Safety, tolerability, and effect of food on the pharmacokinetics of iloperidone (HP 873), a potential atypical antipsychotic

PIMD: An Integrative Approach for Drug Repositioning Using Multiple Characterization Fusion

The accumulation of various types of drug informatics data and computational approaches for drug repositioning can accelerate pharmaceutical research and development. However, the integration of multi-dimensional drug data for precision repositioning remains a pressing challenge. Here, we propose a systematic framework named PIMD to predict drug therapeutic properties by integrating multi-dimensional data for drug repositioning. In PIMD, drug similarity networks (DSNs) based on chemical, pharmacological, and clinical data are fused into an integrated DSN (iDSN) composed of many clusters. Rather than simple fusion, PIMD offers a systematic way to annotate clusters. Unexpected drugs within clusters and drug pairs with a high iDSN similarity score are therefore identified to predict novel therapeutic uses. PIMD provides new insights into the universality, individuality, and complementarity of different drug properties by evaluating the contribution of each property data. To test the performance of PIMD, we use chemical, pharmacological, and clinical properties to generate an iDSN. Analyses of the contributions of each drug property indicate that this iDSN was driven by all data types and performs better than other DSNs. Within the top 20 recommended drug pairs, 7 drugs have been reported to be repurposed. The source code for PIMD is available at https://github.com/Sepstar/PIMD/.

Inhibition of voltage-dependent K+ channels by iloperidone in coronary arterial smooth muscle cells

Iloperidone, a second-generation atypical antipsychotic drug, is widely used in the treatment of schizophrenia. However, the side-effects of iloperidone on vascular K⁺ channels remain to be determined. Therefore, we explored the effect of iloperidone on voltage-dependent K⁺ (Kv) channels in rabbit coronary arterial smooth muscle cells using the whole-cell patch-clamp technique. Iloperidone inhibited vascular Kv channels in a concentration-dependent manner with a half-maximal inhibitory concentration (IC₅₀ ) of 2.11 ± 0.5 μM and a Hill coefficient of 0.68 ± 0.03. Iloperidone had no effect on the steady-state inactivation kinetics. However, it shifted the steady-state activation curve to the right, indicating that iloperidone inhibited Kv channels by influencing the voltage sensors. Application of 20 repetitive depolarizing pulses (1 and 2 Hz) progressively increased the inhibition of the Kv current in the presence of iloperidone. Furthermore, iloperidone increased the recovery time constant from Kv channel inactivation, suggesting that iloperidone-induced inhibition of Kv channels is use (state)-dependent. Pretreatment with a Kv1.5 inhibitor (diphenyl phosphine oxide 1 [DPO-1]) inhibited the Kv current to a level similar to that with iloperidone alone. However, pretreatment with a Kv2.1 or Kv7.X inhibitor (guangxitoxin or linopirdine) did not affect the inhibitory effect of iloperidone on Kv channels. Therefore, iloperidone directly inhibits Kv channels in a concentration- and use (state)-dependent manner independently of its antagonism of serotonin and dopamine receptors. Furthermore, the primary target of iloperidone is the Kv1.5 subtype.

Influences of CYP2D6*10 polymorphisms on the pharmacokinetics of iloperidone and its metabolites in Chinese patients with schizophrenia: a population pharmacokinetic analysis

AIM

Iloperidone is an atypical antipsychotic drug that is mainly metabolized by CYP2D6, CYP3A4, and cytosolic enzymes. Previous studies show that extensive and poor metabolizers of CYP2D6 exhibit different plasma concentrations of iloperidone and its metabolites. The aim of this study was to develop a parent-metabolite population pharmacokinetic (PPK) model to quantify the effects of CYP2D6^*10 allele on the pharmacokinetics of iloperidone and its metabolites in Chinese schizophrenia patients.

METHODS

Seventy Chinese schizophrenia patients were enrolled, from whom limited blood samples were collected on d 15 (0 h) and d 28 (0, 4 and 12 h after drug administration). The plasma concentrations of iloperidone and its metabolites M₁ (P-88) and M₂ (P-95) were simultaneously detected using a validated HPLC-MS assay. CYP2D6^*10 (rs1065852) genotyping was performed. A PPK model was developed based on data from the patients using the NONMEM software (version 7.2). A one-compartment model with first-order absorption and elimination was used to describe the pharmacokinetic data related to iloperidone and its metabolites.

