Emerging drugs for schizophrenia

The Effects of Antipsychotic Treatment on the Brain of Patients With First-Episode Schizophrenia: A Selective Review of Longitudinal MRI Studies

A large number of neuroimaging studies have detected brain abnormalities in first-episode schizophrenia both before and after treatment, but it remains unclear how these abnormalities reflect the effects of antipsychotic treatment on the brain. To summarize the findings in this regard and provide potential directions for future work, we reviewed longitudinal structural and functional imaging studies in patients with first-episode schizophrenia before and after antipsychotic treatment. A total of 36 neuroimaging studies was included, involving 21 structural imaging studies and 15 functional imaging studies. Both anatomical and functional brain changes in patients after treatment were consistently observed in the frontal and temporal lobes, basal ganglia, limbic system and several key components within the default mode network (DMN). Alterations in these regions were affected by factors such as antipsychotic type, course of treatment, and duration of untreated psychosis (DUP). Over all we showed that: (a) The striatum and DMN were core target regions of treatment in schizophrenia, and their changes were related to different antipsychotics; (b) The gray matter of frontal and temporal lobes tended to reduce after long-term treatment; and (c) Longer DUP was accompanied with faster hippocampal atrophy after initial treatment, which was also associated with poorer outcome. These findings are in accordance with previous notions but should be interpreted with caution. Future studies are needed to clarify the effects of different antipsychotics in multiple conditions and to identify imaging or other biomarkers that may predict antipsychotic treatment response. With such progress, it may help choose effective pharmacological interventional strategies for individuals experiencing recent-onset schizophrenia.

Fibroblast Growth Factor: Promising Target for Schizophrenia

Schizophrenia is one of the most debilitating mental disorders around the world. It is characterized by neuroanatomical or biochemical changes. The role of the fibroblast growth factors (FGFs) system in schizophrenia has received considerable attention in recent years. Various changes in the gene expression and/or level of FGFs have been implicated in the etiology, symptoms and progression of schizophrenia. For example, studies have substantiated an interaction between FGFs and the signaling pathway of dopamine receptors. To understand the role of this system in schizophrenia, the databases of Open Access Journals, Web of Science, PubMed (NLM), LISTA (EBSCO), and Google Scholar with keywords including fibroblast growth factors, dopamine, schizophrenia, psychosis, along with neurotrophic were searched. In conclusion, the FGF family represent molecular candidates as new drug targets and treatment targets for schizophrenia.

Kynurenines and the Endocannabinoid System in Schizophrenia: Common Points and Potential Interactions

Schizophrenia, which affects around 1% of the world’s population, has been described as a complex set of symptoms triggered by multiple factors. However, the exact background mechanisms remain to be explored, whereas therapeutic agents with excellent effectivity and safety profiles have yet to be developed. Kynurenines and the endocannabinoid system (ECS) play significant roles in both the development and manifestation of schizophrenia, which have been extensively studied and reviewed previously. Accordingly, kynurenines and the ECS share multiple features and mechanisms in schizophrenia, which have yet to be reviewed. Thus, the present study focuses on the main common points and potential interactions between kynurenines and the ECS in schizophrenia, which include (i) the regulation of glutamatergic/dopaminergic/γ-aminobutyric acidergic neurotransmission, (ii) their presence in astrocytes, and (iii) their role in inflammatory mechanisms. Additionally, promising pharmaceutical approaches involving the kynurenine pathway and the ECS will be reviewed herein.

Long-term effects of cariprazine exposure on dopamine receptor subtypes

INTRODUCTION

All clinically effective antipsychotics are known to act on the dopaminergic system, and previous studies have demonstrated that repeated treatment with antipsychotics produced region-specific changes in dopamine receptor levels. Cariprazine is a dopamine D₃ and D₂ receptor partial agonist with preferential binding to D₃ receptors. We examined the effects of chronic cariprazine administration on dopamine receptor levels.

METHODS

Rats were administered either vehicle or cariprazine (0.06, 0.2, or 0.6 mg/kg) for 28 days. Dopamine receptor levels were quantitated using autoradiographic assays on brain tissue sections from the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), caudate putamen (CPu), hippocampus (HIPP), olfactory tubercle (OT), and islands of Calleja (ICj).

