On the discovery and development of pimavanserin: a novel drug candidate for Parkinson's psychosis

Pharmacotherapy of schizophrenia: Mechanisms of antipsychotic accumulation, therapeutic action and failure

Schizophrenia is a multi-dimensional disorder with a complex and mostly unknown etiology, leading to a severe decline in life quality. Antipsychotic drugs (APDs) remain beneficial interventions in the treatment of the disorder, but vary significantly in binding profile, clinical effects and adverse reactions. The present review summarizes the main principles of APD mechanisms of action with a particular focus on recent findings in APD accumulation and its role in the therapeutic efficacy and treatment failure. High and low doses of APDs were shown to be effective in different dimensions of antipsychotic-like behaviour in rodent models. Efficacy of the APDs correlates with high dopamine D2 receptor occupancy, which occurs quickly after drug administration. However, onset and peak of action are delayed up to several days or weeks. APD accumulation via acidic trapping in synaptic vesicles is considered to underlie the time course of APD action. Use-dependent exocytosis, co-release with dopamine and serotonin and inhibition of ion channels impact on the neuronal transmission and determine effects of APDs. Disruption in accumulating properties leads to diminished APD effects. In addition, long-term APD administration at therapeutic doses leads to treatment failure both in animal models and in humans. APD failure was associated with treatment induced neuroadaptations, including a decline in extracellular dopamine levels, dopamine transporter upregulation, and altered neuronal firing. However, enhanced synaptic vesicle release has also been reported. APD loss of efficacy may be reversed through inhibition of the dopamine transporter or switching the administration regimen from continuous to intermittent. Thus, manipulating the accumulation properties of APDs, changes in the administration regimen and doses, or co-administration with dopamine transporter inhibitors may be considered to yield benefits in the development of new effective strategies in the treatment of schizophrenia.

5-HT2A and 5-HT2C receptors as potential targets for the treatment of nicotine use and dependence

Nicotine use and dependence, typically achieved through cigarette smoking, but increasingly through vape products, is the leading cause of preventable death today. Despite a recognition that many current smokers would like to quit, the success rate at doing so is low and indicative of the persistent nature of nicotine dependence and the high urge to relapse. There are currently three main forms of pharmacotherapy approved as aids to treat nicotine dependence: a variety of nicotine replacement products (NRT's), the mixed NA/DA reuptake inhibitor bupropion (Zyban®), and the preferential nicotinic α4β2 receptor agonist drug, varenicline (Chantix®); the latter being generally recognized to be the most effective. However, each of these approaches afford only limited efficacy, and various other pharmacological approaches are being explored. This chapter focusses on approaches targeted to the serotonin (5-HT) system, namely, selective serotonin reuptake inhibitors (SSRI's) which served a pioneer role in the investigation of serotoninergic modulators in human smoking cessation trials; and secondly drugs selectively interacting with the 5-HT2A and 5-HT2C receptor systems. From an efficacy perspective, measured as smoking abstinence, the 5-HT2A agonist psychedelics, namely psilocybin, seem to show the most promise; although as the article highlights, these findings are both preliminary and there are significant challenges to the route to approval, and therapeutic use of this class should they reach approval status. Additional avenues include 5-HT2C receptor agonists, which until recently was pioneered by lorcaserin, and 5-HT2A receptor antagonists represented by pimavanserin. Each of these approaches has distinct profiles across preclinical tests of nicotine dependence, and may have therapeutic potential. It is anticipated as diagnostic and predictive biomarkers emerge, they may provide opportunities for subject stratification and opportunities for personalizing smoking cessation treatment. The clinical assessment of SSRI, 5-HT2A and/or 5-HT2C receptor-based treatments may be best served by this process.

Spotlight on Pimavanserin Tartrate and Its Therapeutic Potential in the Treatment of Major Depressive Disorder: The Evidence to Date

Major depressive disorder (MDD) is widely prevalent and one of the leading causes of disability. Treatment outcomes remain suboptimal with 1 in 3 patients with MDD responding inadequately to commonly used antidepressants. Pimavanserin, an atypical antipsychotic that modulates serotonergic neurotransmission by selectively binding to serotonin receptor (2A and 2C) subtypes and without dopaminergic activity, may have the potential as an adjunctive treatment for MDD. In a phase 2 trial (n=203), addition of pimavanserin, as compared to placebo, to stable treatment with antidepressants was associated with greater reduction in 17-item Hamilton Depression Rating Scale score [HAMD, least square means (95% confidence interval) of -1.7 (-0.03, -3.37), p=0.039]. Furthermore, treatment with pimavanserin was associated with significantly greater improvement in specific symptoms associated with depression such as impaired sexual function, anxiety, sleepiness, and irritability. However, the availability of pimavanserin for clinical care of patients with MDD remains uncertain. Top-line results of phase 3 studies (n=298) that were announced by the sponsor found similar reductions in HAMD (mean baseline-to-week-5 reduction of 9.0 and 8.1, p=0.296) and rates of adverse events (58.1% and 54.7%) with addition of pimavanserin and placebo respectively to stable treatment with antidepressants. Given the potential benefit for specific symptoms such as impaired sexual function, anxiety and sleep/wakefulness disturbances, future studies that enrich for these symptoms may be needed to clarify the utility of adjunctive pimavanserin in treatment of patients with MDD.

Pimavanserin, a 5HT2A receptor inverse agonist, rapidly suppresses Aβ production and related pathology in a mouse model of Alzheimer's disease

Amyloid-β (Aβ) peptide aggregation into soluble oligomers and insoluble plaques is a precipitating event in the pathogenesis of Alzheimer's disease (AD). Given that synaptic activity can regulate Aβ generation, we postulated that 5HT_2A -Rs may regulate Aβ as well. We treated APP/PS1 transgenic mice with the selective 5HT_2A inverse agonists M100907 or Pimavanserin systemically and measured brain interstitial fluid (ISF) Aβ levels in real-time using in vivo microdialysis. Both compounds reduced ISF Aβ levels by almost 50% within hours, but had no effect on Aβ levels in 5HT_2A -R knock-out mice. The Aβ-lowering effects of Pimavanserin were blocked by extracellular-regulated kinase (ERK) and NMDA receptor inhibitors. Chronic administration of Pimavanserin by subcutaneous osmotic pump to aged APP/PS1 mice significantly reduced CSF Aβ levels and Aβ pathology and improved cognitive function in these mice. Pimavanserin is FDA-approved to treat Parkinson's disease psychosis, and also has been shown to reduce psychosis in a variety of other dementia subtypes including Alzheimer's disease. These data demonstrate that Pimavanserin may have disease-modifying benefits in addition to its efficacy against neuropsychiatric symptoms of Alzheimer's disease. Read the Editorial Highlight for this article on page 560.