RESULTS

Patients with the CYP2D6^*10 T/T genotype had significantly higher concentrations of iloperidone and M₁, and lower concentrations of M₂ than the patients with C/C or C/T genotypes. The CYP2D6^*10 genotype affected the elimination constants for transformation of iloperidone to the metabolites M₁ (K₂₃) and M₂ (K₂₄). The K₂₃ value of the patients with T/T genotype was 1.34-fold as great as that of the patients with C/C or C/T genotype. The K₂₄ value of the patients with C/T and T/T genotypes was 0.693- and 0.492-fold, respectively, as low as that of the patients with C/C genotype.

CONCLUSION

CYP2D6^*10 mutations affect the pharmacokinetics of iloperidone and its metabolites in Chinese schizophrenia patients, suggesting that the clinical doses of iloperidone for patients with CYP2D6^*10 mutations need to be optimized.

An update of safety of clinically used atypical antipsychotics

INTRODUCTION

The atypical antipsychotic (APs) drugs have become the most widely used agents to treat a variety of psychoses because of their superiority with regard to safety and tolerability profile compared to conventional/'typical' APs.

AREAS COVERED

We aimed at providing a synthesis of most current evidence about the safety and tolerability profile of the most clinically used atypical APs so far marketed. Qualitative synthesis followed an electronic search made inquiring of the following databases: MEDLINE, Embase, PsycINFO and the Cochrane Library from inception until January 2016, combining free terms and MESH headings for the topics of psychiatric disorders and all atypical APs as following: ((safety OR adverse events OR side effects) AND (aripiprazole OR asenapine OR quetiapine OR olanzapine OR risperidone OR paliperidone OR ziprasidone OR lurasidone OR clozapine OR amisulpride OR iloperidone)).

EXPERT OPINION

A critical issue in the treatment with atypical APs is represented by their metabolic side effect profile (e.g. weight gain, lipid and glycaemic imbalance, risk of diabetes mellitus and diabetic ketoacidosis) which may limit their use in particular clinical samples. Electrolyte imbalance, ECG abnormalities and cardiovascular adverse effects may recommend a careful baseline and periodic assessments.

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.

Stable-isotope dilution LC–MS/MS assay for determination of iloperidone and its two major metabolites, P 88 and P 95, in human plasma: application to a bioequivalence study

Background: Iloperidone is a novel antipsychotic drug with high affinity for serotonin and D2 dopamine receptors. A sensitive and rapid isotope dilution LC–MS/MS method has been developed for the simultaneous determination of iloperidone and its two major metabolites in human plasma. Results: The analytes and their deuterated analogs as internal standards were quantitatively extracted from 100-µl human plasma by SPE. The method was validated over the concentration range of 0.01–6 ng/ml for all the analytes. Baseline separation of analytes was possible within 3 min on ACE 5 C8 column. The accuracy and precision (%CV) of the method varied from 96.2 to 105%, and 1.17 to 4.75%, respectively. The extraction recovery was >84%, while the internal standard-normalized matrix factors ranged from 0.97–1.03 for all three analytes. Conclusion: The developed method was successfully applied to support a bioequivalence study in healthy volunteers.

Iloperidone for the management of adults with schizophrenia

BACKGROUND

Iloperidone is a second-generation antipsychotic drug approved in May 2009 by the US Food and Drug Administration (FDA) for the acute treatment of schizophrenia in adults. It is a piperidinyl-benzisoxazole derivative with mixed serotonin (5HT2A) and D2 dopamine antagonist properties.

OBJECTIVE

The purpose of this article was to review the pharmacology, pharmacokinetics, efficacy, safety, and role in treatment for iloperidone in schizophrenia.

METHODS

Scientific and clinical data were collected through searches of PubMed, ClinicalTrials.gov, International Pharmaceutical Abstracts, and the FDA, using the search term iloperidone, and limited to English-language articles. Reference lists were reviewed for additional publications. Dates included the beginning of the database through 2010. No limits were placed on study design.