RESULTS

Chronic treatment with cariprazine did not alter D₁ receptor levels in any brain region tested. Cariprazine increased D₂ receptor levels in mPFC (27%-43%), NAc (40%-45%), medial (41%-53%) and lateral (52%-63%) CPu, and HIPP (38%). Cariprazine dose-dependently upregulated D₃ receptor levels in ICj (32%-57%), OT (27%-67%), and NAc shell (31%-48%). Repeated cariprazine treatment increased D₄ receptor in NAc (53%-82%), medial (54%-98%) and lateral (58%-74%) CPu, and HIPP (38%-98%).

CONCLUSION

Similar to other antipsychotics, cariprazine upregulated D₂ and D₄ receptor levels in various brain regions. Cariprazine was unique among antipsychotics in increasing D₃ receptor levels, which may support its unique psychopharmacologic properties.

A randomized placebo-controlled trial of an omega-3 fatty acid and vitamins E+C in schizophrenia

Membrane lipid metabolism and redox regulation may be disturbed in schizophrenia. We examined the clinical effect of adding an omega-3 fatty acid and/or vitamins E+C to antipsychotics. It was hypothesized that lower baseline levels of polyunsaturated fatty acids (PUFAs) would predict more benefit from the add-on treatment. The trial had a multicenter, randomized, double-blind, placebo-controlled 2 × 2 factorial design. Patients aged 18-39 years with schizophrenia or related psychoses were consecutively included at admission to psychiatric departments in Norway. They received active or placebo ethyl-eicosapentaenoate (EPA) 2 g day⁻¹ and active or placebo vitamin E 364 mg day⁻¹+vitamin C 1000 mg day⁻¹ (vitamins) for 16 weeks. The main outcome measures were Positive and Negative Syndrome Scale (PANSS) total and subscales scores, analyzed by linear mixed models. Ninety-nine patients were included. At baseline, erythrocyte PUFA were measured in 97 subjects. Given separately, EPA and vitamins increased drop-out rates, whereas when combined they did not differ from placebo. In low PUFA patients, EPA alone impaired the course of total PANSS (Cohen's d=0.29; P=0.03) and psychotic symptoms (d=0.40; P=0.003), especially persecutory delusions (d=0.48; P=0.0004). Vitamins alone impaired the course of psychotic symptoms (d= 0.37; P=0.005), especially persecutory delusions (d=0.47; P=0.0005). Adding vitamins to EPA neutralized the detrimental effect on psychosis (interaction d=0.31; P=0.02). In high PUFA patients, there were no significant effects of trial drugs on PANSS scales. In conclusion, given separately during an acute episode, EPA and vitamins E+C induce psychotic symptoms in patients with low levels of PUFA. Combined, these agents seem safe.

A randomized clinical trial of histamine 2 receptor antagonism in treatment-resistant schizophrenia

Histamine has important functions as regulator of several other key neurotransmitters. Patients with schizophrenia have lower histamine H1 receptor levels. Since a case report in 1990 of an effect of the H2 antagonist famotidine on negative symptoms in schizophrenia, some open-label trials have been performed, but no randomized controlled trial. Recently, it was shown that clozapine is a full inverse agonist at the H2 receptor. We performed a researcher-initiated, academically financed, double-blind, placebo-controlled, parallel-group, randomized trial with the histamine H2 antagonist famotidine in treatment-resistant schizophrenia. Thirty subjects with schizophrenia were randomized to have either famotidine (100 mg twice daily, n = 16) or placebo (n = 14) orally, added to their normal treatment regimen for 4 weeks. They were followed up weekly with the Scale for the Assessment of Negative Symptoms (SANS), the PANSS (Positive and Negative Syndrome Scale), and Clinical Global Impression (CGI) Scale. In the famotidine group, the SANS score was reduced by 5.3 (SD, 13.1) points, whereas in the placebo group the SANS score was virtually unchanged (mean change, +0.2 [SD, 9.5]). The difference did not reach statistical significance (P = 0.134) in Mann-Whitney U analysis. However, the PANSS Total score and the General subscore as well as the CGI showed significantly (P < 0.05) greater change in the famotidine group than in the placebo group. No significant adverse effects were observed. This is the first placebo-controlled, randomized clinical trial showing a beneficial effect of histamine H2 antagonism in schizophrenia. H2 receptor antagonism may provide a new alternative for the treatment of schizophrenia.

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.