Relevance of 5-HT2A Receptor Modulation of Pyramidal Cell Excitability for Dementia-Related Psychosis: Implications for Pharmacotherapy

Psychosis occurs across a wide variety of dementias with differing etiologies, including Alzheimer's dementia, Parkinson's dementia, Lewy body dementia, frontotemporal dementia, and vascular dementia. Pimavanserin, a selective serotonin 5-HT_2A receptor (5-HT_2AR) inverse agonist, has shown promising results in clinical trials by reducing the frequency and/or severity of hallucinations and delusions and the risk of relapse of these symptoms in patients with dementia-related psychosis. A literature review was conducted to identify mechanisms that explain the role of 5-HT_2ARs in both the etiology and treatment of dementia-related psychosis. This review revealed that most pathological changes commonly associated with neurodegenerative diseases cause one or more of the following events to occur: reduced synaptic contact of gamma aminobutyric acid (GABA)-ergic interneurons with glutamatergic pyramidal cells, reduced cortical innervation from subcortical structures, and altered 5-HT_2AR expression levels. Each of these events promotes increased pyramidal cell hyperexcitability and disruption of excitatory/inhibitory balance, facilitating emergence of psychotic behaviors. The brain regions affected by these pathological changes largely coincide with areas expressing high levels of 5-HT_2ARs. At the cellular level, 5-HT_2ARs are most highly expressed on cortical glutamatergic pyramidal cells, where they regulate pyramidal cell excitability. The common effects of different neurodegenerative diseases on pyramidal cell excitability together with the close anatomical and functional connection of 5-HT_2ARs to pyramidal cell excitability may explain why suppressing 5-HT_2AR activity could be an effective strategy to treat dementia-related psychosis.

An Open-Label, 8-Week Study of Safety and Efficacy of Pimavanserin Treatment in Adults with Parkinson's Disease and Depression

BACKGROUND

Many patients with Parkinson's disease (PD) experience depression.

OBJECTIVE

Evaluate pimavanserin treatment for depression in patients with PD.

METHODS

Pimavanserin was administered as monotherapy or adjunctive therapy to a selective serotonin reuptake inhibitor or serotonin/noradrenaline reuptake inhibitor in this 8-week, single-arm, open-label phase 2 study (NCT03482882). The primary endpoint was change from baseline to week 8 in Hamilton Depression Scale-17-item version (HAMD-17) score. Safety, including collection of adverse events and the Mini-Mental State Examination (MMSE) and Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS III) scores, was assessed in patients who received ≥1 pimavanserin dose.

RESULTS

Efficacy was evaluated in 45 patients (21 monotherapy, 24 adjunctive therapy). Mean (SE) baseline HAMD-17 was 19.2 (3.1). Change from baseline to week 8 (least squares [LS] mean [SE]) in the HAMD-17 was -10.8 (0.63) (95% CI, -12.0 to -9.5; p < 0.0001) with significant improvement seen at week 2 (p < 0.0001) and for both monotherapy (week 8, -11.2 [0.99]) and adjunctive therapy (week 8,-10.2 [0.78]). Most patients (60.0%) had ≥50% improvement at week 8, and 44.4% of patients reached remission (HAMD-17 score ≤7). Twenty-one of 47 patients experienced 42 treatment-emergent adverse events; the most common by system organ class were gastrointestinal (n = 7; 14.9%) and psychiatric (n = 7; 14.9%). No negative effects were observed on MMSE or MDS-UPDRS Part III.

CONCLUSION

In this 8-week, single-arm, open-label study, pimavanserin as monotherapy or adjunctive therapy was well tolerated and associated with early and sustained improvement of depressive symptoms in patients with PD.

Blinded SAPS-PD Assessment After 10 Weeks of Pimavanserin Treatment for Parkinson's Disease Psychosis

BACKGROUND

Parkinson's disease psychosis (PDP) is a common nonmotor symptom that affects up to 60% of patients. Pimavanserin, a selective 5-HT2A inverse agonist/antagonist, is approved for treating hallucinations and delusions associated with PDP.

OBJECTIVE

Evaluate the efficacy and tolerability of pimavanserin in an open-label extension (OLE) study.

METHODS

Patients completing a pivotal 6-week placebo-controlled trial (Core Study) could enroll in the OLE. All patients pimavanserin 34 mg once daily, blinded to previous treatment allocation. Prespecified blinded assessments at Week 4 were the Scale for the Assessment of Positive Symptoms (SAPS) PD version and SAPS H + D scales, Caregiver Burden Scale (CBS), and Clinical Global Impression (CGI) Improvement and Severity scales.

RESULTS

Of 171 who entered the OLE, 148 (87%) completed Week 4. Among patients who received placebo in the Core Study, mean (SD) change from OLE baseline to OLE Week 4 for the SAPS-PD was - 3.4 (6.3); p < 0.0001. Mean change from Core Study baseline to OLE Week 4 for SAPS-PD was similar among prior pimavanserin- and placebo-treated patients (-6.9 vs. -6.3). Improvement was similar with CGI-I, CGI-S, CBS, and SAPS-H + D in patients previously treated with placebo. Adverse events occurred in 92 (53.8%) patients during the 4-week OLE.

CONCLUSION

Improvements at OLE Week 4 from pretreatment baseline were similar with placebo and pimavanserin in the Core Study. The beneficial effects observed with pimavanserin in the 6-week Core Study were maintained for 4 weeks in the blinded OLE, supporting the durability of response with pimavanserin 34 mg for PDP over 10 weeks.

Up-to-date expert opinion on the safety of recently developed antipsychotics

Introduction There are several new and emerging antipsychotic medication strategies recently marketed or under clinical development for the treatment of several mental disorders. There is the need to provide an up-to-date overview on the safety of this new generation of antipsychotic medications, which includes also the third-generation antipsychotics (TGA). Areas covered The authors aimed at providing a synthesis of the most current evidence about the safety profile of the recently developed and/or marketed antipsychotics. Qualitative synthesis followed an electronic search made inquiring of the following databases: MEDLINE, Embase, PsycINFO, and the Cochrane Library from inception until March 2020, combining free terms and MESH headings for the topics of TGA and recently developed and/or marketed antipsychotics as following: ((safety OR adverse events OR side effects) AND ((brexpiprazole OR cariprazine OR inhaled loxapine OR lumateperone (ITI-007) OR lurasidone OR pimavanserin OR roluperidone (MIN-101) OR transdermal patch asenapine)). Expert opinion Overall, newer antipsychotics display a good safety profile, with a well-demonstrated lower metabolic liability compared to second-generation antipsychotics. Furthermore, TGA appear to specifically target negative symptomatology and improving cognitive domains. Abbreviations Aps=Antipsychotic Drugs; AEs = Adverse Effects; EPS = Extrapyramidal Symptoms; NMS = Neuroleptic malignant syndrome; D = Dopamine; K_i = Inhibitory Constant; 5-HT = Serotonin; ECG = Electrocardiogram; H = Histamine; M = Muscarinic; BMI = Body Mass Index.

Pimavanserin exhibits serotonin 5-HT2A receptor inverse agonism for Gαi1- and neutral antagonism for Gαq/11-proteins in human brain cortex

Pimavanserin is claimed as the first antipsychotic drug that shows selectivity for serotonin 5-HT₂ receptors (5-HT₂Rs) and lacks of affinity for dopamine D₂ receptors (D₂Rs). Cell-based functional assays suggest that pimavanserin and antipsychotics with D₂R/5-HT₂R affinity could act as inverse agonists of 5-HT_2ARs. However, there is not evidence of such pharmacological profile in native brain tissue. 5-HT_2ARs are able to engage both canonical G_αq/11- and non-canonical G_αi1-proteins. In the present study, the response to pimavanserin of the 5-HT_2AR coupling to G_αq/11- and G_αi1-proteins was measured in membranes of postmortem human prefrontal cortex by antibody-capture [³⁵S]GTPγS binding scintillation proximity assays. Pimavanserin promoted a concentration-dependant inhibition of the 5-HT_2AR coupling to G_αi1-proteins whereas the response of G_αq/11-proteins was unaltered, suggesting inverse agonism and neutral antagonism properties, respectively. The inhibition was abolished in the presence of the selective 5-HT_2AR antagonist MDL-11,939 and was absent in brain cortex of 5-HT_2AR knock-out mice when compared to respective 5-HT_2AR wild-type animals. In conclusion, the results demonstrate the existence of constitutive 5-HT_2AR activity in human brain for the signalling pathway mediated by G_αi1-proteins. Pimavanserin demonstrates 5-HT_2AR functional selectivity and exhibits inverse agonist profile towards G_αi1-proteins, which is considered the effector pathway promoting hallucinogenic responses. In contrast, pimavanserin behaves as neutral antagonist on the 5-HT_2AR coupling to the canonical G_αq/11-protein pathway. The results strengthen the relevance of inverse agonism as potential mechanism of antipsychotic activity. Moreover, the existence of functional selectivity of 5-HT_2ARs for different G_α-proteins could contribute to better design of 5-HT_2AR-related antipsychotic drugs.