RESULTS

In a 4-week Phase III trial, iloperidone 12 mg twice daily lowered the Positive and Negative Syndrome Scale (PANSS) total scores to a significantly greater extent than did placebo (-12 vs -7.1; P < 0.01). The ziprasidone active control also separated from placebo (-12.3 vs -7.1; P < 0.05). A pooled analysis of 3 Phase III trials compared iloperidone in divided doses to placebo. The primary outcome was reduction in PANSS scores. Study 1 included iloperidone 4, 8, or 12 mg/d, haloperidol as an active control, and placebo. The PANSS reduction in the 12 mg/d group was significantly greater at end point versus baseline when compared with placebo (-9.9 vs -4.6; P = 0.047). Study 2 included iloperidone 4 to 8 mg/d or 10 to 16 mg/d, risperidone 4 to 8 mg/d, or placebo. The primary efficacy measure was change from baseline to end point in the Brief Psychiatric Rating Scale (BPRS). Improvement from baseline on all iloperidone doses was significantly greater than with placebo (4-8 mg/d group: -6.2, P = 0.012; 10-16 mg/d group: -7.2, P = 0.001; placebo, -2.5). Study 3 included iloperidone 12 to 16 mg/d, risperidone 6 to 8 mg/d, and placebo. The results on the primary efficacy variable, reduction in the BPRS score, was not significant for the 12 to 16 mg/d group versus placebo (-7.1 vs -5.0; P = 0.09), but was significant for the 20 to 24 mg/d iloperidone group (-8.6 vs -5.0; P = 0.01) and for the risperidone group (-11.5 vs 5.0; P < 0.001). A 52-week maintenance trial included iloperidone versus haloperidol as an active control. The primary efficacy variable was time to relapse. Comparison of mean time to relapse of the 2 arms showed no significant difference. The most common adverse events (AEs) associated with iloperidone were dizziness (5.1%-23.2%), dry mouth (5.2%-10.4%), somnolence (4%-13%), and dyspepsia (4.8%-7.8%). AEs appeared dose related. Prescribing information recommends a starting dosage of 1 mg twice daily and then titrated over 7 days to reach a target dosage of 12 to 24 mg/d. The titration is necessary to reduce the risk of orthostatic hypotension-related dizziness.

CONCLUSIONS

Data support that when titrated slowly to a therapeutic dosage, iloperidone is generally well tolerated, has a favorable safety profile, and is an effective treatment option in patients with schizophrenia. Its place in therapy and performance in a typical patient population remain to be established. Slow initial titration and twice-daily dosing are potential disadvantages.

Iloperidone: A new drug for the treatment of schizophrenia

PURPOSE

The pharmacology, pharmacokinetics, pharmacogenomics, clinical efficacy, and safety and tolerability profile of iloperidone for the treatment of schizophrenia are reviewed.

SUMMARY

Iloperidone is an atypical antipsychotic that recently received marketing approval from the Food and Drug Administration for the acute treatment of schizophrenia. Iloperidone is a pure antagonist and the first antipsychotic to have pharmacogenomic studies indicate predictive response based on six identified polymorphisms. Pharmacokinetic studies have determined that iloperidone is well absorbed orally, with a bioavailability of 96%. Phase II and III clinical trials have shown iloperidone to improve symptoms of schizophrenia, based on the Positive and Negative Symptom Scale, Brief Psychiatric Rating Scale, and Clinical Global Impressions-Severity scores (p < 0.05). Iloperidone has established tolerability at recommended dosages of up to 24 mg daily; however, the dosage must be slowly increased over seven days, and twice-daily administration is required to avoid orthostatic hypotension. The most common adverse effects associated with iloperidone were dizziness, dry mouth, fatigue, nasal congestion, orthostatic hypotension, somnolence, tachycardia, and weight gain. Safety studies have also found that iloperidone increases the risk of Q-Tc interval prolongation, similar to that seen with ziprasidone. Minimal changes in glucose and lipid abnormalities were seen in short-term (4- and 6-week) and long-term (52-week) studies, indicating a low chance of metabolic disturbance with iloperidone.

CONCLUSION

Iloperidone may be a viable and safe option for the treatment of schizophrenia in adult patients, especially for patients who cannot tolerate other antipsychotic agents. However, iloperidone lacks a clear benefit over other antipsychotic agents.

Iloperidone: chemistry, pharmacodynamics, pharmacokinetics and metabolism, clinical efficacy, safety and tolerability, regulatory affairs, and an opinion

IMPORTANCE OF THE FIELD

Iloperidone is a newly commercialized second-generation (atypical) antipsychotic approved for the acute treatment of schizophrenia in adults.