Predictions of in vivo prolactin levels from in vitro K(i) values of D(2) receptor antagonists using an agonist-antagonist interaction model

Prolactin elevation is a side effect of all currently available D(2) receptor antagonists used in the treatment of schizophrenia. Prolactin elevation is the result of a direct antagonistic D(2) effect blocking the tonic inhibition of prolactin release by dopamine. The aims of this work were to assess the correlation between in vitro estimates of D(2) receptor affinity and pharmacokinetic-pharmacodynamic model-based estimates obtained from analysis of clinical data using an agonist-antagonist interaction (AAI) model and to assess the value of such a correlation in early prediction of full prolactin time profiles. A population model describing longitudinal prolactin data was fitted to clinical data from 16 clinical phases 1 and 3 trials including five different compounds. Pharmacokinetic data were modeled for each compound and the prolactin model was both fitted in per-compound fits as well as simultaneously to all prolactin data. Estimates of prolactin elevating potency were compared to corresponding in vitro values and their predictability was evaluated through model-based simulations. The model successfully described the prolactin time course for all compounds. Estimates derived from experimental preclinical data and the model fit of the clinical data were strongly correlated (p<0.001), and simulations adequately predicted the prolactin elevation in five out of six compounds. The AAI model has the potential to be used in drug development to predict prolactin response for a given exposure of D(2) antagonists using routinely produced preclinical data.

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.

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

Since the introduction of chlorpromazine and throughout the development of the new-generation antipsychotic drugs (APDs) beginning with clozapine, the D(2) receptor has been the target for the development of APDs. Pharmacologic actions to reduce neurotransmission through the D(2) receptor have been the only proven therapeutic mechanism for psychoses. A number of novel non-D(2) mechanisms of action of APDs have been explored over the past 40 years but none has definitively been proven effective. At the same time, the effectiveness of treatments and range of outcomes for patients are far from satisfactory. The relative success of antipsychotics in treating positive symptoms is limited by the fact that a substantial number of patients are refractory to current medications and by their lack of efficacy for negative and cognitive symptoms, which often determine the level of functional impairment. In addition, while the newer antipsychotics produce fewer motor side effects, safety and tolerability concerns about weight gain and endocrinopathies have emerged. Consequently, there is an urgent need for more effective and better-tolerated antipsychotic agents, and to identify new molecular targets and develop mechanistically novel compounds that can address the various symptom dimensions of schizophrenia. In recent years, a variety of new experimental pharmacological approaches have emerged, including compounds acting on targets other than the dopamine D(2) receptor. However, there is still an ongoing debate as to whether drugs selective for singe molecular targets (that is, 'magic bullets') or drugs selectively non-selective for several molecular targets (that is, 'magic shotguns', 'multifunctional drugs' or 'intramolecular polypharmacy') will lead to more effective new medications for schizophrenia. In this context, current and future drug development strategies can be seen to fall into three categories: (1) refinement of precedented mechanisms of action to provide drugs of comparable or superior efficacy and side-effect profiles to existing APDs; (2) development of novel (and presumably non-D(2)) mechanism APDs; (3) development of compounds to be used as adjuncts to APDs to augment efficacy by targeting specific symptom dimensions of schizophrenia and particularly those not responsive to traditional APD treatment. In addition, efforts are being made to determine if the products of susceptibility genes in schizophrenia, identified by genetic linkage and association studies, may be viable targets for drug development. Finally, a focus on early detection and early intervention aimed at halting or reversing progressive pathophysiological processes in schizophrenia has gained great influence. This has encouraged future drug development and therapeutic strategies that are neuroprotective. This article provides an update and critical review of the pharmacology and clinical profiles of current APDs and drugs acting on novel targets with potential to be therapeutic agents in the future.

Cotinine: Beyond that Expected, More than a Biomarker of Tobacco Consumption

A greater incidence of tobacco consumption occurs among individuals with psychiatric conditions including post-traumatic stress disorder (PTSD), bipolar disorder, major depression, and schizophrenia, compared with the general population. Even when still controversial, it has been postulated that smoking is a form of self-medication that reduces psychiatric symptoms among individuals with these disorders. To better understand the component(s) of tobacco-inducing smoking behavior, greater attention has been directed toward nicotine. However, in recent years, new evidence has shown that cotinine, the main metabolite of nicotine, exhibits beneficial effects over psychiatric symptoms and may therefore promote smoking within this population. Some of the behavioral effects of cotinine compared to nicotine are discussed here. Cotinine, which accumulates in the body as a result of tobacco exposure, crosses the blood-brain barrier and has different pharmacological properties compared with nicotine. Cotinine has a longer plasma half-life than nicotine and showed no addictive or cardiovascular effects in humans. In addition, at the preclinical level, cotinine facilitated the extinction of fear memory and anxiety after fear conditioning, improved working memory in a mouse model of Alzheimer’s disease (AD) and in a monkey model of schizophrenia. Altogether, the new evidence suggests that the pharmacological and behavioral effects of cotinine may play a key role in promoting tobacco smoking in individuals that suffer from psychiatric conditions and represents a new potential therapeutic agent against psychiatric conditions such as AD and PTSD.

