regarding chromosomal instability in PSCs and within the brain will be discussed.