AREAS COVERED IN THIS REVIEW

the purpose of this review is to describe the pharmacokinetic profile of iloperidone and its clinical implications in the treatment of schizophrenia. Background information is also provided regarding chemistry, pharmacodynamics, clinical efficacy and safety data, and regulatory affairs.

WHAT THE READER WILL GAIN

the reader will have an understanding of the pharmacokinetics and overall metabolism of iloperidone within the context of efficacy and safety.

TAKE HOME MESSAGE

time to peak plasma concentration occurs in 2 - 4 h but elimination half-life is 18 h for extensive CYP2D6 metabolizers and 33 h for poor CYP2D6 metabolizers, suggesting that once or twice daily dosing would be feasible. Dizziness and/or postural hypotension are the limiting factors for how fast iloperidone can be titrated, and is explained by iloperidone and its metabolites' norepinephrine alpha 1 antagonism. Efficacy of iloperidone appears similar to that for ziprasidone and haloperidol, but iloperidone may be inferior in efficacy to risperidone. Iloperidone can prolong the ECG QT interval. The tolerability profile of iloperidone is noteworthy in terms of modest weight gain, no medically important changes in lipid and glucose, little in the way of prolactin elevation, and an absence of extrapyramidal adverse effects, including akathisia.

Iloperidone—A Second-Generation Antipsychotic for the Treatment of Acute Schizophrenia

Objective:

To review the pharmacology, efficacy, and tolerability of iloperidone, a second-generation antipsychotic, in the treatment of acute schizophrenia in adults.

Data Sources:

English-language articles were obtained via MEDLINE (1966-March 2010) and International Pharmaceutical Abstracts (1970-March 2010) searches using the key words iloperidone, acute schizophrenia, atypical antipsychotics, second-generation antipsychotics, HP 873, P88–8991, P95–12113, and Fanapt. Bibliographies of selected articles were used to identify additional sources.

Study Selection and Data Extraction:

Available published articles reporting the results of human studies of iloperidone were reviewed for inclusion in this article. Additional information regarding pharmacology, adverse events, contraindications, and precautions was obtained from the manufacturer's prescribing information.

Data Synthesis:

Iloperidone is a second-generation antipsychotic approved for the treatment of acute schizophrenia in adults. Iloperidone is well absorbed upon oral administration, highly protein bound, and metabolized primarily by CYP3A4 and 2D6. Phase 3 clinical trials evaluating the efficacy of iloperidone demonstrated significantly higher response rates with iloperidone compared with placebo in the treatment of positive, negative, and cognitive symptoms associated with acute schizophrenia when the drug was given in doses up to 24 mg daily. Dizziness, dry mouth, and nausea were the most commonly reported adverse events and appear to be dose related. Additional adverse events occurring in 5% or more of patients include orthostatic hypotension, somnolence, tachycardia, fatigue, nasal congestion, and weight increase. Iloperidone should be titrated slowly over a 7-day interval to avoid the potential for orthostatic hypotension. Product labeling includes a black box warning against the use of iloperidone in dementia-related psychosis and precautions regarding QT interval prolongation.

Conclusions:

Iloperidone is an effective treatment for the symptoms of acute schizophrenia in adults. Additional studies are needed to assess comparative effectiveness with other pharmacologic treatments of schizophrenia, long-term efficacy, and long-term safety.

ACS chemical neuroscience molecule spotlight on Fanapt

The new mixed dopamaine D(2)/serotonin 5-HT(2A) antagonist, Fanapt (iloperidone), was approved by the FDA on May 6th, 2009 for the treatment of schizophrenia in adults.

Iloperidone for the treatment of schizophrenia

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, and safety data of iloperidone for the treatment of schizophrenia.

DATA SOURCES

Data were selected by searching Pre-MEDLINE, MEDLINE, and International Pharmaceutical Abstracts (1966-January 2010). Abstracts, scientific posters, and unpublished data provided by the manufacturer in the English language were also assessed.

STUDY SELECTION AND DATA EXTRACTION

All published data including pharmacologic, pharmacokinetic, pharmacodynamic, and clinical studies related to iloperidone were considered for inclusion. Selected studies included randomized controlled trials, abstracts, and posters presented at national scientific meetings providing pertinent data.