The Use of Risperidone in Behavioral and Psychological Symptoms of Dementia: A Review of Pharmacology, Clinical Evidence, Regulatory Approvals, and Off-Label Use

Dementia represents a global health challenge due to the increase in elderly population worldwide. In addition to memory loss, dementia often results in severe behavioral and psychological changes where pharmacological treatments might be considered in addition to nonpharmacological strategies for optimal symptomatic control. Risperidone, the second oldest atypical antipsychotic, has been widely used off-label to treat behavioral and psychological symptoms of dementia (BPSD), including agitation, aggression, and psychosis. Several studies have indicated that risperidone offers a modest and statistically significant effectiveness in the clinical setting. However, in the past decade, safety concerns emerged due to increased risk for cerebrovascular adverse events and death following the use of risperidone in the elderly population. Clinical guidelines suggest that, in severe dementia where an older adult is threatening to harm himself or others, pharmacological treatments might be considered when nonpharmacological treatments fail. Risperidone was approved for BPSD in some countries (Australia, Canada, United Kingdom and New Zealand) but not in the United States. This article reviews risperidone’s pharmacological activity, clinical effectiveness and safety, marketing approval, and off-label use in BPSD.

Systematic Literature Review of Quetiapine for the Treatment of Psychosis in Patients With Parkinsonism

OBJECTIVE

The purpose of this article was to determine the efficacy and tolerability of quetiapine compared with placebo or other interventions for psychosis in parkinsonism.

METHODS

Participants with a diagnosis of parkinsonism participated in randomized controlled trials (RCTs) investigating the efficacy and tolerability of quetiapine for psychotic symptoms within a defined follow-up period. The authors conducted searches on PubMed, Cochrane Controlled Register of Trials, and EMBASE for articles published from January 1991 to October 2017. Study methodology and patient- and treatment-level data were independently extracted and summarized by using descriptive statistics. Studies underwent quality assessment for risk of bias.

RESULTS

A total of 17,615 unique records were identified, and seven RCTs (total N=241) met inclusion criteria. Five RCTs were placebo controlled, and two compared quetiapine against clozapine. The mean study duration was 12 weeks, and the mean daily quetiapine dose was 103 mg per day (range, 12.5-300 mg). In four of five placebo-controlled RCTs, quetiapine failed to demonstrate significant improvement of psychosis in parkinsonism compared with placebo. In two clozapine-comparator RCTs, quetiapine was better tolerated but no more effective than clozapine. Across all RCTs, the mean completion rates for quetiapine, clozapine, and placebo were 66%, 68.5%, and 66%, respectively. Quetiapine did not significantly worsen motor function.

CONCLUSIONS

The efficacy of quetiapine in RCTs for psychosis in parkinsonism is no better than that for placebo or clozapine. On the basis of novel data, clinicians should reevaluate traditional viewpoints on the benefits of quetiapine for psychosis in parkinsonism.

Pimavanserin: A Novel Antipsychotic With Potentials to Address an Unmet Need of Older Adults With Dementia-Related Psychosis

Dementia affects more than 40 million people worldwide. When it is accompanied by psychosis, symptom management is especially challenging. Although no drug has been approved by the US Food and Drug Administration (FDA) for psychosis in patients with dementia, atypical antipsychotics are used off-label in severe cases in patients who do not respond to non-pharmacological interventions. However, antipsychotic use in elderly patients with dementia-related psychosis (DRP) is associated with adverse reactions including motor function disorders, cognitive impairment, cerebrovascular events, and increased risk of death. In 2017, the US FDA granted breakthrough therapy designation to the new antipsychotic pimavanserin for the treatment of DRP. Topline result of the pivotal phase III HARMONY (NCT03325556) trial suggests that pimavanserin reduces the relapse of psychosis by 2.8-folds compared to placebo. This favorable result may open path for the potential approval of pimavanserin in DRP. In this review, we discuss the pharmacological activity, clinical efficacy and safety of pimavanserin as a novel atypical antipsychotic with potentials to address the unmet needs of older adults with DRP.

Management of Dementia-Related Psychosis, Agitation and Aggression: A Review of the Pharmacology and Clinical Effects of Potential Drug Candidates

Along with cognitive decline, 90% of patients with dementia experience behavioral and psychological symptoms of dementia, such as psychosis, aggression, agitation, and depression. Atypical antipsychotics are commonly prescribed off-label to manage certain symptoms, despite warnings from the regulatory agencies regarding the increased risk of mortality associated with their use in elderly patients. Moreover, these compounds display a limited clinical efficacy, mostly owing to the fact that they were developed to treat schizophrenia, a disease characterized by neurobiological deficits. Thus, to improve clinical efficacy, it has been suggested that patients with dementia should be treated with exclusively designed and developed drugs that interact with pharmacologically relevant targets. Within this context, numerous studies have suggested druggable targets that might achieve therapeutically acceptable pharmacological profiles. Based on this, several different drug candidates have been proposed that are being investigated in clinical trials for behavioral and psychological symptoms of dementia. We highlight the recent advances toward the development of therapeutic agents for dementia-related psychosis and agitation/aggression and discuss the relationship between the relevant biological targets and their etiology. In addition, we review the compounds that are in the early stage of development (discovery or preclinical phase) and those that are currently being investigated in clinical trials for dementia-related psychosis and agitation/aggression. We also discuss the mechanism of action of these compounds and their pharmacological utility in patients with dementia.

FDA Breakthrough Therapy Designation: Evaluating the Quality of the Evidence behind the Drug Approvals

The United States Food and Drug Administration (FDA) has created approval pathways and designations to accelerate access to medications indicated for serious or life-threatening conditions with limited treatment options. Implemented in 2012, the most recent of these is the breakthrough therapy designation (BTD). The purpose of this article was to review the evidence surrounding approval of medications with nononcology indications approved with the BTD designation from 2012 to 2016. Fifteen medications were identified for eight conditions, ranging from conditions that are relatively common, such as chronic hepatitis C infection, to those that are extremely rare, such as lysosomal acid lipase deficiency. The quality of evidence behind these approvals was highly heterogeneous. Much remains unknown about the safety and efficacy of many agents approved through the BTD. Health care professionals should be aware of these limitations to better educate patients and other providers appropriately.

Psychosis in neurodegenerative disorders: recent developments

PURPOSE OF REVIEW

This review presents the latest developments covered in the literature regarding psychosis in neurodegenerative disorders and discusses possible future research directions.

RECENT FINDINGS

Recent findings in the field of psychosis and neurodegenerative disorders revolve around four main themes. The first theme is the impact of sex on the expression of psychosis in neurodegenerative disorders. The second theme focuses on the relationship between psychosis and neurodegenerative disease biomarkers. The third concerns how psychotic symptoms in neurodegenerative disorders may share common mechanisms with other primary psychotic disorders such as schizophrenia. Finally, there have been some promising developments in the area of therapeutics to treat dementia-related psychosis involving both established and novel treatments.

