Paliperidone extended-release: a review of efficacy and tolerability in schizophrenia, schizoaffective disorder and bipolar mania

Recent Advances in representative small-molecule DRD2 inhibitors: Synthetic Routes and clinical applications

The dopamine D2 receptor (DRD2) represents a pivotal target for therapeutic intervention in the treatment of neuropsychiatric disorders, including schizophrenia, bipolar disorder, and Parkinson's disease. The successful discovery of numerous effective DRD2 inhibitors has led to their clinical application and ongoing evaluation in various clinical trials. This review explores the synthetic approaches and clinical applications of prototypical small-molecule DRD2 inhibitors that have received approval or are currently undergoing clinical trials, highlighting their therapeutic potential and challenges. The synthesis of these inhibitors employs various chemical strategies, including modifications of phenothiazine and butyrophenone structures, which have yielded significant antipsychotic agents like chlorpromazine and haloperidol. Additionally, newer classes of inhibitors, such as aripiprazole, exhibit partial agonist activity at DRD2, offering a unique therapeutic profile. Clinically, DRD2 inhibitors demonstrate efficacy in managing positive symptoms of schizophrenia, manic episodes in bipolar disorder, and dopaminergic imbalance in Parkinson's disease. However, the emergence of adverse effects, including tardive dyskinesia, extrapyramidal symptoms and metabolic syndrome, presents substantial challenges. Advances in the development of second-generation antipsychotics aim to balance efficacy with a better side effect profile by targeting additional neurotransmitter receptors. This review aims to deliver an overview of the synthesis and clinical applications of representative small-molecule DRD2 inhibitors across various clinical phases, thereby offering strategic insights for the advancement of DRD2 inhibitor development.

Korean Medication Algorithm for Schizophrenia 2019, Second Revision: Treatment of Psychotic Symptoms

Objective

In 2001, the Korean College of Neuropsychopharmacology and the Korean Society for Schizophrenia Research developed the Korean Medication Algorithm Project for Schizophrenia (KMAP-SPR 2001, revised 2006) through a consensus of expert opinion. The present study was carried out to support the second revision of the KMAP-SPR.

Methods

Based on clinical guidelines and studies on the treatment of psychotic symptoms in schizophrenia, the Executive committee completed a draft of KMAP-SPR 2019. To obtain an expert consensus, a Review committee of 100 Korean psychiatrists was formed and 69 responded to a 30-item questionnaire. Based on their responses, the KMAP-SPR 2019 was finalized.

Results

The revised schizophrenia algorithm now consists of 5 stages. At Stage 1, monotherapy with atypical antipsychotics was recommended by expert reviewers as the first-line strategy. At Stage 2, most reviewers recommended the use of typical or atypical antipsychotic drugs not used at Stage 1. At Stage 3, many reviewers agreed with the administration of clozapine. At Stage 4, a combination of clozapine and other agents such as antipsychotics, mood stabilizers, antidepressants, or electroconvulsive therapy was recommended. At Stage 5, most reviewers recommended combined treatment with an antipsychotic other than clozapine; and a mood stabilizer, antidepressant, or electroconvulsive therapy. At any stage, prescribing long-acting injectable antipsychotics at the discretion of the clinician was recommended.

Conclusion

Compared with previous versions, the KMAP-SPR 2019 now recommends using clozapine earlier in treatment-refractory schizophrenia. In addition, the use of long-acting injectable antipsychotics is now considered to be available at any stage.

Rats and rabbits as pharmacokinetic screening tools for long acting intramuscular depots: case study with paliperidone palmitate suspension

Development of prodrug of 9-hydroxyrisperidone (paliperidone) long-acting intramuscular injection has enabled delivery over four-week time period with improved compliance. The key aim of this work was to establish a reliable preclinical model which may potentially serve as a screening tool for judging the pharmacokinetics of paliperidone formulation(s) prior to human clinical work. Sparse sampling composite study was used in rats, (Wistar/Sprague-Dawley (SD; n = 10)) and a serial blood sampling study design was used in rabbits (n = 4). Animals received intramuscular injection of paliperidone palmitate in the thigh muscle at dose of 16 (rats) and 4.5 mg/kg (rabbits). Samples were drawn in rats (retro-orbital sinus) and rabbits (central ear artery) and were analysed for paliperidone using liquid chromatography-mass spectrometry/ mass spectrometry (LC-MS/MS) assay. The plasma data was subjected to pharmacokinetic analysis. Following intramuscular injection of depot formulation in Wistar/SD rats and rabbits, absorption of paliperidone was slow and gradual with median value of time to reach maximum concentration (T_max) occurring on day 7. The exposures (i.e. area under the curve (AUC; 0-28) days) were 18,597, 21,865 and 18,120 ng.h/mL, in Wistar, SD and rabbits, respectively. The clearance was slow and supported long half-life (8-10 days). Either one of the two models can serve as a research tool for establishing pharmacokinetics of paliperidone formulation(s).