DATA SYNTHESIS

Iloperidone is a benzisoxazole phenylethanone with a higher affinity for serotonin-2a than dopamine-2 receptors. The recommended therapeutic total daily dose is 12-24 mg divided in 2 doses titrated over 1 week to avoid orthostasis. Acute, 6-week, randomized, placebo-controlled, and active-controlled studies demonstrated iloperidone's efficacy in reducing psychotic symptoms according to changes in the total positive and negative symptom scale (PANSS-T) score from baseline. A long-term maintenance trial demonstrated similar efficacy with haloperidol in preventing time to relapse. Pharmacogenomic studies reported possible single nucleotide polymorphisms related to QT interval prolongation and efficacy with iloperidone. Common adverse effects included dizziness, dry mouth, and sustained orthostasis occurring more frequently with higher doses. Weight gain is possible at any dose. Additionally, studies showed that QTc interval prolongation may be dose related. The incidence of extrapyramidal symptoms appears to be low across all dosage ranges; however, akathisia may be more frequent with higher doses.

CONCLUSIONS

Iloperidone demonstrated efficacy in acute exacerbations and long-term maintenance in adults with schizophrenia. Caution may be warranted in elderly patients and patients with cardiac disease, due to orthostasis. Further studies regarding pharmacogenomic testing related to the drug's efficacy and tolerability are needed to justify its routine use in practice.

New atypical antipsychotics for schizophrenia: iloperidone

The optimal treatment of schizophrenia poses a challenge to develop more effective treatments and safer drugs, to overcome poor compliance, discontinuation and frequent switching with available antipsychotics. Iloperidone is a new dopamine type 2/serotonin type 2A (D(2)/5-HT(2A)) antagonist structurally related to risperidone, expected to give better efficacy with less extrapyramidal symptoms than D(2) receptor antagonist antipsychotics. In double-blind phase III trials iloperidone reduced the symptoms of schizophrenia at oral doses from 12 to 24 mg. It was more effective than placebo in reducing positive and negative syndrome total score and Brief Psychiatric Rating scale scores; it was as effective as haloperidol and risperidone in post-hoc analysis. Its long-term efficacy was equivalent to that of haloperidol. The most common adverse events were dizziness, dry mouth, dyspepsia and somnolence, with few extrapyramidal symptoms and metabolic changes in short- and long-term studies in adults. Akathisia was rare, but prolongation of the corrected QT (QTc) interval was comparable to haloperidol and ziprasidone, which is of particular concern. Further comparative studies are needed to clarify the benefit/risk profile of iloperidone and its role in the treatment of schizophrenia.

Iloperidone: in schizophrenia

Iloperidone is an atypical antipsychotic that is approved for the treatment of adult patients with schizophrenia. In several large (n > 570 per trial), 4- or 6-week, double-blind, multinational, multicentre trials in adult patients with schizophrenia, recommended target dosages of oral iloperidone (6-12 mg twice daily) generally showed better efficacy than placebo, in terms of improvements in Positive and Negative Syndrome Scale (PANSS) total scores or Brief Psychiatric Rating Scale (BPRS) scores (primary endpoints) and also for most secondary endpoints, including PANSS subscale scores. In addition, pharmacogenomic studies identified single nucleotide polymorphisms (SNPs) that were associated with an enhanced response to iloperidone during acute treatment of schizophrenia. More limited data also support the role of these SNPs in enhancing responses to iloperidone during longer-term treatment. In a pooled analysis of three 52-week, double-blind, multinational, multicentre trials (n = 473), iloperidone treatment was shown to be equivalent to that with haloperidol, based on Kaplan-Meier estimates of the time to relapse (primary endpoint). Iloperidone was generally well tolerated and was associated with few extrapyramidal symptoms or changes in metabolic parameters in short- and longer-term clinical trials in adult patients with schizophrenia.

Iloperidone for schizophrenia: a review of the efficacy and safety profile for this newly commercialised second-generation antipsychotic

OBJECTIVE

The aim of the study was to describe the efficacy and safety of iloperidone for the treatment of schizophrenia.

DATA SOURCES

The pivotal registration trials were accessed by querying http://www.pubmed.gov, http://www.fda.gov and http://www.clinicaltrials.gov for the search term 'iloperidone'.