SUMMARY

New findings in the field of neurodegeneration and psychosis parallel new directions in the field of neurodegeneration in general. More specifically, we have seen a shift in focus to issues highlighting the role of sex, biomarkers, translation to other disorders, and therapeutics.

Evaluation of the safety, tolerability, and efficacy of pimavanserin versus placebo in patients with Alzheimer's disease psychosis: a phase 2, randomised, placebo-controlled, double-blind study

BACKGROUND

Pimavanserin is a selective 5-HT_2A receptor inverse agonist and antagonist approved in the USA for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis. No safe or effective pharmacological treatment is approved for psychosis in patients with Alzheimer's disease. Therefore, we aimed to evaluate the safety, tolerability, and efficacy of pimavanserin versus placebo in patients with Alzheimer's disease psychosis.

METHODS

We did a phase 2, randomised, double-blind, placebo-controlled, single-centre (with multiple affiliated nursing home sites across the UK) study. We included participants of either sex who were aged 50 years or older with possible or probable Alzheimer's disease and psychotic symptoms including visual or auditory hallucinations, delusions, or both. Participants were randomly assigned (1:1) to 12 weeks of oral treatment with either pimavanserin (two 17 mg tablets daily) or placebo, with use of permuted block sizes of four and stratified by baseline Mini-Mental State Examination (MMSE) total score (<6 or ≥6) and Neuropsychiatric Inventory-Nursing Home version (NPI-NH) psychosis score (<12 or ≥12). Participants, caregivers, the study sponsor, and study personnel at the clinic site were masked to treatment assignment. The primary endpoint was mean change from baseline to week 6 in the NPI-NH psychosis score for pimavanserin versus placebo in the modified intention-to-treat population. Sustained benefit and safety of pimavanserin were assessed through week 12. This study is registered at ClinicalTrials.gov, number NCT02035553.

FINDINGS

Between Jan 16, 2014, and Oct 27, 2016, 345 participants across 133 nursing homes were screened, of whom 181 were randomly assigned treatment (n=90 pimavanserin and n=91 placebo). 178 participants were included in the modified intention-to-treat population. Mean total baseline NPI-NH psychosis scores were 9·5 (SD 4·8) for the pimavanserin group and 10·0 (5·6) for the placebo group. Mean change in the NPI-NH psychosis score at week 6 was -3·76 points (SE 0·65) for pimavanserin and -1·93 points (0·63) for placebo (mean difference -1·84 [95% CI -3·64 to -0·04], Cohen's d=-0·32; p=0·045). By week 12, no significant advantage for pimavanserin versus placebo was observed for the overall study population (treatment difference -0·51 [95% CI -2·23 to 1·21]; p=0·561). Common adverse events were falls (21 [23%] of 90 participants in the pimavanserin group vs 21 [23%] of 91 in the placebo group), urinary tract infections (20 [22%] vs 25 [28%]), and agitation (19 [21%] vs 13 [14%]). Eight (9%) participants on pimavanserin and 11 (12%) on placebo discontinued treatment because of adverse events. No detrimental effect was observed on cognition or motor function in either group.

INTERPRETATION

Pimavanserin showed efficacy in patients with Alzheimer's disease psychosis at the primary endpoint (week 6) with an acceptable tolerability profile and without negative effect on cognition. Further follow-up to week 12 did not show significant advantage for pimavanserin versus placebo.

FUNDING

ACADIA Pharmaceuticals.

Structures of the 5-HT2A receptor in complex with the antipsychotics risperidone and zotepine

Many drugs target the serotonin 2A receptor (5-HT_2AR), including second-generation antipsychotics that also target the dopamine D₂ receptor (D₂R). These drugs often produce severe side effects due to non-selective binding to other aminergic receptors. Here, we report the structures of human 5-HT_2AR in complex with the second-generation antipsychotics risperidone and zotepine. These antipsychotics effectively stabilize the inactive conformation by forming direct contacts with the residues at the bottom of the ligand-binding pocket, the movements of which are important for receptor activation. 5-HT_2AR is structurally similar to 5-HT_2CR but possesses a unique side-extended cavity near the orthosteric binding site. A docking study and mutagenic studies suggest that a highly 5-HT_2AR-selective antagonist binds the side-extended cavity. The conformation of the ligand-binding pocket in 5-HT_2AR significantly differs around extracellular loops 1 and 2 from that in D₂R. These findings are beneficial for the rational design of safer antipsychotics and 5-HT_2AR-selective drugs.

The 5-HT2A Receptor (5-HT2AR) Regulates Impulsive Action and Cocaine Cue Reactivity in Male Sprague-Dawley Rats

Impulsivity and the attentional orienting response to cocaine-associated cues (cue reactivity) promote relapse in cocaine-use disorder (CUD). A time-dependent escalation of cue reactivity (incubation) occurs during extended, forced abstinence from cocaine self-administration in rats. The investigational serotonin (5-HT) 5-HT2A receptor (5-HT2AR) antagonist/inverse agonist M100907 suppresses impulsive action, or the inability to withhold premature responses, and cocaine-seeking behaviors. The present preclinical study was designed to establish the potential for repurposing the Food and Drug Administration-approved selective 5-HT2AR antagonist/inverse agonist pimavanserin as a therapeutic agent to forestall relapse vulnerability in CUD. In male Sprague-Dawley rats, pimavanserin suppressed impulsive action (premature responses) measured in the 1-choice serial reaction time (1-CSRT) task, similarly to M100907. We also used the 1-CSRT task to establish baseline levels of impulsive action before cocaine self-administration and evaluation of cue reactivity (lever presses reinforced by the discrete cue complex previously paired with cocaine delivery). We observed an incubation of cocaine cue reactivity between day 1 and day 30 of forced abstinence from cocaine self-administration. Baseline levels of impulsive action predicted incubated levels of cocaine cue reactivity in late abstinence. We also found that baseline impulsive action predicted the effectiveness of pimavanserin to suppress incubated cue reactivity in late abstinence from cocaine self-administration at doses that were ineffective in early abstinence. These data suggest that integration of clinical measures of impulsive action may inform refined, personalized pharmacotherapeutic intervention for the treatment of relapse vulnerability in CUD.

Quantification of Pimavanserin in Bulk and Tablet Dosage Form Using A Stability Indicating High Performance Liquid Chromatographic Method

Background: Pimavanserin, an antipsychotic agent, is used to treat patients suffering with Parkinson's disease. Till now no stability indicating reverse phase HPLC method was reported for the quantification of pimavanserin in bulk and tablet dosage form. Hence in the present study, a new sensitive, precise and accurate stability indicating reverse phase HPLC method with photodiode array detector has been developed for the quantification of pimavanserin in bulk and tablet dosage form. Methods: Separation and analysis of pimavanserin was achieved on Kromasil C18 (5 µm, 250 mm × 4.6 mm) column using 0.1M NaH2PO4, methanol and acetonitrile in ratio of 55:30:15 (v/v/v) as mobile phase at 25°C. The flow rate was 1.0 ml/min. The effluents were monitored with detector set at 239 nm. The method validation was done with regard to the guidelines by the International Conference on Harmonization. Pimavanserin was subjected to acid, alkali and neutral hydrolysis, hydrogen peroxide oxidation, thermal degradation, and photo (sunlight) degradation. Results: Linear relationship was obtained between the concentration of drug and peak area response in the range of 4.25-34.0 µg/ml. The limits of detection and quantitation were found to be 0.027 µg/ml and 0.089 µg/ml, respectively. All the validation characteristics were within the acceptance criteria. The peaks of degradation products were well resolved from the pimavanserin peak. Conclusion: The developed and validated method is able to quantify the pimavanserin in the presence of degradation products.