A critical appraisal of paliperidone long-acting injection in the treatment of schizoaffective disorder

Schizoaffective disorder (SCA) is a chronic and disabling mental illness that presents with mixed symptoms of schizophrenia and affective disorders. SCA is recognized as a discrete disorder, but with greater heterogeneity and symptom overlap, leading to difficulty and delay in diagnosis. Although the overall prognosis is intermediate between schizophrenia and mood disorders, SCA is associated with higher rates of suicide and hospitalization than schizophrenia. No treatment guidelines exist for SCA, and treatment is frequently complex, involving off-label use and polypharmacy (typically combinations of antipsychotics, mood stabilizers, and antidepressants). Oral paliperidone extended-release was the first agent to be approved for the treatment of SCA. As in schizophrenia and bipolar disorder, adherence to oral medications is poor, further contributing to suboptimal outcomes. The use of an antipsychotic in a long-acting injection (LAI) addresses adherence issues, thus potentially reducing relapse. Paliperidone palmitate represents the LAI formulation of paliperidone. In a long-term, double-blind, randomized, controlled trial of adult patients (n=334; intent-to-treat [ITT]) with SCA, paliperidone long-acting injection (PLAI) significantly delayed risk of relapse compared to placebo (hazard ratio 2.49, 95% confidence interval, 1.55–3.99; P<0.001). This study demonstrated the efficacy and safety of PLAI when used as either monotherapy or adjunctive therapy for the maintenance treatment of SCA. The results are consistent with a similarly designed study conducted in patients with schizophrenia, which suggests a benefit in the long-term control of not only psychotic but also affective symptoms. No new safety signals were observed. When used in monotherapy, PLAI simplifies treatment by reducing complex pharmacotherapy and obviating the necessity for daily oral medications. PLAI is the second agent, and the first LAI, to be approved for the treatment of SCA; as an LAI formulation, there is the advantage of improved adherence and simplified treatment in the long-term management of SCA.

Safety and efficacy of paliperidone extended-release in Chinese patients with schizophrenia: a 24-week, open-label extension of a randomized, double-blind, placebo-controlled study

OBJECTIVES

The long-term safety, tolerability, and efficacy of paliperidone extended-release (ER) were evaluated in Chinese patients with schizophrenia.

METHODS

Patients (aged ≥18 years) with schizophrenia (Diagnostic and Statistical Manual of Mental Disorders, 4th edition criteria) who had completed run-in (8-week), stabilization (6-week), and double-blind (DB) phases (variable) of a phase-3, placebo-controlled study entered this 24-week, open-label extension (OLE) study. These patients, who had either experienced a relapse or remained relapse-free through DB phase of the study, were treated with flexible-dose paliperidone-ER (3-12 mg/day) during the OLE phase. Major safety evaluations included treatment-emergent adverse events (TEAEs) and extrapyramidal symptoms. Efficacy endpoints included changes in Positive and Negative Syndrome Scale total score, Clinical Global Impression-Severity scale, and Personal and Social Performance scale from OLE baseline to OLE endpoint.

RESULTS

Out of 106 patients who entered the OLE phase (placebo: 59, paliperidone-ER: 47), a total of 85 (80%) completed it. Thirty-five (33%) patients experienced at least one TEAE; most common were akathisia, somnolence, nasopharyngitis, and constipation (3.8% each). Serious TEAEs were noted in two patients (completed suicide; schizophrenia worsening). No TEAEs with an onset during the OLE phase led to discontinuation. Extrapyramidal symptoms related-TEAEs were reported in eight (7.5%) patients. Mean (standard deviation) changes in Positive and Negative Syndrome Scale total scores (-10.4 [13.2]), Clinical Global Impression-Severity scores (-0.6 [0.96]) and Personal and Social Performance scores (7.4 [13.2]) from OLE baseline to OLE endpoint showed patients who had been treated with placebo during the DB phase experienced more pronounced improvements.