STUDY SELECTION

Four published primary reports of phase III studies were identified as well as preclinical animal and receptor affinity studies that describe potential mechanisms of action and pharmacogenomic studies that identify potential genetic biomarkers for efficacy and tolerability. Product labelling provided additional data.

DATA EXTRACTION

Descriptions of the principal results and calculation of number needed to treat (NNT) and number needed to harm (NNH) for relevant dichotomous outcomes were extracted from the study reports. Additional safety outcomes subject to NNH analysis were obtained from product labelling.

DATA SYNTHESIS

Iloperidone is a second-generation antipsychotic agent indicated for the acute treatment of schizophrenia in adults. Iloperidone has been evaluated in several double-blind placebo-controlled clinical trials. The oral formulation has demonstrated efficacy in reducing the symptoms of acute schizophrenia at fixed daily doses ranging from 12 to 24 mg. Data reported for categorical definitions of response using the Positive and Negative Syndrome Scale were limited to one study and specifically to rates of achieving a > or = 20% decrease in the positive subscale from baseline; significantly more patients receiving iloperidone 24 mg/day (72%) than placebo (52%) met this criterion, yielding a NNT of five. Iloperidone should be titrated slowly to avoid orthostatic hypotension, potentially delaying the achievement of a therapeutic dose level. There appears to be a dose relationship for adverse events such as dizziness, somnolence and dry mouth; for example NNH vs. placebo for somnolence was 25 for iloperidone 10-16 mg/day and 10 for 20-24 mg/day. There is a possibility of a therapeutic dose response as well. Iloperidone is essentially free of extra-pyramidal side effects. Iloperidone is associated with weight gain comparable with risperidone. Long-term double-blind maintenance studies have demonstrated iloperidone's non-inferiority to haloperidol for relapse prevention. Product labelling includes a warning about the potential for QT interval prolongation. At present there are no efficacy studies available that are powered to directly compare iloperidone with other second-generation antipsychotics. The development of a depot formulation of iloperidone as well as efforts to identify genetic biomarkers for prediction of both efficacy and tolerability are in progress.

CONCLUSIONS

Aside from paliperidone, iloperidone is the first new second-generation antipsychotic to be commercialised in the USA since 2002. From the limited registration data, iloperidone appears to be relatively well tolerated once titrated to a therapeutic level and can be a useful option to consider. The development of a depot formulation and potential for genetic biomarkers may make this agent compelling. Further comparisons with other available agents among patients with schizophrenia in the 'real world' are needed.

Clinical and pharmacogenetic studies of iloperidone

Antipsychotic drugs have become the mainstay treatment of schizophrenia. However, patients who receive antipsychotic treatment differ with respect to treatment response and adverse events. The problem of antipsychotic response variability has stimulated further search for agents with improved effectiveness and tolerability. Equally intense is the search for novel ways of using DNA information to personalize treatment with antipsychotic drugs. Iloperidone is an investigational, atypical antipsychotic drug of the serotonin/dopamine type. The US FDA is currently reviewing the new drug application for an oral formulation of iloperidone for the treatment of schizophrenia. Data from 35 clinical trials and approximately 3000 patients treated with iloperidone were included in the new drug application submission, as well as data from pharmacogenetic studies of iloperidone. Given the emerging role of pharmacogenetics, knowledge of genetic biomarkers of iloperidone response could lead to personalized medicine.

Iloperidone: a new benzisoxazole atypical antipsychotic drug. Is it novel enough to impact the crowded atypical antipsychotic market?

Iloperidone is a new-generation atypical antipsychotic agent, acting as a serotonin/dopamine (5-HT(2A)/D(2)) antagonist, under development by Vanda Pharmaceuticals for the treatment of schizophrenia, bipolar disorder and other psychiatric conditions. Chemically, iloperidone is a benzisoxazole, like risperidone, and shows a multiple receptor binding profile, sharing this feature with the other atypical antipsychotic agents. Administered orally, the drug is highly bound to plasma proteins and extensively metabolised. Several clinical trials have been carried out, to check efficacy, safety and side effects. In order to introduce iloperidone as an agent for the treatment of schizophrenia, a short overview of the disease and of the most important antipsychotic drugs available or under development will be reported. Iloperidone pharmacokinetics and pharmacodynamics are presented herein, together with an evaluation of clinical safety and efficacy results.