Can pimavanserin help patients with Parkinson disease psychosis?

Pimavanserin is a first-in-class selective serotonin 5-HT2A receptor inverse agonist approved for the treatment of Parkinson disease psychosis. This article discusses pimavanserin's mechanism of action, which patients are appropriate candidates for therapy, adverse reactions, and appropriate dosing.

Guidance for switching from off-label antipsychotics to pimavanserin for Parkinson's disease psychosis: an expert consensus

Patients with Parkinson's disease psychosis (PDP) are often treated with an atypical antipsychotic, especially quetiapine or clozapine, but side effects, lack of sufficient efficacy, or both may motivate a switch to pimavanserin, the first medication approved for management of PDP. How best to implement a switch to pimavanserin has not been clear, as there are no controlled trials or case series in the literature to provide guidance. An abrupt switch may interrupt partially effective treatment or potentially trigger rebound effects from antipsychotic withdrawal, whereas cross-taper involves potential drug interactions. A panel of experts drew from published data, their experience treating PDP, lessons from switching antipsychotic drugs in other populations, and the pharmacology of the relevant drugs, to establish consensus recommendations. The panel concluded that patients with PDP can be safely and effectively switched from atypical antipsychotics used off label in PDP to the recently approved pimavanserin by considering each agent's pharmacokinetics and pharmacodynamics, receptor interactions, and the clinical reason for switching (efficacy or adverse events). Final recommendations are that such a switch should aim to maintain adequate 5-HT2A antagonism during the switch, thus providing a stable transition so that efficacy is maintained. Specifically, the consensus recommendation is to add pimavanserin at the full recommended daily dose (34 mg) for 2-6 weeks in most patients before beginning to taper and discontinue quetiapine or clozapine over several days to weeks. Further details are provided for this recommendation, as well as for special clinical circumstances where switching may need to proceed more rapidly.

[Modern approaches to treatment of psychosis in Parkinson's disease]

Psychotic disorders in Parkinson's disease (PDPD) are common and significantly influence the quality of life and disability level. The pathogenesis of PDPD is complex and not yet fully understood. Taking into consideration the features of the Parkinson's disease (usually older patients with a risk of cognitive decline), and the pharmacodynamics of the antiparkinsonian and traditional antipsychotic drugs, the management of PDPD is a challenging issue of clinical neurology and psychiatry. In this systematic review, scientific publications for the period 2014-2016 were analyzed within two bibliographic databases: MEDLINE/PubMed and eLIBRARY.RU. Additionally, the guidelines of the International Parkinson and Movement Disorders Society, American Academy of Neurology and European Academy of Neurology were included in the analysis. Clozapine is recommended to use in the treatment of PDPD, quetiapine is possible to use, pimavanserin will probably become a remedy of choice. Nonpharmacological approaches have positive effects on the general condition of the patients with PDPD, however the efficacy of such approaches to treat psychosis is unclear.

Interactions of Hallucinogens with the Glutamatergic System: Permissive Network Effects Mediated Through Cortical Layer V Pyramidal Neurons

Recordings made from layer V (L5) pyramidal cells of the prefrontal cortex (PFC) and neocortex in rodent slice preparations have shown that serotonin (5-hydroxytryptamine, 5-HT) and serotonergic hallucinogens induce an increase in the frequency of spontaneous excitatory postsynaptic currents (EPSCs) in the apical dendritic field by activating 5-HT_2A receptors. Serotonergic hallucinogens induce late EPSCs and increase recurrent network activity when subcortical or mid-cortical regions are stimulated at low frequencies (e.g., 0.1 Hz). A range of agonists or positive allosteric modulators (PAMs) for mostly G_i/o-coupled receptors, including metabotropic glutamate₂ (mGlu₂), adenosine A₁, or μ-opioid receptors, suppress these effects of 5-HT_2A receptor stimulation. Furthermore, a range of mostly G_q/11-coupled receptors (including orexin₂ [OX₂]; α₁-adrenergic, and mGlu₅ receptors) similarly induce glutamate (Glu) release onto L5 pyramidal cells. Evidence implicates a number of brain regions in mediating these effects of serotonergic hallucinogens and G_q/11-coupled receptors including the midline and intralaminar thalamic nuclei, claustrum, and neurons in deep PFC. These effects on 5-HT_2A receptors and related GPCRs appear to play a major role in the behavioral effects of serotonergic hallucinogens, such as head twitches in rodents and higher order behaviors such as rodent lever pressing on the differential-reinforcement-of-low rate 72-s (DRL 72-s) schedule. This implies that the effects of 5-HT_2A receptor activation on the activity of L5 pyramidal cells may be responsible for mediating a range of behaviors linked to limbic circuitry with connectivity between the PFC, striatum, thalamus, claustrum, striatum, amygdala, and the hippocampal formation.

Perioperative implications of common and newer psychotropic medications used in clinical practice

Psychotropic medications are widely prescribed by clinicians as both primary therapy for a variety of psychiatric and neurodegenerative diseases and as adjunctive analgesics for use in the perioperative period. It is critical to understand various modes of action, drug-drug interactions, side effects, and clinical implications. Health care providers must understand how these medications interact with anesthetics, as well as other drugs used in perioperative care. We review relevant psychiatric and neurodegenerative diseases, psychotropic medications used to treat them, and how these medications interact with anesthetics and drugs used in perioperative care. We will also discuss emerging psychotropic drugs and the challenges they may create during the perioperative period. Future direction of investigation into the role of these drugs during the perioperative period and implications is also discussed.

Pimavanserin (Nuplazid™) for the treatment of Parkinson disease psychosis: A review of the literature

Introduction:

Pimavanserin (Nuplazid™) is an atypical antipsychotic currently indicated for the treatment of hallucinations and delusions associated with Parkinson disease psychosis. The antipsychotic effects of this new agent are believed to occur via selective inverse agonist activity at serotonin 5-HT_2a receptors.

Methods:

Study authors completed a literature review of 2 published randomized controlled trials of pimavanserin for the treatment of Parkinson disease psychosis. The Food and Drug Administration Briefing Document by the Psychopharmacologic Drugs Advisory Committee for the review of pimavanserin dated March 29, 2016, was reviewed for additional information on 2 unpublished trials.

Results:

Pimavanserin has demonstrated no worsening of motor symptoms of Parkinson disease, but only 1 of 4 trials has shown consistent statistically significant improvements in psychotic symptoms compared with placebo.

Discussion:

Options for the treatment of Parkinson disease psychosis are limited. The selective receptor profile of pimavanserin offers advantages for tolerability. Further studies are warranted to better provide clinicians and patients with information regarding the clinical utility of this agent.

Investigation of metabolic profile of pimavanserin in rats by ultrahigh-performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry

RATIONALE

Pimavanserin, a selective serotonin 2A receptor inverse agonist, is a promising candidate for treating Parkinson's disease psychosis. Our previous study revealed that there might be the presence of extensive metabolites of pimavanserin in rats. However, the metabolic fate of pimavanserin in vivo remains unknown. Thus, it is essential to develop an efficient method to investigate the metabolic profile of pimavanserin in rats. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to date has the highest mass measurement accuracy and resolution of any mass spectrometry platform.

