A review of the pharmacology, efficacy and tolerability of recently approved and upcoming oral antipsychotics: an evidence-based medicine approach

Antipsychotic medication in schizophrenia: a review

INTRODUCTION

Antipsychotic medications are mainstays in the treatment of schizophrenia and a range of other psychotic disorders.

SOURCES OF DATA

Recent meta-analyses of antipsychotic efficacy and tolerability have been included in this review, along with key papers on antipsychotic use in schizophrenia and other psychotic illnesses.

AREAS OF AGREEMENT

The heterogeneity in terms of individuals' response to antipsychotic treatment and the current inability to predict response leads to a trial-and-error strategy with treatment choice. Clozapine is the only effective medication for treatment-resistant schizophrenia.

AREAS OF CONTROVERSY

There are a significant number of side effects associated with antipsychotic use. With a reduction in the frequency of extrapyramidal side effects with the use of second-generation antipsychotics, there has been a significant shift in the side effect burden, with an increase in the risk of cardiometabolic dysfunction.

GROWING POINTS

There exist small and robust efficacy differences between medications (other than clozapine), and response and tolerability to each antipsychotic drug vary, with there being no first-line antipsychotic drug that is suitable for all patients.

AREAS TIMELY FOR DEVELOPING RESEARCH

A focus on the different symptom domains of schizophrenia may lead to endophenotypic markers being identified, e.g. for negative symptoms and cognitive deficits (as well as for positive symptoms) that can promote the development of novel therapeutics, which will rationally target cellular and molecular targets, rather than just the dopamine 2 receptor. Future developments will target additional processes, including glutamatergic, cholinergic and cannabinoid receptor targets and will utilize personalized medicine techniques, such as pharmacogenetic variants and biomarkers allowing for a tailored and safer use of antipsychotics.

Potentiation of neurite outgrowth by brexpiprazole, a novel serotonin-dopamine activity modulator: a role for serotonin 5-HT1A and 5-HT2A receptors

Brexpiprazole, a novel atypical antipsychotic drug, is currently being tested in clinical trials for treatment of psychiatric disorders, such as schizophrenia and major depressive disorder. The drug is known to act through a combination of partial agonistic activity at 5-hydroxytryptamine (5-HT)1A, and dopamine D2 receptors, and antagonistic activity at 5-HT2A receptors. Accumulating evidence suggests that antipsychotic drugs act by promoting neurite outgrowth. In this study, we examined whether brexpiprazole affected neurite outgrowth in cell culture. We found that brexpiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration dependent manner. The selective 5-HT1A receptor antagonist, WAY-100,635, was able to block the effects of brexpiprazole on neurite outgrowth, unlike the selective dopamine D2 receptor antagonist, raclopride. Furthermore, the selective 5-HT2A receptor antagonist M100907, but not DOI (5-HT2A receptor agonist), significantly potentiated NGF-induced neurite outgrowth. Moreover, xestospongin C and 2-aminoethoxydiphenyl borate (2-APB), both specific inhibitors of inositol 1,4,5-triphosphate (IP3) receptors, significantly blocked the effects of brexpiprazole. These findings suggest that brexpiprazole-induced neurite outgrowth is mediated through 5-HT1A and 5-HT2A receptors, and subsequent Ca(2+) signaling via IP3 receptors.

Proof of concept study for designed multiple ligands targeting the dopamine D2, serotonin 5-HT2A, and muscarinic M1 acetylcholine receptors

Herein we describe the hybridization of a benzoxazinone M1 scaffold with D2 privileged structures derived from putative and clinically relevant antipsychotics to develop designed multiple ligands. The M1 mAChR is an attractive target for the cognitive deficits in key CNS disorders. Moreover, activity at D2 and 5-HT2A receptors has proven useful for antipsychotic efficacy. We identified 9 which retained functional activity at the target M1 mAChR and D2R and demonstrated high affinity for the 5-HT2AR.