Developments in the pharmacological treatment of schizophrenia

Schizophrenia is, at once, a biological disease, a neuropsychological disorder and a dysfunction of social interactions. This presents clinicians with a series of problems with regards to therapy. In the first section of this article, some of the clinical challenges that face those attempting to develop new drugs, are summarised. Several potential pharmacological therapeutic targets that have been, and are continuing to be used, in the development of new antipsychotic drugs, are then considered. This is followed by an outline of the pharmacological and clinical profiles of some of the newer generation antipsychotics, as well as investigational drugs in the pipeline for schizophrenia. Finally, the implications of the introduction of these new drugs for the management of schizophrenia, are discussed.

Frequency of Extrapyramidal Adverse Reactions in Schizophrenic Outpatients Treated with Risperidone, Olanzapine, Quetiapine or Haloperidol : Results of the EIRE Study

OBJECTIVE

The EIRE (Estudio de Investigaciön de Resultados en Esquizofrenia - Outcomes Research Study in Schizophrenia) study was initiated in order to assess the frequency of adverse reactions [extrapyramidal symptoms (EPS), hyperprolactinaemia, sexual dysfunction and weight gain] caused by atypical antipsychotics and haloperidol in patients with schizophrenia during routine treatment in clinical practice. This paper presents the results of the assessment of extrapyramidal adverse reactions.

PATIENTS AND STUDY DESIGN

Outpatients diagnosed with schizophrenia according to the Diagnostic and Statistical Manual of mental disorders, 4th edition (DSM-IV), criteria and receiving a single antipsychotic (risperidone, olanzapine, quetiapine or haloperidol) for at least 4 weeks were consecutively recruited. In this cross-sectional and non-interventional study data were collected in a single visit; this included demographic and clinical characteristics, current antipsychotic and concomitant treatment, and data on several adverse effects listed in a modified version of the UKU (Udvalg for Kliniske Undersogelser - Committee on Clinical Investigations) scale. For paired comparisons of the frequency of adverse reactions between treatments the Chi-squared (χ²) test was used. For estimation of the risk of a given adverse reaction with a given treatment a logistic regression method was used.

RESULTS

636 evaluable patients (of 669 recruited) were assessed. The frequency of EPS with haloperidol (78.3% of the cases) was higher than with risperidone (55.1%), quetiapine (39.5%) and olanzapine (35.8%) [χ²: p < 0.05], and the difference between risperidone and olanzapine was also statistically significant (χ²: p < 0.05). Very similar results were obtained in the individualised analysis of the items as regards the occurrence of akathisia, which was also more frequent in the haloperidol (36.8%) and risperidone (19.7%) groups than in the olanzapine (11.4%) and quetiapine (2.6%) groups (χ²: p < 0.05). Olanzapine, quetiapine and risperidone also showed a lower risk of EPS than haloperidol when adjusting by dose.

CONCLUSION

Our results suggest that the atypical antipsychotics studied are less likely to induce extrapyramidal adverse reactions compared with haloperidol in stabilised patients, although these reactions are still common.

An assessment of iloperidone for the treatment of schizophrenia

Iloperidone (Novartis' Zomariltrade mark) is an atypical antipsychotic agent for the treatment of schizophrenia. Current trends in the treatment of schizophrenia indicate that some atypical antipsychotics are being recommended as first-line therapy. Atypical antipsychotics, in addition to being dopamine (D) receptor antagonists, are all relatively potent serotonin (5-HT) receptor antagonists and are less likely than conventional dopamine antagonists to induce movement disorders. However, all of these agents differ in their receptor profiles and clinical profiles. Iloperidone, a benzisoxazole, is a mixed 5-HT(2A)/D(2)antagonist. Iloperidone was found to be more potent than its analogues when compared with haloperidol in antagonising climbing behaviour in mice. Iloperidone is extensively metabolised and the main circulating metabolite is reduced iloperidone. In patients treated with iloperidone, a low incidence of extrapyramidal symptoms and weight gain has been shown. Data from Phase II trials demonstrated efficacy in patients at doses of 8 mg/day and tolerability was good up to 32 mg/day. Phase III prospective, double-blind, randomised trials with iloperidone are in progress under the ZEUS (Zomariltrade mark Efficacy Utility and Safety) programme involving 3300 patients. Iloperidone, with a balance of activity at the dopaminergic and serotonergic receptors, has obvious advantages over clozapine and olanzapine, both of which have a similar receptor profile as they favour serotonergic over dopamine receptors. Iloperidone is likely to reach the market in 2001 and has favourable prospects in the atypical antipsychotic market for schizophrenia, which is expanding from US$ 1.5 billion in 2000 to US$ 3 billion in 2005.