METHODS

After a single intragastric administration of pimavanserin at a dose of 50 mg kg^-1 , plasma, bile, urine and feces were collected from rats. A novel and efficient strategy was developed to analyze the metabolic profile of pimavanserin in vivo based on ultrahigh-performance liquid chromatography (UHPLC) coupled with FT-ICR-MS.

RESULTS

A total of 23 metabolites were detected and tentatively identified through comparing their mass spectrometry profiles with those of pimavanserin. These metabolites were found in feces (22), bile (21), rat urine (16) and plasma (15). Results demonstrated that metabolic pathways of pimavanserin in rats included dehydrogenation, demethylation, deethylation, depropylation, debutylation, hydroxylation, dihydroxylation and trihydroxylation.

CONCLUSIONS

A total of 22 phase I metabolites of pimavanserin were detected and tentatively identified. This report presents the first study of screening and identification of the metabolites of pimavanserin. The UHPLC/FT-ICR-MS method is a powerful tool for exploring and identifying metabolites in complex biological samples.

Pimavanserin: A Novel Drug Approved to Treat Parkinson's Disease Psychosis

Objective: Pimavanserin is the first United States Food and Drug Administration (FDA)-approved treatment for Parkinson's disease psychosis (PDP). This article reviews the safety, efficacy, and pharmacology data for pimavanserin and its role in therapy. Method of Research: Initial literature sources were identified via MEDLINE search (1946-September 2016) of pimavanserin and ACP-103 (original molecular designation). Reference review and search of FDA.gov and clinicaltrials.gov yielded additional studies. English-language studies of pimavanserin for PDP were evaluated. Animal studies were excluded. Randomized, controlled trials (RCTs) were prioritized. Results: Four RCTs were identified. In each, pimavanserin was well-tolerated with few adverse effects and no worsening of motor symptoms. A Phase II trial displayed a nonsignificant trend toward Scale for Assessment of Positive Symptoms (SAPS) improvement (p=0.09), with significant benefits in secondary efficacy markers. However, two Phase III trials, including one that was terminated early, failed to show significant SAPS improvement. A third Phase III trial with an improved research design utilized a nine-item subset of the SAPS, the SAPS-PD, as the primary outcome and demonstrated that pimavanserin 40mg was effective in improving PDP compared to placebo (p=0.0014, effect size=0.50). Secondary outcomes were also significantly improved: Clinical Global Impression of Severity (CGI-S) (p=0.0007, effect size=0.52) and Clinical Global Impression of Improvement (CGI-I) (p=0.0011, effect size=0.51), caregiver burden (p=0.0016, effect size=0.50), nighttime sleep (p=0.0446, effect size=0.31), and daytime wakefulness (p=0.012, effect size=0.39). Conclusion: Evidence suggests pimavanserin attenuates PDP symptoms with few adverse effects and little risk of worsening motor function. With limited treatment options for PDP, pimavanserin represents an important therapeutic innovation.

Treating Hallucinations and Delusions Associated With Parkinson's Disease Psychosis

PURPOSE OF REVIEW

We discuss features of Parkinson's disease psychosis (PDP) including symptomology and pathophysiology. Treatment options, including non-pharmacologic strategies, dose reduction of offending agents, and the addition of non-dopaminergic antipsychotics, are addressed. The efficacy of second-generation antipsychotics and novel agents is examined.

RECENT FINDINGS

Pimavanserin, a 5-HT_2A/C receptor inverse agonist with no other receptor activity, has shown efficacy and tolerability and is now FDA approved for PDP treatment. Research into novel targets is ongoing. PDP is a morbid complication of Parkinson's disease with complex incompletely understood mechanisms. Treatment is directed towards mitigation of psychosis without worsening of motor features.

Pimavanserin: Potential Treatment For Dementia-Related Psychosis

Psychosis is common across dementia types with a prevalence of 20% to 70%. Currently, no pharmacologic treatment is approved for dementia-related psychosis. Atypical antipsychotics are frequently used to treat these disorders, despite significant safety concerns. Pimavanserin, a selective 5-HT2A inverse agonist/antagonist, was approved in the U.S. for treating hallucinations and delusions associated with Parkinson's disease psychosis (PDP). Patients in the pimavanserin group experienced a significant (p=0.001) improvement in Scale for the Assessment of Positive Symptoms - Parkinson's disease (SAPS-PD) scores vs. placebo. In a subgroup analysis of patients with cognitive impairment (MMSE score ≥21 but ≤24), the observed improvement on the SAPS-PD with pimavanserin (N=50) was also significant (p=0.002) and larger than in the overall study population without an adverse effect on cognition. In a Phase 2 study with pimavanserin in Alzheimer's disease psychosis, pimavanserin significantly (p=0.045) improved psychosis at Week 6 vs. placebo on the NPI-NH Psychosis Score (PS). In a prespecified subgroup of patients with a baseline NPI-NH PS ≥12, a substantively larger treatment effect (p=0.011) was observed vs. participants with NPI-NH PS <12. The results of these studies in cognitively impaired patients with PDP provided the scientific foundation for an ongoing study of pimavanserin for treating patients with dementia-related psychosis associated with the most common neurodegenerative disorders. The study uses a relapse-prevention design with the endpoint of time-to-relapse of psychosis to evaluate the long-term efficacy and safety of pimavanserin as a potential treatment for hallucinations and delusions of dementia-related psychosis.

Delusional misidentification in Parkinson's disease: report of two cases and a review

Syndromes of delusional misidentification consist of disordered familiarity and have been reported in diverse diagnoses, including Parkinson's disease. Although the most common delusional misidentification is Capgras syndrome, in which the sufferer believes a familiar person has been replaced by an identical imposter, other forms have been also described. The pathogenesis of delusions of misidentification appears to require dysfunction of or connection to a left cerebral cortical area involved in recognition of familiarity, and also right frontal cortex serving belief evaluation. Two cases of Parkinson's disease with an unusual delusional misidentification, intermetamorphosis, are presented, along with their improvement with pimavanserin, a novel atypical antipsychotic medication.

Treatment of psychotic symptoms in patients with Parkinson disease

Persistent psychotic symptoms will develop in up to 60% of patients with Parkinson disease (PD). The initial approach to the management of PD psychosis (PDP) begins with addressing concurrent systemic conditions associated with psychotic behavior, such as delirium, medical conditions (eg, infections), psychiatric disorders (eg, major depression with psychotic symptoms, mania, schizophrenia), and substance misuse or withdrawal. A review of current medications is recommended, and medications that may trigger psychotic symptoms should be eliminated. If possible, antiparkinson medications should be reduced to the minimum therapeutic dose or discontinued in a sequential manner. Generally, dose reduction or discontinuation of anticholinergics is attempted first, followed by that of monoamine oxidase B inhibitors, amantadine, dopamine agonists, catechol-O-methyltransferase inhibitors, and lastly carbidopa/levodopa. The aim of antiparkinson medication dose reduction is to achieve a balance between improving drug-related psychotic symptoms and not significantly worsening the motor symptoms of PD. If additional measures are needed for chronic PDP treatment, the use of second-generation antipsychotics, such as clozapine, pimavanserin, or quetiapine, must be considered. The first-generation antipsychotics (eg, fluphenazine, haloperidol) are not recommended. In the patient with comorbid dementia, the addition of a cholinesterase inhibitor might also be beneficial for PDP. The choice of agent is based on patient-specific parameters, potential benefit, and side effects.