Pharmacogenetics of second-generation antipsychotics

This review considers pharmacogenetics of the so called 'second-generation' antipsychotics. Findings for polymorphisms replicating in more than one study are emphasized and compared and contrasted with larger-scale candidate gene studies and genome-wide association study analyses. Variants in three types of genes are discussed: pharmacokinetic genes associated with drug metabolism and disposition, pharmacodynamic genes encoding drug targets, and pharmacotypic genes impacting disease presentation and subtype. Among pharmacokinetic markers, CYP2D6 metabolizer phenotype has clear clinical significance, as it impacts dosing considerations for aripiprazole, iloperidone and risperidone, and variants of the ABCB1 gene hold promise as biomarkers for dosing for olanzapine and clozapine. Among pharmacodynamic variants, the TaqIA1 allele of the DRD2 gene, the DRD3 (Ser9Gly) polymorphism, and the HTR2C -759C/T polymorphism have emerged as potential biomarkers for response and/or side effects. However, large-scale candidate gene studies and genome-wide association studies indicate that pharmacotypic genes may ultimately prove to be the richest source of biomarkers for response and side effect profiles for second-generation antipsychotics.

Lack of tolerable treatment options for patients with schizophrenia

PURPOSE

Atypical antipsychotics (AAs), an effective treatment for schizophrenia, have a range of pharmacologic properties leading to differences in tolerability as well as heterogeneity in treatment response. Individual patient characteristics must be considered when making treatment choices, especially from an adverse event (AE) or tolerability perspective. Despite the availability of numerous AAs, after appraising patient characteristics at the time of treatment selection, physicians may quickly run out of tolerable treatment options.

PATIENTS AND METHODS

AE risk factors, defined as having either a prior history of an AE or a risk factor for that AE, were determined for Medicaid-insured and Commercially insured patients using database analysis. Patients receiving AA treatment between January 1, 2010 and December 31, 2012 defined the index date of first observed AA prescription during this period. Nine AAs were evaluated for association with AE risk factors as informed by drug prescribing information from the different manufacturers and published meta-analyses. The proportion of patients with pre-index AE risk factors prescribed an AA associated with that risk factor was then determined.

RESULTS

A high proportion of patients (>80%) were prescribed an AA associated with extrapyramidal symptoms or akathisia despite experiencing extrapyramidal symptoms or akathisia prior to AA treatment initiation. Similar trends were observed among patients with diabetes (>60%) and obesity (>40%). From the nine treatment options available, the number of optimal choices for individual patient segments were limited based on their prior history, including those with cardiometabolic and cardiovascular comorbidities (four); experiencing prolactin elevation-related problems (seven); needing to avoid excessive sedation (four); or at risk of extrapyramidal symptoms or akathisia (two). Options were then further restricted among patients in more than one segment when multiple pre-index AE risk factors were combined.

CONCLUSION

When combining patient risk profile with antipsychotic AE profile, physicians may quickly run out of tolerable treatment options for individual patients, despite the availability of many AAs, suggesting a need for additional treatment options with better tolerability and without compromising efficacy.

Evaluation of the pharmacokinetics, safety and clinical efficacy of ziprasidone for the treatment of schizophrenia and bipolar disorder

INTRODUCTION

Multiple strategies exist for the pharmacological treatment of schizophrenia and related disorders. In the last 20 years, several 'new' compounds have been introduced, called 'atypical antipsychotics', which have higher efficacy and better tolerability than first-generation neuroleptics. Among them, ziprasidone (ZPR) is currently finding widespread use, and it has also been shown to be active as an augmenter in bipolar disorder therapy.

AREAS COVERED

This review aims to provide the latest information on ZPR, an 'atypical' agent for the pharmacological therapy of schizophrenia and bipolar disorder. A literature search has been carried out with the keywords 'ziprasidone', 'schizophrenia', 'psychosis', 'bipolar', 'pharmacokinetics' and 'clinical trials'. In this process, particular attention has been paid to the drug pharmacokinetic characteristics and its safety in clinical use.

EXPERT OPINION

ZPR shares most advantages and disadvantages with other atypical antipsychotics. However, it can be useful for its low tendency to cause metabolic syndrome and hyperprolactinaemia, especially in patients suffering from excess weight, hyperlipidaemia, diabetes or who have suffered from hyperprolactinaemia when using other antipsychotics. However, there are serious doubts as to whether ZPR should be administered to patients suffering from arrhythmias or QTc prolongation, and even more for administration to bipolar patients undergoing polypharmacy with antidepressants.

Asenapine review, part I: chemistry, receptor affinity profile, pharmacokinetics and metabolism

INTRODUCTION

Asenapine is a second-generation (atypical) antipsychotic currently marketed for the treatment of schizophrenia and bipolar mania/mixed episodes.