Biotransformation of post-clozapine antipsychotics: pharmacological implications

The need to develop new antipsychotics that have fewer motor adverse effects and offer better treatment of negative symptoms has led to a new generation of drugs. Most of these drugs undergo extensive first-pass metabolism and are cleared almost exclusively by metabolism, except for amisulpride whose clearance is largely due to urinary excretion. Risperidone has metabolic routes in common with ziprasidone but shows differences in regard to other main pathways: the benzisoxazole moiety of risperidone is oxidised by cytochrome P450 (CYP) 2D6 to the active 9-hydroxyrisperidone, whereas the benzisothiazole of ziprasidone is primarily oxidised by CYP3A4, yielding sulfoxide and sulfone derivatives with low affinity for target receptors in vitro. Olanzapine, quetiapine and zotepine also have some common metabolic features. However, for the thienobenzodiazepine olanzapine a main metabolic route is direct conjugation at the benzodiazepine nucleus, whereas for the dibenzothiazepine quetiapine and the dibenzothiepine zotepine it is CYP3A4-mediated oxidation, leading to sulfoxidation, hydroxylation and dealkylation for quetiapine, but N-demethylation to the active nor-derivative for zotepine. Although the promising benzisoxazole (iloperidone) and benzisothiazole (perospirone) antipsychotics share some metabolic routes with the structurally related available drugs, they too have pharmacologically relevant compound-specific pathways. For some of the new antipsychotics we know the isoenzymes involved in their main metabolic pathways and the endogenous and exogenous factors that, by affecting enzyme activity, can potentially modify steady-state concentrations of the parent drug or its metabolite(s), but we know very little about others (e.g. amisulpride isomers, nemonapride). For yet others, information is scarce about the activity of the main metabolites and whether and how these contribute to the effect of the parent drug. Aging reduces the clearance of most antipsychotics, except amisulpride (which requires further evaluation) and ziprasidone. Liver impairment has little or no effect on the pharmacokinetics of olanzapine, quetiapine, risperidone (and 9-hydroxy-risperidone) and ziprasidone, but information is lacking for amisulpride. Renal impairment significantly reduces the clearance and prolongs the elimination half-life of amisulpride and risperidone. Again, studies are still not available for some drugs (zotepine) and have focused on the parent drug for others (olanzapine, quetiapine, ziprasidone) despite the fact that renal impairment would be expected to lower the clearance of more polar metabolites. Addressing these issues may assist clinicians in the design of safe and effective regimens for this group of drugs, and in selecting the best agent for each specific population.

Iloperidone binding to human and rat dopamine and 5-HT receptors

Iloperidone (HP 873; 1-[4-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]propoxy] -3- methoxyphenyl]ethanone) is a compound currently in clinical trials for the treatment of schizophrenia. Iloperidone displays affinity for dopamine D2 receptors and for 5-HT2A receptors and has a variety of in vivo activities suggestive of an atypical antipsychotic. Here we present an examination of the affinity of iloperidone to a variety of human and rat homologs of dopamine and 5-HT receptor subtypes. We employed receptor binding assays using membranes from cells stably expressing human dopamine D1, D2S, D2L, D3, D4 and D5 and 5-HT2A and 5-HT2C receptors and rat 5-HT6 and 5-HT7 receptors. Iloperidone displayed higher affinity for the dopamine D3 receptor (Ki = 7.1 nM) than for the dopamine D4 receptor (Ki = 25 nM). Iloperidone displayed high affinity for the 5-HT6 and 5-HT7 receptors (Ki = 42.7 and 21.6 nM, respectively), and was found to have higher affinity for the 5-HT2A (Ki = 5.6 nM) than for the 5-HT2C receptor (Ki = 42.8 nM). The potential implications of this receptor binding profile are discussed in comparison with data for other antipsychotic compounds.