CONCLUSION

In this OLE study, flexibly dosed paliperidone-ER (3-12 mg/day) was tolerable and efficacious in Chinese patients with schizophrenia.

A review of paliperidone palmitate

Risperidone long-acting injection (RLAI) was the first second-generation antipsychotic available as a long-acting injection. Paliperidone (9-hydroxyrisperidone) is the active metabolite of risperidone, introduced initially as an extended release oral (ORal Osmotic System, OROS®, Alza Corporation) formulation (Invega®, Janssen). Paliperidone long-acting injection (PLAI) has now been developed as a suspension of paliperidone palmitate nanocrystals in an aqueous formulation (Invega Sustenna®, Xeplion®), administered monthly by intramuscular injection (deltoid or gluteal). Doses of PLAI can be expressed either in milligram equivalents (mg eq) of paliperidone palmitate or in milligrams of the active fraction of paliperidone. The recommended initiation regimen of 150 mg eq (234 mg) on day 1 and 100 mg eq (156 mg) on day 8 (both administered in the deltoid) achieves therapeutic blood levels rapidly and without the necessity of oral supplementation. No refrigeration or reconstitution prior to administration is required. PLAI has been shown in to be effective in controlling the acute symptoms of schizophrenia as well as delaying time to relapse. Safety and tolerability are comparable to RLAI with no new safety signals. Thus, PLAI may represent the rational development of RLAI with greater ease of use.

A case of paliperidone-palmitate-induced tardive dyskinesia

OBJECTIVES

This is one of the first cases reported in the literature of paliperidone-palmitate-induced prolonged dyskinesia.

METHOD

Case report.

RESULTS

We report the case of a 49-year-old woman with paranoid schizophrenia who developed orofacial dyskinesia some 4 months after the commencement of paliperidone long-acting injection.

CONCLUSION

This case serves as a clinical reminder that dyskinesia can occur with all antipsychotic medications.

Paliperidone extended release: in adolescents with schizophrenia

Paliperidone, the major active metabolite of risperidone, is an atypical antipsychotic agent formulated as an extended-release (ER) tablet suitable for once-daily oral administration. Paliperidone ER is approved for the treatment of adolescents aged 12-17 years with schizophrenia in the US (the focus of this review). It is also approved for the treatment of adults with schizophrenia or schizoaffective disorder. Paliperidone ER has shown efficacy in the treatment of patients aged 12-17 years with acutely symptomatic schizophrenia in a randomized, double-blind, parallel-group, placebo-controlled, multicenter, 6-week trial. The primary endpoint was the change from baseline in Positive and Negative Syndrome Scale (PANSS) total score to day 43 or the final assessment point post-baseline. Patients with a PANSS total score of 60-120 received one of three weight-based, fixed once-daily doses of paliperidone ER (patients weighing 29 kg to <51 kg: 1.5 mg [low-dose], 3 mg [medium], or 6 mg [high]; patients weighing ≥51 kg: 1.5 mg [low], 6 mg [medium], or 12 mg [high]), or placebo. Compared with placebo, significant improvements in mean PANSS total scores were reported for the medium-dose (3-6 mg) paliperidone ER treatment groups. There were no significant differences in mean PANSS total scores between the recipients of low-dose or high-dose paliperidone ER versus placebo. Mean PANSS total scores in the actual dose treatment groups (regardless of weight) decreased from baseline (i.e. improved) and were significantly lower for the 3, 6, and 12 mg groups than for the placebo group. Treatment-emergent adverse events were dose related in adolescents with schizophrenia who received weight-based fixed doses of paliperidone ER.

Oral-paliperidone-induced tardive dyskinesia: a case report

OBJECTIVES

Tardive dyskinesia (TD) is generally considered the most severe extrapyramidal sequelae of antipsychotic treatments.

METHOD

Case report.

RESULTS

We present a 20-year-old woman with previous treatment of risperidone 6-7 mg daily for approximately 4 years. She developed TD 2 years later after switching to paliperidone 9 mg daily. To the best of our knowledge, she is the first case report of having direct paliperidone-induced TD. Immediate treatments including paliperidone dose reduction to 6 mg daily, clonazepam 1.5 mg daily and trihexyphenidyl 2 mg daily were performed for 1 month, and her symptoms were relieved eventually after switching to clozapine 75 mg daily.

CONCLUSION

Although second-generation antipsychotics such as paliperidone are considered to have a lowered risk of developing TD, this case could bring awareness to clinicians of the possibility of TD with the use of any antipsychotics.