Pimavanserin: novel pharmacotherapy for Parkinson's disease psychosis

INTRODUCTION

Pimavanserin is the first FDA-approved atypical antipsychotic drug indicated for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis (PDP). Areas covered: This review focuses on the preclinical discovery of pimavanserin. It analyzes the pharmacological, behavioral and molecular mechanisms of pimavanserin and their contribution to the therapeutic advantages of the drug as reported in published preclinical and clinical studies, press releases and product labels. Expert opinion: Pimavanserin exhibits a unique pharmacological profile with nanomolar affinity at serotonin 5-HT_2A and 5-HT_2C receptors. Functionally, it acts as a potent inverse agonist at 5-HT_2A receptors, with selectivity over 5-HT_2C receptors and no appreciable activity at other neurotransmitter receptors. Behavioral studies found that pimavanserin reversed impaired behaviors in animal models predictive of antipsychotic activity, and with no impairment of motor functions. The drug exhibits long plasma half-life (57 hours), which support its once/day administration. A pivotal phase III clinical trial demonstrated significant improvement in PDP symptoms in patients receiving pimavanserin compared to placebo-treated patients. The drug also displayed relatively benign safety and tolerability profiles. Pimavanserin's mechanism of action might contribute to its unique psychopharmacological properties in the improved treatment of PDP, and perhaps psychosis in other diseases including schizophrenia and dementia-related psychosis.

Pimavanserin, a novel antipsychotic for management of Parkinson's disease psychosis

INTRODUCTION

Parkinson's disease psychosis (PDP) may develop in up to 60% of Parkinson's patients and is associated with increased morbidity and mortality. It also correlates with depression and dementia, and can contribute to caregiver stress and burnout. Pimavanserin is the first FDA approved drug for the treatment of hallucinations and delusions associated with PDP. Areas covered: For this review, a MEDLINE literature search (via PubMed) and information provided by ACADIA Pharmaceuticals were used. This review will discuss the pathophysiology and current management of PDP. In addition, this review will focus on the rationales behind the development of pimavanserin, mechanism of action, pharmacokinetics, pharmacodynamics, and the clinical trials evaluating the efficacy and safety of pimavanserin. Last, the review will address the drug's package insert warning. Expert commentary: Pimavanserin, a 5HT2A receptor inverse agonist, is the first FDA approved drug for the treatment of PDP which has been shown to reduce psychosis in PD through its unique mechanism of action. Pimavanserin, does not worsen PD motor symptoms and has an acceptable safety profile. The development of pimavanserin as an antipsychotic opened a new therapeutic avenue in the treatment of PDP as well as targeting psychosis in other disorders such as Alzheimer's disease.

Development of a UPLC-MS/MS method for determination of pimavanserin tartrate in rat plasma: Application to a pharmacokinetic study

A simple, rapid and sensitive method based on an ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) has been developed and validated for the determination of pimavanserin in rat plasma. The analyte was extracted by protein precipitation with methanol and separated on an ACQUITY BEH C₁₈ column (100 × 2.1 mm, 1.7 µm; Waters, USA), with an isocratic elution of acetonitrile-water containing 10 mM ammonium acetate (70:30, v/v), at a flow rate of 0.2 mL/min for 2.5 min. The analyte and clarithromycin (the internal standard) were detected and quantified in positive ion mode using multiple reaction monitoring transitions at m/z 428.2 → 223.0 for pimavanserin and m/z 748.5 → 589.5 for clarithromycin. Relative coefficient (r) for the calibration curve was more than 0.9980. The intra-day and inter-day precisions (relative standard deviation, RSD%) were less than 13.3% and 10.5%, respectively, and the accuracy (relative error, RE%) was within ± 11.5%. The analytical method was successfully applied to a routine pharmacokinetic study of pimavanserin in rats after oral administration at the dose of 10 mg/kg.

Folding Underlies Bidirectional Role of GPR37/Pael-R in Parkinson Disease

Since conformational flexibility, which is required for the function of a protein, comes at the expense of structural stability, many proteins, including G-protein-coupled receptors (GPCRs), are under constant risk of misfolding and aggregation. In this regard GPR37 (also named PAEL-R and ETBR-LP-1) takes a prominent role, particularly in relation to Parkinson disease (PD). GPR37 is a substrate for parkin and accumulates abnormally in autosomal recessive juvenile parkinsonism, contributing to endoplasmic reticulum stress and death of dopaminergic neurons. GPR37 also constitutes a core structure of Lewy bodies, demonstrating a more general involvement in PD pathology. However, if folded and matured properly, GPR37 seems to be neuroprotective. Moreover, GPR37 modulates functionality of the dopamine transporter and the dopamine D2 receptor and stimulates dopamine neurotransmission. Here we review the multiple roles of GPR37 with relevance to potential disease modification and symptomatic therapies of PD and highlight unsolved issues in this field.

Cortical and Striatal Reward Processing in Parkinson's Disease Psychosis

Psychotic symptoms frequently occur in Parkinson's disease (PD), but their pathophysiology is poorly understood. According to the National Institute of Health RDoc programme, the pathophysiological basis of neuropsychiatric symptoms may be better understood in terms of dysfunction of underlying domains of neurocognition in a trans-diagnostic fashion. Abnormal cortico-striatal reward processing has been proposed as a key domain contributing to the pathogenesis of psychotic symptoms in schizophrenia. This theory has received empirical support in the study of schizophrenia spectrum disorders and preclinical models of psychosis, but has not been tested in the psychosis associated with PD. We, therefore, investigated brain responses associated with reward expectation and prediction error signaling during reinforcement learning in PD-associated psychosis. An instrumental learning task with monetary gains and losses was conducted during an fMRI study in PD patients with (n = 12), or without (n = 17), a history of psychotic symptoms, along with a sample of healthy controls (n = 24). We conducted region of interest analyses in the ventral striatum (VS), ventromedial prefrontal and posterior cingulate cortices, and whole-brain analyses. There was reduced activation in PD patients with a history of psychosis, compared to those without, in the posterior cingulate cortex and the VS during reward anticipation (p < 0.05 small volume corrected). The results suggest that cortical and striatal abnormalities in reward processing, a putative pathophysiological mechanism of psychosis in schizophrenia, may also contribute to the pathogenesis of psychotic symptoms in PD. The finding of posterior cingulate dysfunction is in keeping with prior results highlighting cortical dysfunction in the pathogenesis of PD psychosis.

Pimavanserin: A novel therapeutic option for Parkinson disease psychosis

Purpose of review

In April 2016, the Food and Drug Administration (FDA) approved a first-in-class atypical antipsychotic medication called pimavanserin for the treatment of Parkinson disease psychosis (PDP). We aim to inform readers about its indications, effectiveness, and safety profile.

Recent findings

Pimavanserin acts as an inverse agonist at serotonin 5-HT2A receptors and has negligible effects on other receptors, thereby avoiding the D2 receptor antagonism that can potentially worsen motor symptoms. Its FDA approval was based primarily on the results of a single randomized, placebo-controlled phase 3 trial.

Summary

While pimavanserin appears to be a safe, effective, and well-tolerated therapeutic option for PDP, additional clinical trials and open-label extension studies are needed to determine the long-term safety and efficacy of this promising therapy. In the meantime, prescribers need to be aware of the possible adverse effects of pimavanserin including QT interval prolongation and a potential to cause a paradoxical worsening of symptoms.