Is rational antipsychotic polytherapy feasible? A selective review

Antipsychotic polytherapy (APT) has evolved as a common treatment strategy at odds with recommendations from schizophrenia treatment guidelines. The literature on combinations with clozapine as a means to enhance efficacy and with aripiprazole to reduce side effects was reviewed. No solid evidence supporting antipsychotic combinations with clozapine for treatment-resistant patients with schizophrenia was identified. The reason for this may be that most combinations with clozapine increase the D(2)-receptor blockade, and this strategy is probably not efficient for patients with treatment-resistant schizophrenia. Some basic and clinical evidence for the addition of aripiprazole to lower prolactin levels was identified. In conclusion, there is very limited support in the evidence for the feasibility of rational APT.

Adjunctive armodafinil for negative symptoms in adults with schizophrenia: a double-blind, placebo-controlled study

OBJECTIVE

A prior 4-week, proof-of-concept study suggested that adjunctive therapy with armodafinil 200mg/day decreases negative symptoms in patients with clinically stable schizophrenia. This study investigated the efficacy and tolerability of adjunctive armodafinil for treatment of negative symptoms in adults with schizophrenia receiving antipsychotic medications.

METHODS

This parallel-group, 24-week study enrolled adults with schizophrenia who were receiving oral olanzapine, risperidone, or paliperidone for ≥ 6 weeks, and had a Positive and Negative Syndrome Scale (PANSS) negative symptom subscale score of ≥ 15. Patients received one of 3 doses of once-daily armodafinil (150 mg, 200mg, or 250 mg) or placebo. The primary efficacy measure was the change from baseline to final visit in the PANSS negative symptom subscale score. Secondary measures included the PANSS total score, Clinical Global Impression of Severity, Personal and Social Performance Scale, and CNSVitalSigns cognitive battery.

RESULTS

Of 285 randomized patients, 213 received armodafinil and 72 received placebo. The mean (SD) changes in PANSS negative symptom subscale score were -1.9 (3.8) for armodafinil 150 mg (n = 70), -2.3 (3.6) for armodafinil 200mg (n = 69), -2.0 (3.3) for armodafinil 250 mg (n = 71), and -2.2 (4.1) for placebo (n=70) (p ≥ 0.70 for each armodafinil group versus placebo). Secondary measures were generally not different between groups. Armodafinil was generally well tolerated, without worsening positive symptoms.

CONCLUSIONS

This study found no benefit of adjunctive armodafinil versus placebo for negative symptoms in patients with schizophrenia receiving treatment with olanzapine, risperidone, or paliperidone. Armodafinil was generally well tolerated in these patients.

Negative symptoms of schizophrenia are improved by the addition of paroxetine to neuroleptics: a double-blind placebo-controlled study

Despite the availability of atypical antipsychotics, the treatment of negative symptoms in schizophrenia remains a challenge. This study was designed to confirm the positive effect observed in our pilot study with paroxetine as augmentation to antipsychotics in the treatment of negative symptoms in chronic schizophrenia. Twenty-nine patients with chronic schizophrenia, as defined by DSM-IV, who scored at least 20 points on the negative subscale of the Positive and Negative Syndrome Scale (PANSS) were randomized for treatment with 30 mg paroxetine or placebo in a double-blind, placebo-controlled study for 12 weeks. Ratings included the PANSS, the Hamilton Rating Scale for Depression (HAM-D) and scales for extrapyramidal side-effects. An intention-to-treat analysis was based on the 25 patients who were available for at least one follow-up assessment. The last observation carried forward principle was applied. The mean score of the negative subscale of the PANSS decreased in both groups. Using an analysis of covariance, there was a significant treatment effect with paroxetine compared to placebo with respect to negative symptoms (-4.53; 95% confidence interval -9.054 to -0.015). The mean HAM-D scores remained almost constant. The study suggests the efficacy of paroxetine with respect to the treatment of negative symptoms in chronic schizophrenia.