The role of paliperidone extended release for the treatment of bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a chronic, relapsing, episodic mental illness associated with other psychiatric comorbidities. There is a substantial economic burden with BD, which makes it challenging to treat. The aim of this review is to evaluate the pharmacology, clinical efficacy, and safety data related to paliperidone extended release (ER) for the treatment of BD.

METHODS

A literature search was performed from January 1966 through January 2012 using PreMEDLINE, MEDLINE, EMBASE, IPA, and ClinicalTrials.gov to identify articles in English regarding the pharmacology, clinical efficacy, and safety of paliperidone ER in acute mania or mixed episodes or in the maintenance treatment of BD I.

RESULTS

There are currently three published studies relating to the use of paliperidone ER for the treatment of BD. Two of these evaluated paliperidone ER as monotherapy for acute mania, while the other assessed its role as adjunct with a mood stabilizer.

CONCLUSION

According to the limited available evidence, paliperidone at higher doses of ER 9-12 mg/day may be a safe and efficacious treatment option for acute episodes of mania in BD. A once-daily dose formulation may improve patient adherence to treatment; however, the cost of paliperidone ER, which is higher than that of generically available second-generation antipsychotics (such as olanzapine and risperidone), and a lack of alternative dosage forms (ie, liquid, intramuscular) compared with other agents may limit its usefulness in the treatment of BD. The role of paliperidone ER as an adjunctive agent or for long-term use requires further investigation.

Oral paliperidone: a review of its use in the management of schizoaffective disorder

Oral paliperidone extended or prolonged release (Invega®) is an atypical antipsychotic, and is the first agent approved for the treatment of schizoaffective disorder. Paliperidone (or 9-hydroxyrisperidone) is the major active metabolite of the well known atypical antipsychotic risperidone, and its mechanism of action is thought to be the antagonism of dopamine D(2) and serotonin 5-HT(2A) receptors. The clinical efficacy of paliperidone was demonstrated in two 6-week, randomized, double-blind, placebo-controlled, multicentre trials in patients with schizoaffective disorder. One trial was flexible dose in design (3-12 mg/day) and the other was fixed dose in design (3-6 and 9-12 mg/day). Compared with placebo, the change from baseline at study end in the Positive and Negative Syndrome Scale (PANSS) total score (primary endpoint) was significantly greater with paliperidone 3-12 mg/day in one trial and with 9-12 mg/day (but not 3-6 mg/day) in the other trial. However, pooled analyses reported a significantly greater change in PANSS total score across all paliperidone dosages than with placebo. Paliperidone was generally well tolerated in the 6-week trials, and no unexpected adverse events were reported. The most commonly reported treatment-emergent adverse events were headache, tremor, dizziness, insomnia, nausea, akathisia, dyspepsia, hypertonia, somnolence and sedation. Although long-term efficacy and tolerability data and comparisons with other antipsychotics are needed, paliperidone appears to be a useful agent for the short-term management of patients with schizoaffective disorder.

Safety and efficacy of paliperidone extended-release in acute and maintenance treatment of schizophrenia

Paliperidone, the major active metabolite of risperidone, is a second-generation antipsychotic that has been developed as an extended-release (ER) tablet formulation that minimizes peak-trough fluctuations in plasma concentrations, allowing once-daily administration and constant drug delivery. Paliperidone ER has demonstrated efficacy in the reduction of acute schizophrenia symptoms in 6-week, placebo-controlled, double-blind trials and clinical benefits were maintained in the longer-term according to extension studies of up to 52 weeks in duration. Compared with quetiapine, paliperidone ER was associated with a more rapid symptom improvement. In addition, it was more effective than placebo in the prevention of symptom recurrence. Paliperidone ER is generally well tolerated with a predictable adverse event profile. Like risperidone, it is associated with a dose-dependent risk of extrapyramidal symptoms and prolactin elevation. Short- and longer-term studies have indicated a low liability for paliperidone ER to cause metabolic (ie, weight gain, hyperglycaemia and lipid dysregulation) or cardiovascular adverse effects. Available safety data from elderly patients appear to be promising. Due to negligible hepatic biotransformation, paliperidone ER is unlikely to be involved in clinically significant metabolic drug-drug interactions. Additional active comparator trials evaluating efficacy, tolerability and cost-effectiveness are required to better define the role of paliperidone ER in the treatment of schizophrenia in relation to other currently available second-generation antipsychotics, particularly risperidone.