Recent advances in treating Parkinson's disease

This article summarizes (1) the recent achievements to further improve symptomatic therapy of motor Parkinson’s disease (PD) symptoms, (2) the still-few attempts to systematically search for symptomatic therapy of non-motor symptoms in PD, and (3) the advances in the development and clinical testing of compounds which promise to offer disease modification in already-manifest PD. However, prevention (that is, slowing or stopping PD in a prodromal stage) is still a dream and one reason for this is that we have no consensus on primary endpoints for clinical trials which reflect the progression in prodromal stages of PD, such as in rapid eye movement sleep behavior disorder (RBD) —a methodological challenge to be met in the future.

Pimavanserin: A Novel Antipsychotic for Parkinson's Disease Psychosis

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, safety, and place in therapy of pimavanserin for the treatment of hallucinations and delusions of Parkinson's disease psychosis (PDP).

DATA SOURCES

A comprehensive PubMed search (1966 to January 2017) was conducted using the search terms Parkinson's disease psychosis, hallucinations, delusions, pimavanserin, and ACP-103. Additional data were obtained from references of identified articles, governmental sources, manufacturer product labeling and website, and Clinicaltrials.gov.

STUDY SELECTION AND DATA EXTRACTION

All English-language trials evaluating pimavanserin in PDP were included. Data from review articles were included if relevant to clinical practice. One phase II and 3 phase III trials are discussed.

DATA SYNTHESIS

Pimavanserin was approved in April 2016 for the treatment of delusions and hallucinations of PDP. One phase II and 2 phase III trials reported no difference for primary outcomes when pimavanserin was compared with placebo. The pivotal phase III ACP-103-020 trial adapted a scale to target more specific symptoms prevalent in PDP and showed that least-squares mean differences of the total PD-adapted Scale for the Assessment of Positive Symptoms score were significantly improved for pimavanserin-treated patients as compared with placebo-treated patients (difference = -3.06; 95% CI [-4.91 to -1.20]; P = 0.0014]). Pimavanserin's adverse effect profile includes urinary tract infections, falls, peripheral edema, hallucinations, confusion, nausea, and headaches.

CONCLUSION

Pimavanserin is a novel 5-HT_2A inverse agonist that has shown promising results for managing hallucinations and delusions in patients with PDP without worsening motor effects or orthostasis. Yet its high cost and specialty pharmacy access may limit use in clinical practice.

Update on the treatment of Parkinson's disease psychosis: role of pimavanserin

Parkinson's disease (PD) has a prevalence of nearly 1 million people in the USA, with increasing incidence in the elderly population. Generally, the age of presentation is between 55 and 65 years, with the likelihood of diagnosis increasing as patients reach the age of 80 years or above. Some of the common treatments for PD increase dopamine levels in the brain. Dopaminergic therapy helps to improve motor and non-motor symptoms, but it is not without risks. Dopaminergic therapy can cause confusion, delirium, and psychotic-like behavior. It is recommended that these agents are used cautiously in patients with a history of psychosis due to the risk of exacerbation. It is unclear whether Parkinson's disease psychosis (PDP) is due to the disease itself, the treatment, or a combination of both, but it is clear that a safe, effective treatment is necessary. Second-generation (atypical) antipsychotics are the current choice of therapy for PDP. All of these agents have a black box warning from the US Food and Drug Administration (FDA) for elevated risk of mortality in elderly patients with dementia-related psychosis. Pimavanserin (Nuplazid^®) received its novel drug approval by the FDA on April 29, 2016, to treat hallucinations and delusions associated with psychosis experienced by some people with PD. We review in this article the new research that led to this approval as well as its potential place in therapy.

Serotonin 2A Receptor Inverse Agonist as a Treatment for Parkinson's Disease Psychosis: A Systematic Review and Meta-analysis of Serotonin 2A Receptor Negative Modulators

BACKGROUND

There is uncertainty about the efficacy and tolerability of serotonin 2A (5-HT2A) receptor negative modulators for Parkinson's disease psychosis (PDP).

OBJECTIVE

This is the first meta-analysis of randomized placebo-controlled trials (RCTs) testing negative modulators of the 5-HT2A receptor as a treatment for PDP.

METHODS

The primary outcome was the Scale for Assessment of Positive Symptoms (SAPS)-hallucinations (H) and -delusions (D) scores (SAPS-H+D). Other outcome measures were SAPS-H, SAPS-D, the Unified Parkinson's Disease Rating Scale Part II and III (UPDRS-II+III), discontinuation rates, and individual adverse events.

RESULTS

Four RCTs were identified that met inclusion criteria, all assessing the 5-HT2A inverse agonist pimavanserin (including 417 drug-treated and 263 placebo-treated PDP patients). Pimavanserin significantly decreased SAPS-H+D scores compared to placebo [weighted mean differences (WMD) = -2.26, 95% confidence interval (95% CI) = -3.86 to -0.67, p = 0.005, I2 = 30% , N = 4 studies, n = 502 patients]. Moreover, pimavanserin was superior to placebo for reducing SAPS-H (WMD = -2.15, 95% CI = -3.45 to -0.86, p = 0.001, I2 = 0% , N = 2, n = 237) and SAPS-D scores (WMD = -1.32, 95% CI = -2.32 to -0.32, p = 0.010, I2 = 0% , N = 2, n = 237). Pimavanserin was associated with less orthostatic hypotension than placebo (risk ratio = 0.33, 95% CI = 0.15-0.75, p = 0.008, I2 = 0% , number needed to harm = 17, p = 0.01, N = 3, n = 476). There were no significant differences in rates of all-cause discontinuation, adverse events, and death, UPDRS-II+III scores, and incidences of individual adverse events (other than orthostatic hypotension) between pimavanserin and placebo groups.

CONCLUSIONS

Pooled RCT results suggest that pimavanserin is beneficial for the treatment of PDP and is well tolerated. We did not identify other negative modulators of the 5-HT2A receptor for the treatment of PDP.

Morphine-induced Straub tail reaction in mice treated with serotonergic compounds

Constitutively active 5-HT₂ receptors have been suggested to contribute to motoneuronal excitability, muscle spasms and spasticity. Accordingly, 5-HT_2C receptor inverse agonists have been demonstrated in pilot experiments to reduce spasticity in animal model of spasticity and patients with spinal cord injuries. Thus, 5-HT_2C receptor inverse agonists may represent a novel class of anti-spasticity agents justifying a search for compounds with robust 5-HT_2C receptor inverse agonist activity either among the existing medications or via a dedicated drug discovery program. Morphine-induced Straub tail response in mice is regarded as a model of transient spasticity that may be suitable for supporting such drug discovery efforts. Subcutaneous injection of morphine (10-60mg/kg) induced a dose-dependent Straub tail reaction in male Swiss mice with maximum response obtained 15-30min after the morphine administration. When given prior to morphine, 5-HT_2B/2C receptor inverse agonists cyproheptadine (1-10mg/kg, i.p.) and SB206553 (0.3-3mg/kg, i.p.) diminished Straub tail reaction dose-dependently without affecting spontaneous locomotor activity. In contrast, 5-HT_2B/2C receptor antagonist methysergide (1-5.6mg/kg, i.p.) and 5-HT_2C receptor antagonist SB242084 (1-5.6mg/kg, i.p.) as well as 5-HT_2A receptor inverse agonist pimavanserin (1-10mg/kg, i.p.) had no appreciable effects on Straub tail response. Taken together, the findings indicate that constitutive activity of 5-HT_2B/2C receptor may be involved in the mechanisms of morphine-induced spasticity. Thus, morphine-induced Straub tail response may be evaluated further as a candidate higher throughput test to identify 5-HT_2C receptor inverse agonists with anti-spasticity effects in vivo.