AREAS COVERED

The purpose of this review is to describe the chemistry, pharmacodynamics, and pharmacokinetics of asenapine.

EXPERT OPINION

Asenapine has a complex pharmacodynamic profile with affinities at multiple dopamine, serotonin, histamine, and α-adrenergic receptors, all at which asenapine functions as an antagonist. Sublingual asenapine tablets are absorbed in the oral mucosa, with a Tmax occurring between 30 and 90 min. Terminal half-life is approximately 24 h. Asenapine has multiple inactive metabolites, produced via direct glucuronidation (primarily via UGT1A4), demethylation, and oxidative metabolism (primarily via CYP1A2). Hepatic and renal routes contribute approximately equally to the elimination of asenapine and its metabolites. Two notable drug-drug interactions are evident: asenapine (an inhibitor of CYP2D6) can increase plasma levels of paroxetine, and fluvoxamine (a CYP1A2 inhibitor) can increase plasma levels of asenapine. Caution is required when coadministering asenapine with drugs that are both substrates and inhibitors of CYP2D6.

Negative symptoms of schizophrenia: clinical characteristics, pathophysiological substrates, experimental models and prospects for improved treatment

Schizophrenia is a complex and multifactorial disorder generally diagnosed in young adults at the time of the first psychotic episode of delusions and hallucinations. These positive symptoms can be controlled in most patients by currently-available antipsychotics. Conversely, they are poorly effective against concomitant neurocognitive dysfunction, deficits in social cognition and negative symptoms (NS), which strongly contribute to poor functional outcome. The precise notion of NS has evolved over the past century, with recent studies - underpinned by novel rating methods - suggesting two major sub-domains: "decreased emotional expression", incorporating blunted affect and poverty of speech, and "avolition", which embraces amotivation, asociality and "anhedonia" (inability to anticipate pleasure). Recent studies implicate a dysfunction of frontocortico-temporal networks in the aetiology of NS, together with a disruption of cortico-striatal circuits, though other structures are also involved, like the insular and parietal cortices, amygdala and thalamus. At the cellular level, a disruption of GABAergic-glutamatergic balance, dopaminergic signalling and, possibly, oxytocinergic and cannibinoidergic transmission may be involved. Several agents are currently under clinical investigation for the potentially improved control of NS, including oxytocin itself, N-Methyl-d-Aspartate receptor modulators and minocycline. Further, magnetic-electrical "stimulation" strategies to recruit cortical circuits and "cognitive-behavioural-psychosocial" therapies likewise hold promise. To acquire novel insights into the causes and treatment of NS, experimental study is crucial, and opportunities are emerging for improved genetic, pharmacological and developmental modelling, together with more refined readouts related to deficits in reward, sociality and "expression". The present article comprises an integrative overview of the above issues as a platform for this Special Issue of European Neuropsychopharmacology in which five clinical and five preclinical articles treat individual themes in greater detail. This Volume provides, then, a framework for progress in the understanding - and ultimately control - of the debilitating NS of schizophrenia.

Second-generation and newly approved antipsychotics, serum prolactin levels and sexual dysfunctions: a critical literature review

INTRODUCTION

Using antipsychotic (AP) medication can increase prolactin (PRL) levels and place the patient at risk of sexual dysfunction (SD).

AREAS COVERED

The aim of this review is to describe the PRL propensity of the different second-generation and newly approved APs. It then considers the prevalence rates of SDs associated with these compounds in patients with schizophrenia and treatment strategies for the management of SDs and/or hyperprolactinemia (HPRL). Furthermore, we address the lingering question regarding the association between SDs and PRL.

EXPERT OPINION

SD (particularly long-term) data remain scarce for several APs. A wide variety of assessment techniques used in SD research make reliable comparisons between APs impossible. The majority of these reports do not equally allow us to distinguish between treatment (AP and co-medication)-emergent SDs and illness-related SDs. This makes it difficult to assess the degree to which these side effects are associated with 'PRL-raising' APs, and what part of this fraction is directly reducible to serum PRL levels. Also, few evidence-based treatment strategies for HPRL and associated side effects are available. Therefore, longer-term randomized controlled trials, using reliable and valid structured interviews or questionnaires, are necessary to establish the precise relationship between APs, PRL levels and SDs rates and develop valuable treatment options.